Abstract: A method (100) of encoding communications traffic bits onto an optical carrier signal in a pulse amplitude modulation, PAM, format. The method comprises: receiving (102) bits to be transmitted; receiving (104) an optical carrier signal comprising optical pulses having an amplitude and respective phases; performing (106) PAM of the optical pulses to encode at least one respective bit in one of a pre-set plurality of amplitudes of a said optical pulse; and performing (108) phase modulation of the optical pulses to encode at least one further respective bit in a phase difference between a said optical pulse and a consecutive optical pulse.

Abstract: Methods and apparatus are provided for routing Flex Ethernet (FlexE) data in a network. In an example aspect, a method comprises receiving data on a first FlexE physical layer (PHY) group, determining, from first FlexE overhead on the first FlexE PHY group, that data in one or more time slots on the first FlexE PHY group is associated with a predetermined path in the network, determining a second FlexE PHY group for the data in the one or more time slots based on at least a portion of the predetermined path in the network, and sending the data on the second FlexE PHY group.

Abstract: Optical transmitter apparatus (100) comprising: a transmitter optical subassembly (130) configured to transmit forward error correction, FEC, codewords on an optical carrier signal; a memory device (110) containing local configuration data; and processing circuitry (120) configured to: receive client signal data and perform FEC encoding on the client signal data to form a sequence of FEC codewords; receive local configuration data from the memory device; obtain a configuration payload pattern of FEC codewords having a FEC code violation and FEC codewords not having a FEC code violation, the configuration payload pattern representing the local configuration data; create FEC code violations within FEC codewords of said sequence according to the configuration payload pattern to form a configuration payload modified sequence of FEC codewords; and provide the configuration payload modified sequence of FEC codewords to the transmitter optical subassembly for transmission.

Abstract: An optical system and method for seeding an optical transmitter includes a first optical transmitter comprising a first reflective optical amplifier and a second optical transmitter comprising a second reflective optical amplifier. The second optical transmitter is optically coupled to the first optical transmitter. The optical system also includes an optical cavity for seeding the first reflective optical amplifier with a first optical seed signal. The optical cavity is formed between the first reflective optical amplifier of the first optical transmitter and the second reflective optical amplifier of the second optical transmitter. The first reflective optical amplifier is configured to transmit a first optical signal to the second reflective optical amplifier and the second reflective optical amplifier is configured to provide the first optical seed signal by reflecting a portion of the first optical signal back to the first reflective optical amplifier.

Abstract: A transmitter (1) is configured to transmit an optical signal, the transmitter comprising an optical dispersion compensator (10) configured to compensate for chromatic dispersion of the optical signal. The optical dispersion compensator comprises a plurality of delay elements (20; 40). The plurality of delay elements (20; 40) have a combined response providing a delay to the transmitted optical signal which varies with frequency.

Abstract: Methods and apparatus are provided for transmitting data. In one aspect, a method of transmitting data comprises identifying a start of a Common Public Radio Interface (CPRI) frame, identifying CPRI data blocks of the CPRI frame, and transmitting the CPRI data blocks of the CPRI frame in slots of a FlexE calendar of a Flex Ethernet physical layer group (FlexE PHY group).

Abstract: A device (10;150;200) is configured to receive an optical signal. The device comprises a dispersion compensator (210a) comprising a plurality of optical dispersion compensator units (220). Each optical dispersion compensator unit comprises a plurality of delay elements (20;40). The dispersion compensator (210a) is configured to selectively activate one or more of the optical dispersion compensator units (220). The dispersion compensator (210a) is configured to compensate for dispersion of the optical signal with the activated one or more optical dispersion compensator unit (200).

Abstract: A method for scheduling resources for a Wavelength Division Multiplexed, WDM, Passive Optical Network, PON. The WDM PON comprises a central hub (201) and a plurality of remote Optical Network Terminals, ONTs, (220) handling different types of communications traffic. The method (450) comprises receiving (452) a notification message from the plurality of remote Optical Network Terminals, ONTs, indicating a loading status of the ONT, and allocating (454) one or more slots to a plurality of the ONTs based on the received notification messages from the ONTs, wherein the plurality of ONTs (220) handle different types of communications traffic. The slots (301) are allocated based on the received notification messages as a time slot which is time division multiplexed with further time slots, and the slots are further allocated based on the received notification messages as an optical wavelength of a plurality of optical wavelengths of the WDM PON.

Abstract: Methods and apparatus are provided for receiving an optical signal. In one aspect, a method includes receiving a first optical signal comprising time division multiplexed transmissions from a plurality of optical transmitters, and determining that a transmission is not received during a time period from a first optical transmitter of the optical transmitters that is scheduled to transmit during the time period. A second optical signal is inserted into the first optical signal during the time period, the second optical signal having at least a non-zero power portion.

Abstract: A method (100) is disclosed for filtering an optical signal to generate at least one electrical output. The method comprises receiving an optical signal (110) and directing at least a part of the optical signal through an n×m array of wavelength selective elements (120), the n×m array comprising n parallel groups, each group comprising m coupled wavelength selective elements. The method further comprises photodetecting an output from each of the n groups of coupled wavelength selective elements (130), and electrically selecting at least one of the photodetected outputs (140). Also disclosed are an optical filtering module (200, 300) a controller (400) for an optical filtering module and a computer program.

