| 1. |
Evaluation of High-Security Wireless Communication System Utilizing AND Operation Between Two Data
We have proposed a method to improve physical layer security of wireless communication by radiating two data from different locations. In this system, a receiver can decode original data by implementing AND operation between two data. This time, we confirmed feasibility of proposed system by implementing AND operation between two light waves.. |
| 2. |
Shenghong Ye, Ming Che, Takeshi Kuboki, Kazutoshi Kato, Fast Wavelength Switching at Tunable DFB LaserArray by Current/Temperature Cooperative Control, IEEE Photonics Thecnology Letters, 10.1109/LPT.2021.3137808, 34, 1, 51-54, 2022.01. |
| 3. |
Kazutoshi Kato, Photonics-Assisted Terahertz-Wave Beam Steering and Its Application in Secured Wireless Communication, Photonics, 10.3390/photonics9010009, 2022, 9, 9, 2021.12.  |
| 4. |
Younjin Kim, Takeshi Kuboki, Kazutoshi Kato, Demonstration of 600-GHz Wave Beam Forming by Arrayed Light Sources With Arrayed Photomixers, IEEE Photonics Technology Letters, 10.1109/LPT.2021.3124826, 33, 24, 1435-1438, 2021.12. |
| 5. |
Feasibility Demonstration of Encrypted Wireless Communication by Utilizing AND Operation between Two Carriers via Coherent Detection
Utilizing the characteristics that the coherent detection can perform AND operation between two RF signals, we devised a new encryption method for wireless communication at the physical layer. We confirmed the AND operation via heterodyne detection of two 300-GHz band carriers, and the principle of the reception method of the devised system was demonstrated.. |
| 6. |
Ming Che, Ruo Yamamoto, Hiroshi Ito, Tadao Ishibashi, Kazutoshi Kato, Vibration insensitive THz wave interferometry for characterizing optical phase shifter, OPTIK, 10.1016/j.ijleo.2021.167203, 242, 2021.09. |
| 7. |
Ming Che, Haruichi Kanaya, Kazutoshi Kato, Optically controlled THz power tuning based on interference at transmission line, OPTICS EXPRESS, 10.1364/OE.423308, 29, 13, 20043, 2021.06. |
| 8. |
Ming Che, Haruichi Kanaya, Kazutoshi Kato, Optically controlled THz power tuning based on interference at transmission line, OPTICS EXPRESS, 10.1364/OE.423308, 29, 13, 20034-20044, 2021.06. |
| 9. |
Ming Che, Ruo Yamamoto, Hiroshi Ito, Tadao Ishibashi, Kazutoshi Kato, Vibration insensitive THz wave interferometry for characterizing optical phase shifter, OPTIK, 10.1016/j.ijleo.2021.167203, 242, 11, 167203, 2021.05. |
| 10. |
Yuri Niiya, Takeshi Kuboki, Kazutoshi Kato, Full‐range wavelength switching at tunable distributed amplification‐DFB laser with high‐accuracy feedforward control, Electronics Letters, 10.1049/ell2.12122, 57, 6, 270-271, 2021.03. |
| 11. |
Kenta Yamauchi, Kazutoshi Kato, Optical heterodyne AND operation as emulation of physical layer security at wireless communication, IEICE Electronics Express, 10.1587/elex.18.20210008, 18, 4, 1-4, 2021.03, As a physically secured wireless communication method, a novel configuration which deduces ANDed data decoded from heterodyne detection between two wireless data streams was proposed. As a feasibility experiment, the demonstration of a heterodyne AND operation was conducted by devising an optical system to emulate our novel wireless system. Experimental results testified the principle of our proposed physical layer security.. |
| 12. |
Kenta Yamauchi, Kazutoshi Kato, Optical heterodyne AND operation as emulation of physical layer security at wireless communication, IEICE Electronics Express, 10.1587/elex.18.20210008, 18, 4, 1-4, 2021.02. |
| 13. |
