Publishing type：Research paper (scientific journal)  

DOI： 10.1109/JLT.2024.3454977

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Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/IPC57732.2023.10360588

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DOI： 10.1109/ACP/POEM59049.2023.10369884

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DOI： https://doi.org/10.1049/icp.2023.2060

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1049/icp.2023.2621

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.23919/MOC58607.2023.10302866

Language：English   Publishing type：Research paper (other academic)  

Convolutional neural networks are a powerful category of artificial neural networks that can extract hierarchical features of biological data to significantly reduce parametric complexity and increase prediction accuracy. In this paper, we propose high-speed optical convolutional neural network accelerator with 100Gbaud EO-polymer/Si hybrid optical modulator and demonstrated proof of concept both in simulation and experiment.

DOI： 10.1109/OECC56963.2023.10209890

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/OECC56963.2023.10209890

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/OECC56963.2023.10209709

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/photonics10070738

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Language：English   Publishing type：Research paper (other academic)  

We present high-efficiency of 0.18Vcm and 252Gbps of PAM-4 high-speed operation for EO polymer/Si and InP hybrid optical modulators in C-band wavelengths. We also demonstrate record high-efficiency of 0.35Vcm and high-speed operation in O-band wavelengths.

DOI： 10.23919/OFC49934.2023.10117072

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Publishing type：Research paper (scientific journal)  

DOI： 10.1109/JLT.2022.3219866

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DOI： 10.1109/JSTQE.2023.3253846

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Publishing type：Research paper (scientific journal)  

DOI： 10.1109/JLT.2022.3219866

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DOI： 10.1109/JSTQE.2023.3253846

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DOI： 10.1063/5.0109251

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Publishing type：Research paper (scientific journal)   Publisher：Optica Publishing Group  

DOI： 10.1364/OE.465560

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Language：English   Publishing type：Research paper (other academic)  

We demonstrate a >100 Gbaud transmission using a thermo-physically enhanced EO polymer modulator. The error-free signal over a distance of 2.0 km was successfully demonstrated under high-temperature exposure at up to 110 degrees C.

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We demonstrate a >100 Gbaud transmission using a thermo-physically enhanced EO polymer modulator. The error-free signal over a distance of 2.0 km was successfully demonstrated under high-temperature exposure at up to 110 degrees C.

Web of Science

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Publishing type：Research paper (scientific journal)  

DOI： 10.1109/JPHOT.2021.3132805

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Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers ({IEEE})  

DOI： 10.1109/JPHOT.2021.3127220

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DOI： 10.1364/OE.447616

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DOI： 10.1364/OE.471162

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Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.optcom.2021.127865

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Publishing type：Research paper (scientific journal)  

DOI： 10.1364/OE.465560

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Publishing type：Research paper (scientific journal)  

DOI： 10.1109/JPHOT.2021.3132805

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Publishing type：Research paper (scientific journal)  

DOI： 10.1364/OE.447616

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Publishing type：Research paper (scientific journal)  

DOI： 10.1109/JPHOT.2021.3127220

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Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijleo.2022.168968

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Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (scientific journal)  

Silicon nitride waveguides have emerged as an excellent platform for photonic applications, including nonlinear optical signal processing, owing to their relatively high Kerr nonlinearity, negligible two photon absorption, and wide transparent bandwidth. In this paper, we propose an effective approach using 3D finite element method to optimize the dispersion characteristics of silicon nitride waveguides for four-wave mixing (FWM) applications. Numerical studies show that a flat and low dispersion profile can be achieved in a silicon nitride waveguide with the optimized dimensions. Near-zero dispersion of 1.16 ps/km/nm and 0.97 ps/km/nm at a wavelength of 1550 nm are obtained for plasma-enhanced chemical vapor deposition (PECVD) and low-pressure chemical vapor deposition (LPCVD) silicon nitride waveguides, respectively. The fabricated micro-ring resonator with the optimized dimensions exhibits near-zero dispersion of -0.04 to -0.1 ps/m/nm over a wavelength range of 130 nm which agrees with the numerical simulation results. FWM results show that near-zero phase mismatch and high conversion efficiencies larger than -12 dB using a low pump power of 0.5 W in a 13-cm long silicon nitride waveguide are achieved.

DOI： 10.3390/photonics8050161

Language：English   Publishing type：Research paper (other academic)  

Language：Others   Publishing type：Research paper (scientific journal)  

We present an O-band four-level pulse amplitude modulation (PAM4) transmitter based on a dual-drive silicon modulator with binary driving electronics at CMOS voltages, effectively eliminating the need for power-hungry digital-to-analog converters (DACs) and RF drivers. The fabricated dual-drive silicon modulator has cascaded p-n junction and p-i-n junction embedded in each arm of Mach-Zehnder interferometer, implementing high-speed data modulation and efficient bias control, respectively. Power dissipation of around 611 fJ/bit is obtained when synthesizing 46 Gb/s PAM4, showing high power efficiency. The fabricated silicon modulator exhibits a π-voltage-length product of 4.5 V·mm, and a 3-dB bandwidth of up to 27 GHz. Meanwhile, to implement a power-efficient PAM4 transceiver, the digital signal processing (DSP) at the receiver side is also discussed by balancing the performance and complexity. With a low-complexity DSP, negligible power penalty is observed after transmission over 38-km SSMF for both synthesized 20 Gb/s and 40 Gb/s PAM4. The presented PAM4 transmitter takes the advantages of both carrier-depletion and carrier-injection phase shifters for effective data modulation and bias control in PAM4 signalingand provides a power-efficient transmitter solution by eliminating the use of power-hungry DACs or RF drivers for datacenter interconnects.

DOI： 10.1109/JSTQE.2021.3056721

Language：English   Publishing type：Research paper (scientific journal)  

Huffman-coded sphere shaping (HCSS) is an algorithm for finite-length probabilistic constellation shaping, which provides nearly optimal energy efficiency at low implementation complexity. In this paper, we experimentally study the nonlinear performance of HCSS employing dual-polarization 64-ary quadrature amplitude modulation (DP-64QAM) in an extended-reach single-span link comprising 200 km of standard single-mode fiber (SSMF). We investigate the effects of shaping sequence length, dimensionality of symbol mapping, and shaping rate. We determine that the naive approach of Maxwell-Boltzmann distribution matching - which is optimal in the additive white Gaussian noise channel - provides a maximum achievable information rate (AIR) gain of 0.18 bits/4D-symbol with respect to uniform signaling at optimum launch power in the infinite length regime. Conversely, HCSS can achieve a gain of 0.37 bits/4D-symbol over uniform signaling using amplitude sequence length of 32, which may be implemented without multiplications, using integer comparison and addition operations only. Coded system performance, with a net data rate of approximately 425 Gb/s for both shaped and uniform inputs, is also analyzed.

DOI： 10.1109/JSTQE.2021.3055476

Language：English   Publishing type：Research paper (scientific journal)  

A novel maximum-ratio combined receiver (MRC-RX) is proposed and demonstrated through a proof-of-concept experiment, conducted to mitigate the system performance degradation caused by the low linearity of the silicon modulator when deployed in passive optical network (PON)-based access. By employing the proposed MRC-RX, an optimized receiver sensitivity is achieved, which enables the mitigation of the performance degradation induced by the silicon modulator, and a more reliable transmission in both cases of low and high received power. In the proof-of-concept experiment, at a bit error rate of 1.0 x 10(-4), the receiver sensitivity of the MRC-RX was improved by 3.5 dB and 6.7 dB compared with the lite coherent receiver (lite CO-RX) and direct detection receiver (DD-RX), respectively. Compared with a system employing a commercial lithium niobate (LiNbO3) modulator, a maximum improvement of similar to 5.6 dB in the receiver sensitivity was obtained for the MRC-RX in the silicon modulator system. Thus, the system performance degradation caused by the low linearity of the silicon modulator can be effectively reduced by employing the MRC-RX. The proposed method makes sense to the building of next generation high reliable photonics integrated access by employing silicon modulators.

DOI： 10.1109/JSTQE.2020.3021732

Language：English   Publishing type：Research paper (scientific journal)  

To synthesize a single-sideband (SSB) Nyquist high-order QAM, an optical subcarrier processing (OSP) based scheme is proposed and experimentally demonstrated. A Twin-SSB Nyquist in lower-order QAM is firstly generated using an electro-optic approach. OSP-based data aggregation is then deployed to coherently merge two sidebands in the twin-SSB to synthesize an SSB Nyquist QAM with an increased modulation level. The proposed scheme effectively relaxes the requirement for the digital-to-analog (DAC) resolution, thus reducing the power consumption and cost. Besides, the use of the coherent two-carrier pump in the data aggregation avoids the introduction of phase noise from the pump. It allows for the deployment of a low-cost laser as a pump laser source without sacrificing the performance, further reducing the overall implementation cost. Moreover, a hierarchical blind phase search algorithm is proposed to combat the possible distortions introduced in the data aggregation. A 12.5 Gbps SSB Nyquist 16QAM is experimentally synthesized from a 2 x 6.25 Gbps twin-SSB Nyquist QPSK with an error-free operation.

DOI： 10.1109/JSTQE.2020.2976542

Language：English   Publishing type：Research paper (scientific journal)  

In this paper, a phase-sensitive amplifier (PSA)-based two dimensional (2D)-to-one dimensional (1D) constellation reforming system is proposed and analyzed in detail. The proposed system theoretically realizes seven kinds of 10 GBaud quadrature amplitude modulation (QAM)-to-pulse amplitude modulation (PAM) conversions, including quadrature phase shift keying-to-PAM4 and 8QAM-to-PAM8 conversions. The constellation reforming system consists of a constellation squeezing PSA and a multi-level vector moving PSA. The operating principle and formula derivations of constellation squeezing and vector moving processes are fully explained, including the PSA transfer characteristics and PSA gain axis angle analytical solutions. When implementing QAM-to-PAM conversions, the constellations, spectra, eye diagrams, error vector magnitudes and bit error ratio (BER) performances of the QAM and PAM signals are measured. For 8QAM-to-PAM8 conversion, with the input OSNR of 25 dB and 30 dB, at the BER of 10(-3), the converted PAM8 shows the receiver OSNR of 38.9 dB and 35.2 dB, respectively. The proposed and verified 2D-to-1D constellation refbrming system builds an optical bridge connecting long-haul and short-reach networks, which can be employed in the format conversion, high-order format signal generation and shaping, and flexible information aggregation/de-aggregation. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

DOI： 10.1364/OE.417353

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1117/12.2570737

Language：English   Publishing type：Research paper (other academic)  

An optical de-aggregation scheme based on quadrature de-multiplexing and vector moving is proposed. A 10GBaud 9QAM is de-aggregated into two 10GBaud PAM3s and a 10-km short-reach transmission is performed before signal detections. (C) 2020 The Author(s)

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1038/s41467-020-18908-5

Language：English   Publishing type：Research paper (other academic)  

We demonstrate a low voltage driving 100Gbaud transmitter using hybrid silicon modulator with efficient EO polymer. It reaches BER below HD-FEC threshold just with a drive voltage of 1.9 Vpp. It has also shown a good thermal operation at temperature up to 110 degrees C.

