Abstract: An optical signal amplifier for use in optical networks operating in a ring configuration comprising a first doped optical fiber loop pumped by a first laser and a second optical fiber loop pumped by a second laser.

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 transmitter apparatus capable of a transmission rate of at least 100 gbit/second 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 at least equal to 100 Gbit/s, an NRZ to RZ converter associated with each transmitter which converts each NRZ signal into an optical RZ signal with the signal remaining in the optical domain during conversion, the optical RZ signal having the same bit rate as the corresponding NRZ signal, an optical time division multiplexer which converts the RZ signals into at least two further signals, one of the further signals being formed by bitwise interleaving the bits of the at least two of the RZ signals which have the same bit rate, and a polarisation multiplexer which processes the two further signals to pr

Abstract: A method of producing green light signals, comprising coupling pump signals from at least one pump source into at least one erbium doped fiber (EDF) which cause ground state absorption (GSA), and excited state absorption (ESA) in erbium ions of the EDF, which produces green light signals, wherein the majority of the pump signals have a wavelength at which the probability of occurrence of ESA in the EDF is greater than the probability of occurrence of GSA in the EDF. The majority of the pump signals may have a wavelength in the range approximately 920 nm to approximately 980 nm, or in the region of 960 nm. An erbium doped fiber amplifier (EDFA) (1) for amplifying traffic-carrying signals may be pumped by green light signals produced by this method.

Abstract: A system and method for controlling the gain of an optical amplifier receiving one or more optical input signal channels at a first end include a source for generating a gain control signal, which is input to the optical amplifier at the opposite end to the input signal channels. The gain control signal is generated at a power level that produces stimulated Brillouin scattering (SBS) in the optical amplifier.

Abstract: An optical signal amplifier for use in optical networks operating in a ring configuration comprising a first doped optical fibre loop pumped by a first laser and a second optical fibre loop pumped by a second laser.

Abstract: The invention relates to a communications node (10, 90, 100) for routing a plurality of Wavelength Division Multiplexed (WDM) optical signals, the node having a plurality of line units (12) between its inputs and outputs, each line unit including a splitter (14) and a Wavelength Selective Switch (WSS) (16), wherein the splitter (14) is arranged to split an incoming WDM signal into a plurality of WDM signals and to pass them to each WSS in the plurality of line units, each WSS (16) being arranged to selectively route any one or more channels of its received WDM signals to its associated output. Such an arrangement has the advantage of providing a more cost effective realisation of a node with a high nodal degree. The invention provides a technical solution to the problem of connecting a plurality of inputs to a plurality of outputs in a multi-port WDM node. The node has particular application in a mesh network where the nodal degree may be high.

Abstract: A method of producing green light signals, comprising coupling pump signals from at least one pump source into at least one erbium doped fibre (EDF) which cause ground state absorption (GSA), and excited state absorption (ESA) in erbium ions of the EDF, which produces green light signals, wherein the majority of the pump signals have a wavelength at which the probability of occurrence of ESA in the EDF is greater than the probability of occurrence of GSA in the EDF. The majority of the pump signals may have a wavelength in the range approximately 920 nm to approximately 980 nm, or in the region of 960 nm. An erbium doped fibre amplifier (EDFA) (1) for amplifying traffic-carrying signals may be pumped by green light signals produced by this method.

Abstract: A Raman amplifier for amplifying WDM radiation propagating along an optical fiber, the WDM radiation comprising a plurality of radiation components each having a selected waveband, comprises a plurality of optical radiation generators operable to generate pump radiation of a selected wavelength and power, the radiation being coupled into the fiber to optically amplify the WDM radiation. The generators are wavelength tuneable, and the power of the radiation components of the WDM radiation is measured after it has propagated along the fiber and has been amplified. The wavelength and power of operation of the generators are controlled in dependence upon the measured powers such as to make the measured powers substantially equal in magnitude and of a selected magnitude.

Abstract: A system and method for controlling the gain of an optical amplifier receiving one or more optical input signal channels at a first end include a source for generating a gain control signal, which is input to the optical amplifier at the opposite end to the input signal channels. The gain control signal is generated at a power level that produces stimulated Brillouin scattering (SBS) in the optical amplifier.

Abstract: A method of producing green light signals couples pump signals from at least one pump source into at least one erbium doped fiber (EDF) to cause ground state absorption (GSA) and excited state absorption (ESA) in erbium ions of the EDF, which produces green light signals. The majority of the pump signals have a wavelength at which the probability of occurrence of ESA in the EDF is greater than the probability of occurrence of GSA in the EDF. The majority of the pump signals may have a wavelength in the range approximately 920 nm to approximately 980 nm, or in the region of 960 nm. An erbium doped fiber amplifier (EDFA) for amplifying traffic-carrying signals may be pumped by green light signals produced by this method.

Abstract: A Raman amplifier for amplifying WDM radiation propagating along an optical fiber, the WDM radiation comprising a plurality of radiation components each having a selected waveband, comprises a plurality of optical radiation generators operable to generate pump radiation of a selected wavelength and power, the radiation being coupled into the fiber to optically amplify the WDM radiation. The generators are wavelength tuneable, and the power of the radiation components of the WDM radiation is measured after it has propagated along the fiber and has been amplified. The wavelength and power of operation of the generators are controlled in dependence upon the measured powers such as to make the measured powers substantially equal in magnitude and of a selected magnitude.

Abstract: An optical amplifier comprises a pumped Thulium doped fiber amplifier and a Raman amplifier provided in series. The Thulium doped fiber amplifier provides gain over a first wavelength range, and is range is extended by the Raman amplifier by suitable pumping. The Thulium amplifier operates in the S band, but the wavelength range is extended to the C band by the Raman amplifier. The amplifier thus has increased bandwidth, thereby allowing it to be used in higher capacity optical communications systems.