Yuri Niiya, Takeshi Kuboki, Kazutoshi Kato, Full-range wavelength switching at tunable distributed amplification (TDA)-DFB laser with high-accuracy feedforward control, Electronics Letters, 10.1049/ell2.12122, 57, 6, 270-271, 2021.02. |
| 14. |
High-Speed Wavelength Switching Control at Tunable Laser based on Nonlinear Model
To realize high-speed 800-GHz-wide wavelength switching with TDA (tunable distributed amplification)-DFB laser, we developed a higher-accuracy model accounting for the laser nonlinearity. By combining the feedforward control based on our nonlinear model and the feedback control, a high-speed wavelength switching time of 30 ns and long-term wavelength stabilization was achieved.. |
| 15. |
Yuri Niiya, Takeshi Kuboki, Kazutoshi Kato, High-Speed Wavelength Switching at TDA-DFB Laser Based on a Nonlinear Model, IEEE Photonics Thecnology Letters, 32, 21, 1377-1380, 2020.11. |
| 16. |
Yuri Niiya, Takeshi Kuboki, Kazutoshi Kato, High-Speed Wavelength Switching at TDA-DFB Laser Based on a Nonlinear Model, IEEE Photonics Technology Letters, 10.1109/LPT.2020.3026739, 32, 21, 1377-1380, 2020.11. |
| 17. |
Ming Che, Yuki Matsuo, Haruichi Kanaya, Hiroshi Ito,Tadao Ishibashi, Kazutoshi Kato, Optoelectronic THz-Wave Beam Steering by Arrayed Photomixers With Integrated Antennas, IEEE Photonics Technology Letters, 10.1109/LPT.2020.3007415, 32, 16, 979-982, 2020.08. |
| 18. |
Ming Che, Yuki Matsuo, Haruichi Kanaya, Hiroshi Ito, Tadao Ishibashi, Kazutoshi Kato, Optoelectronic THz-Wave Beam Steering by Arrayed Photomixers With Integrated Antennas, IEEE PHOTONICS TECHNOLOGY LETTERS, 10.1109/LPT.2020.3007415, 32, 16, 979-982, 2020.08. |
| 19. |
Ruo Yamamoto, Kohei Ichiyama, Ming Che, Takeshi Kuboki, Hiroshi Ito, Tadao Ishibashi, Kazutoshi Kato, 300 GHz optical waveform measurement by novel THz-wave autocorrelator, Electronics Letters, 56, 11, 562-563, 2020.02. |
| 20. |
Yang Zhou, Nanami Nishiyama, Hiroshi Ito, Tadao Ishibashi, Kazutoshi Kato, 700 GHz terahertz wave beam combination by optical phase control, Japanese Journal of Applied Physics, 10.7567/1347-4065/ab26aa, Vol. 58, SJ, SJJE03, 2019.08. |
| 21. |
Ming Che, Takeshi Kuboki, Kazutoshi Kato, Nonlinear compensation for indoor visible light communication systems with carrierless amplitude and phase modulation, Japanese Journal of Applied Physics, 10.7567/1347-4065/ab1fd8, Vol. 58, SJ, SJJA02, 2019.08. |
| 22. |
CHEN Hao, KATO Kazutoshi, Nonlinear Modeling and Measurement for Tens of Gigahertz Electrical Amplifier in High-baud Multi-level Modulated Coherent Optical System, 10.15017/2195853, 24, 1, 1-8, 2019.01. |
| 23. |
Goki Sakano, Jun Haruki, Kota Tsugami, Haruichi Kanaya, Kazutoshi Kato, 4 x 4 Arrayed THz-wave Combiner Composed of UTC-PDs and Slot Antennas, 2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS PACIFIC RIM (CLEO-PR), 2017.07, We have previously proposed a synchronous THz-wave combiner with linearly arrayed power sources. With four arrayed photomixers we experimentally confirmed directional gain of 5.9 dB. In this paper, for exerting full performance of the array effect, we configured for the first time two-dimensionally arrayed THz-wave combiner and demonstrated a power gain of 4.8 dB compared to the linear array.. |
| 24. |
Y. Yamanaka, G. Sakano, J. Haruki and K. Kato, THz-wave Phase Shift Measurement by THz-wave Interferometer, Electronics Letters, 53, 13, 868-869, 2017.06, A THz-wave interferometer was devised for measurement of the THz-wave phase shift. In this measurement system, the relative phase shift is deduced from the interference between the THz waves generated by two photomixers. Experimental results with this interferometer revealed that the semiconductor phase modulator could be used as a THz-wave phase shifter by utilizing its chromatic dispersion.. |
