The disclosure provides a method and apparatus for adjusting wavelength for an Optical Line Terminal/Optical Network Unit (OLT/ONU). The method for adjusting wavelength for an OLT includes that: a source OLT sends an adjustment notification message to a target OLT, wherein the adjustment notification message is used for indicating that an ONU is to be adjusted into a Time-Wavelength Division Multiplexing Channel (TWDM CH) of the target OLT; and the source OLT receives an adjustment acknowledgement message provided by the target OLT, wherein the adjustment acknowledgement message is used for indicating that an adjustment process of the ONU has been completed. By means of the technical solution provided in the disclosure, an ONU of a source OLT can still work normally after being switched to a channel of a target OLT, thereby achieving the effect that the continuity of a service between the OLT and the ONU may be maintained.

Systems and methods for routing wavelengths in an optical network include responsive to a path request for a wavelength or group of wavelengths, determining a path through the optical network; determining a location on the path where wavelength blocking should occur to form a loop-free path in the optical network; and setting the wavelength blocking at the location. The optical network can utilize a broadcast and select architecture and the wavelength blocking is configured to prevent the wavelength or group of wavelengths from looping back on a port where the wavelength or group of wavelengths has already been received on. The optical network can utilize an all-broadcast architecture and the wavelength blocking is configured to prevent multiple paths for the wavelength or group of wavelengths by constraining the wavelength or group of wavelengths to a single path through the optical network.

A system for transmitting a message from a source entity to a target entity, the system including an input unit connected to the source entity in order to transmit the message via an optical transmission device to an output unit re-directing the message to the target entity. The optical transmission device is configured to transmit the message unidirectionally from the input unit to the output unit; and duplicate an optical input system containing the message into at least two optical output signals each containing the message to be transmitted to the output unit.

It is disclosed a remote node connectable to multiple feeder fibers from one or more central offices, COs, of a wavelength division multiplexing-based passive optical network, WDM-based PON. The remote node comprises one or more splitters each configured to receive a monitoring signal on a connected feeder fiber and to split the monitoring signal into split monitoring signals, wherein the monitoring signal uses one wavelength at a time out of a group of different wavelengths, and an arrayed waveguide grating, AWG, with output ports connectable to drop fibers. The AWG is configured to route the split monitoring signals to output ports of said AWG based on a currently used wavelength of said group of different wavelengths, for supervising drop fibers connected to the output ports. Also, a method for a remote node in the WDM-based PON, of routing a monitoring signal, is disclosed.

Embodiments of this disclosure provide a communication method and device. In the disclosure, when the first device and the second device in the Point-to-Multipoint network communicate with each other, if there is a first channel in inactive state between the two devices, which is active between the second device and the third device, and there is a second channel in inactive state between the second device and the third device, the second channel will be adopted to transmit the signal on the first channel, and then the state of the first channel will be changed to inactive state. After that, the state of the first channel between the first device and the second device will be changed to active state.

Systems and methods for providing communication between an access point and a HUB of a point-to-multipoint optical network are disclosed. The method includes causing the access point to determine a communication wavelength of the HUB, causing the access point to determine, using information on a control channel centered at the communication wavelength, whether the HUB has an amount of available resources allocable within a plurality of data sub-carries to the access point and, in response to identifying the available resources, establishing a bidirectional communication between the access point and the HUB.

A bi-directional optical controller includes an upstream optical interface, a downstream optical interface, and an optical circuit coupling the interfaces such that optical signals received at either interface is routed to the other interface. The optical circuit is adapted to allow, for example, enable or disable, a first set of prespecified optical services to be provided in at least one of the upstream or downstream direction on an optical signal received at the respective downstream or upstream interface.