| 1. |
Amalina Athira Ibrahim, Bo Li, Shenghong Ye, Takashi Shiramizu, Hanwei Chen, Yuya Mikami, Kazutoshi Kato, Phase Stabilization of a Terahertz Wave Using Mach–Zehnder Interference Detection, Electronics, 10.3390/electronics12153366, 12, 15, 3366-3366, 2023.08, As a high-frequency carrier, the terahertz (THz) wave is essential for achieving high-data-rate wireless transmission due to its ultra-wide bandwidth. Phase stabilization becomes crucial to enable phase-shift-based multilevel modulation for high-speed data transmission. We developed a Mach–Zehnder interferometric phase stabilization technique for photomixing, which has proved a promising method for phase-stable continuous THz-wave generation. However, this method faced inefficiencies in generating phase-modulated THz waves due to the impact of the phase modulator on the phase stabilization system. By photomixing, which is one of the promising methods for generating THz waves, the phase of the generated THz waves can be controlled in the optical domain so that the stability of the generated THz wave can be controlled by photonics technologies. Thus, we devised a new phase stabilization approach using backward-directional lightwave, which is overlapped with the THz wave generation system. This study presented a conceptual and experimental framework for stabilizing the phase differences of optical carrier signals. We compared the optical domain and transmission performances between forward-directional and backward-directional phase stabilization methods. Remarkably, our results demonstrated error-free transmission at a modulation frequency of 3 Gbit/s and higher.. |
| 2. |
Hanwei Chen, Ming Che, Naoya Seiki, Takashi Shiramizu, Takuya Yano, Yuya Mikami, Yuta Ueda, Kazutoshi Kato, Physically Encrypted Wireless Transmission Based on XOR between Two Data in Terahertz Beams, Electronics, 10.3390/electronics12122629, 12, 12, 2629-2629, 2023.06, Future wireless communications require higher security as well as a higher data rate. We have been studying physically secured wireless transmission systems and previously proposed encryption/decryption techniques based on the AND operation caused by coherent detection between two encrypted data sequences on two different terahertz carriers. Furthermore, we suggested that by employing the XOR operation as the decryption, the proposed system can be made more secure because XOR increases the computational complexity for eavesdroppers to recover the plaintext. In this paper, we propose the XOR operation between two data sequences on FSK-modulated terahertz waves. By constructing the XOR encryption transmitters/receivers, which consisted of high-speed wavelength tunable lasers and arrayed uni-traveling-carrier photodiodes (UTC-PDs), we successfully demonstrated the XOR operation between two data sequences on 200 GHz waves from the two transmitters.. |
| 3. |
Ming Che, Kazuya Kondo, Kazutoshi Kato, Generating and Enhancing THz Pulses via an Antenna-Coupled Unitraveling-Carrier Photodiode Array, IEEE Transactions on Terahertz Science and Technology, 10.1109/tthz.2023.3251736, 13, 3, 280-285, 2023.05. |
| 4. |
白水孝始, 清木直哉, 松本凌, 桝冨直人, 三上裕也, 上田悠太, 加藤和利, 波長可変レーザーを用いた変調テラヘルツパルス波の生成, レーザー研究, 51, 4, 242-243, 2023.04. |
| 5. |
近藤和哉, 土居諒, 車明, 三上裕也, 加藤和利, 光フェーズドアレーを用いたテラヘルツ波の電子制御ビームステアリング, 電子情報通信学会論文誌C, J106-C, 2, 86-87, 2022.12. |
| 6. |
Ming Che, Kazuya Kondo, Haruichi Kanaya, Kazutoshi Kato, Arrayed Photomixers for THz Beam-Combining and Beam-Steering, Journal of Lightwave Technology, 10.1109/jlt.2022.3204113, 40, 20, 6657-6665, 2022.10. |
| 7. |
河合 優佑, 陳 漢偉, 加藤 和利, 二データ間のアンド演算を用いた高セキュリティ無線通信システムの評価, 10.14923/transelej.2022jcl0001, J105-C, 4, 127-128, 2022.04, 我々は異なる場所から放射した二つのデータを用いて伝送する，無線通信の物理層セキュリティ向上法を提案している．このシステムで受信器は二つのデータ間のアンド演算を実行し，元データを復号する．今回二つのデータの強度比と位相ずれが受信品質に及ぼす影響を評価し，提案システムの実現性を検証した．. |
| 8. |
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. |
