Abstract: A WDM add/drop module for use in a network node of an optical network, the module comprising an optical drop unit for dropping a first wavelength signal travelling along a first path in the optical network traffic, a trunk receiver unit for converting the first wavelength signal into a first electrical signal, a tributary optical transmitter unit for converting an electrical input signal into a first optical signal for transmission along a tributary optical connection, wherein the output of the trunk receiver unit is connected to the tributary optical transmitter unit and to a first interface port of the WDM drop module for interfacing with another WDM drop unit, an electrical switch unit arranged in a manner such that, in use, selectively either the first electrical signal or a second electrical signal received at a second interface port of the WDM add/drop module from another WDM add/drop module is through connected to the tributary transmitter unit for conversion and transmission along the tributary optica

Abstract: A WDM-to-switch interface unit comprising a WDM multiplexer/demultiplexer (mux/demux) for interfacing to a WDM optical network, a switch interface element for interfacing to an external switch unit, and a first conversion component disposed between the WDM mux/demux and the switch interface element for converting one or more layers of a management protocol in the optical network into corresponding layers of a management protocol of the external switch unit.

Abstract: An optical network element comprising a plurality of subscriber line connections, a WDM unit having a plurality of WDM channel connections, a plurality of subscriber line interface cards and a plurality of trunk line interface cards for optical interfacing between the subscriber line connections and the WDM channel connections, and a switch arranged, in use, in a manner such as to be capable of switching transmission directions between the WDM channel connections and individual ones of the subscriber line connections by suitable switching of an optical path configuration between transmitter ports and receiver ports of the subscriber line interface cards and the WDM channel connections.

Abstract: A WDM system comprising a first WDM module having a first multiplexer unit for multiplexing a WDM optical signal, a second WDM module having a first demultiplexer unit for demultiplexing the WDM optical signal, and wherein the system is arranged, in use, such that optical losses experienced by individual channels of the WDM optical signal in the first multiplexing unit and the first demultiplexing unit and optical losses experienced by the channels during un-amplified transmission between the first and second WDM modules are substantially balanced.

Abstract: A WDM assembly comprising a WDM filter structure for multiplexing and demultiplexing optical signals and having a single fibre common connection for transmitting and receiving a WDM optical signal; a housing member for the WDM filter structure; a plurality of E/O transmitter units external to the housing member for receiving a plurality of independent electrical data signals and converting into a plurality of corresponding optical WDM channel signals; plurality of O/E receiver units external to the housing member for receiving a plurality of optical WDM channel signals and converting into a corresponding plurality of independent electrical data signals; wherein each of the E/O transmitter units and O/E receiver units is optically connected to the WDM filter structure via a single fibre link; and wherein excess fibre length in each fibre link is accommodated within the housing member, whereby each fibre length has a predetermined external fibre length between the housing member and the E/O transmitter units an

Abstract: A WDM add/drop module for use in a network node of an optical network, the module comprising an optical drop unit for dropping a first wavelength signal travelling along a first path in the optical network traffic, a trunk receiver unit for converting the first wavelength signal into a first electrical signal, a tributary optical transmitter unit for converting an electrical input signal into a first optical signal for transmission along a tributary optical connection, wherein the output of the trunk receiver unit is connected to the tributary optical transmitter unit and to a first interface port of the WDM drop module for interfacing with another WDM drop unit, an electrical switch unit arranged in a manner such that, in use, selectively either the first electrical signal or a second electrical signal received at a second interface port of the WDM add/drop module from another WDM add/drop module is through connected to the tributary transmitter unit for conversion and transmission along the tributary optica

Abstract: A WDM add/drop multiplexer structure comprising a plurality of WDM laser assemblies, wherein the WDM add/drop structure is arranged, in use, in a manner such that a controlled temperature environment is created around laser sources of the laser assemblies, and in a manner such as to be capable of creating the controlled temperature environment around the laser sources while the WDM add/drop multiplexer structure is subjected to an outside temperature ambient experienced in an Outside plant (OSP) situation.

Abstract: A network node for use in a WDM communications network, the network node comprising a first network interface unit arranged, in use, to demultiplex an incoming WDM optical signal and to convert the incoming WDM optical signal into a plurality of electrical channel signals, a regeneration unit for regenerating the electrical channel signals utilizing at least 2R regeneration, a second network interface unit arranged, in use, to convert and multiplex at least one of the electrical channel signals into an outgoing WDM optical signal, and a secondary interface unit arranged, in use, to convert at least one of the electrical channel signals into an optical signal and to drop the optical signal at the network node.

Abstract: A method of effecting failure protection switching in an optical network, the optical network comprising a ring structure carrying a bi-directional optical data signal, and a plurality of network hubs arranged in-line within the ring structure, each network hub being arranged, in use, to transmit and receive signals bi-directionally along the ring structure, the method comprising the steps of a) detecting a “no signal” at a primary pre-amplifier located at one of the network hubs and arranged to pre-amplify a primary optical signal received from a first direction along the ring structure b) shutting down the primary pre-amplifier and powering up a secondary pre-amplifier located at the one network hub and arranged to pre-amplify a redundant optical signal corresponding to the optical signal and received from the opposing direction along the ring structure.

Abstract: A hub structure for use in an optical network, the optical network comprising a ring structure carrying a bidirectional optical data signal and a plurality of hub structures arranged in-line within the ring structure, the optical data signal comprising primary and secondary path transmission signals having opposing transmission directions on the ring structure, the hub structure comprising a drop unit arranged, in a normal state, to drop and through-connect a primary receive path signal for further processing at the hub structure, and, in a protection state, to drop and through-connect a secondary receive path signal for further processing at the hub structure.