Language：English   Publishing type：Research paper (scientific journal)  

Mode division multiplexing (MDM) silicon photonic integrated circuits (PICs) have been widely developed for achieving high-speed optical interconnects and communications. As an excellent nonlinear optical platform, silicon PICs also receive great attention in applications of optical parametric devices and nonlinear optical signal processing. However, it is still challenging to develop MDM optical parametric devices due to the strong mode dependence of the group velocity dispersion (GVD) in a silicon waveguide. Here, we theoretically design a convex waveguide exhibiting almost the same GVD profiles for quasi-TE0 and quasi-TE1 modes based on the standard fabrication flow of silicon photonic foundries. Specifically, flat GVD curves varying from -1500 ps/nm/km to -1000 ps/nm/km are obtained for the two modes in a convex waveguide within a spectral region of 1.37 mu m to 1.75 mu m covering from E-band to U-band. The study is expected to open an avenue for exploring unprecedented MDM nonlinear applications.

DOI： 10.1109/JPHOT.2020.3005690

Language：English   Publishing type：Research paper (scientific journal)  

To reduce the ever-increasing energy consumption in datacenters, one of the effective approaches is to increase the ambient temperature, thus lowering the energy consumed in the cooling systems. However, this entails more stringent requirements for the reliability and durability of the optoelectronic components. Herein, we fabricate and demonstrate silicon-polymer hybrid modulators which support ultra-fast single-lane data rates up to 200 gigabits per second, and meanwhile feature excellent reliability with an exceptional signal fidelity retained at extremely-high ambient temperatures up to 110 degrees C and even after long-term exposure to high temperatures. This is achieved by taking advantage of the high electro-optic (EO) activities (in-device n(3)r(33)=1021pmV(-1)), low dielectric constant, low propagation loss (alpha, 0.22dBmm(-1)), and ultra-high glass transition temperature (T-g, 172 degrees C) of the developed side-chain EO polymers. The presented modulator simultaneously fulfils the requirements of bandwidth, EO efficiency, and thermal stability for EO modulators. It could provide ultra-fast and reliable interconnects for energy-hungry and harsh-environment applications such as datacentres, 5G/B5G, autonomous driving, and aviation systems, effectively addressing the energy consumption issue for the next-generation optical communication. Information and communication datacentres require a large amount of energy for their cooling systems, which could be decreased by working at higher temperatures. Here, the authors introduce a silicon-polymer hybrid modulator that maintains high data rates for long periods at high temperatures that could be used under such conditions, to reduce energy consumption.

DOI： 10.1038/s41467-020-18005-7

Language：English   Publishing type：Research paper (scientific journal)  

Mode-division multiplexing (MDM) has attracted broad attention as it could effectively boost up transmission capability by utilizing optical modes as a spatial dimension in optical interconnects. In such a technique, different data channels are usually modulated to the respective carriers over different spatial modes by using individual parallel electro-optic modulators. Each modulated channel is then multiplexed to a multi-mode waveguide. However, the method inevitably suffers from a high cost, large device footprint and high insertion loss. Here, we design intensity and phase dual-mode modulators, enabling simultaneous modulations over two channels via a graphene-on-silicon waveguide. Our method is based on the exploration of co-planar interactions between structured graphene nanoribbons (GNs) and spatial modes in a silicon waveguide. Specifically, the zeroth-order transverse electric (TE0) and first-order transverse electric (TE1) modes are modulated separately and simultaneously by applying independent driving electrodes to different GNs in an identical modulator. Our study is expected to open an avenue to develop high-density MDM photonics integrated circuits for tera-scale optical interconnects. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.

DOI： 10.1364/OE.394409

Language：English   Publishing type：Research paper (other academic)  

PAM4 receiver based on QD-SOA preamplifier is experimentally demonstrated with a 2.8-dB sensitivity improvement and a 2.5-dB gain in IPDR when amplifying 20-Gb/s PAM4 signals in contrast to its counterpart with MQW-SOA preamplifier. (C) 2020 The Author(s)

Language：English   Publishing type：Research paper (other academic)  

An FWM-based coherent self-superposition technique is proposed and demonstrated to synthesize 12.5-Gb/s SSB Nyquist 16QAM from Twin-SSB Nyquist QPSK, which effectively relaxes DAC resolution requirement. An equalization algorithm is also proposed for such approach's detection.

Language：English   Publishing type：Research paper (scientific journal)  

We proposed a variable linewidth light source using random walk phase noise. As a demonstration, the impact of the laser linewidth on the error-vector magnitude performance in the optical QPSK transmission was evaluated by using the proposed laser source experimentally, where the linewidth tunable range was from 40 kHz to 5 MHz.

DOI： 10.1587/elex.17.20200216

Language：English   Publishing type：Research paper (scientific journal)  

An optical conversion node scheme for direct detection of complex modulation format is proposed to bridge long-haul transmissions and short-reach interconnects. A noisy 10G Baud quadrature phase shift keying signal is converted into a 10G Baud normal 4-level pulse amplitude modulation (PAM4) signal by the node. The conversion node is realized mainly relies on four-wave mixing-based phase-sensitive amplifiers. The power ratio and constellation shape of the converted PAM4 both can be flexibly designed based on network demands and five kinds of uniform or non-uniform PAM4s are generated to verify the shaping functionality. With the input optical signal-to-noise ratio range of (10 dB similar to 30 dB), the key indicators of the signals went through every part are measured, includes constellations, eye diagrams, error vector magnitudes, bit error rates, normalized impact factors of phase and amplitude. The proposed node scheme has great application potential in intermediate nodes for bridging long-haul transmissions and short-reach interconnects, hierarchical modulation and flexible constellations design for advanced format signals. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

DOI： 10.1364/OE.380482

Language：English   Publishing type：Research paper (scientific journal)  

In this research, a photonic-skin is designed to mimic the tactile perception of real skin. The specimen is made of silicon elastomer and inserted with optical fiber. The optical fiber is an instinctive and alternative sensor of tactile perception with high sensitivity and reliability, and combination with silicone substrate enables high stretchability to have a high wearability. According to the experimental results of tactile tracking, the specimen demonstrates the ability to detect the physical motions like tapping, rubbing and twisting with distinguishable signals. Moreover, the experimental results of on-body mounted perceptual tests (throat, forearm, and finger) validate the wearability with a high sensitivity of vocal vibration, muscle stretching, and bending movements. The photonic-skin has the characteristic of good spatial resolution, high sensitivity, high stretchability which will have wide applications in humanoid, robotic sensing, biomonitoring, perceptual prosthetics, etc.

DOI： 10.1007/s00542-019-04328-z

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1049/cp.2019.0852

Language：English   Publishing type：Research paper (other academic)  

We propose and investigate Conjugated-Paired RoF (C-RoF) transmission with phase-shifted down-conversion, which simultaneously compensates for fiber nonlinearity and dispersive fading effects harmful in Radio-on-fiber (RoF) links, without digital signal processing.

DOI： 10.23919/PS.2019.8817787

Language：English   Publishing type：Research paper (other academic)  

We experimentally demonstrate a 20-Gb/s PAM4 transmitter using EO polymer dual-drive MZM with imbalanced binary driving electronics, eliminating the need of power-hungry DAC or linear drivers and featuring low power consumption and potentially low cost. (C) 2019 The Author(s)

Language：English   Publishing type：Research paper (other academic)  

The high-temperature-resistant electro-optic polymer is used to demonstrate 100 Gbit/s OOK and 112 Gbit/s PAM4 modulations. The polymer is performed on the silicon Mach-Zehnder interferometer toward possible hybrid silicon and polymer photonic platform.

DOI： 10.1364/OFC.2019.M3D.4

Language：English   Publishing type：Research paper (other academic)  

We demonstrate a 110Gbit/s OOK transmitter using a hybrid silicon and polymer EO modulator with BER below FEC threshold. It has high thermal-stability, >100G operation bandwidth, 3.5dB extinction ratio and low driving-voltages of 3.5V.

Language：English   Publishing type：Research paper (scientific journal)  

In this paper, a simple optical vector quadrature de-multiplexer (QD) scheme is proposed for de-aggregating input 10 Gbaud 16/32/64 quadrature amplitude modulation (QAM) signals into two pulse amplitude modulation (PAM) streams. The proposed QD is based on a single bi-directional degenerate phase-sensitive amplifier (PSA), where the wavelength and the polarization status of the extracted in-phase and quadrature components stay the same as the input signal. Since the proposed QD is realized using PSA based on semiconductor optical amplifier (SOA), it is also possible to realize an on-chip QD system, providing an integrated platform for optical signal processing. Through numerical simulation, the transfer characteristics of the proposed QD system show that the SOA-based PSA has a high phase-sensitive gain extinction ratio of 44.1 dB. The constellations, error vector magnitudes (EVMs), and bit-error rates (BERs) of the data streams after the de-aggregation are numerically investigated to verify the proposed QD scheme. For the 10 Gbaud 16/32/64 QAM signals with an input optical signal-to-noise ratio (OSNR) of 25 dB, the de-aggregated PAM4/PAM6/PAM8 signals show 6.1, 5.6, and 8.2 dB receiver OSNR improvements at the BER of 10(-3), respectively. Also, to optimize the performance of the subsystem, the BER performance dependence on the phase difference between two arms in the subsystem is also examined. The simulation results reveal that the proposed QD can accomplish the function of optical vector de-aggregation well for the high-level QAM signals. The proposed QD can be applied to information de-aggregation, format conversion, and direct detection for optical vector signals, which may have great potential values for the flexible optical networks.

