| Co-Investigator(Kenkyū-buntansha) |
HIROSE Akira The University of Tokyo, RCAST, Lecturer, 先端科学技術研究センター, 講師 (70199115)
HOTATE Kazuo The University of Tokyo, RCAST, Associate Professor, 先端科学技術研究センター, 助教授 (60126159)
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| Research Abstract |
We have studied double-stage phase-diversity (DSPD) scheme for coherent optical fiber communications co-invented by the head investigator and Mr. S. Yamashita. Establishment of its fundamental techniques and development of its application to optical communications systems are the main purposes of this project.
For the establishment of its fundamental techniques, we have constructed an experimental setup and measured bit-error-rate. Nearly same sensitivities have been obtained in DSPD and heterodyne scheme. Sensitivity degradation by optical circuit imbalance has been studied both theoretically and experimentally, and it was found that the imbalance does not affect the sensitivity severely. Its application to frequency domain multiplex systems. has also been studied, and it has been shown that this is suitable to such systems.
We have studied its application to ultra-long haul systems with optical fiber amplifiers, and found that it has excellent noise performance in such systems. Besides
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, the noise performance of optical fiber amplifier itself have been calculated and measured ; it has been shown that the backward ASE degrades its noise characteristics.
As an group-delay equalizer to be inserted in the intermediate-frequency stage of a DSPD receiver, the shape of microstrip line have successfully been optimized to compensate the fiber chromatic dispersion almost ideally. The results of simulation has indicated the possibility of long-distance transmission over 10, 000km.
The transmission distance in DSPD scheme is thus limited by stimulated Brillouin scattering (SBS) in optical fiber. NVe have proposed two schemes for SBS suppression ; one using optical spread-spectrum and the other using optical isolators, and studied these theoretically and experimentally.
We have also studied the optical devices and systems which are indispensable in the DSPD scheme, and the techniques for measurement and maintenance of these.
As described above, fruitful results have been obtained on each subject of this project. Less
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