Abstract: In a first aspect, a method performed by a management node for an optical network is provided. The optical network comprising a plurality of receivers and a plurality of amplifiers. The method comprises measurements of received power for the signals received at the receivers and target received power values for the receivers. The method further comprises inputting the received power measurements and target received power values into an optimisation process to determine gain values to be applied by the amplifiers on signals sent to the receivers. The method further comprises outputting the gain values for implementation at the amplifiers.

Abstract: A method performed by second fronthaul network unit for enabling synchronization with a first fronthaul network unit over a first single optical fiber in a fronthaul network is provided. The method includes receiving a first optical signal on the single optical fiber; and separating the received first optical signal into a second optical signal carrying downlink, DL, radio data traffic having a first optical wavelength and a third optical signal carrying packet-based synchronization messages having a second optical wavelength. The method further includes outputting the separated second optical signal towards a first optical port in the second fronthaul network unit; and splitting the separated third optical signal towards a second optical port in the second fronthaul network unit. A second fronthaul network unit and a first fronthaul network unit and method therein are also provided.

Abstract: A method of power control of an optical signal transmitted by a first network element. The first network element comprising a laser and a bandpass filter operating on the optical signal produced by said laser, whereas the method comprises receiving (106) information indicative of a power level of the optical signal transmitted by the first network element; and tuning (110) the laser output wavelength in response to said received information.

Abstract: A communications network remote node having a downstream optical circuit configured to receive downstream, DS, optical signals from an active main node and from a standby main node, the downstream optical circuit switchable between a working mode and a protection mode. Optical receivers are configured to receive the demultiplexed downstream optical signals and output encapsulated downstream client signals. Optical transmitters are configured to receive encapsulated upstream client signals and to transmit upstream, US, optical signals at upstream wavelengths carrying the encapsulated upstream client signals. An upstream optical circuit is configured to multiplex the upstream optical signals carrying the encapsulated upstream client signals and to send the upstream optical signals to both main nodes.

Abstract: An indicator system (200) for optical ports (125) of a passive optical communications equipment (120). The indicator system comprises a plurality of photodetectors (510) configured to detect an optical signal on the optical ports and a plurality of (140) configured to indicate on which optical ports an optical signal is detected by the photodetector. The indicator system further comprises a power source (350) configured to provide power to the photodetectors (510) and indicators (140). The power source is self-contained at the passive optical communications equipment. The power source (350) comprises a mechanical to electrical converter (410).

Abstract: There is provided a security system for use at an enclosure containing one or more passive components of an optical communication link. The security system comprises a sensor configured to detect a physical breach of the enclosure, and an optical alert signal generator coupled to the optical communication link. The optical alert signal generator is self-powered, and configured to generate an optical alert signal and transmit the optical alert signal through the optical communication link when a physical breach of the enclosure is detected by the sensor. The optical alert signal is detectable at an entity external to the enclosure and connected to the optical communication link.

Abstract: A method of power control of an optical signal transmitted by a first network element. The first network element comprising a laser and a bandpass filter operating on the optical signal produced by said laser, whereas the method comprises receiving (106) information indicative of a power level of the optical signal transmitted by the first network element; and tuning (110) the laser output wavelength in response to said received information.

Abstract: An optical device (100) for an optical network, comprising an optical input (110), a passive optical component (112), a memory device (114) for storing information relating to the passive optical component. The optical device further comprises an optical splitter (116) configured to power split off a portion of received optical signals to form split optical signals and to output the remaining optical power of received optical signals to the passive optical component and a photodetector (118) configured to receive the split optical signals and to generate a corresponding photodetector output signal.

Abstract: An optical device (100) for an optical network, comprising an optical input (110), a passive optical component (112), a memory device (114) for storing information relating to the passive optical component. The optical device further comprises an optical splitter (116) configured to power split off a portion of received optical signals to form split optical signals and to output the remaining optical power of received optical signals to the passive optical component and a photodetector (118) configured to receive the split optical signals and to generate a corresponding photodetector output signal.

