Patent ID: 8543004

Claim:
A wavelength locking method for causing a narrow-band wavelength spectrum of an optical transmit signal of an optical transceiver device to track a narrow-band wavelength spectrum of an optical receive signal received by the optical transceiver device, the method comprising the steps of: (a) (i) monitoring the optical power of the optical receive signal (S RX ) filtered by a tunable optical narrow-band filter ( 5 , 5 ′) having at least one narrow filter band and (ii) tuning the tunable optical narrow-band filter ( 5 , 5 ′) with respect to the spectral position of the narrow filter band, which is applied to the receive signal (S RX ), such that the monitored optical power of the filtered optical receive signal (S RX,f ) reaches a maximum value; and (b) simultaneously, or after finishing step (a), (i) monitoring the optical power of the optical transmit signal (S TX ) filtered by said tunable optical narrow-band filter ( 5 , 5 ′) and (ii) tuning the spectral position of the wavelength spectrum of the optical transmit signal (S TX ) with respect to the spectral position of a predetermined one of the at least one narrow filter bands, which is applied to the transmit signal (S TX ), such that the monitored optical power of the filtered optical transmit signal (S TX,f ) reaches a maximum value.