| 摘要 |
<p>An automatic frequency control system, for an optical coherent communication system, in which the frequency of local oscillation light 5 from coherent light communication receiver 100 are swept to pull the intermediate frequency at a stable AFC point. The AFC is caused to operate with an intermediate frequency in the AFC operation range, and interrupted. Subsequently while sweeping the frequency of local oscillation light 5 in a certain direction in a predetermined range, the output voltage of frequency discriminator 9 is monitored. Once the change of the output voltage of frequency discriminator 9 due to the sweep exceeds the predetermined threshold value, the AFC resumes for the pulling to a stable point. <IMAGE></p> |