| 25. |
Haruichi Kanaya, Masahiro Koga, Kota Tsugami, Guan Chai Eu, Kazutoshi Kato, 4 x 4 planar array antenna on indium phosphide substrate for 0.3-THz band application, TERAHERTZ, RF, MILLIMETER, AND SUBMILLIMETER-WAVE TECHNOLOGY AND APPLICATIONS X, 10.1117/12.2248859, 10103, 2017.02, This paper presents a design and fabrication of 4 x 4 one-sided directional slot array antenna on indium phosphide (InP) substrate for 0.3 THz (300 GHz) wireless link. The antenna has top antenna metal layer and bottom floating metal layer. Polyimide dielectric layer is stacked between each metal layer. The antenna is placed on the deep etched InP substrate. By optimizing the length of the bottom floating metal layer, one-sided directional radiation can be realized. The branched coplanar wave guide (CPW) transmission line is connected to each antenna element with the same electrical length. The size of the 4 x 4 array antenna is 2,730 mu m x 3,000 mu m with uni-traveling-carrier photodiodes, DC bias and ground lines. Simulated realized gain in peak direction of the proposed antenna is 11.7 dBi. The transmission measurement is carried and measured received power.. |
| 26. |
Shota Takeuchi, Kazuki Sakuma, Kazutoshi Kato, Yasuyuki Yoshimizu, Yu Yasuda, Shintaro Hisatake, Tadao Nagatsuma, Novel Lightwave-Interferometric Phase Detection for Phase Stabilization of Two-Tone Coherent Millimeter-Wave/Microwave Carrier Generation, IEICE Trans. Electron., 10.1587/transele.e99.c.1048, 10.7567/1347-4065/ab26aa_references_DOI_5YmyZzbRIm9Zdn1o04YvQNbqpIi, Vol. E99-C, 9, 1048-1054, 2016.09, For phase stabilization of two-tone coherent millimeter-wave/microwave carrier generation, two types of phase detection schemes were devised based on lightwave interferometric technique, the Mach-Zehnder interferometric method and the pseudo Mach-Zehnder interferometric method. The former system showed clear eye patterns at both OOK and PSK modulations of 1 Gbit/s on the 12.5-GHz carrier. The latter system demonstrated the error-free transmission at OOK modulation of 11 Gbit/s on the 100-GHz carrier.. |
| 27. |
Jun Tsuboi, Takeshi Kuboki, Kazutoshi Kato, Wide-capture-range, high-precision wavelength stabilization within ±50 MHz for flexible-grid wavelength division multiplexing by photomixing technique, Jpn. J. Appl. Phys., 10.7567/JJAP.55.08RB10, Vol. 55, 8, 2016.07, The lasers for the flexible-grid wavelength division multiplexing (WDM) system are required to have high precision of wavelength stability. Previously, we proposed the wavelength-controlling system of the Distributed FeedBack Laser Diode (DFB-LD) with the photomixing technique and a microwave filter to precisely measure the optical frequency error from the target value. To enlarge the wavelength-capture range, we improve the system to detect the wavelength error with two different microwave filters in parallel. Experimental results show that the wavelength-capture range is extended up to 4 GHz while the wavelength error is still kept within ±50 MHz.. |
| 28. |
Kimura Ryoga, Tatsumoto Yudai, Sakuma Kazuki, Onji Hirokazu, Shimokozono Makoto, Ishii Hiroyuki, Kato Kazutoshi, Sub-microsecond wavelength stabilization of tunable lasers with the internal wavelength locker, Jpn. J. Appl. Phys., 10.7567/JJAP.55.08RB07, Vol. 55, 8, 08RB07, 2016.07, We proposed a method of accelerating the wavelength stabilization after wavelength switching of the tunable distributed amplification-distributed feedback (TDA-DFB) laser using the internal wavelength locker to reduce the size and the cost of the wavelength control system. The configuration of the wavelength stabilization system based on this locker was