Abstract: An Optical Dispersion Compensator (ODC) is disclosed, the ODC being suitable for managing chromatic dispersion of an optical signal for transmission over an optical fiber. The ODC comprises a first ODC unit (202) arranged on a first optical bus (206), a second ODC unit (204) arranged on a second optical bus (208), parallel to the first optical bus (206), and a switching element (210) interconnecting the first and second optical buses (206, 208) between the first and second ODC units (202, 204). The first and second ODC units (202, 204) are operable to provide a delay to the optical signal that varies with frequency. The switching element (210) is configured, in a first state, to switch an optical signal received on one of the first or second optical buses (206, 208) to the other of the first or second optical buses (208, 206) and, in a second state, to maintain an optical signal received on one of the first or second optical buses (206, 208) on the optical bus on which it was received (206, 208).

Abstract: A receiver module (100) is disclosed for receiving an optical input signal and generating an electrical output signal from the optical input signal. The receiver module comprises an input (110) for receiving an optical input signal and a polarising beam splitter (120) for splitting one of the optical input signal and a local recovery optical signal. The receiver module also comprises a multiport optical coupler (130) for coupling the outputs of the polarisation beam splitter and the other of the optical input signal and local recoveiy optical signal and outputting a plurality of outputs. The receiver module further comprises a first photodetector unit (140) for individually photodetecting the outputs of the multiport optical coupler and an optical modulation unit (150) for using each of the photodetected outputs to modulate a respective local conversion optical signal, where each local conversion optical signal has a different frequency from the other local conversion optical signals.

Abstract: A method for managing traffic of a plurality of packets in a plurality of packet flows transmitted using a time-slotted interface. The packet flows traverse a plurality of switches of a transport network according to an assigned path from a source node to a destination node. The method comprises determining an end-to-end latency of a plurality of packets traversing a current switch in packet flows and assigning priority values to the packets traversing the current switch, wherein a priority value of a packet depends on the determined end-to-end latency of said packets. The method further comprises allocating a time slot in an output interface of the current switch to the packet having the highest priority value among the packets competing for said time slot.

Abstract: Methods and apparatus are provided for processing communications. In one aspect, a method comprises receiving first data from a first device and receiving second data from a second device, wherein the first data has a longer latency constraint than the second data. The method also comprises sending the first data over a network link to a processing node for processing the first data.

Abstract: A device (10;150;200) is configured to receive an optical signal. The device comprises a dispersion compensator (210a) comprising a plurality of optical dispersion compensator units (220). Each optical dispersion compensator unit comprises a plurality of delay elements (20;40). The dispersion compensator (210a) is configured to selectively activate one or more of the optical dispersion compensator units (220). The dispersion compensator (210a) is configured to compensate for dispersion of the optical signal with the activated one or more optical dispersion compensator unit (200).

Abstract: A path computation engine, PCE, (100) for an optical communications network comprising a plurality of nodes and a plurality of links.

Abstract: An optical link for a communication network, the optical link having an optical fibre link, a downstream transmitter, a downstream receiver, an upstream transmitter and an upstream receiver. The upstream and downstream transmitters are configured to transmit a respective pilot tone on a respective optical carrier and are configured to tune a frequency of the pilot tone within a preselected frequency range. The upstream and downstream receivers are configured respectively to determine an upstream notch frequency, fnotch-US, and a downstream notch frequency, fnotch-DS, of respective detected photocurrents from at least one respective pilot tone frequency at which the respective detected photocurrent is equal to or lower than a photocurrent threshold. The optical link also includes processing circuitry configured to receive the upstream and downstream notch frequencies and configured to estimate a propagation delay difference of the optical link depending on the upstream and downstream notch frequencies.

Abstract: Device (200,300) and method (500) for processing an optical signal. The device (200,300) comprises a photonic device (202,302) arranged between a first input/output (204,304) and a second input/output (206,306) and optically communicating with the inputs/outputs by a signal path (208,308) for transmission of an optical signal in a first or second direction between the first input/output (204,304) and the second input/output (206,306). The device (200,300) comprises an optical gain element (210,310) for amplifying the optical signal.

Abstract: A method for dual polarisation optical transmission is disclosed. The method comprises splitting a continuous wave light source into first and second sub-channels, optically modulating each sub-channel with a data signal, and superimposing a first pilot tone onto the first optically modulated sub-channel and a second pilot tone, different from the first pilot tone, onto the second optically modulated sub-channel. The method further comprises polarisation multiplexing the first and second sub-channels to form a polarisation multiplexed signal, in which the first and second sub-channels have orthogonal states of polarisation, and transmitting the polarisation multiplexed signal.

Abstract: Methods and apparatus are provided for receiving an optical signal. In one aspect, a method includes receiving a first optical signal comprising time division multiplexed transmissions from a plurality of optical transmitters, and determining that a transmission is not received during a time period from a first optical transmitter of the optical transmitters that is scheduled to transmit during the time period. A second optical signal is inserted into the first optical signal during the time period, the second optical signal having at least a non-zero power portion.