| 摘要 |
PURPOSE:To make the absolute wavelength of a local oscillation light source and a transmission light source stable and to facilitate the wavelength setting by controlling the wavelength of the local oscillation light source while using the wavelength of a wavelength multiplex signal light as a reference and demultiplexing part of the local oscillation light so as to use it as a transmission signal light. CONSTITUTION:A wavelength control circuit 5 changes minutely a wavelength of a local oscillation light and locks a frequency of an intermediate frequency signal through a frequency discriminator. A pilot signal with a different oscillating frequency at 10MHz band is superimposed on each signal light for channel identification. The pilot signal is received by a channel identification circuit 7 to confirm whether or not a reception channel is finally a desired channel. When the channel differs from the desired channel, a wavelength error is detected to set a supplied current again. The control above is entirely implemented by using a microcomputer in the circuit 5. The transmission signal is used to branch part of the local oscillation light, the result is subject to intensity modulation by an external modulator 14 and sent to the station side. |