Abstract: A connection-oriented communications network comprises a plurality of interconnected nodes. A traffic path can be set up across the network. Path delay data is obtained for the traffic path by using control plane signalling messages (e.g. a Resource Reservation Protocol-Traffic Engineering, RSVP-TE signalling message) between nodes of the traffic path. The path delay data can be path delay asymmetry data indicative of an asymmetry in path delay between a forward transmission direction and a reverse transmission direction of the traffic path. Each intermediate node along the traffic path can form a signalling message for forwarding to the downstream node which includes one or more values of path delay incurred by that node, or an accumulated path delay value. The path delay can result from one or more of mapping delay, Forward Error Correction (FEC) coding and propagation delay.

Abstract: A connection-oriented communications network comprises a plurality of interconnected nodes. A traffic path can be set up across the network. Path delay data is obtained for the traffic path by using control plane signalling messages (e.g. a Resource Reservation Protocol-Traffic Engineering, RSVP-TE signalling message) between nodes of the traffic path. The path delay data can be path delay asymmetry data indicative of an asymmetry in path delay between a forward transmission direction and a reverse transmission direction of the traffic path. Each intermediate node along the traffic path can form a signalling message for forwarding to the downstream node which includes one or more values of path delay incurred by that node, or an accumulated path delay value. The path delay can result from one or more of mapping delay, Forward Error Correction (FEC) coding and propagation delay.

Abstract: A method of determining a power correction factor for an optical power of an optical channel of a wavelength division multiplexed communications network. The method comprises configuring an optical source of the communications network to generate an unmodulated optical carrier signal for the optical channel. The method further comprises determining the optical power of the unmodulated optical carrier signal (PHIGH). The method further comprises configuring the optical source to apply a test modulation pattern to the optical carrier signal, to generate a modulated optical carrier signal. The method further comprises determining the optical power of the modulated optical carrier signal (PMOD). The method further comprises determining a power correction factor for the optical channel by determining the difference between the optical powers of the unmodulated optical carrier signal and the modulated optical carrier signal.

Abstract: A method of determining a power correction factor for an optical power of an optical channel of a wavelength division multiplexed communications network. The method comprises configuring an optical source of the communications network to generate an unmodulated optical carrier signal for the optical channel. The method further comprises determining the optical power of the unmodulated optical carrier signal (PHIGH). The method further comprises configuring the optical source to apply a test modulation pattern to the optical carrier signal, to generate a modulated optical carrier signal. The method further comprises determining the optical power of the modulated optical carrier signal (PMOD). The method further comprises determining a power correction factor for the optical channel by determining the difference between the optical powers of the unmodulated optical carrier signal and the modulated optical carrier signal.

Abstract: A method and apparatus for restoration of operating conditions of a WDM optical ring network comprising a plurality of amplifiers linked together in a ring after a break or fault has occurred in the network. The method comprises in response to repair of the break or other fault, increasing output power or/and pump power of an amplifier in the network such that the output power or/and pump power increases substantially in accordance with a ramp function.

Abstract: A method of demultiplexing client data from a constant bit rate (CBR) optical client serial link into lower bit-rate CBR signals for transmitting over a plurality of wavelength division multiplexed (WDM) optical channels. The method comprises mapping blocks of bytes from a client frame received from the optical client serial link into respective CBR transport frames for transmitting over the respective WDM optical channels and such that the number of bytes in the client frame is the same as the number of bytes in the plurality of respective CBR transport frames. Modifying a number of non-payload bytes from the client frame to carry CBR transport frame control data in each said CBR transport frame.

Abstract: A method and apparatus for restoration of operating conditions of a WDM optical ring network comprising a plurality of amplifiers linked together in a ring after a break or fault has occurred in the network. The method comprises in response to repair of the break or other fault, increasing output power or/and pump power of an amplifier in the network such that the output power or/and pump power increases substantially in accordance with a ramp function.