Abstract: An optical processing circuit, such as a combinatorial network, comprises an arrangement of optical logic gates suitable for use in combination with a switched optical node of the kind having at least first and second input ports and two output ports, the node being configurable into either a cross or a bar configuration, and in which the optical processing circuit is arranged so as to receive at least three optical input signals which respectively comprise a packet identifier signal PIH which identifies whether or not a first input signal is present at the first input port of the switched optical node, the first input port being assigned a higher priority than the second input port, a first destination address AH indicating the output port of the switched optical node to which a first information carrying signal, received at the first input port, is intended to be passed, and a second destination address AL indicating the output port of the switched optical node to which a second information carrying signal,

Abstract: An RF signal transceiver comprising a mode-locked laser to output an optical signal having a plurality of phase-locked modes, an optical splitter to power split the optical signal into a transmitter optical signal and a receiver optical signal; a transmitter apparatus to receive the transmitter optical signal and comprising an optical filter to select two of the modes, an optical modulator to modulate a part of the transmitter optical signal to form at least one phase modulated optical signal, and a photodetector to heterodyne the phase modulated optical signal with one of the modes without a corresponding phase modulation to form an RF signal for transmission; and a receiver apparatus arranged to receive an RF signal and the receiver optical signal and comprising an optical modulator to modulate the receiver optical signal with the received RF signal; and an optical to electrical signal conversion apparatus to convert the modulated receiver optical signal into a corresponding electrical signal.

Abstract: An RF signal generator has an optical part for outputting optical carrier signals separated in optical frequency, and a modulator arranged to modulate the optical carrier signals with an intermediate frequency to generate sidebands. A phase modulation is applied to one or more of the sidebands or the optical carriers, without applying the phase modulation to others of the signals, and the modulator has integrated optical paths for both the phase modulated signals and for the others of the signals. A detector part carries out heterodyne detection to combine the phase modulated and other signals to output an RF signal having the phase modulation. By having integrated optical paths, the relative phase of these optical paths can be more stable than using a fiber sagnac interferometer and optical isolator thus enabling use in advanced radio communications.

Abstract: A method of converting an optical communications signal having a differentially encoded multilevel modulation format into communications traffic bits, the multilevel modulation format having a plurality of constellation points, the method comprising: receiving a consecutive pair of symbol signals of said optical communications signal, the pair of symbol signals being arranged to differentially encode a plurality of communications traffic bits; and generating a plurality of optical binary signals in dependence on the symbol signals, each optical binary signal having a respective binary signal level, wherein the optical binary signals form optical versions of the encoded communications traffic bits.

Abstract: A planar waveguide circuit comprises a first optical splitter to receive an input optical signal, a second optical splitter to receive a reference optical signal, a first optical signal combiner, and a second optical signal combiner. First and second optical waveguides are provided to couple first and second outputs of the first optical splitter to respective inputs of the first and second optical signal combiners. Third and fourth optical waveguides are provided to couple first and second outputs of the second optical splitter to respective inputs of the first and second optical signal combiners. A phase-shifter is provided located to affect the phase of an optical signal propagating in one of the third and fourth optical waveguides. The first and second optical splitters and the first and second optical signal combiners are arranged such that the first, second, third and fourth optical waveguides do not intersect one another.

Abstract: The present invention relates to Digital-to-Analog conversion in the optical or photonic domain. The present invention provides a digital-to-analog converter (DAC) (100) arranged to receive an N-bit digital optical signal (105) and to process the N-bit digital optical signal to generate an analog optical signal (110). The DAC comprises a photonic circuit (120a, 120b) arranged to adjust the amplitude of each bit of the N-bit digital optical signal dependent on the amplitudes of at least one of the other bits of the N-bit digital optical signal. The amplitudes are adjusted using a non-linear optical effect in order to generate respective outputs for each bit. The DAC also comprises a photonic combiner (145) arranged to combine the outputs for each bit to generate the analog output signal (110).

