Abstract: An optical amplifier reducing gain deviation caused by wavelength arrangement has a first-stage optical amplifying unit, an attenuator, a second-stage optical amplifying unit, an automatic gain controller controlling the first- and second-stage optical amplifying units so that a gain of signal light outputted from the second-stage optical amplifying unit to signal light inputted to the first-stage optical amplifying unit is constant, and an attenuation amount controller controlling an attenuation amount at the attenuator to adjust gain-versus-wavelength characteristic at the automatic-gain-controlled first- and second-stage optical amplifying units on the basis of information on wavelength arrangement and an input level of the signal light inputted to the first-stage optical amplifying unit so that gain slope characteristic at the first- and second-stage optical amplifying units due to the wavelength arrangement and the input level is flattened.

Abstract: There is provided an optical amplifier including a pump light source to generate a pump light being capable of changing a wavelength thereof, a first rare earth doped medium to amplify an input signal light by using the pump light generated by the pump light source, a second rare earth doped medium to amplify the input signal light output from the first rare earth doped medium by using a residual pump light that is a portion of the pump light generated by the pump light source, and a wavelength controller to control a wavelength of the pump light generated by the pump light source, based on an input level of the input signal light.

Abstract: An optical amplifier includes a rare-earth doped optical fiber for receiving input light through one end and outputting output light through another end, the input light being input from an input port; an excitation light source for generating excitation light; an optical coupler for supplying the generated excitation light to the one end and/or the another end of the rare-earth doped optical fiber; and a reflector for reflecting an amplified spontaneous emission light out of a signal band traveling in opposite direction to the input light, the amplified spontaneous emission light being generated in the rare-earth doped optical fiber.

Abstract: An apparatus includes a first optical amplifier that uses a rare-earth-doped optical medium, an isolator that inputs amplified light amplified by the first optical amplifier, a second optical amplifier that uses a rare-earth-doped optical medium to amplify a light output from the isolator, and a first light router that routes amplified spontaneous emission light generated by the first optical amplifier or the second optical amplifier to input, by a second light router, the routed amplified spontaneous emission light to the optical rare-earth-doped medium other than the optical rare-earth-doped medium where the routed amplified spontaneous emission light is generated.

Abstract: An optical amplifier includes a first excitation light source that outputs a first excitation light; a second excitation light source that outputs a second excitation light; a first amplifying optical fiber doped with a rare-earth element and excited by the first excitation light to amplify light input to the first amplifying optical fiber; and a second amplifying optical fiber doped with a rare-earth element and excited by the second excitation light to amplify the light from the first amplifying optical fiber. A ratio between the intensity of the first excitation light and the intensity of the second excitation light is controlled according to the number of signal lights wavelength-multiplexed in the light input.

Abstract: An optical amplifier of the present invention comprises: first and second optical amplifying sections connected in series to each other between an input port and an output port; a first variable optical attenuator arranged on a former stage of the first optical amplifying section; a second variable optical attenuator arranged between the first and second optical amplifying sections; an optical amplification control section that controls the first and second optical amplifying sections; and an optical attenuation control section that controls the first and second variable optical attenuators.

Abstract: In an optical transmission apparatus, levels of signal lights obtained by demultiplexing a WDM signal and corresponding to channels are detected, based on which a channel in which a signal is transmitted and a channel in which no signal is transmitted are determined. An attenuation amount of a channel in which no signal is transmitted in a predetermined range from the channel in which the signal is transmitted is set to a value equal to an attenuation amount of the channel in which the signal is transmitted. An attenuation amount of a channel in which no signal is transmitted out of the predetermined range from the channel in which the signal is transmitted is set to a value larger than the attenuation amount of the channel in which the signal is transmitted. The signal lights are attenuated based on the values and multiplexed.

Abstract: In an optical transmission apparatus, optical power of each of wavelength contained in a wavelength multiplexing signal is measured, a measured value of the optical power of each wavelength is compared with a predetermined threshold value, a total value of the measured values of the optical power, which are equal to or larger than the threshold value, is calculated as a total value of signal beam power, and a total value of the measured values of the optical power, which are less then the threshold value, is calculated as a total value of ASE power. The number of the measured values of the optical power, which are equal to or larger than the threshold value, is calculated as a wavelength count of the signal beams contained in the wavelength multiplexing signal. A signal-to-ASE ratio is calculated from the total value of the signal beam power and the total value of the ASE power.

Abstract: A photo-detecting apparatus includes a photodiode that coverts light into electricity, a reverse-voltage switching unit that switches a reverse voltage to be applied to the photodiode, a current-difference detecting unit that detects a change in an output current of the photodiode occurring due to switching of the reverse voltage as a current difference, a correspondence retaining unit that retains a correspondence between the current difference and a dark current, a dark-current calculating unit that calculates a dark current by referring to the correspondence based on the current difference detected by the current-difference detecting unit, and a dark-current correcting unit that corrects the output current of the photodiode based on the dark current to find a photocurrent obtained through photoelectric conversion.

Abstract: An optical amplifier including: a first amplifying unit amplifying an input light by utilizing a first excitation light and thereby outputting a first amplified light; a second amplifying unit amplifying the first amplified light by utilizing a second excitation light and thereby outputting a second amplified light; and a control unit detecting a first absorption rate of the first excitation light and a second absorption rate of the second excitation light, and controlling a level of the first excitation light and a level of second excitation light based on the first absorption rate and the second absorption rate. The first absorption rate corresponds to a ratio of the first excitation light absorbed in the first amplifying unit, and the second absorption rate corresponds to a ratio of the second excitation light absorbed in the second amplifying unit.