as follows. At the wavelength locker, the light intensity after an optical filter is detected as a current by the photodiodes (PDs). Then, for estimating the wavelength, the current is processed by the current/voltage-converting circuit (IVC), logarithm amplifier (Log Amp) and field programmable gate array (FPGA). Finally, the laser current is tuned to the desired wavelength with reference to the estimated wavelength. With this control system the wavelength is stabilized within 800 ns after wavelength switching, which is even faster than that with the conventional control system.. |
| 29. |
Ahmed E. A. Farghal, Hossam M. H. Shalaby, Kazutoshi Kato, Ramesh K. Pokharel, Performance Analysis of Multicode OCDM Networks Supporting Elastic Transmission With QoS Differentiation, IEEE TRANSACTIONS ON COMMUNICATIONS, 10.1109/TCOMM.2015.2512922, 64, 2, 741-752, 2016.02, A multicode optical code-division multiplexing (OCDM) is proposed to support the dynamic changes in the requested traffic demand in OCDM networks by adapting the number of allocated codes according to the requested transmission rate. In order to support time-variant data rates and multiservice transmissions; a multicode variable-weight 2D one-coincidence frequency hopping code/optical orthogonal code (OCFHC/OOC) is employed as the signature code in the proposed system. Two multicode assignment methods, namely, random multicode assignment (RMA) policy and uniform multicode assignment (UMA) policy, are presented. For each code assignment method, we drive the probability density function (pdf) of the number of active codes in each wavelength group. The bit error probability (BEP), the probability of degradation, and the blocking probability are derived as network performance key parameters. The proposed system has a simplified routing and code assignment process with a lower blocking probability. Our numerical results indicate that the network teletraffic capacity and blocking probability can be improved significantly using UMA policy and call admission control.. |
| 30. |
K. Sakuma, J. Haruki, G. Sakano, K. Kato, S. Hisatake, T. Nagatsuma, Coherent THz wave combiner composed of arrayed uni-traveling carrier photodiodes and planar lightwave circuit, Proceedings of SPIE - The International Society for Optical Engineering, 10.1117/12.2212017, 9747, 2016.01, For high-power THz wave generation by photomixing of two lightwaves, we proposed the synchronous power combiner which consists of eight-arrayed photomixers/antennas and the THz phase control system. We experimentally confirmed the effectiveness of the power combination by synchronizing the phases of the THz wave by the mechanical optical delay lines and also demonstrated the same functionality at the lightwave-circuit-based optical phase control system. We found that the directional gain is increasing with increasing the number of photomixers from two to three and it reached up to 4.5 dB.. |
| 31. |
Haruichi Kanaya, Tomoki Oda, Naoto Iizasa, Kazutoshi Kato, 300 GHz One-Sided Directional Slot Array Antenna on Indium Phosphide Substrate, IEICE Proceeding Series, 10.34385/proc.37.s2.1.1, 37, S2.1.1, 2015.11, This paper presents a novel design of 300 GHz band 1 x 4 one-sided directional slot dipole array antenna fed by coplanar waveguide (CPW) on indium phosphide (InP). The proposed antenna has four antenna elements and branched CPW structure to achieve a high antenna gain and a sharp beam. We fabricated and measured the array antenna. In the EM simulation, forward directional peak gain is 7.35 dBi. The measured reflection coefficient is agreed with the simulation results.. |
| 32. |
