Abstract: A control-target-value setting unit sets a control target value corresponding to the number of multiplexed wavelengths measured by a number-of-multiplexed-wavelengths measuring unit. A controller controls the variable optical attenuator based on the control target value. An optical amplifier performs an optical amplification with a constant gain regardless of power of a wavelength-multiplexed light. The controller performs feedback control of the variable optical attenuator such that a result of measurement of the total power of the wavelength-multiplexed light coincides with the control target value.

Abstract: A control-target-value setting unit sets a control target value corresponding to the number of multiplexed wavelengths measured by a number-of-multiplexed-wavelengths measuring unit. A controller controls the variable optical attenuator based on the control target value. An optical amplifier performs an optical amplification with a constant gain regardless of power of a wavelength-multiplexed light. The controller performs feedback control of the variable optical attenuator such that a result of measurement of the total power of the wavelength-multiplexed light coincides with the control target value.

Abstract: A gain switching circuit switches a conversion gain of a preamplifier that is configured with a series circuit formed with a first resistor and a first switching element and a series circuit formed with a second resistor and a second switching element respectively connected in parallel with a feedback resistor. The gain switching circuit includes a first operating unit that generates a first switching element operating signal for closing the first switching element within a first gain switching period, and a second operating unit that generates a second switching element operating signal for closing the second switching element within a second gain switching period.

Abstract: A laser light source outputs a virtually linearly-polarized light beam that has plural mode components arranged at an interval of an almost equal angular frequency. A polarization dispersion device is connected to the laser light source in such a way that a polarization axis of the polarization dispersion device is at 45° with respect to a polarization axis of the light beam output from the laser light source. This polarization dispersion device effects on the light beam output from the laser light source a polarization mode dispersion that is not in the vicinity of (2?/??), where ?? is a mode interval angular frequency.

Abstract: An optical transceiver 1 comprises first and second pseudo-random pattern generators 23 and 28 for generating a pseudo-random pattern signal, which are placed in a transmitting side path 6 and in a receiving side path 11 of the optical transceiver 1, respectively; first and second pseudo-random pattern detectors 21 and 26 for evaluating an inputted pseudo-random pattern signal, which are placed in the transmitting side path 6 and in the receiving side path 11 of the optical transceiver 1, respectively; a first loopback path 31 that loops back from a multiplexing circuit 3 to a demultiplexing circuit 8; and a second loopback path 32 that loops back from a light-electricity converter 7 to an electricity-light converter 4.

Abstract: Light signals of first to n-th bands amplified en bloc undergo proper attenuation through an adjustable optical attenuator in conformance with attenuation in an optical fiber connected to input of an optical amplifying repeater apparatus, whereon the light signals are demultiplexed or separated into individual bands and amplified by first to n-th fixed-gain optical amplifiers (#1, . . . , #n) each having a high fixed gain in the respective bands to be subsequently multiplexed by an optical multiplexer and then sent out onto a transmission line. A monitoring light branching device extracts a part of light power of a specific monitoring wavelength, which is then fed to an adjustable attenuator control circuit which controls the attenuation factor of the adjustable optical attenuator so that the light power of the specific wavelength remains constant. The gain of the optical amplifying repeater apparatus at the specific wavelength can thus be determined.

Abstract: A gain switching circuit switches a conversion gain of a preamplifier that is configured with a series circuit formed with a first resistor and a first switching element and a series circuit formed with a second resistor and a second switching element respectively connected in parallel with a feedback resistor. The gain switching circuit includes a first operating unit that generates a first switching element operating signal for closing the first switching element within a first gain switching period, and a second operating unit that generates a second switching element operating signal for closing the second switching element within a second gain switching period.

