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.

Embodiments of the present disclosure provide a passive optical network communications method and apparatus, and a system. The method includes: determining a wavelength channel group of an optical network unit (ONU) and a wavelength channel in the wavelength channel group; and sending a first message to the ONU, where the first message carries identification information of the wavelength channel group and identification information of the wavelength channel in the wavelength channel group. In the embodiments of the present disclosure, such a logical channel group as a wavelength channel group is established, and when a channel in a channel group is faulty, a scheduling module of an OLT can rapidly and easily reallocate a service to another member in the channel group, so that channel interaction is avoided. Therefore, bandwidth scheduling efficiency and bandwidth utilization of a PON system are higher.

A system for delivering multiple passive optical network services is disclosed. The system includes a first optical transmission service comprising a common wavelength pair routed from a source to each of a plurality of subscribers. The system further includes a second optical transmission service comprising a plurality of unique wavelength pairs, where each of the unique wavelength pairs is routed from the source to a subscriber among the plurality of subscribers. The system delivers the first optical transmission service and the second optical transmission service to the subscriber on a single optical fiber.

Embodiments of the disclosure relate to wireless distribution systems (WDSs) employing an optical star communications architecture based on quad small form-factor pluggable (QSFP) coarse wavelength division multiplexing (CWDM) transceivers. In one aspect, a selected QSFP CWDM transceiver among one or more QSFP CWDM transceivers wavelength multiplexes a plurality of downlink optical communications signals to generate a WDM downlink communications signal and provides WDM downlink communications signal to a selected remote unit branch among one or more remote unit branches in the WDS. In another aspect, the selected QSFP CWDM transceiver wavelength de-multiplexes a WDM uplink communications signal received from the selected remote unit branch into a plurality of uplink optical communications signals. By supporting an optical star communications architecture based on the selected QSFP CWDM transceiver, it may be possible to reduce total length of optical fibers in the WDS, thus leading to reduced optical fiber material and installation costs.

[Consistent with the present disclosure an apparatus and related method are provided for controlling the leaf-receiver local oscillator laser and leaf-transmitter laser for cases where separate transmit and receive local oscillator lasers are included in a transceiver. As a result, full capacity in bidirectional transmission can be realized on a single fiber. The leaf local oscillator frequency is controlled using a feedback signal generated based on an output from the leaf-digital signal processor (DSP), and the leaf transmit laser is controlled using a feedback signal based on an output of the remote hub-DSP, which is carried from the hub to the leaf nodes by a general communication channel (GCC) as part of a data signal, or a separate subcarrier also referred to as an auxiliary channel or out-of-band channel. This ensures that the frequencies transmitted subcarriers from the leaf nodes do not collide or overlap with one another in frequency.

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 method for measuring asymmetry in propagation delay of first and second links which connect a first node to a second node of a communication network. The method comprises measuring (101) a round trip delay of the first link. The round trip delay can be measured by transmitting (102) a test signal from the first node to the second node over the first link and receiving a reply to the test signal from the second node over the first link. The method further comprises measuring (105) a round trip delay of the second link. The round trip delay can be measured by transmitting (106) a test signal to the second node over the second link and receiving a reply to the test signal from the second node over the second link. A difference in the propagation delay of the first link with respect to the second link is determined (109) using the measured round trip delays of the first link and the second link.

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 system and method in a wavelength division multiplexing passive optical network is provided. A multiplexed optical downstream signal is transmitted from an optical line terminal to a passive distribution node. The signal is demultiplexed into a plurality of optical sub-signals. A sub-signal is transferred to an optical network termination. The received at least one sub-signal is identified. An optical wavelength of an upstream optical signal is set as a function of a predefined relationship between an optical wavelength of the received at least one sub-signal and the optical wavelength of the upstream signal. The upstream signal is transmitted to the optical line terminal via the passive distribution node.

According to one aspect of the present invention is an optical transmission apparatus including: a division unit configured to divide a frequency-multiplexed input signal into signals with a plurality of bands; a plurality of phase modulators that are allocated to the plurality of bands divided by the division unit and perform phase modulation on the signals with the allocated bands; and a synchronous addition unit configured to synchronously add the signals modulated by the plurality of phase modulators. The input signal may be a multichannel video signal. An output from the same laser diode may be input to each of the plurality of phase modulators.