Ahmed E. Farghal, Hossam M. H. Shalaby, Kazutoshi Kato, Ramesh K. Pokharel, Optical Code-Division Multiplexing (OCDM) Networks Adopting Code-Shift Keying/Overlapping PPM Signaling: Proposal and Performance Analysis, IEEE TRANSACTIONS ON COMMUNICATIONS, 10.1109/TCOMM.2015.2467372, 63, 10, 3779-3788, 2015.10, Optical code-division multiplexing (OCDM) systems use short pulses compared with bit-duration to achieve high transmission rate. The use of short pulses poses several problems as a result of group velocity dispersion (GVD), intersymbol interference (ISI) (due to avalanche photodiode (APD) buildup time), and receivers limited bandwidth. In this paper, an OCDM system employing code-shift keying (CSK) and overlapping pulse-position modulation (OPPM) signaling is proposed and theoretically investigated. By using CSK while maintaining same data rate, the chip duration can be increased to counteract the GVD effect in 2D OCDM systems. Moreover, by increasing the chip duration, the chip rate is decreased and the stringent requirement on receiver bandwidth is relaxed. In addition, using overlapping property in OPPM allows for further chip duration increase. We consider using correlation receivers with hard-limiters and APDs at the receiver side. The bit error probability (BEP) of the proposed system is derived taking into account the impacts of APD noise, thermal noise, GVD, ISI, and multiple-access interference (MAI). A performance comparison between OOK-, PPM-, OPPM-OCDM and the proposed system is carried out. Our results reveal that the use of CSK/OPPM-OCDM with data rate constraint allows the reduction of MAI, GVD and ISI effects with improved spectral efficiency.. |
| 33. |
Tadao Nagatsuma, Kazutoshi Kato, Jeffrey Hesler, Enabling technologies for real-time 50-Gbit/s wireless transmission at 300 GHz, Proceedings of the 2nd ACM International Conference on Nanoscale Computing and Communication, ACM NANOCOM 2015, 10.1145/2800795.2800824, 2015.09, There has been a growing interest in the application of terahertz (THz) waves to broadband wireless communications. Particularly, use of THz waves at frequencies above 275 GHz is one of the big concerns among researchers, because these frequency bands have not yet been allocated for specific active services, and there is a possible opportunity to utilize extremely large bandwidths for ultra-broadband wireless communications. In this paper, we describe photonics-based approaches to realizing most practical and robust 300-GHz-band wireless links to meet and explore realworld applications at the earliest opportunity as a technology driver. We present enabling technologies for a real-time 50-Gbit/s transmission at over 20-m distance.. |
| 34. |
Onji Hirokazu, Takeuchi Shota, Tatsumoto Yudai, Nunoya Nobuhiro, Shimokozono Makoto, Ishii Hiroyuki, Kato Kazutoshi, Fast wavelength switching with tunable distributed amplification distributed feedback laser by feedforward control technique, Jpn. J. Appl. Phys., 10.7567/JJAP.53.08MB11, Vol. 53, 8, 08MB11, 2014.07, We proposed a method of accelerating the wavelength switching of a tunable distributed amplification distributed feedback (DFB) laser by feedforward control. From experimental laser responses, we designed and simulated feedforward controllers using MATLAB/Simulink so as to reduce the time for wavelength stabilization. We applied this method to two different cases involving a laser drive circuit with a large output current and a 50 ns rise time, and a laser drive circuit with a moderate output current and a 5 ns rise time. In both cases, we showed that the wavelength switching times were improved from 450 to 150 ns and from 75 to 35 ns, respectively. From these results, the proposed control technique is confirmed to be efficient for possible practical applications.. |