Abstract: A pre-amplifier amplifies an output current of a photodetector that converts a burst optical signal into an electrical signal, and outputs an electric voltage signal. A gain switching circuit is connected with a serial circuit comprising a resistor and a switch and a serial circuit comprising a resistor and a switch, in parallel with a feedback resistor. The gain switching circuit includes an arrangement to receive the electric voltage signal output from the pre-amplifier, close the switch at a specific bit position, close the switch at the other specific bit position, upon occurrence of a situation that the switch is to be closed, provided that the switch is closed.

Abstract: Light signals of first to n-th bands amplified en bloc undergo proper attenuation through an adjustable optical attenuator in conformance with attenuation in an optical fiber connected to input of an optical amplifying repeater apparatus, whereon the light signals are demultiplexed or separated into individual bands and amplified by first to n-th fixed-gain optical amplifiers (#1, . . . , #n) each having a high fixed gain in the respective bands to be subsequently multiplexed by an optical multiplexer and then sent out onto a transmission line. A monitoring light branching device extracts a part of light power of a specific monitoring wavelength, which is then fed to an adjustable attenuator control circuit which controls the attenuation factor of the adjustable optical attenuator so that the light power of the specific wavelength remains constant. The gain of the optical amplifying repeater apparatus at the specific wavelength can thus be determined.

Abstract: An optical transmitter includes a semiconductor laser module that outputs continuous light to be modulated. A light intensity varying unit in the semiconductor laser module varies the light intensity of the continuous light. An optical module includes an electric-field-absorbing-type semiconductor optical modulator device that modulates the continuous light with a modulating electric signal and output the modulated optical signal.

Abstract: In an non-polarized pump light source (5), a laser light source (1) transmits a virtually linearly-polarized light beam that has plural mode components arranged at an interval of an almost equal angular frequency. The transmitted light beam of the laser light source (1) is connected with a polarization dispersion device (3) in such a way that the polarization axes of the transmitted light beam and the polarization dispersion device (3) meet to form a 45° angle. In the polarization dispersion device (3), when the mode interval angular frequency is considered to be &Dgr;&ohgr;, the polarization mode dispersion that is not in the vicinity of (2&pgr;/&Dgr;&ohgr;) is effected on the incident light from the laser light source (1). As a result, though the optical path difference between the two polarization modes becomes less than the coherent length, an effectively non-polarizing light is transmitted as a pump light from the non-polarized pump light source (5).

Abstract: A pre-amplifier (2) amplifies an output current of a photodetector (1) that converts a burst optical signal into an electrical signal, and outputs an electric voltage signal. A gain switching circuit (3) is connected with a serial circuit comprising a resistor (6) and a switch (9) and a serial circuit comprising a resistor (7) and a switch (10), in parallel with a feedback resistor (2b). The gain switching circuit (3) includes an arrangement to receive the electric voltage signal output from the pre-amplifier (2), close the switch (9) at a specific bit position, close the switch (10) at the other specific bit position, upon occurrence of a situation that the switch (10) is to be closed, provided that the switch (9) is closed.

Abstract: Light signals of first to n-th bands amplified en bloc undergo proper attenuation through an adjustable optical attenuator in conformance with attenuation in an optical fiber connected to input of an optical amplifying repeater apparatus, whereon the light signals are demultiplexed or separated into individual bands and amplified by first to n-th fixed-gain optical amplifiers (#1, . . . , #n) each having a high fixed gain in the respective bands to be subsequently multiplexed by an optical multiplexer and then sent out onto a transmission line. A monitoring light branching device extracts a part of light power of a specific monitoring wavelength, which is then fed to an adjustable attenuator control circuit which controls the attenuation factor of the adjustable optical attenuator so that the light power of the specific wavelength remains constant. The gain of the optical amplifying repeater apparatus at the specific wavelength can thus be determined.

Abstract: The amplifier circuit includes differential amplifier circuits (3 to 4); a peak detector circuit (7) for detecting a peak value of an output voltage of a differential amplifier circuit 4 of the last stage; an offset compensation voltage generator circuit (8) for generating an offset compensation voltage for offset compensation on the basis of a detection result of the peak detector circuit (7); and an offset output limiter circuit (9) for limiting the offset compensation voltage generated by the offset compensation voltage generator circuit (8) into a predetermined range and feeding back the limited offset compensation voltage to a differential amplifier circuit (3) of the first stage.