Abstract: An all-optical contention manager includes at least two inputs and at least two outputs. The outputs are configured to output signals to a Banyan switch. The contention manager detects and resolves routing contentions between incoming optical signals prior to outputting the signals to the Banyan switch. The signals have tags that include routing information. A photonic comparator in the contention manager compares the tags of incoming optical signals in order to detect contention.

Abstract: A synchronous packet switch comprises output modules, input modules, optical connections and a switch control unit. The output modules comprise optical receivers each configured to receive optical signals at a different wavelength. The input modules receive electric signals carrying data cells to be routed. Each input module comprises optical transmitters, each configurable to generate an optical signal at a different wavelength, and routing apparatus comprising output ports. Each output module has at least one output port allocated to it. The routing apparatus is configurable to route a received optical signal to a selected output port. The optical connections are arranged to couple output ports to respective output modules. The switch control unit controls routing of the optical signals from the transmitters to the output modules and generates a routing control signal for configuring the routing apparatus to route an optical signal from a transmitter to a selected output port.

Abstract: An optical device comprises an optical device stage, which comprises an optical input, an optical AND gate, an optical flip-flop and an optical output. The optical input is arranged to receive an optical input pulse at an input wavelength. The optical AND gate comprises a first input arranged to receive a part of said optical input pulse, a second input arranged to receive at least a part of a flip-flop optical output signal, and an output. The optical AND gate is arranged to generate an AND gate optical output pulse dependent on said flip-flop optical output signal. The optical flip-flop comprises a first input arranged to receive a further part of said optical input pulse, a second input arranged to receive a said AND gate optical output pulse, and an output. The optical flip-flop is arranged to generate said flip-flop output signal at a flip-flop output wavelength. At least a part of the flip-flop output signal is provided to said output.

Abstract: An optical linear feedback circuit has an optical loop delay path (10) for recirculating a sequence of optical signals, and an output path for outputting delayed optical signals after circulating one or more times around the loop. A selector (50) is provided for selecting one or more of the delayed optical signals from the sequence, and an optical logic circuit (20) is coupled to carry out a logical operation on the selected delayed optical signals to create an optical feedback signal which is coupled to the optical loop delay path, so that the optical feedback signal can be added to the sequence of optical signals already circulating. By recirculating around a loop, each round trip can be regarded as equivalent to a shift of a shift register, so longer sequences can be built up without needing an additional storage cell for each shift function.

Abstract: An optical flip-flop comprises first (102) and second (104) flip-flop elements arranged to respectively provide first (output 1) and second (output 3) optical outputs. Each output is in one of a plurality of states, wherein switching the output from a relatively high power state to a relatively low power state has an associated falling edge transition time, and switching the output from a relatively low power state to a relatively high power state has an associated rising edge transition time. The rising edge transition time is greater than the falling edge transition time.

Abstract: An analogue to digital converter is arranged to receive and process an analogue optical input signal to produce an N bit digital optical output signal quantised to 2N levels, where N is greater than or equal to 2. The converter has an input for receiving the optical input signal and N processing channels which are each coupled to the input, at least one of said processing channels comprising an optical processing circuit arranged to generate a plurality of digital optical output signals. The optical processing circuit is arranged to change the state of each digital optical output signal corresponding to a respective different value of the analogue optical input signal, and an optical combining circuit for combining the optical output signals in order to generate one bit of the N-bit digital optical signal.

Abstract: An optical signal processor may include an optical waveguide loop, and first and second phase modulator loops. Each of the first and second phase modulator loops may be in optical communication with the optical waveguide loop. The first and second phase modulator loops may include respective control signal input ports to control phase modulation applied by the first and second phase modulation loops. The optical waveguide loop may include two input ports to direct input signals in opposite directions in the optical waveguide loop and may further include an output port to output resulting signals.

Abstract: An optical transmitter apparatus comprises at least three input transmitters that each provide at an output an NRZ optical signal, at least two of the NRZ optical signals having substantially the same bit rate, each of the signals having a bit rate which is less than 100 Gbit/s and the sum of the bit rates of all of the at least three transmitters being equal to or greater than 100 Gbit/s, an NRZ to RZ converter associated with each transmitter which converts each NRZ signal into an optical RZ signal, an optical time division multiplexer which converts the RZ signals into at least two further signals, and a polarization multiplexer which processes the two further signals to provide two output signals of differing polarization.

