Research Institute of Electrical Communication Tohoku University


Masataka Nakazawa,Professor

Toshihiko Hirooka,Associate Professor

Masato Yoshida,Associate Professor

Keisuke Kasai,Assistant Professor

Yixin Wang,Research Fellow

Kodai Harako,Research Fellow

Hisao Kuroda,Research Fellow

(From left)K.Harako K.KASAI M.Yoshida M.Nakazawa T.Hirooka H.Kuroda Y.Wang


Research Activities

With the vast growth of traffic on the Internet from simple text data to high quality voice, image, and real-time video content, it has become increasingly important to realize an ultrafast, high-capacity network to support the daily needs of modern communications. Ultrahigh-speed optical communication is the key technology for building such an interconnected world. This laboratory aims to realize a global ultrahigh-speed optical network by engaging in research on ultrashort pulse generation and transmission. Our research areas include optical solitons, high-speed mode-locked lasers, optical signal processing, and the development of fibers with new functions.

Laboratory Web Page

ECEI Web Page

Optical Transmission (Prof. Nakazawa)

Ultrahigh-speed optical transmission is the driving force behind attempts to realize advanced high-speed networks that support ultrahigh-precision image transmission or ultra-realistic communication. At the same time, there is a strong need to realize spectrally efficient optical transmission to expand the transmission capacity for a given optical bandwidth. With a view to achieving an ultrahigh bit rate exceeding 1 Tbit/s/channel, we are actively engaged in realizing ultrafast optical time division multiplexed (OTDM) transmission using ultrashort pulse lasers. To expand the spectral density, we are working intensively on ultra-multi-level coherent QAM transmission technology in which the spectral efficiency is greatly improved by encoding the information in both the amplitude and phase of an optical beam. Another important aspect of our research relates to the development of multi-core fibers and their applications to ultrahigh-capacity space division multiplexing.

Research topics

  • Terabit/s OTDM transmission using a femto-second pulse train
  • Ultra-multi-level coherent optical transmission toward the Shannon limit
  • Multi-core fibers and optical fibers with new functionality

Optical Signal Processing (Assoc. Prof. Hirooka)

We are engaged in the development of all-optical technologies using nonlinear optical effects by taking advantage of ultrafast optical properties, where optical signals are processed without the need to convert them into the electrical domain. Specifically, we are developing femtosecond pulse compression, pulse shaping, optical demultiplexing, and distortion elimination techniques, which are indispensable for realizing ultrahigh-speed OTDM transmission exceeding terabit/s.

Research topics

  • Distortion elimination technique using time-domain optical Fourier transformation
  • All-optical signal processing using nonlinear optical effects and their application to ultra-high-speed OTDM transmission

High Accuracy Measurements using Optical Fibers(Assoc. Prof. Yoshida)

We are engaged in the development of frequency stabilized laser operated at 1.55 μm and its application to high accuracy measurements using optical fibers. Furthermore, we are developing ultra-short pulse lasers.

Research topics    

  • Frequency stabilized lasers and their application to high accuracy measurements using optical fibers
  • Ultrashort mode-locked lasers and their appli-cation to frequency standards and microwave-photonics

Experiment on ultrahigh-speed optical transmission
2048 QAM coherent optical signal (left)
and cross section of 19-core fiber (right)