| 9. |
Shenghong Ye, Ming Che, Takeshi Kuboki, Kazutoshi Kato, Fast Wavelength Switching at Tunable DFB Laser Array by Current/Temperature Cooperative Control, IEEE Photonics Technology Letters, 10.1109/LPT.2021.3137808, 34, 1, 51-54, 2022.01, We proposed a new control method of the tunable distributed feedback (DFB) laser array (TLA) to realize high-speed optical switching by changing the injection current without sacrificing reliability. Previous studies of high-speed wavelength switching at DFB lasers achieved a sub-second switching time by injecting a large current to the active layer. However, a large injection current caused laser degradation that seriously reduced laser lifetime and reliability. In this paper, based on fast wavelength switching by injection current control, a new switching method was proposed that reduces an averaged injection current by increasing temperature. We successfully demonstrated 400-GHz-wide wavelength switching, which is the maximum tuning range of a single DFB laser in the TLA, with a switching time of 130 ms and reduced the injection current from 402 to 52 mA. Thus, we were able to greatly improve the reliability and increase the lifetime of the TLA by 60 times.. |
| 10. |
Kazutoshi Kato, Photonics-Assisted Terahertz-Wave Beam Steering and Its Application in Secured Wireless Communication, Photonics, 10.3390/photonics9010009, 2022, 9, 9, 2021.12.  |
| 11. |
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. |
| 12. |
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, — For photonic-based continuous THz-wave generation for a wireless communication, a fiber-based configuration has been used. Without the fiber-optics, THz-wave generation system could be minimized by monolithic integration. Thus, based on the monolithic integration, a THz-wave generator consisting of arrayed light sources and arrayed photomixers was proposed. Arrayed light sources that can be operated at 600 GHz were designed and fabricated. Experimental results showed that the light sources have a practically uniform optical output. And then, 600-GHz power combining and directional gain were obtained in combination with arrayed photomixers.. |
| 13. |
山内 健太, 河合 優佑, 車 明, 伊藤 弘, 石橋 忠夫, 加藤 和利, コヒーレント検波による2キャリア間のアンド演算を用いた暗号化無線伝送システムの原理実証, 10.14923/transelej.2021JCL0002, J104-C, 4, 118-119, 2021.10, 二つのRF信号のコヒーレント検波により，それらのアンド信号が得られることを利用し，無線の物理レイヤでの新たな暗号化手法を考案した．二つの300GHz帯無線キャリアのヘテロダイン検波によるアンド演算を確認し，考案した手法の受信原理を実証した．. |
| 14. |
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. |
| 15. |
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. |
| 16. |
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. |
| 17. |
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. |
| 18. |
山内 健太, 河合 優佑, 車 明, 伊藤 弘, 石橋 忠夫, 加藤 和利, コヒーレント検波による2キャリア間のアンド演算を用いた暗号化無線伝送システムの原理実証, 電子情報通信学会和文論文誌C, J-104-C, 4, 118-119, 2021.04. |
| 19. |
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. |
| 20. |
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.. |
| 21. |
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. |
| 22. |
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. |
| 23. |
新谷友里, 久保木猛, 加藤和利, 非線形モデルによる波長可変レーザの高速波長切替制御, 電子情報通信学会和文論文誌C, J104-C, 3, 67-68, 2021.01. |
| 24. |
新谷友里, 久保木猛, 加藤和利, 非線形モデルによる波長可変レーザの高速波長切替制御, 電子情報通信学会和文論文誌C, 10.14923/transelej.2020jcl0009, J104-C, 3, 67-68, 2021.01, 波長可変分布活性DFBレーザの最大波長可変幅800 GHzでの高速波長切替を目指して，レーザの非線形性を考慮したモデルを開発した．フィードフォワード制御の高精度化により30 nsの高速波長切替を達成し，更にフィードバック制御の併用で長期波長安定化を実現した．. |
| 25. |
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. |
| 26. |
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. |
| 27. |
