Abstract: A network node (30) for a radio access network, wherein the network node comprises a switch system (35) configured to switch traffic for a plurality of base stations (3, 5; 8) of the radio access network. The switch system (35) is configured to provide for communication between a remote radio unit (3) and a baseband processing unit (5, 12) of the said plurality of base stations. The switch system (35) is configured to provide for communication between a first base station (8) and a second base station (3, 5) of said plurality of base stations. At least one of the first or second base station is a radio base station (8) comprising baseband processing.

Abstract: Digital data (11) is encoded to a set of five line symbols for optical transmission. The line symbols have amplitude values of 0, ±A1, ±A2, where |A2|>|A1|. A first binary value maps to the line symbols 0 and ±A2 and a second binary value maps to the line symbols ±A1. The amplitude values of the line symbols can be in the ratio A1:A2=1:sqrt(2). At a receiver, the received signal is photodetected to generate an electrical signal which can represent a set of three possible received symbols (RS1, RS2, RS3). Digital data (26) is recovered from the received symbols by comparing the electrical signal with a first amplitude threshold (TH1) and a second amplitude threshold (TH2).

Abstract: A digital signal processing, DSP, unit (10) for use in a coherent optical receiver for an optical communications network. The DSP unit comprises an adaptive equalizer (12) and a processing block (22). The equalizer (12) comprises input ports for receiving electrical signals, each corresponding to a different state of polarization of an optical signal received by the coherent optical receiver, and output ports, each connected to a processing branch (14). A processing branch comprises a symbol sequence estimator, SSE, (16) and a carrier phase estimator, CPE, (18) comprising an input for receiving signal taped from an output of the processing branch. An output of the CPE is connected to a phase adjuster (20) interconnecting the respective output port of the equalizer and the SSE. The processing block (22) is connected to an output of the CPE, an output of the processing branch and at least one of the output of the phase adjuster and the outputs of the equalizer.

Abstract: A method in a node of a telecommunication network comprises receiving a digital communication signal from a first signal source, source, wherein the digital communication signal comprises a wherein the digital communication signal comprises a plurality of low amplitude windows, step 101, and receiving one or more analog subcarrier signals from a second signal source, step 103. The method further comprises multiplexing the one or more analog subcarrier signals into one or more of the plurality of low amplitude windows of the digital communication signal, step 105.

Abstract: A beamforming device for a phased array antenna, comprising: a laser light source (2) arranged to provide an optical spectrum comprising a plurality of spaced wavelengths, and a distribution unit (4) configured to distribute one or more of the plurality of spaced wavelengths onto a plurality of optical paths (6). A wavelength selection device (8) configured to receive the plurality of spaced wavelengths on each of the plurality of optical paths. One or more phase shift unit (12) connected to a said wavelength selection device, wherein the phase shift unit is configured to introduce a phase shift to a received wavelength. The wavelength selection device on each optical path is configured to selectively transmit a wavelength to the phase shift unit. The wavelength selection device is configured to receive the said phase shifted wavelength from the phase shift unit (12).

Abstract: A method for switching data signals transmitted over a transport network is disclosed. The method comprises receiving a plurality of input data signals of a first signal type wherein the plurality of data signals of the first signal type comprises data signals exchanged between a Radio Equipment and a Radio Equipment Controller and aggregating the plurality of input data signals into an aggregated first data signal. The method also comprises receiving a second data signal of a second signal type different to the first signal type, and multiplexing the first data signal with the second data signal to form a combined data signal. The method further comprises forwarding the combined data signal to the transport network. Multiplexing the first data signal with the second data signal comprises, for a frame of the combined data signal, allocating the first data signal to a portion of the frame reserved for the first data signal, and allocating the second data signal to a remaining portion of the frame.

Abstract: The present invention provides an optical source comprising a laser, a first optical power splitter, phase changing equipment, polarisation state setting equipment, a polarisation beam coupler and an output. The laser is configured to generate an optical signal. The first optical power splitter is configured to split the optical signal into a first optical signal and a second optical signal. The phase changing equipment is configured to change the phase of at least one of the first optical signal and the second optical signal such that the first optical signal has a first phase and the second optical signal has a second phase different from the first phase by a preselected phase difference.

Abstract: The invention provides a free space optical (FSO) communications terminal for a first telecommunications card or a backplane. The FSO terminal comprises a plurality of transmission interfaces. The FSO terminal further comprises a light signal generating unit adapted to generate a plurality of light signals. Each of the plurality of light signals carries the same information as the other one or more of the plurality of light signals and is arranged for transmission through a respective one of the plurality of transmission interfaces. Each of the plurality of light signals is at a different orthogonal mode from the other one or more of the plurality of light signals. The invention further provides a free space optical (FSO) communications terminal for a second telecommunications card or a backplane. The FSO terminal comprises a plurality of receive interfaces. Each of the plurality of receive interfaces adapted to receive a light signal carrying information.

Abstract: A wireless communications network radio unit (10) comprising: an input (12) arranged to receive a radio over fiber, RoF input optical signal (14) carrying digital radio communications traffic for transmission from a plurality of antenna elements, synchronization traffic and control and management traffic; a digital receiver (16) arranged to receive and terminate the RoF input optical signal to obtain the digital radio communications traffic; a framer (18) arranged to frame the digital radio communications traffic into at least one digital traffic stream consisting of the digital radio communications traffic for transmission from a plurality of the antenna elements and clock recovery information; and at least one optical transmitter (20) arranged to generate an RoF output optical signal (22) carrying the digital traffic stream.

