| 摘要 |
PROBLEM TO BE SOLVED: To provide a light clock extraction circuit that stably generates a light clock pulse train whose frequency is 1/integer as high as the bit rate of a light signal pulse train. SOLUTION: A light signal pulse train of clock frequency f that contains a pre- multiplexed frequency component f/m is made to impinge on a semiconductor laser device 1 whose resonator is prescribed in length through the intermediary of an optical waveguide 62 connected to a ring-shaped optical waveguide 61 prescribed in length. The transmissivity of a waveguide is frequency-dependent and shows a minimum at a frequency interval f, so that a clock frequency f component of the light data pulse train is restrained, and an f/m component is effectively extracted. A forward current is injected into a gain region 101 by a DC current source, and a reverse bias voltage is applied to a saturable absorption region 102 from a DC voltage source, whereby the laser device 1 is put in a mode synchronous operation nearly on a f/m repetition frequency. When optical data transmitted through a optical waveguide 62 are made to impinge on the laser device 1, the absorption by the region 102 is effectively modulated by a frequency f/m, a mode synchronous frequency is brought over to a clock frequency f/m 1/integer as high as a light signal pulse train, and the laser device 1 outputs stable light clock pulses of repetition frequency f/m.
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