Shenghong Ye, Shunta Kono, Yuri Niiya, Ming Che, Takeshi Kuboki, Kazutoshi Kato, Demonstration of 2-ms High-Reliability Wavelength Switching at TLA with Current/Temperature Cooperative Control, 25th Opto-Electronics and Communications Conference, OECC 2020, 10.1109/OECC48412.2020.9273595, 2020.10, We optimized the current/temperature cooperative control to improve the reliability of the tunable distributed feedback laser array (TLA) at high-speed wavelength switching. We demonstrated a 2-ms wavelength switching with a practically low average injection current.. |
| 28. |
Yuri Niiya, Takeshi Kuboki, Kazutoshi Kato, Wide-Range Wavelength Switching at TDA-DFB Laser by Nonlinear Model, 25th Opto-Electronics and Communications Conference, OECC 2020, 10.1109/OECC48412.2020.9273522, 2020.10, In order to realize a high-speed wavelength switching of the TDA-DFB laser at a wide switching width, we developed an accurate control model accounting for the laser nonlinearity. We applied our nonlinear model to 400-GHz-wide and 600-GHz-wide switching and achieved a switching time within 50 ns.. |
| 29. |
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. |
| 30. |
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. |
| 31. |
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. |
| 32. |
Shunta Kono, Yuri Niiya, Takeshi Kuboki, Kazutoshi Kato, Cooperative Control of Injection Current and Temperature at DFB-LD for High-speed High-Reliability Wavelength Switching, MOC 2019 - 24th Microoptics Conference, 10.23919/MOC46630.2019.8982899, 178-179, 2019.11, We devise cooperative control of injection current and temperature for wavelength switching at the DFB-LD. Prompt change of the current makes high-speed switching and gradual cooperative change of current/temperature results in wavelength stabilization at lower current. Experiment shows a switching within 31 ms as well as long term stabilization with the current of less than 100 mA.. |
| 33. |
Yuri Niiya, Shunta Kono, Takeshi Kuboki, Kazutoshi Kato, High-Speed Wide-Range Wavelength Switching for Tunable Distributed Amplification (TDA-) DFB Laser Based on Nonlinear Model, MOC 2019 - 24th Microoptics Conference, 10.23919/MOC46630.2019.8982905, 136-137, 2019.11, The TDA-DFB laser has nonlinearity on the current-wavelength characteristic and needs high accuracy control model for realizing high-speed wide-range switching We designed a nonlinear model for high-speed 600-GHz-wide wavelength switching and showed the feasibility of this control model for much wider range switching.. |
| 34. |
Ming Che, Nanami Nishiyama, Kenta Yamauchi, Takeshi Kuboki, Hiroshi Ito, Tadao Ishibashi, Kazutoshi Kato, 450-GHz-wave beam-steering with 1 kHz repetition by optical phase control, IET Conference Publications, 2019, CP765, 2019.09, Beam-steering is an effective method for future terahertz-wave wireless communications because the power is concentrated to a certain direction. A 2×8 optical phased array was designed and fabricated using a silica-based lightwave circuit for THz phase control, and 450-GHz-wave beam-steering with 1 kHz repetition was demonstrated.. |
| 35. |
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. |
| 36. |
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. |
| 37. |
Ming Che, Takeshi Kuboki, Kazutoshi Kato, Trellis Coded Three Dimensional Carrierless Amplitude and Phase Modulation, OECC/PSC 2019 - 24th OptoElectronics and Communications Conference/International Conference Photonics in Switching and Computing 2019, 10.23919/PS.2019.8818137, 2019.07, The multi-dimensional carrierless amplitude and phase (MD-CAP) modulation is a high spectral efficiency modulation technology which has begun to draw more attention in recent years. Meanwhile, how to improve the energy efficiency is also an important issue within the limited bandwidth. In this paper, a 3D-CAP modulation with trellis coded constellation has been proposed. At the premise of increasing the transmission bandwidth, the bit error rate is reduced through the unified design of channel coding and modulation.. |
| 38. |
坂野豪紀, 周洋, 金谷晴一, 加藤和利, フォトミキサアレーを用いた空間合成によるテラヘルツ波高出力化, 電子情報通信学会論文誌C, 2019.04. |
| 39. |
