Abstract: A method of manufacturing a coupling element configured to couple light between an optical device and one or more optical fiber comprises forming one or more waveguide in the silica. The one or more waveguide having a refractive index configured to guide the light between the optical device and the optical fiber. The forming of the one or more waveguide comprises photo-inducing a refractive index variation of the silica material.

Abstract: There is provided an optical switch. The optical switch comprises a first optical waveguide, a second optical waveguide, a first optical ring resonator and a second optical ring resonator. The first optical ring resonator is arranged between the first optical waveguide and the second optical waveguide, wherein the first optical ring resonator is capable of coupling an optical signal travelling along the first optical waveguide in a first direction to the second optical waveguide such that the optical signal travels in a second direction along the second optical waveguide. The second optical ring resonator is arranged between the first optical waveguide and the second optical waveguide; wherein the second optical ring resonator is capable of coupling an optical signal travelling along the first optical waveguide in the first direction to the second optical waveguide such that the optical signal travels in a third direction along the second optical waveguide opposite to the second direction.

Abstract: A silicon photonic device (1) comprising: a silicon core (2) having a core refractive index; and a structure formed in the silicon core, comprising: a first refractive index variation pattern (4) across the core in a first direction (x) and having a first modulation depth (Hi); and a second refractive index variation pattern (6) across the core in a second, orthogonal, direction (y) and having a second modulation depth (H2), less than the first modulation depth. The first refractive index variation pattern overlays the second refractive index variation pattern, forming a three-dimensional structure. The first refractive index variation pattern only supports propagation of light having a TM mode between the first direction and a third direction (z) and the second refractive index variation pattern only supports propagation of light having a TE mode between the second direction and the third direction. An optical waveguide coupler is also disclosed.

Abstract: An optical switch, comprising: a first optical waveguide, a first optical add path, a second optical add path and a micro-ring resonator. The micro-ring resonator is operable to add a first optical signal at a preselected wavelength received from the first optical add path to the first optical waveguide to travel in a first direction through the first optical waveguide. The micro-ring resonator is further operable to add a second optical signal at the preselected wavelength received from the second optical add path to the first optical waveguide to travel in a second direction through the first optical waveguide opposite to the first direction. There is also provided an optical drop switch, an optical switching apparatus, an optical communications network node and an optical communications network.

Abstract: There is provided an optical source. The optical source comprises a reflective optical amplifier configured to generate an optical signal, the optical signal comprising an amplified spontaneous light emission having a plurality of light modes each having a respective wavelength. The optical source further comprises a reflective mirror, spaced from the reflective optical amplifier, and arranged to receive the optical signal and to rotate a polarization of each light mode in the received optical signal, to form a further optical signal. The optical source further comprises an optical power splitter arranged to receive the further optical signal and to split the further optical signal into a first optical signal which is directed to the reflective optical amplifier for amplification thereby, and a second optical signal. The optical source further comprises an output arranged to output the second optical signal.

Abstract: An optical switch has four optical ports; a first optical waveguide coupled between a first of said ports and a second of the ports; a first switch element provided between the first waveguide and a second optical waveguide that is coupled to a third of the ports; a second switch element provided between the first waveguide and a third optical waveguide that is coupled to a fourth of the ports. Each switch element has a micro-ring resonator having an active state in which it is coupled to the first waveguide and to a respective one of the second and third waveguides for optical signals at a preselected wavelength, and an inactive state in which no coupling occurs. Each switch element has a control element arranged to receive a respective control signal configured to cause it to switch the micro-ring resonator between said states.

Abstract: A silicon photonic device (1) comprising: a silicon core (2) having a core refractive index; and a structure formed in the silicon core, comprising: a first refractive index variation pattern (4) across the core in a first direction (x) and having a first modulation depth (Hi); and a second refractive index variation pattern (6) across the core in a second, orthogonal, direction (y) and having a second modulation depth (H2), less than the first modulation depth. The first refractive index variation pattern overlays the second refractive index variation pattern, forming a three-dimensional structure. The first refractive index variation pattern only supports propagation of light having a TM mode between the first direction and a third direction (z) and the second refractive index variation pattern only supports propagation of light having a TE mode between the second direction and the third direction. An optical waveguide coupler is also disclosed.