DOI： 10.1109/ACCESS.2018.2885815

Language：English   Publishing type：Research paper (scientific journal)  

Combining the fascinating advantages of ultrathin two-dimensional (2D) nanosheets with the nanostructuration of spin-crossover (SCO) materials represents an attractive target of controlled fabrication of SCO nano-objects at the device level. Here, we demonstrate that through facile-operating ultrasonic force-assisted liquid exfoliation technology the three-dimensional (3D) van der Waals SCO bulk precursor {[Fe(1,3-bpp)(2)(NCS)(2)](2) (1, 1,3-bpp = 1,3-di(4-pyridyl)-propane)} can be exfoliated into single-layered 2D nanosheets (NS-1). As consequence, the magnetism has been tuned from complete paramagnetic (bulk precursors) to SCO transition at around 250 K (2D nanosheets). In addition, the metal-to-ligand charge transition (MLCT), the intraligand pi-pi* transition and the color display also have been altered both in colloidal suspension and in the solid state. These dramatic changes of physical-chemical properties at different forms and states can be attributed to the efficient cooperativity derived from the interlayer van der Waals interactions within the curly or vertically stacked 2D building blocks.

DOI： 10.1021/acs.jpclett.8b03298

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/ECOC.2018.8535460

Language：English   Publishing type：Research paper (scientific journal)  

In this paper, a reconfigurable optical network intermediate node scheme with format conversion capacity and full-quadrature regeneration functionality is proposed. With a degraded input quadrature phase-shift keying (QPSK), the proposed network node can he dynamically reconfigured based on the network situation to output a QPSK or a four-level pulse amplitude modulation (PAM4), both full-quadrature regenerated. The input QPSK is first converted into the two full-quadrature regenerated binary phase-shift keying tributaries after phase sensitive amplifier-based quadrature de-multiplexing and self-phase modulation-based amplitude regeneration. Then the output regenerated QPSK or PAM4 are generated through vector addition by tuning the relative phase and amplitude between two tributaries. For an input 20 Gb/s QPSK with optical signal-to-noise ratio (OSNR) of 15 dB, the output regenerated QPSK gets 10.4% decrease in error vector magnitude (EVM), 2 dB receiver OSNR improvement at the bit error rate of 10(-3), and regeneration factors of 6.4 dB and 3.7 dB in amplitude and phase, respectively. In the case with regenerated PAM4 as the output, compared with the input QPSK, it has 10.4% improvement in EVM and regeneration factors of 7.1 dB and 2.5 dB in amplitude and phase, respectively. The numerical simulation results reveal that the system effectively regenerates input signal in full-quadrature with format conversion capacity. The proposed node scheme can he applied as a full-quadrature QPSK regenerator between optical networks, which both employ QPSK to increase the transmission distance, or an all-optical interconnection node between different optical networks where different modulation formats are used individually.

DOI： 10.1109/JLT.2018.2865015

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/ECOC.2018.8535506

Language：English   Publishing type：Research paper (scientific journal)  

To meet the ever-increasing bandwidth demands in the future broadband wireless networks, the millimeter-wave (mm-wave) frequency region is being actively perused, owing to its broad bandwidth and high frequencies. In this paper, a photonic mm-wave system is proposed and experimentally demonstrated based on the injection locking of a direct multilevel modulated laser to a spacing-tunable two-tone light. Since the mm-wave frequency of the generated signal is locked to the frequency spacing of the injected two-tone light, it shows better frequency stabilization than the schemes based on two free-running lasers. Moreover, by simply tuning the tone spacing, the mm-wave frequency could be easily re-configured, offering flexibility in the mm-wave signal generation. Instead of using complex and expensive optical modulators, the multilevel modulation on the mm-wave data carrier is implemented through the direct multilevel modulation of a laser and the injection locking. A 28 Gbps four-level pulse amplitude modulation (PAM4) is realized by biasing a 10 G-class laser at a current far from the threshold, providing a cost-effective and simple mm-wave generation scheme. In the experiment, a photonic approach to generating 28 Gbps PAM4 60 GHz/80 GHz mm-wave signals is experimentally demonstrated. A power penalty of less than 0.2 dB is observed for the filtered-out PAM4 signals with respect to the original PAM4. Besides, an ultra-low phase noise of up to -98 dBc/Hz is obtained for the mm-wave carriers after the injection locking. The proposed scheme possesses the flexibility and frequency stability of the mm-wave frequency, and also has low cost and implementation complexity. (c) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

DOI： 10.1364/OE.26.020603

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1364/CLEO_SI.2018.SM3B.2

Language：English   Publishing type：Research paper (other academic)  

We experimentally demonstrate fiber nonlinearity cancellation using photonic homodyne down conversion in conjugated-paired radio-on-fiber (C-RoF) system. 20-km SMF transmission of 156-Mb/s BPSK-C-RoF is demonstrated, naturally cancelling nonlinear phase shift without using digital signal processing.

Language：English   Publishing type：Research paper (other academic)  

A 28Gbps PAM4 60GHz radio-over-fiber system is proposed and experimentally demonstrated by injection locking a two-tone light to a directly-modulated laser. Experimental results show negligible power penalty for the obtained PAM4 after the injection locking.

DOI： 10.1364/CLEO_AT.2018.JTh2A.195

Language：English   Publishing type：Research paper (scientific journal)  

In this research, based on the principle of optical interferometry, the Mach-Zehnder and Optical Phase-locked Loop (OPLL) vibro-perception systems of bio-inspired fiber-skin are designed to mimic the tactile perception of human skin. The fiber-skin is made of the optical fiber embedded in the silicone elastomer. The optical fiber is an instinctive and alternative sensor for tactile perception with high sensitivity and reliability, also low cost and susceptibility to the magnetic interference. The silicone elastomer serves as a substrate with high flexibility and biocompatibility, and the optical fiber core serves as the vibro-perception sensor to detect physical motions like tapping and sliding. According to the experimental results, the designed optical fiber-skin demonstrates the ability to detect the physical motions like tapping and sliding in both the Mach-Zehnder and OPLL vibro-perception systems. For direct contact condition, the OPLL vibro-perception system shows better performance compared with the Mach-Zehnder vibro-perception system. However, the Mach-Zehnder vibro-perception system is preferable to the OPLL system in the indirect contact experiment. In summary, the fiber-skin is validated to have light touch character and excellent repeatability, which is highly-suitable for skin-mimic sensing.

DOI： 10.3390/s18051531

Language：English   Publishing type：Research paper (other academic)  

A single-stage phase-sensitive amplifier based quadrature de-multiplexer is proposed and validated for de-aggregating QAM signals into in-phase and quadrature components with wavelength and polarization preserved. A 10Gbaud 16QAM/64QAM is successfully deaggregated into two PAM4s/PAM8s.

DOI： 10.1364/CLEO_AT.2018.JTu2A.36

Language：English   Publishing type：Research paper (scientific journal)  

As one of the promising multiplexing and multicarrier modulation technologies, Nyquist subcarrier multiplexing (Nyquist SCM) has recently attracted research attention to realize ultra-fast and ultra-spectral-efficient optical networks. In this paper, we propose and experimentally demonstrate optical subcarrier processing technologies for Nyquist SCM signals such as frequency conversion, multicast and data aggregation of subcarriers, through the coherent spectrum overlapping between subcarriers in four-wave mixing (FWM) with coherent multi-tone pump. The data aggregation is realized by coherently superposing or combining low-level subcarriers to yield high-level subcarriers in the optical field. Moreover, multiple replicas of the data-aggregated subcarriers and the subcarriers carrying the original data are obtained. In the experiment, two 5 Gbps quadrature phase-shift keying (QPSK) subcarriers are coherently combined to generate a 10 Gbps 16 quadrature amplitude modulation (QAM) subcarrier with frequency conversions through the FWM with coherent multi-tone pump. Less than 1 dB optical signal-to-noise ratio (OSNR) penalty variation is observed for the synthesized 16QAM subcarriers after the data aggregation. In addition, some subcarriers are kept in the original formats, QPSK, with a power penalty of less than 0.4 dB with respect to the original input subcarriers. The proposed subcarrier processing technology enables flexibility for spectral management in future dynamic optical networks. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

DOI： 10.1364/OE.26.001488

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1038/s41598-017-01201-9

Language：English   Publishing type：Research paper (scientific journal)  

In this paper, a simple self-homodyne detection scheme is proposed and experimentally demonstrated for applications in optical access networks. Unmodulated pilot subframes are periodically inserted and interleaved with data subframes to form an orthogonal frequency-division multiplexing (OFDM) signal. Owing to the coherence between the embedded pilot and data subframes, a Mach-Zehnder delay interferometer with a free spectral range equal to the frequency of the subframe is deployed for the self-homodyne detection of the OFDM signal. It saves the local oscillator and optical hybrid, which are usually used in a conventional coherent receiver, thus reducing the hardware complexity and implementation cost. Meanwhile, the digital signal processing (DSP) for the self-homodyne detection is free from carrier-frequency-offset compensation and carrier-phase estimation, reducing the complexity, power consumption, and latency of the system. It also allows the use of a low-cost laser source as the source for the downstream signal. The proposed scheme provides a cost-effective and energy-efficient downstream solution for optical access networks, owing to the hardware saving and complexity reduction in DSP. A 10-Gb/s OFDM downstream transmission over a 20-km standard single-mode fiber is experimentally demonstrated with an error-free operation, using both a 10-MHz distributed feedback laser and a 100-kHz external cavity laser as downstream laser sources.

DOI： 10.1109/ACCESS.2017.2765336

Language：English   Publishing type：Research paper (other academic)  

We propose and demonstrate spatial coherent matched detection using two-dimensional high-speed photodiode array. Capturing amplitude and phase distribution, all tributaries of 3x20-Gb/s MDM-QPSK are simultaneously demultiplexed and coherently demodulated without using optical modal fan-out devices.

DOI： 10.1109/ECOC.2017.8346130

Language：English   Publishing type：Research paper (other academic)  

We propose coherent spectrum overlapping through FWM with coherent multi-carrier pump, for coherently combining low-level subcarriers to high-level ones in Nyquist SCM. 16QAM subcarriers are obtained with <1dB sensitivity variation and no error floor at up to 10(-5) BER.

DOI： 10.1109/ECOC.2017.8345897

Language：English   Publishing type：Research paper (other academic)  

We design and fabricate a silicon based 1x2 optical switch based on the free-carrier plasma dispersion effect, with a Mach-Zehnder interferometer structure on silicon-on-insulator (SOI) wafer. The experimental result shows that it has an extinction ratio of 21.8 dB at 1546 nm, which meets the requirements of the most applications in optical telecommunication networks.

DOI： 10.1109/ICOCN.2017.8121409

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/CLEOE-EQEC.2017.8086942

Language：English   Publishing type：Research paper (other academic)  

A cost-effective and energy-efficient self-homodyne downstream scheme is proposed for WDM-PON with inserted pilot sub-samples and interferometer-based detection. A 10-Gbps self-homodyne OFDM downstream transmission is experimentally demonstrated over 20-km SSMF with error-free operations.

