Abstract: We disclose embodiments of a WDM transmitter having an in-band OTDR capability for at least a subset of the WDM channels thereof. In an example embodiment, an OTDR-enabled WDM channel of the WDM transmitter is implemented using an optical transceiver that comprises an optical transmitter and a coherent optical receiver. The optical transmitter is configured to generate a modulated optical signal by modulating a respective carrier wavelength, transmit the modulated optical signal through an optical link as a component of the corresponding WDM signal, and provide the respective carrier wavelength to the coherent optical receiver for being used therein as an optical local oscillator. The optical receiver is configured to estimate an impulse response of the optical link by coherently detecting and processing a return optical signal produced within the optical link due to distributed reflection and/or backscattering of the modulated optical signal.

Abstract: We disclose embodiments of a WDM transmitter having an in-band OTDR capability for at least a subset of the WDM channels thereof. In an example embodiment, an OTDR-enabled WDM channel of the WDM transmitter is implemented using an optical transceiver that comprises an optical transmitter and a coherent optical receiver. The optical transmitter is configured to generate a modulated optical signal by modulating a respective carrier wavelength, transmit the modulated optical signal through an optical link as a component of the corresponding WDM signal, and provide the respective carrier wavelength to the coherent optical receiver for being used therein as an optical local oscillator. The optical receiver is configured to estimate an impulse response of the optical link by coherently detecting and processing a return optical signal produced within the optical link due to distributed reflection and/or backscattering of the modulated optical signal.

Abstract: An apparatus and method for deriving fiber characteristics between two nodes in an optical communication network are disclosed. A roundtrip time for a signal to travel between two nodes is measured by sending the signal via the optical supervisory channel from a first node to a second node, which is configured for loopback operation. Fiber characteristics can be calculated based on the measured roundtrip time.

Abstract: A switching method is provided having improved accuracy in monitoring a network to determine when to switch. The method collects and stores a plurality of bit error rate (BER) values. The BER values are analyzed using a BER hysterisis algorithm to check BER degradation. Thereafter, the method switches a transmission port when the degradation exceeds a predetermined BER threshold level for a predetermined period of time. In another embodiment, a feature which transmits a switch polling signal for a predetermined duration is used with the above switching method.

Abstract: A method and system for maximizing wavelength reuse in an optically protected wavelength-division-multiplexed (WDM) network, the WDM network supporting a plurality of service connections, includes associating service connections supported by non-overlapping paths to form respective service channel groups, and for each service channel group, assigning at least one common wavelength channel for establishing the service connections. In addition, for each of said groups, at least one common wavelength channel is assigned for establishing a shared protection path for the service connections of each of said groups. In addition, the wavelength channels assigned for establishing the shared protection paths for each of the groups may be used for providing service connections for the WDM network when not in use as shared protection paths. However such provisional service connections are dropped when the wavelength channels are needed to establish shared protection paths.

Abstract: An apparatus and method for deriving fiber characteristics between two nodes in an optical communication network are disclosed. A roundtrip time for a signal to travel between two nodes is measured by sending the signal via the optical supervisory channel from a first node to a second node, which is configured for loopback operation. Fiber characteristics can be calculated based on the measured roundtrip time.

Abstract: A switching method is provided having improved accuracy in monitoring a network to determine when to switch. The method collects and stores a plurality of bit error rate (BER) values. The BER values are analyzed using a BER hysterisis algorithm to check BER degradation. Thereafter, the method switches a transmission port when the degradation exceeds a predetermined BER threshold level for a predetermined period of time. In another embodiment, a feature which transmits a switch polling signal for a predetermined duration is used with the above switching method.