Abstract: An optical amplification device which includes first and second optical amplifiers, and a controller. The first optical amplifier receives a light and amplifies the received light. The second optical amplifier receives the light amplified by the first optical amplifier, and amplifies the received light. When a level of the light received by the first optical amplifier changes by ?, the controller controls a level of the light received by the second optical amplifier to change by approximately ??. In various embodiments, the controller causes the sum of the gains of the first and second optical amplifiers to be constant. In other embodiments, the optical amplification device includes first and second optical amplifier and a gain adjustor. The gain adjustor detects a deviation in gain of the first optical amplifier from a target gain, and adjusts the gain of the second optical amplifier to compensate for the detected deviation.

Abstract: An optical channel monitor includes: a first optical device to include first, second and third optical ports, light input through the first optical port being led to the second optical port, light input through the second optical port being led at least to the third optical port; a second optical device to include fourth, fifth and sixth optical ports, light input through the fourth optical port being led to the fifth optical port, light input through the fifth optical port being led at least to the sixth optical port; an optical filter to include seventh and eighth optical ports optically connected to the second and fifth optical ports, respectively, a specified wavelength being transmitted between the seventh and eighth optical ports; a first photo detector to detect light output from the sixth optical port; and a second photo detector to detect light output from the third optical port.

Abstract: A dispersion compensating apparatus includes a tunable dispersion compensator that dispersion-compensates an optical signal using a group delay property that is asymmetrical in bands outside an effective band; a set device that sets a dispersion compensation amount in the tunable dispersion compensator; and a shifter that shifts a central frequency of the effective band of the tunable dispersion compensator, based on the dispersion compensation amount set by the set device.

Abstract: A light receiving circuit includes: a filter, arranged in a downstream of an electric signal amplifier to amplify an electric signal based on a light signal, to adjust a bandwidth of an amplified electric signal; a monitor circuit to monitor a communication quality of the light signal and output a monitored value; and a control circuit to control a bandwidth of the filter based on a control value corresponding to the monitored value.

Abstract: An optical amplification apparatus includes an optical amplification medium configured to receive a first light signal from an end of the optical amplification medium and a second light signal from the other end of the optical amplification medium in opposite directions, the first and second light signals being branched from a light signal, an excitation light source configured to supply excitation light to the optical amplification medium through a multiplexer, a monitor configured to monitor the first and second light signals input to the optical amplification medium, respectively and to output monitoring signals respectively, and a controller configured to control the excitation light source in accordance with the monitoring signals.

Abstract: In an optical amplification apparatus an optical amplifier amplifies an optical signal at set gain. An equalizer changes loss of the amplified optical signal according to wavelengths. A processor controls the equalizer so as to make the equalizer have a loss-wavelength characteristic corresponding to a gain tilt of the optical amplifier which occurs according to the set gain.

Abstract: A communication system including: a transmission apparatus configured to modulate a first light by using a first signal to be transferred and a second signal having a frequency different from a frequency of the first signal so as to generate a first optical signal, modulate a second light by using a third signal to be transferred and a fourth signal having a frequency different from a frequency of the third signal so as to generate a second optical signal, polarization-multiplex the first optical signal and the second optical signal, and transmit a polarization-multiplexed optical signal in which the first optical signal and the second optical signal are polarization-multiplexed, each of the first light and the second light being polarized; and a measuring apparatus configured to measure powers of the second signal and the fourth signal which are included in the polarization-multiplexed optical signal transmitted from the transmission apparatus.

Abstract: There is provided an optical transmission apparatus including: a transmitter to output an optical signal to be transferred to other optical transmission apparatus; a first dummy light source to generate first dummy light having a wavelength which is not included in an optical signal received from other optical transmission apparatus; a first wavelength-multiplexer to wavelength-multiplex the optical signal received from other optical transmission apparatus, the optical signal output from the transmitter, and an optical signal with a wavelength, of the first dummy light, which is not included in the optical signal received from other optical transmission apparatus and in the optical signal output from the transmitter; and an optical amplifier to amplify an optical signal multiplexed by the first wavelength-multiplexer.

Abstract: An optical amplifier includes a light source that outputs light having an intensity corresponding to a supplied driving power; a modulator that modulates the light output from the light source in response to an input modulation signal; a Raman amplifier that performs Raman amplification on the light modulated by the modulator using a highly-nonlinear medium; and a driver that supplies the driving power to drive the light source and inputs the modulation signal to the modulator. The driver starts inputting the modulation signal to the modulation unit before the intensity of the light propagating through the Raman amplifier exceeds an intensity value at which stimulated Brillouin scattering occurs in the Raman amplifier.

Abstract: An optical amplifier includes an optical signal path that optically couples an input port and an output port, and transmits an optical signal input from the input port to the output port; an optical amplification medium that is arranged in the optical signal path, and amplifies the optical signal in a predetermined amplification wavelength band; and an optical filter that is arranged between the optical amplification medium and the output port in the optical signal path, flattens gain wavelength characteristics of the optical amplification medium in the amplification wavelength band, and attenuates amplified spontaneous emission (ASE) at a center of the amplification wavelength band more greatly than ASE at both sides of the amplification wavelength band among ASE that occurs in the optical amplification medium on the optical signal amplified by the optical amplification medium.

Abstract: An optical transmission apparatus includes an optical amplifier configured to amplify a wavelength-division multiplexed signal light using an amplifying medium doped with a rare earth ion, a first optical transmitter configured to output a wavelength of a dual-polarization-multiplexed signal to a short wavelength side of an amplification band of the optical amplifier, a second optical transmitter configured to output a wavelength of a non polarization-multiplexed signal to a long wavelength side of the amplification band of the optical amplifier, and an optical multiplexer configured to input a wavelength-division multiplexed signal to the optical amplifier, the wavelength-division multiplexed signal comprising the non polarization-multiplexed signal and the dual-polarization-multiplexed signal.