Abstract: A radio manager unit for a radio access network, wherein the radio manager unit is configured to connect to a transport control unit configured to control a transport network between a baseband processing unit and a plurality of remote radio units. The radio manager unit is further configured to connect to a radio control unit configured to control the baseband processing unit. The radio manager unit is further configured to be connected to one or more tenant system of a tenant. The radio manager unit is configured to arrange for resources of the transport network and resources of the baseband processing unit to be configured for use by a said tenant.

Abstract: A method (10) of encapsulating digital communications traffic for transmission on an optical link, the method comprising: a. receiving an input digital communications signal having an input line code (12); b. performing clock and data recovery on the input digital communications signal to obtain input line coded digital communications traffic and a recovered clock signal (14); c. decoding the input digital communications traffic to obtain information bits and non-information bits (16); d. removing the non-information bits (18); e. adding service channel bits for monitoring or maintenance (20); f. assembling the service channel bits and information bits into frames (22); and g. line coding the assembled frames using an output line code to form an encapsulated digital communications signal for transmission on an optical link (24), wherein steps c. to g. are performed using the timing of the recovered clock signal. A communications network receiver configured to implement the method is also provided.

Abstract: A method in a node of a telecommunication network comprises receiving a digital communication signal from a first signal source, source, wherein the digital communication signal comprises a wherein the digital communication signal comprises a plurality of low amplitude windows, step 101, and receiving one or more analog subcarrier signals from a second signal source, step 103. The method further comprises multiplexing the one or more analog subcarrier signals into one or more of the plurality of low amplitude windows of the digital communication signal, step 105.

Abstract: A transceiver (4) comprising a receive part (70) configured to receive and detect a first signal carried on an optical carrier, wherein the signal is in a first part of a RF spectrum. The transceiver (4) further comprises a modulator (68) configured to modulate the same optical carrier with a second signal in a second part of the RF spectrum. The transceiver comprises a transmit part (60) configured to transmit the optical carrier modulated with the second signal. The first part of the RF spectrum is separate to the second part of the RF spectrum. The first signal and/or second signal are spectrally compressed signals.

Abstract: A switch configured to connect a plurality of remote radio units with a plurality of main units in a radio access network. The switch comprises a first stage comprising one or more first units configured to receive a signal originating from a remote radio unit, and configured to output one or more spectral component having a wavelength. The switch further comprises a central stage configured to receive the one or more optical wavelength, and transfer the spectral component to an output port determined by the wavelength. The switch further comprises a second stage comprising one or more second units configured to receive the one or more spectral component from the central stage and output a signal towards a main unit. The first unit is configured to control the wavelength of the output spectral component such that the spectral component is transferred by the central stage to a selected one of said second units.

Abstract: A method of automatically tuning subcarriers of a superchannel transmission. The method comprises determining (71) a received parameter of transmission quality of one or more of the plurality of subcarriers. The method further comprises tuning (72) a frequency of the one or more subcarrier based on the determined parameter of the transmission quality.

Abstract: A method of transmitting communications traffic, the method comprising steps of receiving a sequence of communications traffic bits; and mapping the sequence of communications traffic bits onto a respective one of a plurality of transmission symbols for transmission during a symbol time. Each transmission symbol is identified by a respective first symbol identifier indicative of a respective one or more of a plurality, M, of wavelengths for a transmission signal and a respective second symbol identifier indicative of a respective one or more of a plurality, N, of optical fibres on which to transmit the transmission signal.

Abstract: A method of controlling a parameter in the generation of a coherent optical signal, the method comprising the steps of: receiving a set of signal samples relating to detection of a coherent optical signal; transforming the set of signal samples into a set of spectrum samples in the frequency domain, the set of spectrum samples being an estimation of the spectrum of the coherent optical signal; calculating at least one feedback variable based on the spectrum samples; and adjusting the parameter based on the at least one feedback variable.

Abstract: An optical node (100) is disclosed. The optical node (100) comprises first and second line ports (104, 106) for Wavelength Division Multiplexing (WDM) signals and first and second pluralities of local add/drop ports (108, 110) for optical signals. The optical node further comprises a wavelength selective switch (112), coupled between the first and second line ports (104, 106) and configured to drop optical signals from a WDM signal traversing the optical node between the first and second line ports (104, 106), and a node optical combiner (114) coupled between the first and second line ports (104, 106) and configured to add optical signals to a WDM signal traversing the optical node between the first and second line ports (104, 106).

Abstract: A transport network (10) is configured to connect a plurality of remote radio units (3) with a plurality of digital units (5) in a radio access network. The transport network comprises an electronic cross-connect (31) common to the plurality of remote radio units and digital units, and a control unit (32) configured to control the electronic cross-connect. The transport network further comprises an optical link (40) between the electronic cross-connect and remote radio units. The electronic cross-connect is a multi-layer switch. The electronic cross-connect is configured to switch data flows between one or more of said plurality of digital units (5) and one or more of said plurality of remote radio units (3).

Abstract: Techniques are disclosed for determining propagation delay of a first path and or of a second path which connect a first transceiver unit associated with a first clock to a second transceiver unit associated with a second clock in a communications network, based on a first time reference representing a time of transmission of a first signal from the first transceiver unit, a second time reference representing the time of receipt of the first signal at the second transceiver unit, a third time reference representing a time of transmission of a reply to the second signal from the second transceiver unit, and a fourth time reference representing the time of receipt of the reply to the second signal at the first transceiver unit.