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. |
| 40. |
Hiroki Fukuda, Kenta Yamaguchi, Takeshi Kuboki, Kazutoshi Kato, High-speed and long-term wavelength stabilization of tunable distributed amplification distributed feedback laser after laser activation with feedforward and feedback control, Japanese Journal of Applied Physics, 10.7567/jjap.57.08pd04, 57, 8S2, 08PD04, 2018.07. |
| 41. |
山中友輔・久保木猛・加藤和利, 半導体光増幅器の相互利得変調を用いた光－無線メディア変換法の伝送性能向上の検討, 電子情報通信学会論文誌C, J101-C, 4, 2018.04. |
| 42. |
Haruichi Kanaya, Kota Tsugami, Goki Sakano, Guan Chai Eu, Kazutoshi Kato, Development of 4x4 phased array antenna on chip for 300GHz band application, Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XI, 10.1117/12.2287326, 10531, 2018.02. |
| 43. |
Hiroki Fukuda, Kenta Yamaguchi, Takeshi Kuboki, Kazutoshi Kato, Fast wavelength stabilization of tunable laser after starting laser oscillation, 22nd Microoptics Conference, MOC 2017, 10.23919/MOC.2017.8244600, 2017-November, 290-291, 2017.11, For fast wavelength switching within the full available wavelength range of the tunable laser array, we investigated a wavelength stabilizing method after switching on the injection current to the laser's active layer. Experimental results demonstrated that our feedback controller dramatically reduced wavelength switching time from 800 μs to 2.0 μs.. |
| 44. |
Masataka Gohara, Ryoga Kimura, Kenta Yamaguchi, Takeshi Kuboki, Kazutoshi Kato, Linearizer for wavelength sweep at tunable DBR-LD and linearity evaluation of sweep, 22nd Microoptics Conference, MOC 2017, 10.23919/MOC.2017.8244604, 2017-November, 298-299, 2017.11, We constructed the linear wavelength sweeping system with 2-μm-band distributed Bragg reflector laser for the second-harmonic-detection wavelength modulation spectroscopy. Using our devised linearity evaluation method with a germanium etalon filter, we experimentally confirmed that the nonlinearity of the laser can be efficiently compensated.. |
| 45. |
Yusuke Yamanaka, Younjin Kim, Takeshi Kuboki, Kazutoshi Kato, Optical-to-wireless media conversion by utilizing cross gain modulation at semiconductor optical amplifier, 22nd Microoptics Conference, MOC 2017, 10.23919/MOC.2017.8244486, 2017-November, 42-43, 2017.11, We devise an optical-to-wireless media conversion method by XGM at the SOA aiming for a future use at a THz-wave access. We investigate the XGM characteristics and the performance of our proposed media conversion method. We configure the media-converted data transmission system and demonstrate an error free transmission.. |
| 46. |
Yusuke Yamanaka, Takeshi Kuboki, Kazutoshi Kato, Proposal of THz phase control system utilizing chromatic dispersion at optical device and its feasibility demonstration, 2017 Opto-Electronics and Communications Conference, OECC 2017 and Photonics Global Conference, PGC 2017, 10.1109/OECC.2017.8114812, 2017-November, 1-2, 2017.11, We propose a novel THz wave phase control system consisting of an optical device whose chromatic dispersion changes the phase difference between two lightwaves for photomixing. Our devised Mach-Zehnder modulation technique reveals the feasibility of full-range THz wave phase control with the semiconductor phase modulator.. |
| 47. |
Ming Che, Takeshi Kuboki, Kazutoshi Kato, Proposal of cost-efficient and low-complexity platform for software defined visible light communication, 22nd Microoptics Conference, MOC 2017, 10.23919/MOC.2017.8244620, 2017-November, 330-331, 2017.11, With the increasing popularity of LED lighting and a growing demand for bandwidth in wireless communication, the visible light communication (VLC) is one of the promising scheme for addressing the bottleneck in the emerging broadband access networks. For research in the field of VLC focused on solutions of contradiction between massive available bandwidth and limited modulation bandwidth of LED, the purpose of this paper is to design an VLC experiment platform with characteristics of high flexibility and rapid productization. As a result, this platform not only expand the concept of software defined communication, but has the advantage of simple structure and low cost.. |