Abstract: An optical network node. A plurality of subscriber line connections. A WDM unit has a plurality of WDM channel connections connected to corresponding ones of the subscriber line connections and are arranged, in use, to multiplex optical signals carried on selected transmission connections of the WDM channel connections onto a trunk optical network connection. The WDM unit is arranged in a manner such that, in use, each transmission connection filters a specific wavelength associated with that transmission connection, whereby cross talk between the WDM channel connections is reduced.

Abstract: An optical network hub structure comprising a WDM unit arranged in line with a fiber trunk carrying a bi-directional optical network signal to drop/add blocks of wavelengths destined to/originating from the network hub structure and to through connect other blocks of wavelengths, and at least one amplifier structure disposed in line on the fiber trunk at each side of the WDM unit, each amplifier structure comprising at least two propagation dependent optical junction elements, at least two optical paths optically connected in parallel between the two junction elements, and a first amplifier in only one of the optical paths, whereby a bi-directional, multiplexed optical signal comprising different blocks of wavelengths, each block of wavelengths having a specified propagation direction with respect to the amplifier structure, is, in use, uni-directionally amplified, whereby at each side of the WDM unit the optical network signal is, in use, uni-directionally amplified.

Abstract: A rack structure for a network node system, the rack structure comprising a first rack portion arranged, in use, to receive a plurality of circuit cards in slots and having a plurality of first connector elements disposed on a backplane thereof, each first connector element being arranged to make contact with a corresponding second connector element of one of the cards when it is inserted into one of the slots, and a patch panel rack portion comprising, on a frontplane thereof, a plurality of third connector elements, each third connector element being internally connected to one of the first connectors, whereby the patch panel enables, in use, rewiring of the rack structure from the front of the rack structure.

Abstract: A network hub structure for connecting network elements of a first WDM network supporting a first bit rate WDM data stream to other network elements on a second optical network supporting a second bit rate data stream which is substantially a multiple n of the first bit rate; the hub structure comprising a multiplexing system comprising a plurality of multiplexing units, each multiplexing unit being arranged to multiplex n first WDM data streams into one second data stream, and a switching unit arranged, in use, to selectively cross connect any n first WDM data streams originating from one or more of the network elements of the WDM network destined for any same one of said other network elements to one of the multiplexing units for multiplexing into one said second data stream.

Abstract: A DWDM network supporting first bit rate data streams, the DWDM network comprising a plurality of network hubs interfacing to subscriber line connections, and a core hub for providing cross connections between the network hubs, wherein each of the network hubs comprises a first bi-directional multiplexing unit arranged to multiplex n subscriber data streams each having a second bit rate which is substantially 1/nth of the first bit rate into a single first bit rate data stream for distribution on the DWDM network, and wherein the core hub comprises a plurality of second bi-directional multiplexing units each for de-multiplexing one of the single first bit rate data streams originating from the network hubs into the subscriber data streams and a switching unit arranged to selectively cross-connect the individual subscriber data streams back to individual ones of the second multiplexing units for distribution of the subscriber data streams to their respective destination network hubs in single first bit rate da

Abstract: An optical modulation system for independently modulating multiple wavelengths and transmitting them along a single output waveguide, the system comprising: a series of optical modulator elements each having at least one modulator waveguide input for inputting a single wavelength and modulation means for modulating the input single wavelength to produce a modulated wavelength output; an array of optical laser emitters, each emitting at a separate wavelength, the array having a series of wavelength outputs, one each of which is interconnected to the waveguide modulator input of the series of optical modulator elements; and an optical multiplexer taking a series of a modulated wavelength outputs having differing wavelengths and for multiplexing the multiple wavelengths together for output onto the single output waveguide.

Abstract: An optical ring network comprising; a plurality of network elements including a core network element interfacing the ring network with an external core network, and at least one ring network element; wherein the core network element includes a first CWDM unit, a first DWDM unit and switching means arranged to cross connect any wavelength channel within or between wavelength bands on the ring network or between the ring network and the core network, and wherein the ring network elements each include, a second CWDM unit and a second DWDM unit, the second CWDM unit being arranged to add/drop at least a first wavelength band at said ring network element from and to the second DWDM unit and to express other wavelength bands onto the next network element

Abstract: An optical ring network structure comprising two or more network elements, and a single optical fiber connection between each pair of neighboring network elements for carrying an optical signal, wherein the ring network structure is arranged in a manner such that, in use, band allocation utilizing multiplexing on each single fiber connection is chosen in a manner such that groups of wavelengths for bi-directional data transfer and for bi-directional redundant data transfer for protection respectively are provided on each single fiber connection.

Abstract: An optical network element comprising a plurality of subscriber line connections, a WDM unit having a plurality of WDM channel connections, a plurality of subscriber line interface cards and a plurality of trunk line interface cards for optical interfacing between the subscriber line connections and the WDM channel connections, and a switch arranged, in use, in a manner such as to be capable of switching transmission directions between the WDM channel connections and individual ones of the subscriber line connections by suitable switching of an optical path configuration between transmitter ports and receiver ports of the subscriber line interface cards and the WDM channel connections.

Abstract: A bi-directional optical amplifier arrangement for use in an optical path along which a bi-directional optical signal is travelling, the arrangement comprising at least two amplifier units disposed to amplify, in use, in different propagation directions, at least two propagation direction dependent optical junction elements, at least two optical paths disposed in parallel between the junction elements, wherein each optical paths comprises one of the amplifier units; and wherein gain settings of the amplifier units are chosen in a manner such that, in use, a total gain experienced by an optical signal re-circulating along both optical paths is less than unity.