Abstract: In one aspect, the present invention embraces 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 Further, the present invention embraces a wavelength lockable optical transceiver device, especially for a passive optical transmission network, using this wavelength locking method.

Abstract: The present invention embraces an optical wavelength division multiplex (WDM) transmission system, especially a WDM passive optical network, typically including a central node having a first and a second WDM port and a remote node having a first and a second WDM port and a plurality of channel ports, the central node first WDM port being connected to the remote node first WDM port via a bidirectional single-fiber optical working path and the central node second WDM port being connected to the remote node second WDM port via a single-fiber bidirectional optical protection path, and a group of basic optical node units (ONU's) each of which is connected to a respective remote node channel port via a bidirectional optical ONU path, each ONU including an optical receiver for receiving a downstream optical channel signal and an optical tunable transmitter for creating an upstream channel signal.