Abstract: An optical modulation apparatus includes a first modulator, a second modulator, a multiplexer, a detector and an adjustor. The first modulator modulates light emitted by a light source using a first input signal and outputs a first modulated signal. The second modulator modulates the light using a second input signal and outputs a second modulated signal. The multiplexer multiplexes the first and second modulated signals and outputs a multiplexed signal. The detector is configured to detect a dip where power in a waveform of the multiplexed signal is equal to or smaller than a predetermined value. The adjustor is configured to adjust a delay of the first and second input signals based on power at the dip.

Abstract: An optical modulation apparatus includes a first modulator, a second modulator, a multiplexer, a calculator and an adjustor. The first modulator configured to modulate light emitted by a light source using a first input signal and output a first modulated signal. The second modulator configured to modulate the light using a second input signal and output a second modulated signal. The multiplexer configured to multiplex the first and second modulated signals and output a multiplexed signal. The calculator configured to calculate a power difference between a higher-side frequency component having a frequency higher than a center frequency of the multiplexed signal and a lower-side frequency component having a frequency lower than the center frequency. The adjustor configured to adjust delays of the first and second input signals based on the power.

Abstract: A polarized-wave-multiplexing optical transmitter including: an optical combiner generating a polarized-wave-multiplexed optical signal by polarized-wave-multiplexing a first optical modulation signal and a second optical modulation signal; an optical power fluctuation portion fluctuating optical power of the first optical modulation signal and the second optical modulation signal periodically; a total-optical-power detection portion detecting fluctuation amount of total optical power of the polarized-wave-multiplexed optical signal; and an optical power controller reducing an optical power difference between the first optical modulation signal and the second optical modulation signal based on detection result of the total-optical-power detection portion.

Abstract: A signal regeneration device which makes an extracted clock signal highly accurate while maintaining superior receiving sensitivity. To this end, a device of the present invention is configured to have a branch section for branching an input electrical signal which has been demodulated from a differential phase-shift modulated state; a first filter for equalizing a waveform of one of the demodulated electrical signals branched by the branch section; a clock recovery section for recovering a clock signal from the demodulated electrical signal whose waveform has been equalized by the first filter; and a data regeneration section for regenerating a data signal from a remaining one of the demodulated electrical signals branched by the branch section and from a clock signal recovered by the clock recovery section.

Abstract: A segmented-in-series solid oxide fuel cell stack of the invention comprises: an electrically-insulating porous support body having a gas passage therein; and a plurality of fuel cells arranged side by side on a surface of the support body. Each fuel cell have a first inner electrode layer; a current collector and a second inner electrode layer arranged side by side on the first inner electrode layer; and a solid electrolyte layer and an outer electrode layer sequentially laminated on the second inner electrode layer, and have a multilayer structure in which the solid electrolyte layer is extended and connected to the current collector through an intermediate layer. These fuel cells are connected in series. The current collector and the second inner electrode layer are arranged with a predetermined clearance therebetween on the first inner electrode layer. A fuel cell of the invention is formed by storing these segmented-in-series solid oxide fuel cell stacks in a storage container.

Abstract: In an optical transmitter of the invention, continuous light from a light source is a (CS)RZ-D(Q)PSK modulated by two optical modulators connected in series, and a part of the optical signal output from a post-stage optical modulator is branched by an output monitor section, and the power of a preset frequency component, excluding a frequency component corresponding to a baud rate, included in an electrical spectrum acquired by photoelectrically converting the branched beams is measured. The relative phase of drive signals applied to the optical modulators is then feed-back controlled so that the power becomes a minimum. As a result, a delay shift due to a temperature change or the like between drive signals applied to respective optical modulators, can be reliably compensated.

Abstract: A delay device that provides a delay amount to at least one of the in-phase signal and the quadrature signal, and a delay control section that controls the delay amount provided by the delay device based on a quality of the signals when the in-phase signal and the quadrature signal, to the at least one of which the delay amount is provided, at the delay device are converted into digital signals by the analog-digital converter, and the digital signal processing is carried out at the processor are provided. Thereby, the signal quality of recovered data at a receiving end of a multi-level phase modulation communication system is improved.

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 fiber includes: a first core portion doped with rare earth ions; a second core portion having a lower refractive index than that of the first core portion, provided along an outer circumference of the first core portion, and doped with the rare earth ions; and a clad portion having a lower refractive index than that of the second core portion and provided along an outer circumference of the second core portion, and is configured such that a concentration of the rare earth ions added to the second core portion is higher than that to the first core portion. With this configuration, it is possible to suppress an amount of FWM crosstalk in an optical amplification by decreasing the length of a fiber while alleviating efficiency deterioration due to concentration quenching.

