| 摘要 |
PROBLEM TO BE SOLVED: To stabilize the polarized state of an output light pulse train caused by restraining the change of the polarized state occurring when a light pulse circulates in an optical ring circuit by making propagated light pass between a light frequency shifter and a Faraday polarized wave rotating element while moving it back and forth in an optical path. SOLUTION: An FRMa 13 and an FRMb 14 consisting of the Faraday polarized wave rotating element and a mirror accurately rotate the plane of polarization of the light pulse by 90 deg.. The light pulse is frequency-shifted byΔf by means of the light frequency shifter 21, reflected after its polarized state is rotated by 90 deg. in the FRMb 14, and frequency-shifted by the shifter 21 again, then propagated toward a coupler 5. Then, it is moved back and forth in the optical resonator. An optical switch for segmenting a pulse 10 and an optical switch 20 are synchronously controlled by a synchronous control circuit 25 in order to attain periodic actions. As a result, the light pulse train frequency- shifted by 2Δf is periodically obtained from the output port 15 of the coupler 5.
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