DOI： 10.1364/CLEO_SI.2017.STh1O.5

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1364/CLEO_AT.2017.JTh2A.85

Language：English   Publishing type：Research paper (other academic)  

We propose all-optical sibsignal upconversion scheme using optically-injected DFB in combine with embedded optoelectronics oscillator for RoF application. The low-noise LO provided by OEO and near-SSB modulation implemented by injection locking enables highperformance in transmission.

DOI： 10.1364/OFC.2017.Tu2F.2

Language：English   Publishing type：Research paper (other academic)  

We demonstrate demultiplexing of ultrafast optical time-division multiplexed (OTDM) signals by parallel time-frequency domain sampling. With a loop-assisted coherent matched detector configuration, all subchannels of 4x20-Gb/s Gaussian-/Nyquist-shaped OTDM-QPSK signals were simultaneously demultiplexed and detected.

DOI： 10.1364/OFC.2017.M2J.5

Language：English   Publishing type：Research paper (scientific journal)  

Optical sampling is performed mostly in either time or frequency domain. In the former approach, sampling points are temporally taken by photo-mixing of received signals with locally generated ultrashort pulses. In the latter approach, the received signal is spectrally sliced and decomposed, which are taken as sampling points in the frequency domain. In this paper, as an alternative way, we propose and investigate an optical sampling technique called optical time-frequency-domain sampling, in which sampling points are taken in the time-frequency domain in an optoelectronic manner, by means of optoelectronic coherent matched detectors. Using this technique, it is possible to demultiplex and detect subchannels of ultrawideband multi-carrier signals at e.g. 100, 400 Gb/s,1 Tb/s or higher, without relying on either ultrashort pulses or high-resolution optical filters necessary in the conventional time-or frequency-domain sampling approaches. Moreover, in this paper, we propose and demonstrate a loop-assisted coherent matched detector that simply and practically extends the time-frequency sampling to parallel sampling configuration just using a single coherent matched detector. Provided are some experimental proof focusing on demultiplexing and detection of orthogonal time-frequency-domain multipelxed (OTFDM) signals, a sort of ultrawideband multicarrier signals. All subchannels of 160-Gb/s QPSK-OTFDM signals are simultaneously detected and measured with the loop-assisted coherent matched detector employing a single set of low-speed 10-Gbaud photo-receivers.

DOI： 10.1109/JLT.2016.2645224

Language：English   Publishing type：Research paper (other academic)  

We experimentally demonstrate fiber-nonlinearity-tolerant conjugated-paired radio-on-fiber (C-RoF) system for the first time. A C-RoF signal is simply generated by dual-sideband modulation and fiber nonlinearity is cancelled through asymmetric photonic heterodyne down-conversion. A QPSK-CRoF signal is transferred over 20-km SMF fiber.

DOI： 10.1109/MWP.2016.7791283

Language：English   Publishing type：Research paper (scientific journal)  

Recently the ever-growing demand for dynamic and high-capacity services in optical networks has resulted in new challenges that require improved network agility and flexibility in order for network resources to become more "consumable" and dynamic, or elastic, in response to requests from higher network layers. Flexible and scalable wavelength conversion or multicast is one of the most important technologies needed for developing agility in the physical layer. This paper will investigate how, using a reconfigurable coherent multi-carrier as a pump, the multicast scalability and the flexibility in wavelength allocation of the converted signals can be effectively improved. Moreover, the coherence in the multiple carriers prevents the phase noise transformation from the local pump to the converted signals, which is imperative for the phase-noise-sensitive multi-level single- or multi-carrier modulated signal. To verify the feasibility of the proposed scheme, we experimentally demonstrate the wavelength multicast of coherent optical orthogonal frequency division multiplexing (CO-OFDM) signals using a reconfigurable coherent multi-carrier pump, showing flexibility in wavelength allocation, scalability in multicast, and tolerance against pump phase noise. Less than 0.5 dB and 1.8 dB power penalties at a bit-error rate (BER) of 10(-3) are obtained for the converted CO-OFDM-quadrature phase-shift keying (QPSK) and CO-OFDM-16-ary quadrature amplitude modulation (16QAM) signals, respectively, even when using a distributed feedback laser (DFB) as a pump source. In contrast, with a free-running pumping scheme, the phase noise from DFB pumps severely deteriorates the CO-OFDM signals, resulting in a visible error-floor at a BER of 10(-2) in the converted CO-OFDM- 16QAM signals. (C) 2016 Optical Society of America

DOI： 10.1364/OE.24.022573

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

We propose a phase-noise-tolerantc oherent PM-QPSK system with differential coding and half-symbol-period timing-offset in polarizations. Owing to the improved phase noise tolerance, error-free operation of lOGbaud PM-QPSK is experimentally demonstrated even using similar to 30MHz-line width DFB laser.

Language：English   Publishing type：Research paper (other academic)  

We experimentally investigate the phase-sensitive amplification characteristics in quantum-dot semiconductor optical amplifier. Phase-sensitive dynamic ranges (PSDRs) of similar to 3dB and similar to 11dB are obtained for degenerate and non-degenerate components, respectively, with 5-dBm total launch power.

DOI： 10.1364/CLEO_SI.2016.STu3G.5

Language：English   Publishing type：Research paper (other academic)  

We clarify that fiber nonlinearity cancellation in the conjugated-paired radio-on-fiber system is a phase sensitive process. The best nonlinearity tolerance is achieved if the dual sidebands are constructively superposed during photonic down conversion.

DOI： 10.1364/CLEO_AT.2016.JW2A.130

Language：English   Publishing type：Research paper (scientific journal)  

In order to adapt to the dynamics in the future optical networks, we propose and experimentally demonstrate two flexible high-order quadrature amplitude modulation (QAM) transmitter schemes: (a) a flexible transmitter using a tandem in-phase/quadrature modulators for generating 16QAM, 32QAM, 64QAM signals; and (b) a scheme based on monolithically integrated quad-Mach-Zehnder in-phase/quadrature with binary driving electronics for synthesizing minimum phase-shift keying (MSK), quadrature phase-shift-keying (QPSK), 8-ary phase-shift keying (8PSK), and 16QAM. These schemes provide different approaches to configure a flexible high-order QAM transmitter, either using cascaded off-the-shelf modulators or via highly integrated monolithic modulator. These flexible and reconfigurable transmitter schemes exhibit different characteristics in terms of system performance, which provides the network operators different flexible transmitter solutions suitable for different application scenarios in elastic optical networks.

DOI： 10.1007/s11107-015-0548-5

Language：English   Publishing type：Research paper (other academic)  

We experimentally demonstrate an OWC scheme for CO-OFDM using coherent DFB pumping. The tolerance against pump phase noise with coherent pumping enables the use of low-cost 2MHz-linewidth DFB as pump to realize OWC of 12Gbps QPSK-CO-OFDM with 1dB penalty.

DOI： 10.1364/OFC.2016.W3D.3

Language：English   Publishing type：Research paper (scientific journal)  

Optical logic gate, especially exclusive-or (XOR) gate, plays important role in accomplishing photonic computing and various network functionalities in future optical networks. On the other hand, optical multicast is another indispensable functionality to efficiently deliver information in optical networks. In this paper, for the first time, we propose and experimentally demonstrate a flexible optical three-input XOR gate scheme for multiple input phase-modulated signals with a 1-to-2 multicast functionality for each XOR operation using four-wave mixing (FWM) effect in single piece of highly-nonlinear fiber (HNLF). Through FWM in HNLF, all of the possible XOR operations among input signals could be simultaneously realized by sharing a single piece of HNLF. By selecting the obtained XOR components using a followed wavelength selective component, the number of XOR gates and the participant light in XOR operations could be flexibly configured. The re-configurability of the proposed XOR gate and the function integration of the optical logic gate and multicast in single device offer the flexibility in network design and improve the network efficiency. We experimentally demonstrate flexible 3-input XOR gate for four 10-Gbaud binary phase-shift keying signals with a multicast scale of 2. Error-free operations for the obtained XOR results are achieved. Potential application of the integrated XOR and multicast function in network coding is also discussed. (C) 2016 Optical Society of America

DOI： 10.1364/OE.24.002299

Language：English   Publishing type：Research paper (scientific journal)  

An important challenge for implementing optical signal processing functions such as wavelength conversion or wavelength data exchange (WDE) is to avoid the introduction of linear and nonlinear phase noise in the subsystem. This is particularly important for phase noise sensitive, high-order quadrature-amplitude modulation (QAM) signals. In this paper, we propose and experimentally demonstrate an optical data exchange scheme through cascaded 2nd-order nonlinearities in periodically-poled lithium niobate (PPLN) waveguides using coherent pumping. The proposed coherent pumping scheme enables noise from the coherent pumps to be cancelled out in the swapped data after WDE, even with broad linewidth distributed feedback (DFB) pump lasers. Hence, this scheme allows phase noise tolerant processing functions, enabling the low-cost implementation of WDE for high-order QAM signals. We experimentally demonstrate WDEs between 10-Gbaud 4QAM (4QAM) signal and 12.5-Gbaud 4QAM (16QAM) signal with 3.5-MHz linewidth DFB pump lasers and 50-GHz channel spacing. Error-free operation is observed for the swapped QAM signals with coherent DFB pumping whilst use of free-running DFB pumps leads to visible error floors and unrecoverable phase errors. The phase noise cancellation in the coherent pump scheme is further confirmed by study of the recovered carrier phase of the converted signals. In addition to pump phase noise, the influence of crosstalk caused by the finite extinction ratio in WDE is also experimentally investigated for the swapped QAM signals. (C) 2016 Optical Society of America

DOI： 10.1364/OE.24.003702

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1364/ACPC.2015.AM1J.5

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1109/ecoc.2015.7341854

Language：English   Publishing type：Research paper (scientific journal)  

In dynamic optical networking scenarios, it is desirable that the optical transmitter chooses the most suitable modulation format in order to achieve optimal transmission performance. Owing to the ability of switching among different modulation formats, flexible optical transmitters based on reconfigurable optical devices are becoming a key component for the implementation of future flexible optical networks. In this paper, we experimentally demonstrate a flexible 8-ary transmitter to achieve adaptive switching between 8-ary phase-shift keying (8PSK) and circular 8-ary quadrature-amplitude modulation (8QAM) through reconfiguration of two cascaded in-phase/quadrature (IQ) modulators with different driving signals and biasing conditions. An arbitrary binary quadrature-amplitude modulation (2QAM) with constant or non-constant amplitude is proposed and experimentally demonstrated using an IQ modulator. Then, optical 8PSK or 8QAM modulation formats are successfully synthesized when a standard squared QPSK modulator is cascaded with a constant-amplitude or non-constant-amplitude 2QAM, respectively. (C) 2015 Optical Society of America

DOI： 10.1364/OE.23.021366

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/ogc.2015.7336843

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/PHOSST.2015.7248206

Language：English   Publishing type：Research paper (other academic)  

We propose and demonstrate pump-phase-noise-free 2-to-7 multichannel wavelength multicasting for QAM signals using flexible coherent multi-carrier pump. <0.4dB penalty is obtained after multicasting with the proposed scheme even using 3-MHz-linewidth DFB laser as pump source.

