1988 Fiscal Year Final Research Report Summary
Devices for Transmitter, Wave-Propagation, and Receiver in Coherent Optical Communication Systems
| Project/Area Number |
61420031
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
電子機器工学
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| Research Institution | University of Tokyo |
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Principal Investigator |
KIKUCHI Kazuro Associate Professor, Faculty of Engineering, University of Tokyo, 工学部, 助教授 (50134458)
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| Co-Investigator(Kenkyū-buntansha) |
HOTATE Kazuo Associate Professor, Research Center for Avdanced Science and Technology, Univer, 先端科学技術研究センター, 助教授 (60126159)
OKOSHI Takanori Professor, Research Center for Avdanced Science and Technology University of Tok, 先端科学技術研究センター, 教授 (70010709)
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| Project Period (FY) |
1986 – 1988
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| Keywords | Coherent Optical Communication / Semiconductor Laser / 光ファイバ |
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| Research Abstract |
The improvement of the spectral purity of the sdignal laser and the local laser is a crucial step to realize practical coherent optical communication systems. The effect of the 1/f noise on the spectral spread of semiconductor lasers is investigated, and the results are given in the following: In the high power limit, the narrowest linewidth is determined from the 1/f noise. Since the 1/f noise is harmless in the high bit-rate system, it is most important to achieve the high power state keeping a high longitudinal mode stability.
The frequency modulation is also a key technology in coherent optical communication systems. We show that DFB lasers haveing the separated-electrode structure are suitable for frequency modulation.
We develop two methods for analyzing polarization maintaining optical fibers with the asymmetrical refractive-index distribution: One is based upon the finite-element method, and the other the boundary-integral method. Both are used for the design of new refractive-index distributions.
We propose two countermeasures to cope with the polarization fluctuation of the transmitted signal. One is the polarization recombining scheme, and the other is the polarization diversity scheme. The latter is especially useful in practical systems, because the power penalty is less than 0.5dB and the phase diversity can be implemented in the same receiver.
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