Department of Electrical and Electronic Engineering, Ritsumeikan University, Japan

Biography: Koichi Takiguchi was born in Ibaraki, Japan. He received the B.S. degree in electronic engineering, and M.S. and Ph.D. degrees in electrical engineering, all from the University of Tokyo, Tokyo, Japan, in 1987, 1989, and 1992, respectively. His graduation thesis and dissertation were in a GaAs/AlGaAs distributed feedback (DFB) semiconductor laser and a resonator-type fiber-optic gyroscope (RFOG), respectively.
He joined NTT Laboratories in 1992, where he engaged in the research and development of integrated-optic (silica waveguide technology-based) functional devices including the first tunable optical chromatic dispersion compensator and optical OFDM demultiplexer. From 1998 to 1999, he stayed at University of California at Santa Barbara (UCSB), USA, as a visiting scholar, where he engaged in semiconductor-based photonic functional devices.
In 2012, he joined Department of Electrical and Electronic Engineering, Ritsumeikan University, Japan, as a professor. He is now interested in optical signal processing technology and their applications to next generation optical and THz-wireless communication, and optical and THz-wave sensing systems.
Dr. Takiguchi is a member of IEEE, OSA, the Institute of Electronics, Information, and Communication Engineers (IEICE) of Japan, and the Japan Society of Applied Physics (JSAP). He serves on an associate editor of IEEE Photonics Technology Letters (PTL).

Speech Title: Tunable optical OFDM sub-carrier channel demultiplexer utilizing time lens-based optical Fourier transform

Abstract: Optical orthogonal frequency division multiplexing (OFDM) is attractive because of its high spectral efficiency. Optical OFDM is applicable for adaptive optical networks as well as point-to-point transmission. In these advanced networks, the minimal bands are adaptively and flexibly allocated corresponding to the traffic and transmission distance in order to save the network resources. In this talk, I report on our tunable OFDM sub-carrier demultiplexer based on time lens-based optical Fourier transform [1], [2], which has the possibility of contributing to the oncoming adaptive optical networks. The optical Fourier transform is indispensable for demultiplexing the optical OFDM sub-carriers in the optical-domain [3].
Our tunable OFDM demultiplexer is composed of a LiNbO3 phase modulator and a fiber Bragg grating-type tunable chromatic dispersion compensator [1], [2]. As the phase shift of the modulator and chromatic dispersion can almost continuously be tuned, the demultiplexer can be applicable to flexible processing of an OFDM signal with wide capacity range. In addition, the combination of the phase modulator and tunable dispersion compensator is adequate for the future integration of the demultiplexer. In this talk, after explaining the configuration and operating principle of our tunable OFDM demultiplexer in detail, I report on the design of some operating parameters and preliminary experimental results to show the effectiveness of the demultiplexer. In addition, I touch our other type of (integrated-photonic) tunable OFDM sub-carrier demultiplexer whose main component is a slab star coupler-type optical Fourier transform circuit [4]-[6].
This work was partly supported by JSPS KAKENHI Grant No. 16H04369 and No. 19H02144.

[1] K. Takiguchi et al., in Proc. OSA Advanced Photonics 2016, SpM3E.3, Vancouver, Canada.
[2] K. Takiguchi et al., IEICE Trans. Electron., E101-C, 112, 2018.
[3] K. Takiguchi et al., OSA Opt. Lett., 36, 1140, 2011.
[4] K. Takiguchi, in Proc. ECOC 2016, W.4.P1.SC2.19, Dusseldorf, Germany.
[5] K. Takiguchi et al., in Proc. OFC 2019, Tu2J.1, San Diego, USA.
[6] K. Takiguchi et al., submitted to IEEE Photonics Technol. Lett.

Keywords: optical OFDM, optical Fourier transform, tunable demultiplexer, time lens method