Abstract: In an optical transmission system according to one aspect of the present invention, for transmitting a WDM light from a transmission station to a reception station, utilizing a Raman amplifier, the Raman amplifier comprises: an optical amplification medium; a pumping light source generating a plurality of pumping lights having wavelengths different from each other; an optical device introducing the plurality of pumping lights to the optical amplification medium; and control means for controlling the pumping light source, the transmission station sends out a plurality of reference lights having wavelengths at which respective Raman gain obtained by the plurality of pumping lights reach peaks or wavelengths close to the above wavelengths, and the control means controls the plurality of pumping lights based on the optical powers of the plurality of reference lights. Thus, it becomes possible to accurately manage the optical power balance of the WDM light and the optical power of the entire WDM light.

Abstract: A Raman amplifier inputs pump light into an optical fiber (transmission path) through which an optical signal passes, to amplify the optical signal. An optical receiving unit is provided downstream of the Raman amplifier and monitors the power of the optical signal amplified by the Raman amplifier. A calculating unit determines Raman amplification gain based on the power of the optical signal monitored by the optical receiving unit, and calculates the power of a noise component included in the optical signal based on the gain. The calculating unit, in real-time, calculates the power, which varies in complicated manners depending on conditions, and outputs information concerning to the power to another apparatus at a frequency on the order of milliseconds.

Abstract: A multi-wavelength light amplifier includes a first-stage light amplifier which has a first light amplifying optical fiber amplifying a light input, a second stage light amplifier which has a second light amplifying optical fiber amplifying a first light output from the first-stage light amplifier, and an optical system which maintains a second light output of the second-stage light amplifier at a constant power level. The first-stage and second-stage light amplifiers have different gain vs wavelength characteristics so that the multi-wavelength light amplifier has no wavelength-dependence of a gain thereof.

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 multi-wavelength light amplifier includes a first-stage light amplifier which has a first light amplifying optical fiber amplifying a light input, a second stage light amplifier which has a second light amplifying optical fiber amplifying a first light output from the first-stage light amplifier, and an optical system which maintains a second light output of the second-stage light amplifier at a constant power level. The first-stage and second-stage light amplifiers have different gain vs wavelength characteristics so that the multi-wavelength light amplifier has no wavelength-dependence of a gain thereof.

Abstract: A wavelength division multiplexing system according to the present art adjusts the amount of dispersion compensation (the amount of dispersion compensation of an NZ-DSF and a DCF) every all spans on the basis of the time slot when an intensity modulation signal transmitter outputs an intensity modulation signal and the wavelength interval when a wavelength coupler multiplexes a phase modulation signal (output from a phase modulation signal transmitter) and the intensity modulation signal.

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 an apparatus for controlling a gain of an optical amplifier, and the apparatus comprises a target gain calculating unit for calculating, as a target gain for an optical amplifier, a value obtained by increasing or decreasing a gain (output) of signal light as the number of wavelengths of wavelength-multiplexed signal light decreases, and a control signal outputting unit for outputting a control signal to the optical amplifier so as to amplify the wavelength-multiplexed signal light with the target gain calculated by the target gain calculating unit. This promptly suppresses a fluctuation of signal light level, particularly, a fluctuation of output light power of an optical amplifier stemming from a variation of the number of wavelengths of wavelength-multiplexed signal light.

Abstract: The present invention relates to an optical transmission apparatus capable of suppressing a transitional gain variation when a number of signal wavelengths changes, and maintaining communication quality in optical signals. The optical transmission apparatus is provided with an optical power control device that varies light power of light for each wavelength component corresponding to a wavelength channel, the light including signal light and spontaneous emission light; a wavelength arrangement information obtaining unit that obtains arrangement information of the wavelength channel of the signal light; and a control unit that controls the power control device based on the arrangement information obtained at the wavelength arrangement information obtaining unit so that light power of a wavelength component of the signal light and light power of a wavelength component other than the wavelength component of the signal light become substantially equal.

Abstract: In a distributed Raman amplifier according to the present invention, a WDM signal light and a reference light are supplied to one end of an optical transmission path to which a pumping light is supplied; the WDM signal light and the reference light, which are propagated through the optical transmission path, are subjected to the distributed Raman amplification; the powers of the WDM signal light and the reference light, which are output from the other end of the optical transmission path, are monitored; and pumping light sources are controlled based on the monitor result. A wavelength of the reference light is set within a gain band of the distributed Raman amplification but longer or shorter than a wavelength of the WDM signal light, and also, set to be in a wavelength region in which a fluctuation amount of a Raman gain in the wavelength of the reference light becomes equal to or smaller than ? of a fluctuation amount of a Raman gain in the wavelength band of the WDM signal light.

Abstract: In an optical transmission system according to one aspect of the present invention, for transmitting a WDM light from a transmission station to a reception station, utilizing a Raman amplifier, the Raman amplifier comprises: an optical amplification medium; a pumping light source generating a plurality of pumping lights having wavelengths different from each other; an optical device introducing the plurality of pumping lights to the optical amplification medium; and control means for controlling the pumping light source, the transmission station sends out a plurality of reference lights having wavelengths at which respective Raman gain obtained by the plurality of pumping lights reach peaks or wavelengths close to the above wavelengths, and the control means controls the plurality of pumping lights based on the optical powers of the plurality of reference lights. Thus, it becomes possible to accurately manage the optical power balance of the WDM light and the optical power of the entire WDM light.