Abstract: A Raman amplifier provided with a pump source outputting a pumping light; a rare-earth doped fiber inputting the pumping light and outputting an excitation light; and a guiding unit guiding the excitation light to an optical fiber to a direction opposite to which a signal light propagates in the optical fiber. Also a Raman amplifier provided with a plurality of pump sources outputting a plurality of pumping lights, a plurality of rare-earth doped fibers inputting the each of the plurality of pumping lights and outputting a plurality of excitation lights; a guiding unit guiding the plurality of excitation lights to an optical fiber to a direction opposite to which a signal light propagates in the optical fiber.

Abstract: An optical amplifier reducing gain deviation caused by wavelength arrangement has a first-stage optical amplifying unit, an attenuator, a second-stage optical amplifying unit, an automatic gain controller controlling the first- and second-stage optical amplifying units so that a gain of signal light outputted from the second-stage optical amplifying unit to signal light inputted to the first-stage optical amplifying unit is constant, and an attenuation amount controller controlling an attenuation amount at the attenuator to adjust gain-versus-wavelength characteristic at the automatic-gain-controlled first- and second-stage optical amplifying units on the basis of information on wavelength arrangement and an input level of the signal light inputted to the first-stage optical amplifying unit so that gain slope characteristic at the first- and second-stage optical amplifying units due to the wavelength arrangement and the input level is flattened.

Abstract: A wavelength division multiplexed optical amplifier, enabling elimination of the problems of oscillation and fluctuation in output due to ASE at the time of a rapid change in the number of input wavelengths, provided with a first-stage optical amplifying unit, second-stage optical amplifying unit, a common AGC circuit for common AGC of the first and second optical amplifying units, and a pumping light distribution means for applying pumping light to the first and second-stage optical amplifying units with a predetermined distribution ratio.

Abstract: In an optical transmission apparatus, optical power of each of wavelength contained in a wavelength multiplexing signal is measured, a measured value of the optical power of each wavelength is compared with a predetermined threshold value, a total value of the measured values of the optical power, which are equal to or larger than the threshold value, is calculated as a total value of signal beam power, and a total value of the measured values of the optical power, which are less then the threshold value, is calculated as a total value of ASE power. The number of the measured values of the optical power, which are equal to or larger than the threshold value, is calculated as a wavelength count of the signal beams contained in the wavelength multiplexing signal. A signal-to-ASE ratio is calculated from the total value of the signal beam power and the total value of the ASE power.

Abstract: An optical amplifier of the present invention comprises: first and second optical amplifying sections connected in series to each other between an input port and an output port; a first variable optical attenuator arranged on a former stage of the first optical amplifying section; a second variable optical attenuator arranged between the first and second optical amplifying sections; an optical amplification control section that controls the first and second optical amplifying sections; and an optical attenuation control section that controls the first and second variable optical attenuators.

Abstract: A contrivance, if a WDM signal state changes, is to improve an optical transmission quality by compensating gain flatness. A first excitation control unit sets a first optical pumping light source unit to emit excitation power needed to get the same amplifying operating level of a first amplifying medium as at the time of a maximum wavelength count when allocating wavelengths after a change in wavelength count at an equal interval in a wavelength range. A wavelength allocation bias estimation unit compares a present monitor value of optical power after outputting of a gain equalizer 13 with wavelength equi-allocation power associated with the recognized wavelength count, and thus estimates a wavelength allocation bias occurred as a concomitant of the change in the wavelength count. A primary gradient calculation unit obtains a primary gradient quantity defines as a gain deviation from the wavelength allocation bias.

Abstract: The present invention has an object to provide an optical amplifier capable of realizing a good response characteristic in a wide frequency band, even when a population inversion state is formed by a pumping light supplied to an optical amplification medium and an ASE light generated in the optical amplification medium. To this end, in the optical amplifier according to the present invention, a delayed phase matching fiber in which a first fiber whose response speed is relatively low is arranged on the input side and a second fiber whose response speed is relatively high is arranged on the output side, is used as the optical amplification medium doped with a rare-earth element.

Abstract: A dispersion compensator and method of dispersion compensation in which an input light is converted to a selected second wavelength, the converted light beam having the second wavelength is dispersion compensated in an amount dependent upon the second wavelength, and the compensated light beam having the second wavelength is converted to the first wavelength.

Abstract: The present invention has an object to provide an optical amplifier capable of realizing a good response characteristic in a wide frequency band, even when a population inversion state is formed by a pumping light supplied to an optical amplification medium and an ASE light generated in the optical amplification medium. To this end, in the optical amplifier according to the present invention, a delayed phase matching fiber in which a first fiber whose response speed is relatively low is arranged on the input side and a second fiber whose response speed is relatively high is arranged on the output side, is used as the optical amplification medium doped with a rare-earth element.

Abstract: An optical amplifier of the invention comprises first and second optical amplification sections connected in a cascade manner between an input terminal and an output terminal. Optical isolators which block C-band ASE travelling in an opposite direction to L-band signal light, are inserted on the amplification medium of each of the optical amplification sections. A constant gain control section calculates the number of wavelengths based on the input power of signal light, and controls the pumping light power of each optical amplification section at a constant slope with respect to the number of wavelengths, so that the respective gains in the optical amplification sections corresponding to the number of wavelengths each become constant. As a result, it is possible to maintain flat gain wavelength characteristics even when receiving input of WDM light where the number of wavelengths varies rapidly over a wide range.