Ultrahigh-Speed Optical Communication Group

Group Web Site

[ Professor ]Toshihiko Hirooka
Ultrahigh-Speed Optical Communication

[ Associate Professor ] Keisuke Kasai

Research Activities

Optical communication systems have evolved as a core technology of the ICT infrastructure and become widely used in society. This widespread deployment has been enabled by the progress made on light sources, transmission media, and signal processing, and by taking advantage of their high-speed and broadband operation. In the future, further innovation is expected that will realize flexible communication links capable of accommodating massive increases in the amount of information at any time, and transmitting it anywhere, and between any devices. In this laboratory, we aim at establishing ultrahigh-speed, large-capacity, highly secure and resilient optical communication technologies that can even be integrated with wireless communication by taking ultimate advantage of the coherence of lightwaves. We also intend to develop functional optical systems capable of handling such transmissions with extremely high energy efficiency.

Optical Signal Processing (Assoc. Prof. Hirooka)

Research topics

  • Ultrahigh-speed and highly efficient optical transmission and signal processing
  • Digital coherent optical communication and its application to optical mobile fronthaul

In this group, we are engaged in research on ultrahigh-speed optical transmission using optical time division multiplexing with a single-channel Tbit/s-class capacity, digital coherent QAM optical transmission, and high-speed and spectrally efficient optical transmission by combining these two approaches. With a view to supporting innovative new ICT services such as 5G and IoT, our goal is also to apply digital coherent transmission to access networks and mobile fronthaul, and to develop novel transmission schemes integrating optical and wireless communications through an electromagnetic wave, and optical measurements and functionalities taking full advantage of coherence.

Experiment on ultrahigh-speed optical transmission

Lightwave Control System (Assoc. Prof. Kasai)

Research topics

  • Optical phase control techniques and their application to digital coherent optical communication
  • Frequency-stabilized lasers and their application to precise optical interferometric measurement systems

In this field, we are engaged in research on precise optical phase control technologies such as optical phase-locked loop and optical injection-locking, and digital coherent multilevel optical transmission system by employing these technologies. Furthermore, we are studying an absolute frequency-stabilized laser at 1.5 μm and its application to high precision optical interferometric measurement systems.

2048 QAM coherent optical signal (left) and cross section of 19-core fiber (right)