HOME > Organization / Research > Hirooka Laboratory

Organization / Research

Hirooka Laboratory


photo Toshihiko HIROOKA Associate Professor
Keisuke KASAI, Associate Professor

Fig.1: Experiment on ultrahigh-speed optical transmission

Fig.2: Photonic crystal fiber
(Upper photo:cleaved end face of a PCF, Lower photo:enlarged cross section)

With the vast growth of traffic on the Internet from simple text data to high quality voice, images, and real-time video, it has become increasingly important to realize a high-capacity and high-speed 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 achieve a global ultrahigh-speed optical network in the 21 century by engaging in the research of ultrashort pulse generation and transmission. The research areas include optical solitons, high-speed mode-locked lasers, optical signal processing, and the development of fibers with new functions.

For soliton transmission, we have shown that with the adoption of dispersion management in an optical fiber transmission line, the dispersion tolerance and power margin of a soliton system can be greatly increased in comparison to conventional systems. In the next phase of this work, it is important to increase the bit rate of a single channel to greater than 100 Gbit/s and to apply solitons to high-speed optical signal processing.

We are also actively engaged in work on femtosecond pulse generation and its application to ultrahigh-speed optical time division multiplexed (OTDM) transmission. We have recently generated a 40 GHz-100 fs pulse train with the use of an adiabatic soliton compression technique. We also started to develop a new transmission technique which employs the optical Fourier transformation in the time domain. In addition, we are developing a new frequency standard by stabilizing the mode-locked laser so that it has a highly controlled longitudinal mode separation. This technique is also applicable to the microwave-photonics area. Another important area of our research is in the development of photonic crystal fibers. These special fibers have many air holes in the fiber cross-section, and they have potential applications for new optical communication systems operating in the currently unused 500-1000 nm band.

Research topics:

  1. Ultrahigh-speed optical soliton transmission and nonlinear optics in optical fibers
  2. Terabit/s OTDM transmission using femtosecond pulse train
  3. Ultrashort mode-locked lasers and their application to frequency standard and microwave-photonics area
  4. Photonic crystal fibers and optical fibers with new functionality
Group of Electrical Engineering, Communication Engineering,
Electronic Engineering, and Information Engineering, Tohoku University
6-6-05, Aramaki Aza Aoba, Aoba-ku, Sendai, Miyagi 980-8579, Japan
TEL : 022-795-7186 (Japanese Only)
Email :