Abstract: Two signal lights having different wavelengths are bidirectionally transmitted on an optical-fiber transmission-line. A Raman pump light source generates a first Raman pump light having predetermined wavelengths with a Raman gain-bandwidth for amplifying the first signal light and without response to the second signal light. Another Raman pump light source generates a second Raman pump light having predetermined wavelengths with a Raman gain-bandwidth for amplifying the second signal light and without response to the first signal light. The first Raman pump light and the second Raman pump light are differently injected from respective input/output terminals into the optical-fiber transmission-line by optical combining and branching filters.

Abstract: An optical repeating system includes an optical transmitter and an optical amplifying repeater. The optical transmitter transmits a supervisory command and a control command to the optical amplifying repeater as a first sub-signal. The supervisory command is a command to supervise internal circuits of the optical amplifying repeater, and the control command is a command to control the optical amplifying repeater. The optical amplifying repeater includes multiple sub-modules each for amplifying and repeating main signals on multiple sets of optical transmission lines. When receiving the supervisory command via the optical transmission line, each sub-module transmits a supervisory signal indicating the supervisory result associated with the supervisory command to an optical receiver as a second sub-signal.

Abstract: An optical repeating system includes an optical transmitter and a plurality of optical amplifying repeaters. The optical transmitter specifies one of the optical amplifying repeaters, and transmits a supervisory command and a control command to the specified optical amplifying repeater as a first sub-signal. The supervisory command is a command to supervise internal circuits of the optical amplifying repeater, and the control command is a command to control amplification factors of optical amplifiers of the optical amplifying repeater. Receiving the supervisory command via the uplink or downlink optical transmission line, the optical amplifying repeater transmit a supervisory signal indicating a supervisory result corresponding to the supervisory command to optical receivers via the uplink and downlink optical transmission lines as a second sub-signal.

Abstract: An optical repeating system includes an optical transmitter and a plurality of optical amplifying repeaters. The optical transmitter specifies a part or all of the optical amplifying repeaters, and transmits a supervisory command to the specified optical amplifying repeaters as a first sub-signal via an uplink or downlink optical transmission line. The supervisory command is a command to supervise internal circuits of the optical amplifying repeaters. Receiving the supervisory command addressed thereto via the uplink or downlink optical transmission line, the optical amplifying repeaters each transmit a supervisory signal indicating a supervisory result corresponding to the supervisory command to optical receivers via the uplink and downlink optical transmission lines as a second sub-signal. The optical system can reduce the time take to acquire the supervisory information about the plurality of the optical amplifying repeaters.

Abstract: Detection of an optical pulse position uses an optical pulse string with a determined repetitive ratio and an electric clock signal with a same frequency as the repetitive ratio of the optical pulse string. A phase of the electric clock signal oscillator is shifted and supplied to an optical modulator. The optical modulator modulates the optical pulse string based on the electric clock signal and outputs a modulated optical signal. A photo detector converts the modulated optical signal output from the optical modulator to an electric signal. The phase shift amount of the electric clock signal is controlled to maximize an output from the photo detector. Additionally, a dither signal may be used in the control of the phase shift, more than the optical modulator may be employed, and/or more than color light source may be employed. The use of at least one of feed forward and feedback control provided by maximizing an output of the photo detector allows an optical pulse having a short width to be realized.

Abstract: An optical switching system is implemented by providing a transmitting section with a preparatory transmitted optical signal selector and a working transmitted optical signal splitter, which are each implemented by a 1×2 optical space switch, and by providing a receiving section with a receiving optical switch which is implemented by a 2×2 optical space switch, and with a preparatory receiving optical gate which is implemented by a 1×2 optical space switch. This makes it possible to switch between the working system and preparatory system without employing any 4×4 optical space switch, thereby implementing a practical optical switching system without causing such problems as communication interruption during maintenance or impairment of transmission path working efficiency.

Abstract: A supervisory system and supervisory method of an optical amplifier repeater are proposed that can implement operation supervision taking account of the characteristics of individual supervisory targets of the optical amplifier repeater, thereby achieving higher reliability.

Abstract: A dispersion compensation device comprises a chirped grating, and a first optical unit for guiding at least a lightwave signal with a wavelength of &lgr;i that needs a positive dispersion compensation and is applied thereto to one end portion of the chirped grating whose grating pitch is shorter, and for furnishing light reflected by the chirped grating to outside the device. The device further comprises a second optical unit for guiding at least a lightwave signal with a wavelength of &lgr;i that needs a negative dispersion compensation and is applied thereto to another end portion of the chirped grating whose grating pitch is longer, and for furnishing light reflected by the chirped grating to outside the device. Both the first and second optical units can be either optical circulators or optical couplers.