Abstract: An optical device comprises an optical device stage, which comprises an optical input, an optical AND gate, an optical flip-flop and an optical output. The optical input is arranged to receive an optical input pulse at an input wavelength. The optical AND gate comprises a first input arranged to receive a part of said optical input pulse, a second input arranged to receive at least a part of a flip-flop optical output signal, and an output. The optical AND gate is arranged to generate an AND gate optical output pulse dependent on said flip-flop optical output signal. The optical flip-flop comprises a first input arranged to receive a further part of said optical input pulse, a second input arranged to receive a said AND gate optical output pulse, and an output. The optical flip-flop is arranged to generate said flip-flop output signal at a flip-flop output wavelength. At least a part of the flip-flop output signal is provided to said output.

Abstract: An optical linear feedback circuit has an optical loop delay path (10) for recirculating a sequence of optical signals, and an output path for outputting delayed optical signals after circulating one or more times around the loop. A selector (50) is provided for selecting one or more of the delayed optical signals from the sequence, and an optical logic circuit (20) is coupled to carry out a logical operation on the selected delayed optical signals to create an optical feedback signal which is coupled to the optical loop delay path, so that the optical feedback signal can be added to the sequence of optical signals already circulating. By recirculating around a loop, each round trip can be regarded as equivalent to a shift of a shift register, so longer sequences can be built up without needing an additional storage cell for each shift function.

Abstract: An optical label extractor (10) comprising a non-linear optical element (12), a pump source (14) and optical filter apparatus (16). Said non-linear optical element (12) is arranged to receive optical data packets (18) at data signal wavelengths. Each said data packet comprises at least one data bit and at least one label bit. Said pump source (14) is arranged to pump said non-linear optical element such that any non-zero label bit experiences a non-linear optical effect on propagation through said non-linear optical element and an output label bit (20) comprising a respective further wavelength is thereby generated. Said optical filter apparatus (16) is arranged to receive any said output label bit from said non-linear optical element and being further arranged to prevent transmission of a part of said output label at said respective data signal wavelength and to transmit a part of said output label bit at said respective further wavelength.

Abstract: An optical switch controller controls an optical interconnection network that variably connects at least one input data channel to a plurality of outputs channels via at least one switching element. An address reader module has at least one semiconductor optical amplifier optically processes an optical signal. The address reader module obtains information by reading a data tag from the input data channel, and outputs an address control signal based on the information. The address control signal can be used to control switching elements in the optical interconnection network.

Abstract: A synchronous packet switch comprises output modules, input modules, optical connections and a switch control unit. The output modules comprise optical receivers each configured to receive optical signals at a different wavelength. The input modules receive electric signals carrying data cells to be routed. Each input module comprises optical transmitters, each configurable to generate an optical signal at a different wavelength, and routing apparatus comprising output ports. Each output module has at least one output port allocated to it. The routing apparatus is configurable to route a received optical signal to a selected output port. The optical connections are arranged to couple output ports to respective output modules. The switch control unit controls routing of the optical signals from the transmitters to the output modules and generates a routing control signal for configuring the routing apparatus to route an optical signal from a transmitter to a selected output port.

Abstract: An optical logic gate (10) comprising inputs (12) for optical signals on which to perform a chosen logical operation. An SOA (11) element receives such input signals to be piloted thereby in saturation and its output is connected to at least one optical filter (14, 15, 16) that filters components of signals output from the SOA and which represent a desired logical result of the signals input at the gate so that at the output (13) of the filter there is an optical signal as the result of the desired logical operation. A probe signal (17) can also be provided. An appropriate combination of power of the input, power and probe signal wavelength and central wavelength of the filter allows obtaining a plurality of logic functions such as NOR, NOT, inverted XOR, AND, OR.