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1364/CLEO_AT.2015.JTh2A.49

Language：English   Publishing type：Research paper (other academic)  

We propose and demonstrate pump-phase-noise-tolerant 1-to-7 wavelength multicasting for QAM signals using flexible coherent multi-carrier pump. Less than 0.8dB penalty is obtained after multicasting with the elimination of phase noise from pump using coherent pumping.

DOI： 10.1364/OFC.2015.M2E.2

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1364/ofc.2015.th2a.5

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1364/ofc.2015.m2e.6

Language：English   Publishing type：Research paper (scientific journal)  

We experimentally demonstrate multichannel wavelength multicasting for two nonreturn-to-zero quadrature phase-shift keying (NRZ-QPSK) channels based on four-wave mixing (FWM) in semiconductor optical amplifier (SOA). Through the interaction with the two pumps in SOA, the input two 25 Gb/s NRZ-QPSK channels are successfully simultaneously multicast to five and two new wavelengths, respectively. All the multicast channels are with a power penalty less than 2.5 dB at a bit error rate (BER) of 10(-3). A characterization of the system performance using conversion efficiency and BER as figures-of-merit in terms of pump and signal powers is also presented. The results indicate that the pump and signal powers can be optimized to eliminate the introduced deleterious nonlinear components. The wavelengths of the two NRZ-QPSK channels and the two pumps need to be specified to avoid the crosstalk induced by high-order FWM.

DOI： 10.3788/COL201513.010601

Language：English   Publishing type：Research paper (scientific journal)  

In this paper, we experimentally demonstrate simultaneous multichannel wavelength multicasting (MWM) and exclusive-OR logic gate multicasting (XOR-LGM) for three 10Gbps non-return-to-zero differential phase-shift-keying (NRZ-DPSK) signals in quantum-dot semiconductor optical amplifier (QD-SOA) by exploiting the four-wave mixing (FWM) process. No additional pump is needed in the scheme. Through the interaction of the input three 10Gbps DPSK signal lights in QD-SOA, each channel is successfully multicasted to three wavelengths (1-to-3 for each), totally 3-to-9 MWM, and at the same time, three-output XOR-LGM is obtained at three different wavelengths. All the new generated channels are with a power penalty less than 1.2dB at a BER of 10(-9). Degenerate and non-degenerate FWM components are fully used in the experiment for data and logic multicasting. (C) 2014 Optical Society of America

DOI： 10.1364/OE.22.029413

Language：English   Publishing type：Research paper (other academic)  

We propose and investigate Conjugated-Paired Radio-on-Fiber (C-RoF) transmission, which shows high tolerance against optical nonlinearity in optical fiber links, aiming for achieving higher RF link gain. It is shown that the nonlinear distortion is cancelled out by the C-RoF technique.

DOI： 10.1109/MWP.2014.6994583

Language：English   Publishing type：Research paper (scientific journal)  

We experimentally demonstrate one-to-five quadrature phase-shift keying (QPSK) wavelength multicasting based on four-wave mixing in bulk semiconductor optical amplifier. The input 25 Gb/s nonreturn-to-zero QPSK signal is successfully multicast to five new wavelengths with all information preserved. All the multicast channels are with a power penalty less than 1.1 dB at a bit error rate (BER) of 10(-3). A characterization of the conversion efficiency in terms of pump and signal powers using the BER as figure of merit is also presented, the results indicate that the pump and signal powers should be optimized to eliminate the introduced deleterious nonlinear components.

DOI： 10.3788/COL201412.110601

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1109/icocn.2014.6987061

Language：English   Publishing type：Research paper (other academic)  

In order to adapt to the dynamics in the future optical networks, we propose and experimentally two flexible high-order quadrature amplitude modulation (QAM) transmitter schemes: i) a flexible transmitter using a tandem in-phase/quadrature (IQ) modulators for generating 16-/32-/64-QAM signals; and ii) a scheme based on monolithically-integrated quad Mach-Zehnder in-phase/quadrature (QMZ-IQ) with binary driving electronics for synthesizing minimum phase-shift keying (MSK), quadrature phase-shift keying (QPSK), 8-ary phase shift keying (8PSK), and 16QAM. The flexibility and re-configurability of the proposed schemes are experimentally verified.

DOI： 10.1109/ICOCN.2014.6987086

Language：English   Publishing type：Research paper (scientific journal)  

Laser-phase-fluctuation-insensitive optical coherent detection scheme with two-tone local light and digital signal processing technique for a radio-over-fiber (RoF) signal is proposed and experimentally demonstrated. Data recovery with the error vector magnitude of less than 14&#37; rms is successfully performed for 10- and 2.5-Gbaud 25-GHz-band QPSK RoF signals. In addition, bit error rate of less than 10(-5) is also verified for 10-Gbaud 25-GHz-band QPSK RoF signal after 20-km fiber-optic transmission even if the light source with the linewidth of more than 10 MHz in the transmitter is used.

DOI： 10.1109/JLT.2014.2313620

Language：English   Publishing type：Research paper (other academic)  

We propose and demonstrate phase-conjugated twin signals generation using oppositely-biased paired IQ modulators. Phase conjugation is electro-optically realized without relying on electrical-domain processing. Nonlinear phase shift of 20-Gb/s QPSK is experimentally compensated for.

DOI： 10.1109/IPCon.2014.6995363

Language：English   Publishing type：Research paper (other academic)  

We demonstrate electro-optic dual-channel coherent signal emulator, where multiplexed signal is artificially generated by using an optical IQ modulator driven with an arbitrary-waveform generator. 2x20-Gb/s dual-carrier QPSK signal generation is emulated.

DOI： 10.1109/IPCon.2014.6995364

Language：English   Publishing type：Research paper (other academic)  

We propose an optical data overlay scheme through level-scalable flexible modulation. Using this proposed scheme, Optical multicast overlay over point-to-point unicast in WDM-PON is experimentally demonstrated by scaling up the modulation from QPSK to 16QAM at 10Gbaud.

DOI： 10.1109/IPCon.2014.6995220

Language：English   Publishing type：Research paper (scientific journal)  

We propose a multifunctional optical switching unit based on the bidirectional liquid crystal on silicon (LCoS) and semiconductor optical amplifier (SOA) architecture. Add/drop, wavelength conversion, format conversion, and WDM multicast are experimentally demonstrated. Due to the bidirectional characteristic, the LCoS device cannot only multiplex the input signals, but also de-multiplex the converted signals. Dual-channel wavelength conversion and format conversion from 2 x 25Gbps differential quadrature phase-shift-keying (DQPSK) to 2 x 12.5Gbps differential phase-shift-keying (DPSK) based on four-wave mixing (FWM) in SOA is obtained with only one pump. One-to-six WDM multicast of 25Gbps DQPSK signals with two pumps is also achieved. All of the multicast channels are with a power penalty less than 1.1 dB at FEC threshold of 3.8 x 10(-3). (C) 2014 Optical Society of America

DOI： 10.1364/OE.22.021847

Language：English   Publishing type：Research paper (other academic)  

We propose and experimentally demonstrate optical data exchange scheme between 16QAM and QPSK with narrow spacing of 50GHz. The use of coherent pump makes it free of phase noise from pumps, and enables the use of low-cost DFB as pump source.

DOI： 10.1109/ECOC.2014.6964158

Language：English   Publishing type：Research paper (other academic)  

We experimentally demonstrate a 50-Gbps 16QAM wavelength conversion with <0.2dB penalty, based on FWM in HNLF using coherent pumps. The coherent pumping makes it independent of the phase noise from pumps and enables the use of cost-effective pump laser.

DOI： 10.1109/ECOC.2014.6964154

Language：English   Publishing type：Research paper (other academic)  

We experimentally demonstrate an optical wavelength shifting scheme of 20Gbaud 16QAM based on cascaded 2nd-order nonlinearities in PPLN using coherent pumps, which is free of the phase noise from pumps.

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1364/CLEO_SI.2014.SW3J.1

Language：English   Publishing type：Research paper (other academic)  

We experimentally investigate the sampling phase dependence of baud-rate sampled and equalized coherent receiver for Nyquist Pulse-shaped high-order QAM signals on the modulation format and roll-off factors.

DOI： 10.1364/CLEO_SI.2014.SW1J.2

Language：English   Publishing type：Research paper (scientific journal)  

Optical wavelength conversion (OWC) is expected to be a desirable function in future optical transparent networks. Since high-order quadrature amplitude modulation (QAM) is more sensitive to the phase noise, in the OWC of high-order QAM signals, it is crucial to suppress the extra noise introduced in the OWC subsystem, especially for the scenario with multiple cascaded OWCs. Here, we propose and experimentally demonstrate a pump-linewidth-tolerant OWC scheme suitable for high-order QAM signals using coherent two-tone pumps. Using 3.5-MHz-linewidth distributed feedback (DFB) lasers as pump sources, our scheme enables wavelength conversion of both 16QAM and 64QAM signals with negligible power penalty, in a periodically-poled Lithium Niobate (PPLN) waveguide based OWC. We also demonstrate the performance of pump phase noise cancellation, showing that such coherent two-tone pump schemes can eliminate the need for ultra-narrow linewidth pump lasers and enable practical implementation of low-cost OWC in future dynamic optical networks. (C)2014 Optical Society of America

DOI： 10.1364/OE.22.005067

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1364/ofc.2014.th2a.63

Language：English   Publishing type：Research paper (other academic)  

Laser-phase-noise-insensitive optical coherent transmission of a radio-over-fiber signal with two-tone local light and digital signal processing technique is experimentally demonstrated. The estimated BER of less than 10(-9) is successfully achieved after 20-km-long fiber-optic transmission.

