A communication system includes a first multiplexer configured to multiplex a first optical line terminal signal having a first multiplexing group and a second optical line terminal signal having a second multiplexing group into a first multiplexed signal. The communication system includes a second multiplexer configured to demultiplex a second multiplexed signal into a third optical line terminal signal having the first multiplexing group and a fourth optical line terminal signal having the second multiplexing group. Moreover, the communication system includes a third multiplexer optically connected with the first multiplexer and the second multiplexer, the third multiplexer configured to multiplex/demultiplex between a feeder optical signal and the first and second multiplexed signals. The first and second optical line terminal signals include a legacy upstream free spectral range, and the third and fourth optical line terminal signals include a legacy downstream free spectral range.

Methods, systems, and apparatus, for an external cavity FP laser. In one aspect, an apparatus is provided that includes a FP laser diode; a Faraday rotator (FR) coupled to receive an optical output of the FP laser diode and that rotates a polarization of the optical output; an optical fiber coupled at a first end to receive the output of the FR; a WDM filter coupled to a second end of the optical fiber to receive the optical signal from the optical fiber; and a FRM coupled directly or indirectly to an output of the WDM filter, wherein an optical output of the WDM filter is partially reflected by the FRM such that the polarization of a reflected beam is rotated, and wherein the reflected optical signal then passes through the FR with its polarization being rotated by the FR before it is injected back into the FP laser diode.

The present application provides a wavelength configuration method for a multi-wavelength passive optical network, which includes: scanning, by an ONU, a downstream receiving wavelength, and receiving, downstream wavelength information of each downstream wavelength channel that is broadcast by an OLT separately through each downstream wavelength channel of a multi-wavelength PON system; establishing, by the ONU, a downstream receiving wavelength mapping table, where an entry of the downstream receiving wavelength mapping table includes downstream receiving wavelength information, drive current information of a downstream optical receiver and receiving optical physical parameter information of the ONU; selecting, by the ONU, one downstream wavelength from the downstream wavelength information broadcast by the OLT, and setting, according to the drive current information of the downstream optical receiver recorded in a related entry of the downstream receiving wavelength mapping table, an operating wavelength of the downstream optical receiver to the selected downstream wavelength.

A system and method for performing an in-service optical time domain reflectometry test, an in-service insertion loss test, and an in-service optical frequency domain reflectometry test using a same wavelength as the network communications for point-to-point or point-to-multipoint optical fiber networks while maintaining continuity of network communications are disclosed.

The invention provides a method and apparatus for downstream flow control in an (x)GPON system. First, ONU sends a DS_FlowControl_Request message to OLT, wherein the DS_FlowControl_Request message includes information of transmission inhibiting period and is used for requesting OLT to inhibit downstream transmission for a transmission inhibiting period corresponding to the information of transmission inhibiting period. After receiving the DS_FlowControl_Request message from ONU, OLT inhibits the downstream transmission for the transmission inhibiting period corresponding to the information of transmission inhibiting period based on the information of transmission inhibiting period included in the DS_FlowControl_Request message. After inhibiting the downstream transmission for the transmission inhibiting period corresponding to the information of transmission inhibiting period, OLT resumes the downstream transmission to ONU.

A system and method for performing an in-service optical time domain reflectometry test, an in-service insertion loss test, and an in-service optical frequency domain reflectometry test using a same wavelength as the network communications for point-to-point or point-to-multipoint optical fiber networks while maintaining continuity of network communications are disclosed.

A communication system includes a first multiplexer configured to multiplex a first optical line terminal signal having a first multiplexing group and a second optical line terminal signal having a second multiplexing group into a first multiplexed signal. The communication system includes a second multiplexer configured to demultiplex a second multiplexed signal into a third optical line terminal signal having the first multiplexing group and a fourth optical line terminal signal having the second multiplexing group. Moreover, the communication system includes a third multiplexer optically connected with the first multiplexer and the second multiplexer, the third multiplexer configured to multiplex/demultiplex between a feeder optical signal and the first and second multiplexed signals. The first and second optical line terminal signals include a legacy upstream free spectral range, and the third and fourth optical line terminal signals include a legacy downstream free spectral range.

The present application provides a wavelength configuration method for a multi-wavelength passive optical network, which includes: scanning, by an ONU, a downstream receiving wavelength, and receiving, downstream wavelength information of each downstream wavelength channel that is broadcast by an OLT separately through each downstream wavelength channel of a multi-wavelength PON system; establishing, by the ONU, a downstream receiving wavelength mapping table, where an entry of the downstream receiving wavelength mapping table includes downstream receiving wavelength information, drive current information of a downstream optical receiver and receiving optical physical parameter information of the ONU; selecting, by the ONU, one downstream wavelength from the downstream wavelength information broadcast by the OLT, and setting, according to the drive current information of the downstream optical receiver recorded in a related entry of the downstream receiving wavelength mapping table, an operating wavelength of the downstream optical receiver to the selected downstream wavelength.

An optical line terminal (OLT) in a time and wavelength division multiplexed (TWDM) passive optical network (PON). The OLT comprises a first optical port, a second optical port, and a processor. The first optical port is configured to couple to a plurality of optical network units (ONUs) via an optical distribution network (ODN). The second optical port is configured to couple to the ONUs via the ODN. The processor is coupled to the first optical port and the second optical port and is configured such that, responsive to receiving information indicating that the first optical port has experienced a greater power loss over time than the second optical port, the OLT assigns to the first optical port a first wavelength with a power greater than the power of a second wavelength assigned to the second optical port.

Methods, systems, and apparatus, for an external cavity FP laser. In one aspect, an apparatus is provided that includes a FP laser diode; a Faraday rotator (FR) coupled to receive an optical output of the FP laser diode and that rotates a polarization of the optical output; an optical fiber coupled at a first end to receive the output of the FR; a WDM filter coupled to a second end of the optical fiber to receive the optical signal from the optical fiber; and a FRM coupled directly or indirectly to an output of the WDM filter, wherein an optical output of the WDM filter is partially reflected by the FRM such that the polarization of a reflected beam is rotated, and wherein the reflected optical signal then passes through the FR with its polarization being rotated by the FR before it is injected back into the FP laser diode.