The invention relates to a method for establishing a communication channel, preferably an embedded control channel, between a central network node and at least one network unit to be integrated in a communication network including the central network node and an arbitrary but limited number of network units. The central network node is adapted to create and output a wavelength-division multiplex (WDM) downstream signal including downstream channel signals to be transmitted to the network units and to receive a WDM upstream signal including upstream channel signals created by the network units.

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.

An ONU communicates with an OLT that can transmit optical signals having different wavelengths simultaneously and receive optical signals having different wavelengths simultaneously. The ONU includes: an optical transceiver that receives any one of the optical signals that the OLT can transmit and transmits any one of the optical signals that the OLT can receive; a communication failure detection unit that detects a communication failure between the OLT and the ONU; and a wavelength selection unit that, when the communication failure detection unit detects a communication failure, changes a setting of a downstream wavelength to be received by the optical transceiver and an upstream wavelength to be transmitted by the optical transceiver.

An approach to proving a flexible grid architecture for time and wavelength division multiplexed passive optical networks is described. One embodiment includes an optical transmitter array configured to transmit an optical signal, an optical combiner coupled to the optical transmitter array configured to receive unlocked wavelengths from the optical transmitter array and output a single optical signal, and an optical amplifier coupled to the optical combiner configured to boost downstream optical power. In some embodiments, a WDM filter is coupled to the optical amplifier, and a tunable optical network unit (ONU) coupled to the WDM filter is configured to transmit and receive the optical signals. In still other embodiments, a cyclic demultiplexer is coupled to the optical splitter and connects to an optical receiver array configured to receive optical signals.

An optical add/drop multiplexer branching apparatus is provided in the embodiments of the present invention, where the optical add/drop multiplexer branching unit includes: a trunk input end, a branch input end, a trunk output end, a branch output end, an optical add/drop multiplexer, a first coupler, a first detection circuit, and a control circuit, where the optical add/drop multiplexer includes an optical switch. A detection circuit detects whether a fault occurs in a trunk, and in a case in which a fault occurs in the trunk, a working mode is switched from a first working mode to a second working mode, to implement automatic redundancy on the trunk and ensure normal communication on a branch.

An assembly of waveguide wavelength multiplexers and demultiplexers, together with continuous wave (CW) laser transmitters that interface to grating couplers on a silicon photonics chip, providing CW sources, multiplexed output and optionally multiplexed input, all using a single photonic lightwave circuit (PLC).

An optical transmission apparatus includes: a plurality of optical transmitters configured to transmit optical signals having variable wavelengths, respectively; a multiplexer configured to wavelength-multiplex the optical signals transmitted from the plurality of optical transmitters in a transmission band of an optical device through which the optical signals is transmitted; and a controller configured to control, in response to nonexistence of an optical signal having a second wavelength adjacent to a first wavelength closest to an outer edge of the transmission band in the optical signals, an optical transmitter corresponding to the first wavelength so as to shift the first wavelength in a direction toward the second wavelength.

A network device in a RPR network receives a RPR flooding data packet sent by another network device in the RPR network, determines whether a next-hop network device of the RPR flooding data packet is a source network device sending the RPR flooding data packet, and strips the RPR flooding data packet when determining that the next-hop network device of the RPR flooding data packet is the source network device sending the RPR flooding data packet.

A wavelength selective switch includes: N input ports, an input-side fiber array, an input-side collimator array, an input-side beam deformation and polarization conversion component, an input-side wave-demultiplexing component, an input-side switching engine, a focusing transformation lens group, an output-side switching engine, an output-side wave-combining component, an output-side beam deformation and polarization conversion component, an output-side collimator array, an output-side fiber array, and M output ports. The focusing transformation lens group includes two identical aspheric convex lenses that are placed in parallel, where a curvature from a center to an edge of a surface of the aspheric convex lens changes continuously. A spatial position of the focusing transformation lens group and the curvature from the center to the edge of the surface are so set that light with different wavelengths from the input-side switching engine is focused to a corresponding position of the output-side switching engine respectively.

A PON system comprising multiple PONs, each having a respective intelligent splitter monitor (ISM). In addition to having a passive optical splitter therein, an ISM also has several remotely powered active components configured to monitor the presence of uplink light signals on the ports of the splitter and communicate with the central office using out-of-band optical signals. These ISM functionalities enable the network operator, e.g., to automatically map PON connectivity, pairing each port on the splitter with a distinct optical network unit. The PON system further comprises an optical module connected to the multiple PONs through an optical switch in a manner that supports shared access to said module by the corresponding multiple ISMs. In an example embodiment, the optical module comprises an optical transceiver capable of communicating with the ISM transceivers and one or more lasers configured to provide high-intensity light for remotely charging the ISM batteries.