DOI： 10.1364/OFC.2014.M3D.8

Language：English   Publishing type：Research paper (scientific journal)  

All-optical wavelength conversion (AOWC) plays an important role in the future transparent optical networks, in order to enhance the reconfigurability and non-blocking capacity. On the other hand, high-order quadrature amplitude modulations (QAMs) have been extensively studied for achieving the high-speed and high-spectral-efficiency optical transmission. Since high-order QAMs are more sensitive to phase and amplitude noise, to implement an AOWC sub-system suitable for highorder QAM signals with minimized power penalty, it is important to optimize the operation conditions in order to avoid extra nonlinear distortions co-existed in the AOWC process. Our experimental results show that, constellation monitoring provides a more intuitive and accurate approach to monitor the converted high-order QAM signals, especially in presence of nonlinear phase noise such as self-phase modulation (SPM). We experimentally demonstrate an AOWC of 64QAM signal through fourwave mixing (FWM) in highly-nonlinear (HNLF). The performance of the AOWC is optimized through the constellation monitoring of the converted signal, achieving a negligible power penalty (< 0.3dB at BER of 10-3) for 60-Gbps 64QAM after conversion. (C) 2013 Optical Society of America

DOI： 10.1364/OE.22.000015

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1109/mwp.2013.6724085

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1049/cp.2013.1411

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/ipcon.2013.6656476

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1109/ipcon.2013.6656502

Language：English   Publishing type：Research paper (scientific journal)  

This paper presents multi-tone parallel coherent matched detection that orthogonally detects superchannels without crosstalk between neighboring channels. The receiver consists of multiple sets of multi-tone coherent matched detector employed in parallel. In each detector, the received superchannels signal is homodyne mixed in multi frequency with locally generated multi-tone optical frequency comb; detected is a signal set that has the amplitude and phase exactly matched with the local comb. By launching orthogonal sets of local comb to the multiple parallel coherent matched detectors, the received superchannels are orthogonally downconverted to the baseband frequencies keeping the amplitude and phase information of all channels included. With an aid of n x n transform matrix, all channels are separately recovered from the downconverted signal sets. The system does not rely on any optical filters for channel demultiplexing and separation, with increased flexibility in wavelength arrangement. In addition, the parallel configuration equivalently enhance the bandwidth of the coherent matched detector keeping the speed in each tributary channel as high as possible. In this paper, it is experimentally demonstrated that even-odd interleaved 23 x 20-Gb/s QPSK superchannels are orthogonally demultiplexed and detected by two-tone coherent matched detection. (c) 2013 Optical Society of America

DOI： 10.1364/OE.21.018602

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1364/NETWORKS.2013.NW3C.2

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1364/oecc_ps.2013.mo1_2

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1364/cleo_si.2013.cm1g.1

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/CLEOE-IQEC.2013.6801251

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/cleoe-iqec.2013.6801251

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/cleoe-iqec.2013.6801250

Language：English   Publishing type：Research paper (scientific journal)  

In order to adapt to the dynamics in the future optical networks, we propose a flexible high-order QAM transmitter using a tandem in-phase/quadrature (IQ) modulators to synthesize different high-order quadrature amplitude modulation (QAM) formats, such as 16QAM, 32 or 36QAM and 64QAM. To generate high-order QAMs, an offset-QAM is firstly generated using an IQ modulator driven by electronics with reduced modulation-level, and then mapped to other quadrants through another following IQ modulator configured as a standard quadrature phase-shift keying (QPSK) modulator. All of the embedded sub-Mach-Zehnder modulators are operated in push-pull configurations to avoid introducing excess phase chirp. In contrast with the schemes based on a single IQ modulator driven by multilevel electronics or a highly-integrated parallel modulator, by deploying commercially-available optical modulators and driving electronics with reduced modulation-level, the transmitter complexity in optics and electronics is well-balanced. In the case of generating optical 64QAM, different from another tandem scheme deploying dual-drive IQ modulator driven by independent four binary streams, less phase chirp is observed in our proposed scheme, and comparable implementation penalty is obtained even without applying additional specific compensation algorithm in the coherent receiver. Moreover, thanks to the tandem structure and the deployment of QPSK modulator, the obtained high-order QAM is naturally differentially coded, which is helpful to solve the phase ambiguity at coherent receiver. We experimentally demonstrate the generations of these high-order QAMs including 16QAM, 32/36QAM and 64QAM, and confirm the error-free operations with comparable BER performance to the "electrical" approach based on a single IQ modulator. (c) 2013 Optical Society of America

DOI： 10.1364/OE.21.006213

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1364/ofc.2013.otu3b.5

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1364/ofc.2013.om3c.2

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1364/nfoec.2013.jth2a.47

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/OECC.2012.6276715

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1364/NFOEC.2012.JTh2A.22

Language：English   Publishing type：Research paper (scientific journal)  

Quadrature phase-shift keying (QPSK) is usually generated using an in-phase/quadrature (IQ) modulator in a balanced driving-condition, showing a square-shape constellation in complex plane. This conventional QPSK is referred to as square QPSK (S-QPSK) in this paper. On the other hand, when an IQ modulator is driven in an un-balanced manner with different amplitudes in in-phase (I) and quadrature (Q) branches, a rectangular QPSK (R-QPSK) could be synthesized. The concept of R-QPSK is proposed for the first time and applied to optical eight-ary phase-shift keying (8PSK) transmitter. By cascading an S-QPSK and an R-QPSK, an optical 8PSK could be synthesized. The transmitter configuration is based on two cascaded IQ modulators, which also could be used to generate other advanced multi-level formats like quadrature amplitude modulation (QAM) when different driving and bias conditions are applied. Therefore, the proposed transmitter structure has potential to be deployed as a versatile transmitter for synthesis of several different multi-level modulation formats for the future dynamic optical networks. A 30-Gb/s optical 8PSK is experimentally demonstrated using the proposed solution. (C) 2011 Optical Society of America

DOI： 10.1364/OE.19.018479

Language：English   Publishing type：Research paper (scientific journal)  

An optical format conversion scheme of multilevel phase-shift keying (M-ary PSK) signals using the four-wave mixing based optical phase erasure is discussed in this paper. The conversion from differential quadrature phase-shift keying (DQPSK) to differential phase shift keying at 10 and 160 Gbaud, and the conversion from differential eight-ary phase-shift keying to DQPSK at 40 Gbaud have been experimentally demonstrated. The proposed scheme could be used as a phase erasure, in which a redundant tributary of the M-ary PSK signal is removed, or as an "updater" where the unwanted phase pattern is replaced with the new pattern.

DOI： 10.1109/JLT.2011.2160977

Language：English   Publishing type：Research paper (scientific journal)  

We examine the impact of filtering on self-homodyne coherent WDM systems using the interleaved polarization division-multiplexing scheme. To investigate the performance limit and to provide more insight into previously obtained experimental results, we perform numerical simulations in which different filter shapes and filter bandwidths are used. It is shown that with proper prefiltering of the data and filtering of the pilot tone in the receiver, performance can approach that of an intradyne system. This would make it possible to implement coherent systems with high spectral efficiency without any digital signal processing in the receiver.

DOI： 10.1109/JLT.2011.2114638

Language：English   Publishing type：Research paper (other academic)  

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1364/cleo_si.2011.cthh5

Language：English   Publishing type：Research paper (scientific journal)  

We propose and demonstrate a reconfigurable multilevel transmitter using a monolithically-integrated quad Mach-Zehnder inphase/quadrature (QMZ-IQ) modulator with binary driving electronics. Different from previous parallel-integrated quadrature amplitude modulation (QAM) transmitter solutions, only one electrode is required to adjust the relative phase offset among embedded sub-Mach-Zehnder modulators in the proposed IQ superstructure. By feeding different RF driving electronics and operating the integrated modulator as different bias conditions, different advanced multilevel modulation formats, such as QAM and 8-ary phase-shift keying (8-PSK), could be synthesized. In this paper, a 40-Gb/s 16-QAM and a 30-Gb/s 8-PSK are generated using the proposed multilevel transmitter, respectively. Offline digital processing is employed for bit-error rates estimation and constellation reconstruction. (C)2011 Optical Society of America

DOI： 10.1364/OE.19.005596

Language：English   Publishing type：Research paper (other academic)  

We experimentally demonstrate 1-to-9 optical wavelength multicasting, based on dual-pump four-wave mixing in highly-nonlinear fiber. A 100-km field trial experiment is also conducted to demonstrate the feasibility of optical wavelength multicasting.

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1364/ofc.2011.owl2

Language：English   Publishing type：Research paper (scientific journal)  

An optical format conversion scheme from 120-Gb/s return-to-zero differential 8-ary phase-shift keying (RZ-D8PSK) to 80-Gb/s RZ differential quadrature phase-shift keying (RZ-DQPSK) is demonstrated by optically removing one tributary through optical phase erasure. It is achieved through four-wave mixing in a highly nonlinear fiber. An 8-dB sensitivity improvement is obtained for the converted DQPSK signal relative to that of the input D8PSK signal. This is potentially useful to enable the interconnection among neighboring networks where different formats are deployed.

DOI： 10.1109/LPT.2010.2087322

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/acp.2010.5682833

Language：English   Publishing type：Research paper (scientific journal)  

We propose a novel 16-quadrature amplitude modulation (QAM) transmitter based on two cascaded IQ modulators driven by four separate binary electrical signals. The proposed 16-QAM transmitter features scalable configuration and stable performance with simple bias-control. Generation of 16-QAM signals at 40 Gbaud is experimentally demonstrated for the first time and visualized with a high speed constellation analyzer. The proposed modulator is also compared to two other schemes. We investigate the modulator bandwidth requirements and tolerance to accumulated chromatic dispersion through numerical simulations, and the minimum theoretical insertion attenuation is calculated analytically. (C) 2010 Optical Society of America

DOI： 10.1364/OE.18.023062

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1049/cp.2010.1190

Language：English   Publishing type：Research paper (other academic)  

0.87 Tbit/s 160 Gbaud dual-polarization D8PSK OTDM transmission over 110 km

DOI： 10.1109/ECOC.2010.5621495

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1109/ecoc.2010.5621405

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1109/ecoc.2010.5621519

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/PHOSST.2010.5553735

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/PHOSST.2010.5553626

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1049/el.2010.3512

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1364/cleo.2010.cpda7

Language：English   Publishing type：Research paper (scientific journal)  

We experimentally demonstrated ultra-fast phase-transparent wavelength conversion using cascaded sum-and difference-frequency generation (cSFG-DFG) in linear-chirped periodically poled lithium niobate (PPLN). Error-free wavelength conversion of a 160-Gb/s return-to-zero differential phase-shift keying (RZ-DPSK) signal was successfully achieved. Thanks to the enhanced conversion bandwidth in the PPLN with linear-chirped periods, no optical equalizer was required to compensate the spectrum distortion after conversion, unlike a previous demonstration of 160-Gb/s RZ on-off keying (OOK) using fixed-period PPLN. (C) 2010 Optical Society of America

DOI： 10.1364/OE.18.006064

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1364/ofc.2010.oms5

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1364/nfoec.2010.jtha2

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1364/ofc.2010.own5

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1364/ofc.2010.owp3

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1109/ondm.2010.5431592

Language：English   Publishing type：Research paper (other academic)  

We experimentally demonstrated format conversion from 320-Gb/s RZ-DQPSK to 160-Gb/s RZ-DPSK through the proposed all-optical phase drop scheme. It can be applied to drop a binary tributary from a multilevel modulation format.

