Patent ID: 7899337

Claim:
An optical transmitter applied to a WDM system that transmits a number of optical signals each having a signal wavelength different from each other, the transmitter comprising: a semiconductor laser diode for outputting the optical signal; an auto-power-control circuit for adjusting a magnitude of the optical signal to a target value; and a control unit having a reference table to hold a plurality of references, the control unit being configured to receive a command to stop the output of the optical signal when the optical transmitter is in an operating mode or to start the output of the optical signal when the optical transmitter is in a hold mold, and to sequentially set, synchronizing with the reception of the command, one of references read from the table in the auto-power-control circuit as the target value, wherein the magnitude of the optical signal output from the laser diode gradually in decreases step wise when the command is to stop the output of the optical signal or gradually increases in step wise when the command is to start the output of the optical signal.