Abstract: An optical network comprises a plurality of nodes connected by an optical fiber. The nodes each comprise a pump combiner coupled to the optical fiber and operable to insert pump power into the fiber to provide Raman amplification of a signal in a connected section of the optical fiber. A pump source remote from the nodes and coupled to the pump combiners is operable to provide pump power to each of the pump combiners for Raman amplification.

Abstract: A method and system for control signaling in an open ring optical network includes transmitting traffic in an optical ring. At each of a plurality of nodes along the ring, local traffic is passively added to and passively dropped from the connected ring. At each node, an ingress optical supervisory channel (OSC) signal is dropped from the ring to a managing element. An egress OSC signal is added to the ring from the managing element. The OSC signals may be in-band signal or out-of-band signals.

Abstract: An add/drop node for an optical network comprises a passive splitter to split an ingress signal from the network into a first ingress signal and a second ingress signal. A first amplified splitter stages module is operable to passively split and amplify the first ingress signal into a plurality of drop signals. A filter module is operable to filter the second ingress signal to provide a filtered pass-through signal. A second amplified splitter stages module is operable to passively combine a plurality of add signals into a combined add signal and to combine the combined add signal with the filtered pass-through signal to create an egress signal forwardable to the network.

Abstract: An optical network includes an optical ring and at least three subnets. Each subnet includes a plurality of add/drop nodes coupled to the optical ring. The add/drop nodes are operable to passively add a first traffic stream in a first direction on the optical ring and a second traffic stream in a second direction on the optical ring. The first traffic stream comprises different content than the second traffic stream, and the first traffic stream and the second traffic stream are transmitted on the same wavelength. The network also includes a plurality of gateway nodes. The gateway nodes are each coupled to the optical ring at a boundary between neighboring subnets and are operable to selectively pass and terminate wavelengths between subnets to allow wavelength reuse in the subnets.

Abstract: The invention provides an optical fiber amplifier which assures stable operation of a pump light source and efficiently makes use of residual pump power to achieve improvement in conversion efficiency. The optical fiber amplifier includes a rare earth doped fiber. Pump light from a pump light source is introduced into one end of the rare earth doped fiber by way of a first optical coupler, and residual pump light originating from the pump light and arriving at the other end of the rare earth doped fiber is applied to the other rare earth doped fiber amplifier or the loss compensation of a dispersion compensating fiber by Raman amplification.

Abstract: An optical network includes an optical ring and a plurality of add/drop nodes coupled to the optical ring. Each of the add/drop nodes is operable to passively add and drop one or more traffic streams to and from the optical ring, and each traffic stream comprises a channel. A hub node also coupled to the optical ring is operable to selectively pass and terminate individual traffic streams.

Abstract: The present invention aims at providing a method for controlling wavelength characteristics of optical transmission powers by Raman amplification, in which the wavelength characteristics of optical transmission powers are automatically compensated without giving any losses to channel lights to thereby improve transmission characteristics, and an apparatus adopting the same. To this end, the method for controlling wavelength characteristics of optical transmission powers by Raman amplification according to the present invention supplies Raman pump light to an optical transmission path (Raman amplifying medium); compensates the wavelength characteristics of optical transmission powers caused by transmission of WDM signal light through the optical transmission path, by gain wavelength characteristics of generated Raman amplification; and monitors the wavelength characteristics of optical transmission powers after Raman amplification to thereby control the gain wavelength characteristics of Raman amplification.

Abstract: An optical amplifier, or optical repeater, for amplifying wavelength division multiplexed (WDM) light A first demultiplexer demultiplexes the WDM light into first and second lights corresponding to different wavelengths in the WDM light. First and second optical amplifiers amplify the first and second lights, respectively. A first multiplexer multiplexes the amplified first and second lights into a multiplexed light. A dispersion compensator compensates for dispersion in the multiplexed light. A second demultiplexer demultiplexes the dispersion compensated, multiplexed light into the first and second lights. Third and fourth optical amplifiers amplify the demultiplexed first and second lights, respectively. A second multiplexer multiplexes the amplified first and second lights from the third and fourth optical amplifiers into a WDM light. The optical amplifier can be configured so that the first and second lights travel through the dispersion compensator in opposite directions.

Abstract: A method and system for controlling the gain of the amplification of an optical signal is provided that includes both electrical feedforward and feedback. In a feedforward portion of an optical amplifier, the method includes receiving an optical signal and measuring an input power. Based on the measured input power and a desired gain, a feedforward pump power is determined. The pump power is adjusted based on the determined pump power. In a feedback portion of an optical amplifier, an output power is measured and gain is determined based on the output power and the measured input power. The measured gain is compared to a desired gain and the pump power is adjusted based on that comparison.

Abstract: The invention provides an optical fiber amplifier which assures stable operation of a pump light source and efficiently makes use of residual pump power to achieve improvement in conversion efficiency. The optical fiber amplifier includes a rare earth doped fiber. Pump light from a pump light source is introduced into one end of the rare earth doped fiber by way of a first optical coupler, and residual pump light originating from the pump light and arriving at the other end of the rare earth doped fiber is applied to the other rare earth doped fiber amplifier or the loss compensation of a dispersion compensating fiber by Raman amplification.