Language：English   Publishing type：Research paper (other academic)  

An optical MSK transmitter is proposed and experimentally demonstrated using a single monolithically integrated high-speed quad-MZ IQ modulator, where four sub-MZMs are integrated on a main MZ superstructure.

Language：English   Publishing type：Research paper (scientific journal)  

Through four-wave mixing (FWM) process in highly-nonlinear fiber (HNLF) or semiconductor device, the phase-modulation depth of one converted FWM component could be doubled compared with that of the original input signal. Therefore, with a multilevel phase-modulated signal and a CW light as inputs, after FWM process in a nonlinear media, phase pattern (0, pi) carried in the input multilevel phase-modulated signal will not be transferred to one converted FWM component, which could be referred to as an optical phase erasure process. We experimentally demonstrated format conversion from 320-Gb/s return-to-zero differential quadrature phase-shift keying (RZ-DQPSK) to 160-Gb/s return-to-zero differential phase-shift keying(RZ-DPSK) through the proposed all-optical phase erasure scheme. The phase information carried in the converted binary RZ-DPSK is logically equal to the input Q-component, or a logical XOR operation result between I and Q components of the input RZ-DQPSK, which correspond to a serial or parallel DQPSK transmitter for the input RZ-DQPSK signal. It can be applied to erase a binary tributary from a multilevel modulation format. (C) 2009 Optical Society of America

DOI： 10.1364/OE.17.013346

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1109/cleopr.2009.5292602

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1117/12.853532

Language：English   Publishing type：Research paper (scientific journal)  

We propose and experimentally demonstrate an optical phase noise extraction and amplification (OPNEA) technique for phase-shift keying (PSK) signals. It could effectively extract and amplify the phase noise carried in the incoming PSK signals. By applying this OPNEA technique to optical phase-noise (PN) monitoring, a 13-dB monitoring dynamic range and a 0.2-dB/degree monitoring sensitivity were achieved. The monitoring performance is effectively improved compared with an optical PN direct-monitoring scheme based on a Mach-Zehnder interferometer.

DOI： 10.1109/LPT.2009.2019969

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1109/oecc.2009.5213773

Language：English   Publishing type：Research paper (scientific journal)  

We propose and demonstrate an optical minimum-shift-keying (MSK) transmitter using a single-quad Mach-Zehnder (MZ) in-phase and quadrature modulator, where four sub-Mach-Zehnder modulators are monolithically integrated on a main MZ superstructure. Using the proposed transmitter, a MSK signal at bit rate of B could be successfully generated by orthogonally superposing two low-speed (B/2) carrier-suppressed return-to-zero differential phase-shift-keying streams with a relative time offset, 1/B. MSK signals at bit rate of 20 and 80 Gbits/s were successfully generated using the proposed MSK transmitter. A continuous changed phase trajectory of the obtained MSK was confirmed using a complex spectrum analyzer. The filtering tolerance of the MSK was also characterized using a bandwidth-variable tunable filter. (C) 2009 Optical Society of America

DOI： 10.1364/OL.34.002144

Language：English   Publishing type：Research paper (other academic)  

We propose an optical phase noise extraction and amplification (OPNEA) technique. By applying OPNEA to phase noise monitoring, for (D)PSK, 13-dB dynamic range and 0.2-dB/degree sensitivity were achieved with a 50-120-degree phase deviation.. (C) 2009 Optical Society of America

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/LPT.2008.2011371

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1364/ofc.2009.omo1

Language：English   Publishing type：Research paper (scientific journal)  

Optical demultiplexing for a 40 Gbit/s RZ-DPSK OTDM signal using a fibre optical parametric amplifier with a sinusoidal-clock-modulated pump is experimentally demonstrated. Less than 1.3 dB power penalty and around 30 dB gain are obtained for all four demultiplexed channels. Superior performance is obtained for the demultiplexed tributaries in RZ-DPSK OTDM systems compared with those in RZ-OOK OTDM.

DOI： 10.1049/el:20092990

Language：English   Publishing type：Research paper (scientific journal)  

RZ-DPSK OTDM demultiplexing from 40 to 10Gbps is achieved using OPA with clock-modulated pump. <1.3-dB penalty and similar to 28-dB gain were achieved for four demultiplexed channels.

DOI： 10.1049/el:20092990

Language：English   Publishing type：Research paper (scientific journal)  

We propose am all-optical phase-interleaving technology based on dual-pump four-wave mixing (FWM) in highly nonlinear fiber (HNLF). The proposed all-optical phase-interleaving technology is applied in an all-optical phase-multiplexing scheme to successfully phase-multiplex 2x or 3 x 10-Gb/s DPSK-WDM signals to a 20- or 30-Gb/s DPSK in non-return-to-zero (NRZ) formats. The proposed all-optical phase multiplexing scheme is demonstrated using dual-pump FWM in highly nonlinear silica and bismuth fibers. In contrast with optical time-division multiplexing technology, the proposed all-optical phase-multiplexing technology does not require pulse-carving, thus offering a high spectral-efficiency. Differential precoder for each input tributary is operated independently, and no additional encoder or postcoder is required to recover the original data after demodulation on the receiver side.

DOI： 10.1109/JLT.2008.928962

Language：English   Publishing type：Research paper (scientific journal)  

In this paper, we discuss the multicast efficiency issue in the optical layer multicast. A 1-to-8 phase-preserved different phase-shifted keying (DPSK) wavelength multicast is experimentally demonstrated using four-wave mixing (FWM) in a piece of Bismuth highly nonlinear fiber (Bi-HNLF). DPSK signal is successfully delivered from one wavelength to up to eight different wavelengths using only three pumps. Compared with the existing schemes, the multicast efficiency is greatly improved by delivering the phase information to more destination wavelengths. (C) 2008 Optical Society of America

DOI： 10.1364/OE.16.021964

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/IPGC.2008.4781440

Language：English   Publishing type：Research paper (scientific journal)  

In this letter, we propose and experimentally demonstrate an optical amplitude and phase multiplexing scheme to generate a multilevel modulation format signal, return-to-zero eight-amplitude and phase-shifted keying (RZ-8-APSK). The proposed optical amplitude and phase multiplexing is mainly based on four-wave mixing (FWM) in highly nonlinear fiber. Cross-absorption modulation in an electroabsorption modulator is employed to intentionally adjust the extinction ratio of the generated RZ-8-APSK signal. Amplitude and phase information carried in the inputs is multiplexed and transparently transferred to the generated FWM components. In the experiment, 30-Gb/s RZ-8-APSK signals are generated from input 10-Gb/s on-off keying and 20-Gb/s RZ differential quadrature phase-shifted keying in an all-optical manner.

DOI： 10.1109/LPT.2008.2006000

Language：English   Publishing type：Research paper (scientific journal)  

We propose and experimentally demonstrate an all-optical broadband wavelength conversion scheme with simultaneous power amplification based on a pump-modulated fiber optic parametric amplifier (FOPA). All-optical tunable wavelength conversion from one to two wavelengths was achieved with >= 13 dB extinction ratio and < 2.7-dB power penalty, accompanied by a high (>= 37 dB) and flat (similar to 3 dB variation) FOPA gain spectrum over 47 nm.

DOI： 10.1093/ietcom/e91-b.11.3712

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1109/ecoc.2008.4729566

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1109/oeccacoft.2008.4610524

Language：English   Publishing type：Research paper (scientific journal)  

All-optical cross-phase modulation through the intersubband transition in an InGaAs/AlAsSb coupled quantum well was examined by using a sinusoidal intensity-modulated pump. For probe waves in the wavelength range of 1330-1620 nm and a pump modulation at a repetition rate of 76 GHz, cross-phase modulation (XPM) occurred with an efficiency eta, of 0.653-0.142 rad/W. Based on the efficiency we derived a transfer function for the intersubband transition (ISBT) modulator that can be conveniently used in simulating the characteristics of the modulated output (probe) for long excitation pulses with arbitrary waveforms. (c) 2008 Optical Society of America.

DOI： 10.1364/OE.16.009684

Language：English   Publishing type：Research paper (scientific journal)  

We experimentally demonstrate a spectrum-efficient 80-Gbit/s differential phase- shift keying ( DPSK) transmitter for a single wavelength channel using phaseinterleaving technology without any optical-time or polarization-division multiplexing. Two cascaded independent 40-Gbit/s modulations were time-interleaved to generate an 80-Gbit/s DPSK signal with a compact spectrum. The proposed 80-Gbit/s DPSK transmitter consists of two independent 40-Gbit/s phase modulators only. No additional high-speed pre- or postcoder is required at the transmitter or receiver side. The proposed scheme is potentially cost-effective. (c) 2008 Society of Photo-Optical Instrumentation Engineers.

DOI： 10.1117/1.2931597

Language：English   Publishing type：Research paper (other academic)  

We propose and experimentally demonstrate a compact 1-to-5 DPSK wavelength multicasting scheme using FWM with three unequally-spaced pumps in a 2-m-long Bi-HNLF. Power penalties are within 1.9-dB for all the converted signals. (C) 2008 Optical Society of America

Language：English   Publishing type：Research paper (other academic)  

We propose and experimentally demonstrate a compact all-optical DPSK wavelength multicasting scheme using dual-pump FWM in a Bi-HNLF with only 2-m long. Less than 0.6-dB power penalty is obtained for the converted signals. (c) 2008 Optical Society of America.

DOI： 10.1109/OFC.2008.4528382

Language：English   Publishing type：Research paper (scientific journal)  

We propose and experimentally demonstrate a chirp-free carrier-suppressed optical pulse generator using a simple and cost-effective approach. An 80-GHz carrier-suppressed optical pulse train was successfully obtained by using two cascaded 20-GHz clock-driven dual-drive Mach-Zehnder modulators. Compared with the conventional scheme using 40-GHz clock driving signal to generate an 80-GHz pulse train, the proposed scheme is cost-effective and scalable to high repetition rate pulse generation by using low-speed devices.

