| 摘要 |
PURPOSE:To exactly select a channel by detecting an optical frequency of a selection channel corresponding to a transmitting side, and selecting the channel, based on this frequency as a reference. CONSTITUTION:An optical frequency corresponding to a channel 1 can be detected by a bias current 205 from a center frequency control circuit 11. In this state, a control current 203 corresponding to an optical frequency corresponding to a desired channel, in this case, a channel 4 is derived by a channel designating device 13. An optical frequency difference of the desired channel 4 and the present selection channel 1 is obtained by the product of a channel interval DELTAf of a known equal interval and a channel number difference 3. Subsequently, by changing an optical frequency of a local oscillation use light source 6 to a target optical frequency, the channel selection is completed. In such a way, even if a fluctuation is generated between the transmitting optical frequency and the local oscillation optical frequency, the channel selection can be executed without causing a malfunction. |