Abstract: Detection of an optical pulse position uses an optical pulse string with a determined repetitive ratio and an electric clock signal with a same frequency as the repetitive ratio of the optical pulse string. A phase of the electric clock signal oscillator is shifted and supplied to an optical modulator. The optical modulator modulates the optical pulse string based on the electric clock signal and outputs a modulated optical signal. A photo detector converts the modulated optical signal output from the optical modulator to an electric signal. The phase shift amount of the electric clock signal is controlled to maximize an output from the photo detector. Additionally, a dither signal may be used in the control of the phase shift, more than the optical modulator may be employed, and/or more than color light source may be employed. The use of at least one of feed forward and feedback control provided by maximizing an output of the photo detector allows an optical pulse having a short width to be realized.

Abstract: Detection of an optical pulse position uses an optical pulse string with a determined repetitive ratio and an electric clock signal with a same frequency as the repetitive ratio of the optical pulse string. A phase of the electric clock signal oscillator is shifted and supplied to an optical modulator. The optical modulator modulates the optical pulse string based on the electric clock signal and outputs a modulated optical signal. A photo detector converts the modulated optical signal output from the optical modulator to an electric signal. The phase shift amount of the electric clock signal is controlled to maximize an output from the photo detector. Additionally, a dither signal may be used in the control of the phase shift, more than the optical modulator may be employed, and/or more than color light source may be employed. The use of at least one of feed forward and feedback control provided by maximizing an output of the photo detector allows an optical pulse having a short width to be realized.

Abstract: When an intensity modulating operation and a phase modulating operation are carried out by employing a 2-electrode MachZehnder type optical modulator preferably a LN-MZ type optical modulator, a drive signal of this 2-electrode LN-MZ type optical modulator is produced from an intensity modulation signal and a phase modulation signal with a low loss and a simple arrangement.

Abstract: A branch circuit is formed by forming an optical filter by means of connecting a wavelength selective reflector to between two units of directional coupler and further assembling three units of the optical filter.

Abstract: A branch circuit is formed by forming an optical filter by means of connecting a wavelength selective reflector to between two units of directional coupler and further assembling three units of the optical filter.

Abstract: A branch circuit is formed by forming an optical filter by means of connecting a wavelength selective reflector to between two units of directional coupler and further assembling three units of the optical filter.

Abstract: Reflectors each having a reflectance peak wavelength within a band of the wavelength characteristics of a laser amplification factor in the unsaturated state of each light source for excitation are provided between light sources for excitation and an optical coupler, and stable wavelength locking is effected by returning a portion of a small portion of excited light reflected by the reflectors into the light sources for excited light.

Abstract: An optical fiber which amplifies an input signal by a pump source, a compensation-signal source which injects a compensation-signal propagating contra-directionally with respect to the input signal Into the optical fiber, a gain detector which measures a spontaneous emission light of the pump source at an input side of the optical fiber and a compensation-signal source controller which controls output of the compensation-signal source based on output of the gain detector are provided. In addition, a coupler and a wavelength selective reflector which reflects a light of the same wavelength as the compensation-signal selectively, are provided at the input side of the optical fiber.

Abstract: An optical-fiber light amplifier using rare-earth-doped optical fibers. The light amplifier combines first and second excitation light from first and second sources to form combined excitation light and divides the combined excitation light for inverted distribution to both two optical fibers. The light entered one optical fiber and that entered the other optical fiber are polarized so as to be perpendicular to each other so that fluctuation of output level is prevented without mutual interference. Alternatively the first excitation light and the second excitation light may have different wavelengths; also in this case, fluctuation of level is prevented without any interference.

Abstract: Multiplex communication system for transmitting different signals through a plurality of channels comprises a transmitter and a receiver. The transmitter comprises a transmitting section for multiplexing and transmitting the different signals through the plurality of channels, and an adder for adding channel identification signals for identifying the respective channels to the signals to be transmitted through the respective channels. The receiver comprises a setting device for setting a desired channel, a detector for detecting the channel identification signals from the signals transmitted from the transmitter, and a channel selector for selecting the channel signal preset by the setting device in accordance with the outputs of the setting device and the detector.

Abstract: An optical-fiber light amplifier using rare-earth-doped optical fibers. The light amplifier combines first and second excitation light from first and second sources to form combined excitation light and divides the combined excitation light for inverted distribution to both two optical fibers. The light entered one optical fiber and that entered the other optical fiber are polarized so as to be perpendicular to each other so that fluctuation of output level is prevented without mutual interference. Alternatively the first excitation light and the second excitation light may have different wavelengths; also in this case, fluctuation of level is prevented without any interference.

Abstract: A optical signal from the input terminal 6a is amplified and goes through the optical fiber doped with rare earth. The excitation lights from the excitation light sources 2 and 3 are synthesized at the optical coupler 4 and outputted to the optical fiber doped with rare earth 1 through the optical coupler 5. A part of the light is branched from the optical coupler 11 to optical receiver 14 through the band pass light filter 13. The optical receiver 14 converts the received optical signal to an electrical signal and outputs it to the error signal output circuit 114. The receiving current is amplified in the error signal output circuit 114 and branched to the excitation light source output control circuits 9 and 10.