I proposed a new optical pulse called the Nyquist pulse, which enables ultrahigh-speed coherent transmission with high spectral efficiency. This research was adopted as a Grant-in-Aid for Specially Promoted Research (KAKENHI) and has made significant progress worldwide. I also proposed a laser that generates a Nyquist pulse and later demonstrated that arbitrary optical pulses can be generated from a mode-locked laser by generalizing the Nyquist laser . I also succeefully demonstrated long-distance, high-speed and large-capacity QAM/QNSC cipher transmission which has been difficult to achieve with other previous schemes by taking advantage of the quantum noise.
I am working on application of digital coherent transmission and our proposed full-coherent transmission to mobile fronthaul. In particular, full-coherent transmission has been attracting attention as a promising technology for 6G because it enables high-speed system with high reliability and low cost. I also demonstrate the importance of Guided Acoustic-Wave Brillouin Scattering (GAWBS) noise as a new problem in coherent transmission, and show that compensation for this noise is important for long-distance transmission.
I have developed a frequency-stabilized fiber laser whose frequency is locked to the absorption line of acetylene molecules at a wavelength of 1.5 μm. As an application of this laser, I have developed a new gravity accelerometer with the Earthquake Research Institute of the University of Tokyo, and have been collaborating with JAMSTIC on crustal strain and tsunami measurements using optical fiber interferometry.
M. Nakazawa, T. Hirooka, P. Ruan, and P. Guan, "Ultrahigh-speed “orthogonal” TDM transmission with an optical Nyquist pulse train," Opt. Express vol. 20, no. 2. pp. 1129-1140, Jan. (2012).
M. Nakazawa, M. Yoshida, T. Hirooka, and K. Kasai, "QAM quantum stream cipher using digital coherent optical transmission," Opt. Express vol. 22, no. 4, pp. 4098-4107, February (2014).
M. Yoshida, T. Kan, K. Kasai, T. Hirooka, K. Iwatsuki, and M. Nakazawa, “10 channel WDM 80 Gbit/s/ch, 256 QAM bi-directional coherent transmission for a high capacity next-generation mobile fronthaul,” J. Lightwave Technol., vol. 39, no. 5, pp. 1289-1295, March (2021).
M. Nakazawa, M. Yoshida, M. Terayama, S. Okamoto, K. Kasai, and T. Hirooka, "Observation of guided acoustic-wave Brillouin scattering noise and its compensation in digital coherent optical fiber transmission," Opt. Express vol. 26, no. 7, pp. 9165-9181, April (2018).
M. Nakazawa, M. Yoshida, and K. Kasai, "Diastrophism and tsunami measurement using optical fiber network," Optical and Electro-Optical Engineering Contact, vol. 54, no. 12, pp. 22-31 (2016).
On April 1, 2023, Dr. Masataka Nakazawa was awarded the prominent title of "Distinguished Professor Emeritus of Tohoku University.