Abstract: Light signals of first to n-th bands amplified en bloc undergo proper attenuation through an adjustable optical attenuator in conformance with attenuation in an optical fiber connected to input of an optical amplifying repeater apparatus, whereon the light signals are demultiplexed or separated into individual bands and amplified by first to n-th fixed-gain optical amplifiers (#1, . . . , #n) each having a high fixed gain in the respective bands to be subsequently multiplexed by an optical multiplexer and then sent out onto a transmission line. A monitoring light branching device extracts a part of light power of a specific monitoring wavelength, which is then fed to an adjustable attenuator control circuit which controls the attenuation factor of the adjustable optical attenuator so that the light power of the specific wavelength remains constant. The gain of the optical amplifying repeater apparatus at the specific wavelength can thus be determined.

Abstract: An optical transceiver 1 comprises first and second pseudo-random pattern generators 23 and 28 for generating a pseudo-random pattern signal, which are placed in a transmitting side path 6 and in a receiving side path 11 of the optical transceiver 1, respectively; first and second pseudo-random pattern detectors 21 and 26 for evaluating an inputted pseudo-random pattern signal, which are placed in the transmitting side path 6 and in the receiving side path 11 of the optical transceiver 1, respectively; a first loopback path 31 that loops back from a multiplexing circuit 3 to a demultiplexing circuit 8; and a second loopback path 32 that loops back from a light-electricity converter 7 to an electricity-light converter 4.

Abstract: Light signals of first to n-th bands amplified en bloc undergo proper attenuation through an adjustable optical attenuator in conformance with attenuation in an optical fiber connected to input of an optical amplifying repeater apparatus, whereon the light signals are demultiplexed or separated into individual bands and amplified by first to n-th fixed-gain optical amplifiers (#1, . . . , #n) each having a high fixed gain in the respective bands to be subsequently multiplexed by an optical multiplexer and then sent out onto a transmission line. A monitoring light branching device extracts a part of light power of a specific monitoring wavelength, which is then fed to an adjustable attenuator control circuit which controls the attenuation factor of the adjustable optical attenuator so that the light power of the specific wavelength remains constant. The gain of the optical amplifying repeater apparatus at the specific wavelength can thus be determined.

Abstract: The amplifier circuit includes differential amplifier circuits (3 to 4); a peak detector circuit (7) for detecting a peak value of an output voltage of a differential amplifier circuit 4 of the last stage; an offset compensation voltage generator circuit (8) for generating an offset compensation voltage for offset compensation on the basis of a detection result of the peak detector circuit (7); and an offset output limiter circuit (9) for limiting the offset compensation voltage generated by the offset compensation voltage generator circuit (8) into a predetermined range and feeding back the limited offset compensation voltage to a differential amplifier circuit (3) of the first stage.

Abstract: In a clock reproduction and identification device, a clock extraction circuit extracts a transmission line clock from input data and a phase synchronization section reproduces an identification clock synchronized with the transmission line clock in frequency and phase. An identification section identifies the input data based on the identification clock.

Abstract: Voltage controlling/oscillating device comprises a terminal for setting the delay rate in the delay unit and the delay interpolator. Clock signal whose phase is inverted by the inverting gate is inputted into a first input terminal of the delay interpolator and into the delay unit. The delay unit delays the signal by d1 and inputs into second input terminal of the delay interpolator. Oscillation frequency control voltage is fed into a terminal of the delay interpolator through an oscillation frequency control terminal of the device. Delay control voltage is fed into a terminal of the device in order to control a propagation delay rate in the delay unit and the delay interpolator. The delay rate in a delay unit and a delay interpolator can be adjusted by a delay control voltage.