A protection method wherein an ONU switches a reception wavelength to a backup wavelength so as to be logically connected to a backup OSU designated in advance for each ONU when the ONU detects a failure in an OSU to which the ONU is originally assigned, while the ONU keeps on holding its own connection information with the OLT. In the OLT, a backup OSU for the ONU which is originally assigned to the failed OSU is notified of the information on the ONU when the OLT detects a failure in an OSU. In this way, the ONUs which are originally assigned to the failed OSU resumes communication in a short period.

A method for assigning spectral resources comprises assigning spectral resources for a plurality of communication channels. The spectral resources for the plurality of communication channels comprise excess resources that are at least tentatively kept unoccupied. The excess resources of a plurality of communication channels are assigned to be spectrally contiguous.

Provided is an optical communication device including: a first channel card configured to convert an input first signal into a first optical signal and output the first optical signal to any one of a first MUX/DEMUX connected to a first optical line and a second MUX/DEMUX connected to a second optical line; a second channel card configured to convert an input second signal into a second optical signal and output the second optical signal to any one of the first MUX/DEMUX and the second MUX/DEMUX; and a controller configured to monitor states of the first optical line and the second optical line to determine a MUX/DEMUX from which the first optical signal and the second optical signal are respectively output, from among the first MUX/DEMUX and the second MUX/DEMUX.

A terminal node, an optical network and/or a method are described in which a first processor of a first optical protection switching module having a first optical switch, and a second processor of a second optical protection switching module having a second optical switch coordinate switching of the first optical switch and the second optical switch upon detection of a first failure by the first processor, or the detection of a second failure by the second processor. The first processor monitors optical signals received by a first line port to determine a first failure in a first working path at a first layer (e.g., physical layer) within an optical communication model. The second processor monitors the optical signals received by another line port to determine a second failure in the first working path at a second layer (e.g., optical layer) within the optical communication model.

Provided is an optical communication device including: a first channel card configured to convert an input first signal into a first optical signal and output the first optical signal to any one of a first MUX/DEMUX connected to a first optical line and a second MUX/DEMUX connected to a second optical line; a second channel card configured to convert an input second signal into a second optical signal and output the second optical signal to any one of the first MUX/DEMUX and the second MUX/DEMUX; and a controller configured to monitor states of the first optical line and the second optical line to determine a MUX/DEMUX from which the first optical signal and the second optical signal are respectively output, from among the first MUX/DEMUX and the second MUX/DEMUX.

A terminal node, an optical network and/or a method are described in which a first processor of a first optical protection switching module having a first optical switch, and a second processor of a second optical protection switching module having a second optical switch coordinate switching of the first optical switch and the second optical switch upon detection of a first failure by the first processor, or the detection of a second failure by the second processor. The first processor monitors optical signals received by a first line port to determine a first failure in a first working path at a first layer (e.g., physical layer) within an optical communication model. The second processor monitors the optical signals received by another line port to determine a second failure in the first working path at a second layer (e.g., optical layer) within the optical communication model.

A regen node is described. The regen node includes a coherent receiver, a control module and a coherent transmitter. The coherent receiver has circuitry to convert a first optical signal received from an upstream node in an optical layer of an optical network to a first digital data stream in a digital layer having a first FEC frame and a data traffic. The control module extracts a first fault signal from the first FEC frame; generates a second fault signal based at least in part on the first fault signal; and encodes the second fault signal within a second FEC frame with the data traffic into a second digital data stream on the digital layer. The coherent transmitter has circuitry to convert the second digital data stream into a second optical signal on the optical layer and to transmit the second optical signal to a downstream node.

Disclosed herein are switch devices in terminal ends of a network and methods of using same. One embodiment relates to a terminal end of a network including a terminal end transceiver configured to communicate with one or more end user devices, and a switch device configured to automatically route communication at the terminal end transceiver between a primary communication path with a central office and an auxiliary communication path with the central office. Another embodiment relates to a method of switching between primary and auxiliary communication paths at a terminal end. Automatic switching is particularly applicable in a looped communication architecture with redundant communication paths for preventing interruption and increasing reliability for an improved user experience. Another embodiment relates to indexing with splices to reduce connections in a communication path and increase signal quality.

Embodiments disclosed herein provide a hybrid fiber-copper access network in which a main OLT sends data to the DSLAMs via a plurality of point-to-point optical fiber connections. A standby OLT is provided which has a plurality of point-to-multi-point optical fiber connections to the DSLAMs. In the event of a failure, data can be sent to some of the DSLAMs via the standby OLT and the point-to-multi-point optical fiber connections. Following the rectification of the fault, the network can revert to its normal state and transmit data to the DSLAMs via the main OLT and the plurality of point-to-point optical fiber connections.

An optical end terminal in which protection switching is implemented by using (i) the optical data receiver thereof for detecting a path failure and (ii) the optical data transmitter thereof for signaling the detected path failure to the protection-switching circuit. In an example embodiment, the optical data receiver is configured to detect a path failure based on the presence of certain data-recovery errors. The optical data transmitter is operatively connected to the optical data receiver and configured to generate an in-band dither tone of a predetermined frequency in response to such failure detection. The protection-switching circuit is configured to (i) detect dither tones in the optical signals passing therethrough and (ii) connect the optical data receiver to the protection path instead of the working path in response to detecting the dither tone of the predetermined frequency.