| 摘要 |
PROBLEM TO BE SOLVED: To reduce cross talk and facilitate switching superior in SN ratio by giving light pulses of appropriate power also to the pulses not supjected to separation by a control pulse pattern generating circuit. SOLUTION: The control pulses which are emitted form a control pulse light source 7 with a repeat frequency corresponding to N channels and have wavelengths different from that of the signal light are branched into N branches by a 1×N branch circuit 9 to be made incident on each light delay line 10. The relative time delay corresponding to the channel interval exists between the light delay lines 10 and the control pulse passing through the jth pass becomes the control pulse for the jth channel. The light on each pass is set at an appropriate peak power by each variable attenuator 11, merged by a N×1 coupler 12, and then inputted to an optical loop 3 through a wave synthesizer 4. When the first channel pulse is extracted, the control pulse for the channel adjusts the variable attenuator 11 so that the two bi-directional light in the optical loop 3 generates a phase difference ofπ.
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