DOI： 10.1587/elex.5.1

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1049/el:20082230

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1109/leoswt.2008.4444394

Language：English   Publishing type：Research paper (scientific journal)  

An optical cross connect (OXC) is an integral component of all-optical networks. As OXC malfunction leads to data loss or misrouting. Surveillance of OXCs is critical to network reliability. A recent OXC supervisory scheme, based on different time-delay recognition, identifies the state of the input output connection through the OXC, including any possible effect of link failure or misrouting. However, for a large-scale OXC or OXCs in cascade, this approach requires excessively long delay fibers, raising feasibility issues such as power amplification and length of surveillance period. We propose modified schemes for reducing the length of delay fibers without downgrading the performance. (C) 2007 Optical Society of America.

DOI： 10.1364/JON.7.000080

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1117/12.747236

Language：English   Publishing type：Research paper (other academic)  

We propose and demonstrate the use of 10-Gb/s inverse-RZ data as downstream signal in WDM-PON to injection-lock a directly modulated Fabry-Perot laser used for the upstream signal at 1Gb/s.

DOI： 10.1117/12.745425

Language：English   Publishing type：Research paper (other academic)  

We propose and experimentally demonstrate an all-optical phase multiplexing scheme using four-wave mixing in a highly nonlinear fiber. Two 10-Gb/s pi/2-shifted return-to-zero (RZ) differential phase-shift-keying (DPSK) wavelength-division-multiplexing (WDM) signals are successfully phase-multiplexed into a 20-Gb/s RZ differential quadrature phase-shift-keying signal with a negative 1.6-dB power penalty. With more input DPSK WDM signals, the proposed scheme can be applied to obtain a multilevel phase-shift-keying signal with increased capacity and enhanced spectral efficiency.

DOI： 10.1109/LPT.2007.905199

Language：English   Publishing type：Research paper (other academic)  

Wideband all-optical phase interleaving technology enabling phase-multiplexing of 3×10-Gb/s DPSK-WDM into 30-Gb/s DPSK using FWM in HNLF

Language：English   Publishing type：Research paper (other academic)  

Language：Others   Publishing type：Research paper (other academic)  

DOI： 10.1109/cleopr.2007.4391590

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.34385/proc.49.10C1-3

Language：English   Publishing type：Research paper (other academic)  

We experimentally demonstrate a cost-effective 80-Gbit/s DPSK transmitter using phase interleaving without optical-time/polarization-division multiplexing. Two cascaded independent 40-Gbit/s modulations are time-interleaved to generate 80-Gbit/s DPSK with high spectrum efficiency: 20-dB bandwidth of only 0.68mn.

DOI： 10.1109/LEOSST.2007.4288430

Language：English   Publishing type：Research paper (scientific journal)  

We experimentally demonstrated ultimately phase-noise tolerant 20-Gbps QPSK-homodyne transmission over 160 km using a 3-nm spectrum-sliced ASE light source. We applied an optical phase noise cancellation technique based on self-homodyne detection using a polarization-multiplexed pilot-carrier, which included identical phase noise to that of modulated optical signal. BER of less than 1 x 10(-6) after the transmission was achieved. We also characterized DGD and dispersion tolerances. To the author's best knowledge, this is the first experimental demonstration of multi-bit-per-symbol modulation/demodulation using an incoherent ASE light source.

DOI： 10.1587/elex.4.406

Language：English   Publishing type：Research paper (other academic)  

An all-optical phase multiplexing scheme for phase-modulated signals is proposed and experimentally demonstrated using four-wave mixing (FWM) in a highly-nonlinear fiber (HNLF). Two 10-Gb/s pi/2-shifted differential phase-shift keying (DPSK) wavelength-division multiplexing (WDM) signals are experimentally demonstrated to be converted and phase-multiplexed into a 20-Gb/s differential quadrature phase-shift keying (DQPSK) signal with non-return-to-zero (NRZ) and return-to-zero (RZ) formats, respectively. Experimental results show that, due to phase-modulation-depth doubling effect and phase multiplexing effect in the FWM process, a DQPSK signal is successfully generated through the proposed all-optical phase multiplexing with improved receiver sensitivity and spectral efficiency.

DOI： 10.1093/ietele/e91-c.7.1121

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

We proposed and experimentally demonstrated 40-Gb/s quadrature phase-shifted keying (QPSK) and 20-Gb/s binary phase-shifted keying (PSK) transmission systems with inserted pilot symbols, using a return-to-zero radio frequency (RZ-RF) driving signal in the transmitter and self-homodyne direct detection in the receiver. Different from other existing homodyne or conventional differential PSK/QPSK systems, the proposed PSK and QPSK modulation formats do not need any complicated pre-coder, post-processor or local oscillator. In the proposed QPSK systems, simultaneous detection of in-phase and quadature components is successfully achieved by using one Mach-Zehnder delay interferometer and following balanced detector, which significantly reduces the system complexity and implementation cost. (c) 2007 Optical Society of America.

DOI： 10.1364/OE.15.007660

Language：English   Publishing type：Research paper (other academic)  

Ultimate linewidth-tolerant 20-Gbps QPSK-homodyne transmission using a spectrum-sliced ASE light source

DOI： 10.1109/OFC.2007.4348659

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/OFC.2007.4348807

Language：English   Publishing type：Research paper (scientific journal)  

Recently, OSNR monitoring based on the measurement of degree of polarization (DOP) has attracted much attention, thanks to its simplicity and high efficiency. However, the OSNR monitoring sensitivity is quite poor in the high OSNR region, resulting in high estimation error and narrow dynamic range. In this paper, we propose and experimentally demonstrate a narrow-band off-center optical filtering technique for DOP-based OSNR monitors. In 40-Gb/s RZ-OOK systems, OSNR monitoring sensitivity and DOP dynamic range are successfully enhanced to 3.14&#37;/dB and 31.4&#37;, respectively, in the high OSNR region (25 similar to 35dB/0.1nm). (c) 2007 Optical Society of America.

DOI： 10.1364/OE.15.000823

Language：English   Publishing type：Research paper (scientific journal)  

We showed that cross-gain modulation is dominant over another kind of common signal quality degradation, namely four-wave mixing, in a two-pump fiber optical parametric amplifier (OPA) WDM system. We also demonstrated experimentally that the signal quality degradation can be improved significantly by a two-orthogonal-pump OPA (20P-OPA) over the conventional two-parallel-pump OPA (2PP-OPA). (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optcom.2006.09.067

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/ECOC.2006.4801260

Language：English   Publishing type：Research paper (scientific journal)  

Multiwalled carbon nanotubes and BaTiO3 composite films have been prepared by pulsed-laser deposition technique at room temperature and high temperature of 600 degrees C, separately. The structures of the composite films are investigated by using scanning electron microscopy and x-ray diffraction. The optical behaviours of the samples produced at different temperatures are compared with Raman spectroscopy, and UV-visible absorption. And the observation by Z-scan technique reveals that the composite films have a larger optical nonlinearity, and the samples prepared at high temperatures have better transmittance and opposite sign imaginary part of optical third-order nonlinearity.

Language：English   Publishing type：Research paper (scientific journal)  

We have demonstrated, for the first time to our knowledge, simultaneous all-optical inverted and noninverted wavelength conversion by using a single-stage two-pump fiber-optical parametric amplifier with an extinction ratio between 7 and 14 dB over 24 mn.

DOI： 10.1109/LPT.2006.877231

Language：English   Publishing type：Research paper (other academic)  

A supervisory scheme based on different time-delay recognition is proposed for optical cross-connects (OXCs). Besides providing actual routing information, it can detect and locate multiple faults. Additionally, the length of longest path is minimized.

DOI： 10.1109/COINNGNCON.2006.4454521

Language：English   Publishing type：Research paper (other academic)  

Optical cross connects (OXCs) are critical components of all-optical networks. As OXC malfunction leads to data loss or misrouting, surveillance of OXCs is essential to network reliability. A recent OXC supervisory scheme based on different time-delay recognition identifies the state of I/O connection through the OXC, including any possible effect of link failure or misrouting. For large-scale OXCs, however, this approach requires excessively long delay fibers, which raises feasibility issues such as power amplification and length of surveillance period. This paper proposes a modified scheme for reducing the length of delay fibers without downgrading the performance.

DOI： 10.1109/ICTON.2006.248435

Language：English   Publishing type：Research paper (scientific journal)  

A technique for monitoring the timing alignment between a pulse carver and a phase modulator in return-to-zero differential phase-shift keying systems is proposed. An optical frequency discriminator and a microwave detector centered at a half of the phase modulation data rate are used to monitor the spectrum broadening caused by timing misalignment., The proposed method has a large detection dynamic range and is polarization-independent.

DOI： 10.1109/LPT.2006.873962

Language：English   Publishing type：Research paper (other academic)  

We have demonstrated a polarization-interleaved wavelength-division multiplexed system with a two-orthogonal-pump optical parametric amplifier. The sensitivity has been improved by about 2dB compared to its counterpart with all channels co-polarized, with the same signal gain, which itself dramatically improved over the conventional two-parallel-pump OPA. (c) 2007 Optical Society of America.

DOI： 10.1364/OE.15.000056

Language：English   Publishing type：Research paper (other academic)  

We experimentally demonstrate a 10-Gb/s NRZ-to-RZ format conversion with tunable pulsewidth using phase modulation followed by interleaver. RZ signals with pulsewidth of 34 similar to 84 ps are obtained with extinction ratio over 15 dB and negative power penalty. (C) 2005 Optical Society of America.

DOI： 10.1109/OFC.2006.215813

Language：English   Publishing type：Research paper (other academic)  

We have demonstrated, for the first time to our knowledge, simultaneous all-optical inverted and non-inverted wavelength conversion by using a single-stage two-pump fiber optical parametric amplifier with extinction ratio between 7 and 14dB over 24nm. (C) 2005 Optical Society of America.

DOI： 10.1109/OFC.2006.215523

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1364/OPEX.14.000058

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.optcom.2005.05.039

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1049/cp:20050715

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1049/cp:20050699

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/OFC.2005.192758

Language：English   Publishing type：Research paper (other academic)  

Use of downstream inverse-RZ signal for upstream data re-modulation in a WDM passive optical network

DOI： 10.1109/OFC.2005.193126

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/LPT.2004.823767

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/LPT.2004.841028

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1049/el:20057444

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/LPT.2004.831564

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/LPT.2005.859162

Language：English   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/CLEOPR.2003.1274791