Abstract: It is aimed at providing an inter-wavelength light power deviation monitoring method capable of directly measuring the signal light power to thereby detect the light power deviations among channels without requiring a higher wavelength resolution, and providing an optical equalizer and an optical amplifier adopting such a monitoring method. To this end, the monitoring method of the present invention comprises the steps of: obtaining channel information concerning WDM signal light; setting, based on the channel information, at least two measuring wavelength regions; measuring channel light power of the WDM signal light, for only the measuring wavelength regions; and obtaining light power ratio for the respective measuring wavelength regions making use of the measured values, to thereby judge the inter-wavelength light power deviations of the WDM signal light.

Abstract: A node for an optical network includes a first transport element operable to be coupled to an optical ring and to transport traffic in a first direction and a second transport element operable to be coupled to the optical ring and to transport traffic in a second, disparate direction. The first and second transport elements each include an optical splitter element operable to split an ingress signal into an intermediate signal and a drop signal. A filter in each node is operable to reject a first sub-band of the network from the intermediate signal to generate a passthrough signal including a plurality of disparate sub-bands of the network. Each node further includes an add element operable to add local traffic in the first sub-band to the passthrough signal for transport in the network.

Abstract: An optical amplifier includes an optical amplification medium, an excitation source to stimulate the amplification medium to output at least one wavelength gain peak, and a gain equalizer to equalize the output of the amplification medium such that gain is produced at wavelengths other than the wavelength gain peak. The gain equalizer may attenuate gain at the peak wavelength. The gain equalizer may equalize the output of the amplification medium such that gain is produced at wavelengths less than the wavelength gain peak. The optical amplifier may include both a gain equalizer and automatic level control circuitry to respectively maintain substantially uniform gain at wavelengths within an optical signal band and maintain constant output power.

Abstract: An optical amplifying apparatus which includes an optical amplifier, an optical attenuator and a controller. The optical amplifier amplifies a light signal having a variable number of channels. The optical attenuator passes the amplified light signal and has a variable light transmissivity. Prior to varying the number of channels in the light signal, the controller varies the light transmissivity of the optical attenuator so that a power level of the amplified light signal is maintained at an approximately constant level that depends on the number of channels in the light signal prior to the varying the number of channels. While the number of channels in the light signal is being varied, the controller maintains the light transmissivity of the optical attenuator to be constant.

Abstract: A method and system for controlling the gain of the amplification of an optical signal is provided that includes both electrical feedforward and feedback. In a feedforward portion of an optical amplifier, the method includes receiving an optical signal and measuring an input power. Based on the measured input power and a desired gain, a feedforward pump power is determined. The pump power is adjusted based on the determined pump power. In a feedback portion of an optical amplifier, an output power is measured and gain is determined based on the output power and the measured input power. The measured gain is compared to a desired gain and the pump power is adjusted based on that comparison.

Abstract: An optical ring is operable to transport traffic signals between nodes. A Raman pump source is coupled to the optical ring. The Raman pump source is operable to provide pump power to at least a portion of the optical fiber ring. Each node comprises an optical splitter operable to at least passively drop traffic to the optical fiber ring. Each node further comprises a pump filter operable to separate at the node the pump power from traffic signals.

Abstract: A system for distributing optical signals comprises a plurality of optical splitter stages. The optical splitter stages are each operable to passively split each of one or more optical signals provided to the stage into a plurality of optical signals. At least one of the optional splitter stages comprises an amplification stage, with the amplification stage including a plurality of gain media. The gain media are each operable to amplify an optical signal with pump power.

Abstract: An add/drop node (OADN) comprises a network optical fiber carrying a signal on an optical network. A network drop splitter is coupled to the network optical fiber and to stages of drop splitters, the stages of drop splitters being operable to passively split an optical signal from the network drop splitter into multiple copies of the signal. The OADN further comprises at least one filter operable to receive at least a copy of the signal from at least one drop splitter to create a filtered copy, and further comprises at least one broadband receiver operable to receive the filtered copy from the filter.

Abstract: An optical amplifying apparatus which includes an optical amplifier, an optical attenuator and a controller. The optical amplifier amplifies a light signal having a variable number of channels. The optical attenuator passes the amplified light signal and has a variable light transmissivity. Prior to varying the number of channels in the light signal, the controller varies the light transmissivity of the optical attenuator so that a power level of the amplified light signal is maintained at an approximately constant level that depends on the number of channels in the light signal prior to the varying the number of channels. While the number of channels in the light signal is being varied, the controller maintains the light transmissivity of the optical attenuator to be constant.

Abstract: The present invention relates to a wavelength-multiplexed light amplifying apparatus to be used in a state of being connected to a branching portion of a multiplexing/branching unit or to be used for a m×n matrix optical switch of an optical cross-connect. The wavelength-multiplexed light amplifying apparatus is composed of a plurality of wavelength-multiplexed light amplifying units and an optical feedback loop system. A signal input port of an optical branching section in one wavelength-multiplexed light amplifying unit is connected to an output side of an optical amplifying section in the preceding wavelength-multiplexed light amplifying unit. This configuration disperses the power loss of an optical signal to perform amplification with high efficiency and further enables the expansion of the branching port in the in-service.