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: An optical switch, comprising: a first optical waveguide, a first optical add path, a second optical add path and a micro-ring resonator. The micro-ring resonator is operable to add a first optical signal at a preselected wavelength received from the first optical add path to the first optical waveguide to travel in a first direction through the first optical waveguide. The micro-ring resonator is further operable to add a second optical signal at the preselected wavelength received from the second optical add path to the first optical waveguide to travel in a second direction through the first optical waveguide opposite to the first direction. There is also provided an optical drop switch, an optical switching apparatus, an optical communications network node and an optical communications network.

Abstract: A reconfigurable optical switch apparatus comprising m input ports, m output ports, k add ports, k drop ports and a switch matrix comprising m×k wavelength selective optical switches arranged in m rows and k columns. Each switch comprises first, second, third and fourth ports. The columns are grouped in adjacent pairs, in each pair a first column being connected to a respective drop port on a first side of the switch matrix and each wavelength selective switch in said first column having the fourth port arranged on said first side and a second column, adjacent the first column, being connected to a respective drop port on a second side, opposite the first side, of the switch matrix and each wavelength selective switch in said second column having the fourth port arranged on said second side.

Abstract: An optical source (10) comprising: a first laser (12) arranged to generate a first optical signal (14) having a first state of polarisation and a first optical frequency; a second laser (16) arranged to generate a second optical signal (18, 48, 78) having a second state of polarisation, substantially orthogonal to the first state of polarisation, and having a second optical frequency, different to the first optical frequency by a preselected frequency difference, Av; a polarisation beam coupler (20) arranged to combine the first optical signal and the second optical signal into a composite optical signal comprising both the first optical signal and the second optical signal having said substantially orthogonal states of polarisation; and an output (22) arranged to output the composite optical signal (24).

Abstract: Optical add and drop switch and aggregator apparatus comprising: N first wavelength selective routing apparatus each configured to split a wavelength multiplexed input signal into L sub-signals; demultiplexers each configured to demultiplex a respective sub-signal into K optical signals; output ports each configured to output a respective output optical signal; add ports configured to receive optical signals to be added; M second wavelength selective routing apparatus each having X outputs, each said apparatus being configured to receive optical signals from a respective add port and to route each received optical signal to a respective one of its outputs; drop ports configured to output optical signals to be dropped; and a switch matrix coupled between the demultiplexers, the output ports, the drop ports and the second wavelength selective routing apparatus, the switch matrix comprising a plurality of optical switches arranged in XM columns and KLN rows.

Abstract: There is provided an optical source. The optical source comprises a reflective optical amplifier configured to generate an optical signal, the optical signal comprising an amplified spontaneous light emission having a plurality of light modes each having a respective wavelength. The optical source further comprises a reflective mirror, spaced from the reflective optical amplifier, and arranged to receive the optical signal and to rotate a polarisation of each light mode in the received optical signal, to form a further optical signal. The optical source further comprises an optical power splitter arranged to receive the further optical signal and to split the further optical signal into a first optical signal which is directed to the reflective optical amplifier for amplification thereby, and a second optical signal. The optical source further comprises an output arranged to output the second optical signal.

Abstract: An optical switch has four optical ports; a first optical waveguide coupled between a first of said ports and a second of the ports; a first switch element provided between the first waveguide and a second optical waveguide that is coupled to a third of the ports; a second switch element provided between the first waveguide and a third optical waveguide that is coupled to a fourth of the ports. Each switch element has a micro-ring resonator having an active state in which it is coupled to the first waveguide and to a respective one of the second and third waveguides for optical signals at a preselected wavelength, and an inactive state in which no coupling occurs. Each switch element has a control element arranged to receive a respective control signal configured to cause it to switch the micro-ring resonator between said states.