| 35. |
T Otsuji, K Kato, S Kimura, T Nagatsuma, Wide-band high-efficiency optical-to-electrical conversion stimulus probe heads for testing large-signal responses of high-speed electronic devices, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, 47, 5, 525-533, 1999.05, Wide-band high-efficiency optical-to-electrical conversion stimulus probe heads have been developed for testing large-signal responses of high-speed electronic devices, Two types of such probes were demonstrated using a 155-mu m 85-GHz-bandwidth waveguide p-i-n photodiode, The type-I probe employs a simple semirigid coaxial cable with a bias network for the electrical-signal transmission, resulting in a very low modal dispersion of |
| 36. |
M. Yaita, T. Nagatsuma, K. Kato, K. Noguchi, H. Miyazawa, T. Otsuji, Ultrafast optical signal measureent using optoelectronic techniques, Opt. Quantum Electron., 10.1023/A:1006964727065, 30, 11, 1119-1133, 1998.11. |
| 37. |
Taiichi Otsuji, Kazutoshi Kato, Tadao Nagatsuma, 50-GHz bandwidth, 0.75-A/W, optoelectronic stimulus probe head employing multimode waveguide p-i-n photodiode, IEEE Photonics Technology Letters, 10.1109/68.481134, 8, 3, 411-413, 1996.03, We developed a highly efficient, broad-band optoelectronic stimulus probe head employing a 1.55-μm waveguide p-i-n photodiode (WGPD). The novel multimode waveguide structure of the WGPD and optical lens-based rigid coupling assembly yielded a very high responsivity of 0.75 A/W. The OE probe has an effective 3-dB bandwidth of 50 GHz which is currently limited by the frequency dispersion of the CPW used in the probe. 2-mW, 64-Gb/s RZ optical pulse patterns were successfully able to be converted to 200 mVpp electrical pulses.. |
| 38. |
M YAITA, T NAGATSUMA, K SUZUKI, K IWATSUKI, K KATO, Y MURAMOTO, ULTRAFAST OPTICAL PULSE-PATTERN SIGNAL MEASUREMENT USING OPTOELECTRONIC TECHNIQUES, ELECTRONICS LETTERS, 31, 17, 1501-1502, 1995.08, A novel ultrafast optical pulse-pattern signal measurement technique using a fast photodetector and electro-optic sampling is demonstrated. The technique can measure 100Gbit/s optical pulse-pattern signals with high sensitivity and polarisation independence.. |
| 39. |
K KATO, A KOZEN, Y MURAMOTO, Y ITAYA, T NAGATSUMA, M YAITA, 110-GHZ, 50-PERCENT-EFFICIENCY MUSHROOM MESA WAVE-GUIDE P-I-N PHOTODIODE FOR A 1.55-MU-M WAVELENGTH, IEEE PHOTONICS TECHNOLOGY LETTERS, 6, 6, 719-721, 1994.06, A mushroom-mesa structure is proposed to reduce the CR-time constant which originates from the waveguide photodiode structure. Experimental results at a 1.55-mum wavelength show that the multimode waveguide p-i-n photodiode with mushroom-mess structure has an electrical 3-dB bandwidth of more than 75 GHz in the frequency domain and an electrical 3-dB bandwidth of 110 GHz in the time domain. The external quantum efficiency is 50% or 0.63 A/W, which leads to a record bandwidth-efficiency product of 55 GHz for long wavelength p-i-n photodetectors.. |
| 40. |
T NAGATSUMA, M YAITA, M SHINAGAWA, K KATO, A KOZEN, K IWATSUKI, K SUZUKI, ELECTROOPTIC CHARACTERIZATION OF ULTRAFAST PHOTODETECTORS USING ADIABATICALLY COMPRESSED SOLITON PULSES, ELECTRONICS LETTERS, 30, 10, 814-816, 1994.05, The response of ultrafast photodetectors at 1.55mum wavelength has been measured by electro-optic sampling using adiabatically compressed soliton pulses. 750fs-duration pulses with no wings were used to both pump and probe the waveguide pin photodiode. The measured bandwidth of the photodiode is more than 110 GHz, which is the highest value for a detector operating at 1.55 mum.. |