| 48. |
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.. |
| 49. |
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.. |
| 50. |
木村 凌河, 久保木 猛, 加藤 和利, 2017 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2017, 電子情報通信学会論文誌C, vol. J100-C, 4, 166-167, 2017.04, 波長可変分布活性DFBレーザの波長切替幅400GHz(3.2nm)での高速高安定化を目指してレーザモデルの高精度化を行った。モデルをもとに設計したフィードフォワード／フィードバック併用制御により100ns以下の波長切替時間と切替後の波長安定性を実現した。. |
| 51. |
加藤 和利, 波長可変レーザの400GHz(3.2nm)幅高速高安定波長切替, 電子情報通信学会和文論文誌C, J100-C, 166-167, 2017.04. |
| 52. |
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.. |
| 53. |
山中 友輔, 久保木 猛, 加藤 和利, マッハ・ツェンダ干渉計型強度変調法を用いた半導体光増幅器の光位相変化測定, 電子情報通信学会論文誌C, vol. J100-C, 9, 35-36, 2017.01, 半導体光増幅器(SOA)における注入電流変化に対する光位相変化を測定するためにマッハ・ツェンダ干渉計型強度変調器を模した測定系を光ファイバで構成し、かつ光ファイバ長の揺らぎの影響を受けない測定法を提案している。本測定により、SOAの注入電流に対する光位相変化を高精度で測定でき、本測定法が有効である事を確認した. |
| 54. |
Kenta Yamaguchi, Yudai Tatsumoto, Ryoga Kimura, Takeshi Kuboki, Kazutoshi Kato, Sub-millisecond wavelength switching of tunable DFB laser array (TLA) with injection current control, Conference Digest - IEEE International Semiconductor Laser Conference, 2016.12, For the purpose of sub-millisecond wavelength switching, the feedforward current control technique was applied to the DFB laser. At the switching from 191.2 THz to 191.0 THz, our designed controller successfully reduced the wavelength switching time of the tunable DFB laser array down to 800 μs.. |
| 55. |
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.. |
| 56. |
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.. |
| 57. |
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.. |
| 58. |
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.. |
| 59. |
Jun Tsuboi, Takeshi Kuboki, Kazutoshi Kato, Wavelength stabilization within 0.05 GHz with photo-mixing technique and laser current controlling, MOC 2015 - Technical Digest of 20th Microoptics Conference, 10.1109/MOC.2015.7416475, 2016.02, The lasers for the WDM system with the flexible grid need to have highly accurate wavelength tuning and stability. Instead of using optical filters, we propose the microwave photonics approach with photo-mixing technique and the laser current controlling. Experimental results show that the optical frequency is stabilized with the accuracy of 0.05GHz.. |
| 60. |
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.. |
| 61. |
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.. |
| 62. |
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.. |
| 63. |
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.. |
| 64. |
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.. |
| 65. |
Mohammad Nasir Uddin, Takaaki Kizu, Yasuhiro Hinokuma, Bingzhou Hong, Akio Tajima, Kazutoshi Kato, Kiichi Hamamoto, High intrinsic modulation bandwidth InGaAsP/InGaAsP 1.55 µm asymmetric active multimode interferometer laser diode by using split pump configuration, Japanese Journal of Applied Physics, 10.7567/jjap.53.08mb09, 10.7567/jjap.55.08rd04_references_DOI_Tdkkh8ulZvCb0YVD8qOC3zLOGvM, 53, 8S2, 08MB09, 2014.07. |
| 66. |
武内翔太, 加藤 和利, 久武信太郎, 永妻忠夫, マッハ・ツェンダ型二光波間位相安定化による低雑音キャリア周波数生成, 電子情報通信学会論文誌C, vol. J97-C, 9, 273-274, 2014.06, 高周波キャリアを二光波のビート信号で生成する光学系をマッハ・ツェンダ干渉計として構成し，干渉光強度の安定化制御で高周波キャリアの位相安定化を行う方法を提案している．実験により10 Hz以下の位相ゆらぎが低減され本提案の有効性が確認された．. |
| 67. |
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 |
| 68. |
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. |
| 69. |
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.. |
| 70. |
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.. |
| 71. |
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.. |
| 72. |
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.. |