Abstract: An optical switch (10) comprising: input ports (12, 14) arranged to receive optical signals from directions D1 to Dn; output ports (16, 18) arranged to output optical signals to the said directions; drop ports (20); add ports (22); a first switch array (24) arranged to receive from a first said input port (12) optical signals at a plurality of wavelengths, and comprising switch elements (26) each arranged to selectively direct optical signals to a respective drop port.

Abstract: A reconfigurable optical switch apparatus comprising m input ports, m output ports, k add ports, k drop ports and a switch matrix comprising m×k wavelength selective optical switches arranged in m rows and k columns. Each switch comprises first, second, third and fourth ports. The columns are grouped in adjacent pairs, in each pair a first column being connected to a respective drop port on a first side of the switch matrix and each wavelength selective switch in said first column having the fourth port arranged on said first side and a second column, adjacent the first column, being connected to a respective drop port on a second side, opposite the first side, of the switch matrix and each wavelength selective switch in said second column having the fourth port arranged on said second side.

Abstract: Path computation involves determining (120, 930) an aggregate cost for a portion of the path, based at least on the power consumption attributable to use of interfaces along that portion, comparing (130, 930) the portion of the first possible path with a different portion corresponding to a different possible path for the traffic request, based at least on their respective aggregate costs, and selecting (140, 930) which portion to use for the traffic request based on the comparison. Having path selection influenced by the power consumption values, can lead to lower overall consumption in operation than relying only on optimizing nodes individually without regard to how the nodes are used. Path selection can take into account indications of which parts are in a power down mode, and can involve powering up such parts if needed.

Abstract: An apparatus for an optical communications network comprising a demultiplexer, a plurality of add/drop optical switches for adding and dropping wavelength channels. The add/drop optical switches arranged in a matrix with a number of rows corresponding to a number of output ports of the demultiplexer and a number of columns corresponding to a number of transponders. Each drop optical switch has an express input port associated with an output port of the demultiplexer, a drop output port associated with an individual transponder, and an express output port. Each add optical switch has an express input port, an add input port associated with an individual transponder, and an express output port. The apparatus also comprises a multiplexer with a plurality of input ports associated with express output ports of the add/drop optical switches.

Abstract: Optical add and drop switch and aggregator apparatus comprising: N first wavelength selective routing apparatus each configured to split a wavelength multiplexed input signal into L sub-signals; demultiplexers each configured to demultiplex a respective sub-signal into K optical signals; output ports each configured to output a respective output optical signal; add ports configured to receive optical signals to be added; M second wavelength selective routing apparatus each having X outputs, each said apparatus being configured to receive optical signals from a respective add port and to route each received optical signal to a respective one of its outputs; drop ports configured to output optical signals to be dropped; and a switch matrix coupled between the demultiplexers, the output ports, the drop ports and the second wavelength selective routing apparatus, the switch matrix comprising a plurality of optical switches arranged in XM columns and KLN rows.

Abstract: A packet switch 40 comprises wavelength tunable optical transmitters 12, an optical switch fabric 42, optical detectors 30 and a controller 32. The transmitters 12 are arranged to receive at least one electrical signal packet to be switched and convert it into a corresponding optical signal packet at an input wavelength. The optical switch fabric 42 comprises an ingress stage 44 comprising wavelength selective routers 46 and an egress stage 50 comprising wavelength selective routers 54 and tunable wavelength converters 26 arranged to receive an optical signal at the input wavelength and to output an optical signal at an output wavelength. The controller 32 is arranged to set the input wavelength of a transmitter 12 and the output wavelength of a wavelength converter to configure a path across the switch fabric 42 connecting the transmitter 12 to a detector 30. A communications network router 90 comprises an input module 92, a packet switch 40, an output module 96 and a scheduler 94.