Abstract: A control apparatus comprises a light monitoring unit for dividing a signal wavelength band into at least a band in which output light power of an optical amplifier tends to decrease at an decrease in the number of signal wavelengths and a band including a gain deviation band, and for monitoring inputted light power for the individual divided bands, a calculation unit for obtaining the number of signal wavelengths in the individual divided bands based on a monitor result, and a target gain correction unit for correcting a target gain based on a result of the calculation. This suppresses a transient variation of signal light level due to SHB or SRS at a high speed with a simple configuration without deteriorating noise characteristic, thus enabling optical amplifiers to be further disposed in a multi-stage fashion, which can lengthen the transmission distance of a transmission system including an optical add/drop unit.

Abstract: In an optical modulator, a DQPSK modulating section, a waveguide optical amplifying section, and an RZ modulating section are cascade connected on an optical path between input and output ports, and power of RZ-DQPSK signal light output from the output port is monitored by a photodetector, to feed-back control the waveguide optical amplifying section by an output control section so that the monitored power becomes constant at a target level. As a result, a small and low-cost optical modulator that can reliably compensate respective losses in a phase modulating section and an intensity modulating section, and differences of the respective losses, can be realized.

Abstract: An optical modulation device and method thereof is provided. The optical modulation device includes a decision circuit making a decision with respect to an input data signal in accordance with a timing of a first clock signal, a first modulator modulating light output based on the data signal by the decision circuit; a second modulator modulating the modulated light in accordance with a timing of a second clock signal; and delay controller delaying the first clock signal within a range of a phase margin of a decision circuit, and delaying the second clock signal, thereby controlling a state of a phase difference between the data signal and the second clock signal.

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: In an optical amplification characteristics simulation apparatus according to the present invention, using spectrums of a signal light input to an optical amplifier and a characteristic parameter for amplification medium, gain wavelength characteristics of the amplification medium are calculated. A calculating formula for the above has a parameter corresponding to a gain fluctuation portion due to a gain spectral hole burning (GSHB) phenomenon, and this parameter is defined by a function obtained by modeling a physical phenomenon in which a population inversion rate is reduced due to the GSHB, based on that electron occupation numbers in each Stark level on the end level side are increased. Then, based on the calculated gain wavelength characteristics, the output power of the signal light is obtained, to thereby perform the optical amplification characteristics simulation on the optical amplifier.

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 modulation device including waveform shapers that waveform-shape input data signals in synchronism with a rising or falling timing based on comparison with a reference level of an input clock signal, a multi-level phase modulator that generates a multi-level-phase-modulated optical signal based on the data signals waveform-shaped by the plurality of waveform shapers, and outputs the generated optical signal, and a level ratio controller that varies a relative level ratio of the reference level to an amplitude level of the clock signal input to the waveform shapers, based on the optical signal output from the multi-level phase modulator.

Abstract: A control apparatus comprises a light monitoring unit for dividing a signal wavelength band into at least a band in which output light power of an optical amplifier tends to decrease at an decrease in the number of signal wavelengths and a band including a gain deviation band, and for monitoring inputted light power for the individual divided bands, a calculation unit for obtaining the number of signal wavelengths in the individual divided bands based on a monitor result, and a target gain correction unit for correcting a target gain based on a result of the calculation. This suppresses a transient variation of signal light level due to SHB or SRS at a high speed with a simple configuration without deteriorating noise characteristic, thus enabling optical amplifiers to be further disposed in a multi-stage fashion, which can lengthen the transmission distance of a transmission system including an optical add/drop unit.

Abstract: The disclosed optical transmitter and control method include performing phase modulation of a light propagating through a corresponding optical path in accordance with a data signal, supplying bias voltages for regulating an operating point of each of phase modulation performed, imparting a predetermined phase difference, supplying bias voltages for phase difference regulation and coupling lights output from the corresponding optical paths. The optical transmitter includes superimposing a pilot signal on either one of bias voltages where the pilot signal has a frequency lower than a frequency of a bit rate of the data signal, and performing a feedback control in accordance with a result of monitoring.

Abstract: The disclosed device and method include varying phases of two data signals at a first predetermined frequency, performing multi-level phase modulation of a light based on the two data signals whose phases are varied at the first predetermined frequency, extracting a component having the first predetermined frequency from an optical signal subjected to the phase modulation, and controlling the phases of the two data signals based on the component extracted from the optical signal.

Abstract: In an optical amplification characteristics simulation apparatus according to the present invention, using spectrums of a signal light input to an optical amplifier and a characteristic parameter for amplification medium, gain wavelength characteristics of the amplification medium are calculated. A calculating formula for the above has a parameter corresponding to a gain fluctuation portion due to a gain spectral hole burning (GSHB) phenomenon, and this parameter is defined by a function obtained by modeling a physical phenomenon in which a population inversion rate is reduced due to the GSHB, based on that electron occupation numbers in each Stark level on the end level side are increased. Then, based on the calculated gain wavelength characteristics, the output power of the signal light is obtained, to thereby perform the optical amplification characteristics simulation on the optical amplifier.