Abstract: An OSNR measuring device n OSNR measuring device includes an input port to which a signal light is given; a wavelength filter which includes a variable passband, and selectively takes out an optical component corresponding to a signal optical wavelength to be measured from the signal light; a wavelength control circuit which controls the passband of the wavelength filter; a delay interferometer which branches a light output from the wavelength filter and delays one of the branched lights with respect to the other branched light and in which the branched lights are made to interfere with each other; a photodetector which detects a power of a delay interference light output; and an OSNR calculation circuit which calculates, based on a bandwidth of a passband of the wavelength filter and the power of the delay interference light, an optical signal to noise ratio of a signal optical wavelength to be measured.

Abstract: In an optical amplifier, an input light is supplied to one end of an optical fiber connected to an output port, and the power of a light in an opposite direction which is input to the output port from the one end of the optical fiber, is measured, thereby obtaining a stimulated Brillouin scattering (SBS) occurrence threshold in the optical fiber based on the measurement result. Then, using the SBS occurrence threshold, a relation between the input light power and an occurrence amount of the self phase modulation (SPM) or the like in the optical fiber is obtained to be reflected on a control of the optical amplifier, so that an occurrence of the SPM or the like in the optical fiber is suppressed. As a result, it becomes possible to accurately measure, with a simple configuration, the nonlinear optical properties of the optical fiber actually connected to the output port of the optical amplifier, so that the optical S/N ratio degradation due to a nonlinear optical effect can be effectively suppressed.

Abstract: A signal light processing apparatus includes a first wavelength selection switch, a dispersion compensator, and a second wavelength selection switch. The first wavelength selection switch divides an input wavelength-multiplexed signal light into signal lights of each wavelength and outputs the signal lights from a first output port or a second output port in accordance with wavelengths of the divided signal lights. The dispersion compensator compensates dispersion compensation on the signal light output from the first output port by the first wavelength selection switch. The second wavelength selection switch combines the signal light on which dispersion compensation is compensated by the dispersion compensator and the signal light output from the second output port by the first wavelength selection switch.

Abstract: An optical amplification device which includes first and second optical amplifiers, and a controller. The first optical amplifier receives a light and amplifies the received light. The second optical amplifier receives the light amplified by the first optical amplifier, and amplifies the received light. When a level of the light received by the first optical amplifier changes by ?, the controller controls a level of the light received by the second optical amplifier to change by approximately ??. In various embodiments, the controller causes the sum of the gains of the first and second optical amplifiers to be constant. In other embodiments, the optical amplification device includes first and second optical amplifier and a gain adjustor. The gain adjustor detects a deviation in gain of the first optical amplifier from a target gain, and adjusts the gain of the second optical amplifier to compensate for the detected deviation.

Abstract: An optical amplification device which includes first and second optical amplifiers, and a controller. The first optical amplifier receives a light and amplifies the received light. The second optical amplifier receives the light amplified by the first optical amplifier, and amplifies the received light. When a level of the light received by the first optical amplifier changes by ?, the controller controls a level of the light received by the second optical amplifier to change by approximately ??. In various embodiments, the controller causes the sum of the gains of the first and second optical amplifiers to be constant. In other embodiments, the optical amplification device includes first and second optical amplifier and a gain adjustor. The gain adjustor detects a deviation in gain of the first optical amplifier from a target gain, and adjusts the gain of the second optical amplifier to compensate for the detected deviation.

Abstract: According to an aspect of the embodiment of the invention, an optical amplifier including an input port, an output port, a plurality of amplifying parts, an optical attenuator, a gain controller and an optical attenuator controller. The plurality of amplifying parts includes an optical amplification medium and a pumping light source for generating pump light. The optical attenuator is optically connected between the amplifying parts. The gain controller controls the pump light power of the pump sources, respectively, in such a way that the ratio decreases in accordance with the gain set value increasing and the ratio interpose between a first threshold level and a second threshold level. The optical attenuator controller controls attenuation of the optical attenuator in order to maintain the sum of generating gains of the amplifying parts in the gain set value in accordance with a state of the signal light inputted into the input port.

Abstract: An optical amplification device which includes first and second optical amplifiers, and a controller. The first optical amplifier receives a light and amplifies the received light. The second optical amplifier receives the light amplified by the first optical amplifier, and amplifies the received light. When a level of the light received by the first optical amplifier changes by ?, the controller controls a level of the light received by the second optical amplifier to change by approximately ??. In various embodiments, the controller causes the sum of the gains of the first and second optical amplifiers to be constant. In other embodiments, the optical amplification device includes first and second optical amplifier and a gain adjustor. The gain adjustor detects a deviation in gain of the first optical amplifier from a target gain, and adjusts the gain of the second optical amplifier to compensate for the detected deviation.

Abstract: An optical fiber reel storing a plurality of optical fibers having an annular frame; a first reel portion provided around an radially outer peripheral surface of the annular frame and receiving at least one of the plurality of optical fibers wound up around the radially outer peripheral surface; and, a second reel portion provided radially inside the annular frame and housing at least one of the plurality of optical fiber therein.

Abstract: An OSNR monitor device includes an optical receiver including a delay interferometer which inputs an optical signal in accordance with a given bandwidth and outputs two optical signals and causes the optical signals to interfere with each other and optical detectors which outputs currents in accordance with optical powers of the optical signals output from the interferometer, an optical power monitor configured to obtain the optical powers of the optical signals received by the optical detectors included in the optical receiver, and an OSNR calculator configured to calculate an optical signal-to-noise ratio in accordance with the optical powers obtained from the optical power monitor and the reception bandwidth.