出版者・発行元：Optics Letters  

We introduce an innovative channel estimation technique, in-phase and quadrature separation pulse compression noise rejection (IQS-PCNR), for intensity modulation and direct detection (IMDD) optical orthogonal frequency division multiplexing (OFDM) systems. IQS-PCNR uses pulse compression to estimate the channel impulse response (CIR) and employs a noise rejection window to mitigate residual noise, resulting in significant performance improvements. Experimental results show that IQS-PCNR outperforms conventional methods, such as least squares (LS) and intra-symbol frequency-domain averaging (ISFA), while preserving comparable complexity. Specifically, IQS-PCNR provides a 2.87 dB and 0.61 dB enhancement in optical receiver sensitivity, along with a 3.65 Gbps and 1.85 Gbps increase in achievable bitrate at the hard-decision forward error correction (HD-FEC) threshold of 3.8 × 10⁻³, after transmission over a 2-km standard single-mode fiber (SSMF) link, compared to LS and ISFA, respectively. Additionally, IQS-PCNR enables the generation of real pilot signals with greater hardware efficiency.

DOI： 10.1364/OL.558876

Web of Science

Scopus

PubMed

出版者・発行元：Optics Letters  

We propose and experimentally demonstrate a modulation technique, termed orthogonal chirp division multiplexing with chirp index modulation (OCDM-CIM), where partial chirps are deliberately unmodulated to reduce interference and energy consumption. OCDM-CIM exhibits the combined advantages of interference rejection from the chirp-spread spectrum in OCDM and energy efficiency (EE) from index modulation, achieving an attractive trade-off among spectral efficiency (SE), EE, and performance by flexibly controlling the number of active chirps per subblock to adapt to different granularity requirements of the system. In addition, a distributed subblocking strategy is introduced to obtain additional coding and diversity gains. Experimental results show that compared to conventional orthogonal frequency division multiplexing (OFDM) with subcarrier index modulation under the same index parameter setting, the proposed OCDM-CIM reduces the peak-to-average power ratio by 2.5 dB at the complementary cumulative distribution function of 10⁻³, enhances optical receiver sensitivity by 2.7 dB, and increases the achievable bitrate by 8.7 Gbps at the bit error rate threshold of 3.8 × 10⁻³ for hard-decision forward error correction. Moreover, an improvement of 25% in EE can be achieved compared to OCDM at the same SE.

DOI： 10.1364/OL.544048

Web of Science

Scopus

PubMed

出版者・発行元：Communications Materials  

The gap between the performance of optoelectronic components and the demands of fiber-optic communications has narrowed significantly in recent decades. Yet, the expansion of data communications traffic remains substantial, with fiber-link speeds increases anticipated in the near future. Here, we demonstrate an ultra-high-speed electro-optic waveguide modulator constructed using a thin film of lanthanum-modified lead zirconate titanate with a ferroelectric phase exhibiting a strong Pockels effect. The modulator has a wide optical window; thus, the modulation was demonstrated for 1550 and 1310 nm wavelengths. This device showed electro-optical intensity signaling with line rates of 172 Gbit s−1, in conjunction with on–off keying modulation; this performance could be increased to 304 Gbit s−1 using four-level pulse modulation. The signaling performance of this modulator was found to be robust, with stable performance at temperatures as high as 100 °C. This technology is expected to have applications in a wide range of classical optoelectronic devices and in quantum science and technology.

DOI： 10.1038/s43246-024-00558-5

Web of Science

Scopus

出版者・発行元：2024 IEEE Photonics Conference IPC 2024 Proceedings  

Electro-optic (EO) polymer modulators have been extensively studied as ultra-high-speed transmitter devices due to their high EO coefficient and effective velocity matching between optical and microwave frequencies. However, material absorption losses in the EO polymer restrict the device's use in longer wavelength regions, such as the C-band. In this paper, we have developed an EO polymer capable of transmitting light at 1310 nm, making it suitable for O-band transmitter applications. Our modulator features a Si slot phase shifter structure embedded with the EO polymer. The measured Vπ for the modulator, with a phase shifter length of 1.5 mm, was 1.9 V. We successfully demonstrated high-speed transmission at 80 Gbit/s using OOK.

DOI： 10.1109/IPC60965.2024.10799803

Web of Science

Scopus

出版者・発行元：IEEE International Conference on Group IV Photonics Gfp  

The photoreliability test of the EO polymer-based modulator was performed. In an oxygen-free system, the device exhibited excellent V<inf>π</inf> stability at 80^○C for over 2,000 hours under an optical density of 0.74 mW um^-2

DOI： 10.1109/SiPhotonics60897.2024.10544062

Web of Science

Scopus

開催年月日： 2024年11月

記述言語：英語   会議種別：ポスター発表  

国名：イタリア共和国  

DOI： 10.1109/IPC60965.2024.10799803

開催年月日： 2024年3月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

種別：査読等 

外国語雑誌　査読論文数：1