Abstract: An optical transmission apparatus includes an optical add drop multiplexer (OADM) that adds/drops an optical signal to/from a transmission path. The optical transmission apparatus further includes a pump light multiplexer and a dispersion compensation fiber that are located downstream of the OADM on the transmission path. The optical transmission apparatus is configured to house a pump light source connectable to the pump light multiplexer to Raman amplify an optical signal in the dispersion compensation fiber.

Abstract: In an optical transmission system according to one aspect of the present invention, for transmitting a WDM light from a transmission station to a reception station, utilizing a Raman amplifier, the Raman amplifier comprises: an optical amplification medium; a pumping light source generating a plurality of pumping lights having wavelengths different from each other; an optical device introducing the plurality of pumping lights to the optical amplification medium; and control means for controlling the pumping light source, the transmission station sends out a plurality of reference lights having wavelengths at which respective Raman gain obtained by the plurality of pumping lights reach peaks or wavelengths close to the above wavelengths, and the control means controls the plurality of pumping lights based on the optical powers of the plurality of reference lights. Thus, it becomes possible to accurately manage the optical power balance of the WDM light and the optical power of the entire WDM light.

Abstract: An aspect of the embodiments utilizes an optical transmission apparatus which includes a rough adjustment execution portion that monitors a bit error rate of an optical signal for set values of a dispersion compensator where the set values have been set less closely to each other within a dispersion compensation control range than when a wavelength dispersion value set in the dispersion compensator is determined, and carries out a rough adjustment to determine a comparison threshold value used to set the wavelength dispersion value based on the monitored bit error rate, and a fine adjustment execution portion that monitors the bit error rate for the dispersion compensator the set values have been set more closely to each other, and carries out an adjustment to determine a wavelength dispersion value corresponding to the midpoint between the two acquired bit error rates as the wavelength dispersion value of the dispersion compensator.

Abstract: An optical transmission apparatus includes a demultiplexing unit that demultiplexes a light input to the optical transmission apparatus into a plurality of lights; an optical attenuator that adjusts an output level of a light within a band that includes a signal light from among demultiplexed lights; a bypass unit that bypasses a light outside the band from among demultiplexed lights; a multiplexing unit that multiplexes adjusted light and the light from the bypass unit; and an optical amplifier that amplifies input light. The optical amplifier is provided at least one of a stage prior to the demultiplexing unit and a stage subsequent to the multiplexing unit.

Abstract: An optical node apparatus according to the present invention amplifies a WDM signal light input to an input port, and thereafter, branches the amplified WDM signal light by an optical branching coupler to send the branched lights to first and second optical paths, and selects the light propagated through the first optical path by an optical switch to amplify the selected light by a post-amplifier, thereby outputting the amplified light from an output port, when the optical node apparatus is operated as an optical amplification repeating node. When the operational state is upgraded to an optical add/drop multiplexing node, an OADM section is connected between a set of connecting ports on the second optical path, and the adjustment of the OADM section is performed utilizing the WDM signal light branched by the optical branching coupler, and thereafter, the switching of the optical switch is performed to select the light on the second optical path side.

Abstract: In a wavelength-division-multiplexing optical transmission system in which optical-node apparatuses that perform relay transmission of wavelength-division-multiplexed light are located at specified nodes in a main optical transmission path, an optical amplifier switches level control to constant-gain control when there is a notification of a change in the number of multiplexed wavelengths, and then after a specified amount of time restarts level control so that the level becomes a target level that corresponds to the actual number of wavelengths.

Abstract: An optical node apparatus according to the present invention amplifies a WDM signal light input to an input port, and thereafter, branches the amplified WDM signal light by an optical branching coupler to send the branched lights to first and second optical paths, and selects the light propagated through the first optical path by an optical switch to amplify the selected light by a post-amplifier, thereby outputting the amplified light from an output port, when the optical node apparatus is operated as an optical amplification repeating node. When the operational state is upgraded to an optical add/drop multiplexing node, an OADM section is connected between a set of connecting ports on the second optical path, and the adjustment of the OADM section is performed utilizing the WDM signal light branched by the optical branching coupler, and thereafter, the switching of the optical switch is performed to select the light on the second optical path side.

Abstract: A multi-wavelength light amplifier includes a first-stage light amplifier which has a first light amplifying optical fiber amplifying a light input, a second stage light amplifier which has a second light amplifying optical fiber amplifying a first light output from the first-stage light amplifier, and an optical system which maintains a second light output of the second-stage light amplifier at a constant power level. The first-stage and second-stage light amplifiers have different gain vs wavelength characteristics so that the multi-wavelength light amplifier has no wavelength-dependence of a gain thereof.

Abstract: In an optical transmission system according to one aspect of the present invention, for transmitting a WDM light from a transmission station to a reception station, utilizing a Raman amplifier, the Raman amplifier comprises: an optical amplification medium; a pumping light source generating a plurality of pumping lights having wavelengths different from each other; an optical device introducing the plurality of pumping lights to the optical amplification medium; and control means for controlling the pumping light source, the transmission station sends out a plurality of reference lights having wavelengths at which respective Raman gain obtained by the plurality of pumping lights reach peaks or wavelengths close to the above wavelengths, and the control means controls the plurality of pumping lights based on the optical powers of the plurality of reference lights. Thus, it becomes possible to accurately manage the optical power balance of the WDM light and the optical power of the entire WDM light.