Abstract: An embodiment of the invention is an optical node configured to transmit/receive a wavelength-division-multiplexed signal. An optical monitoring unit monitors power levels of the wavelength-division-multiplexed signal on a wavelength-by-wavelength basis to acquire wavelength-by-wavelength power level values of the optical signals. A comparison arithmetic unit performs a comparison between each of the acquired wavelength-by-wavelength power level values of the optical signals, and a predetermined upper limit value and a predetermined lower limit value. A target value calculation unit determines target values of power levels at wavelengths whose acquired power level values exceed the upper limit value to be values between a center value and the upper limit value, and determines target values of power levels at wavelengths whose acquired power level values fall below the lower limit value to be values between the center value and the lower limit value.

Abstract: An embodiment of the invention is an optical node configured to transmit/receive a wavelength-division-multiplexed signal. An optical monitoring unit monitors power levels of the wavelength-division-multiplexed signal on a wavelength-by-wavelength basis to acquire wavelength-by-wavelength power level values of the optical signals. A comparison arithmetic unit performs a comparison between each of the acquired wavelength-by-wavelength power level values of the optical signals, and a predetermined upper limit value and a predetermined lower limit value. A target value calculation unit determines target values of power levels at wavelengths whose acquired power level values exceed the upper limit value to be values between a center value and the upper limit value, and determines target values of power levels at wavelengths whose acquired power level values fall below the lower limit value to be values between the center value and the lower limit value.

Abstract: In a quaternary phase modulator including two phase modulators disposed in parallel and a phase adjuster that adjusts a phase difference when the outputs of the two phase modulators are combined, there are provided a second light source that introduces light propagated in a backward direction, a first controller that controls the bias of the two phase modulators so that the intensity of the backward light is a minimum on the input side of the quaternary phase modulator, and a second controller that controls the bias of the phase adjuster so that a result monitored by a photodiode having a bandwidth not exceeding the bit rate on the output side of the quaternary phase modulator is a minimum, the first controller being implemented after the second controller is implemented.

Abstract: A data transmission system comprising a transmitter and a receiver. The transmitter comprises a phase encoder for partitioning consecutive bit data to be input in data in units of X bits; and converting a 2x value indicated by the data of X bits in unique association with an (N/2?1)Y value of a Y symbol, and for confining use of signal points, from among the signal points of N-ary phase, only to a signal point P1 (at a phase angle 0) and N/2?2 signal points P(2n+2) (where 1?n<N/2?2). The receiver comprises a phase decoder for notifying an error detection when a signal point other than a signal point that are permitted to be used is received, and performing an error correction by changing the signal point to a signal point which has a smaller hamming distance.

Abstract: In an optical receiver of a long-haul high-speed WDM/OADM system, a control technique is provided that can accurately control a variable dispersion compensator with an inexpensive configuration even under strict SNR conditions. Signal reception characteristic data (a bit error rate, a clock extraction result, and a frame synchronization result) is obtained and an optimum dispersion compensation amount of the dispersion compensator is calculated. The signal reception characteristic data is saturated by a high SNR. In the case where desired dispersion control accuracy cannot be obtained, an input level of a photodiode is reduced by controlling an output level of an amplifier or a variable optical attenuator. Further, in a state in which a received SNR is deteriorated, the signal reception characteristic data is obtained and the optimum dispersion compensation amount of the dispersion compensator is calculated again.

Abstract: To provide an optical transceiver module comprising an optical prism for optical communications which has mounting portions, a light emitting portion, light receiving portions, a substrate and a sub-mount that are used as the basis of the optical transceiver module, whose configuration is compact with reduced components which are accurately mounted. A sub-mount is provided on the substrate. The composite optical prism is formed with an optical lens provided with mounting supports and a wavelength division film in an integrated fashion. By using marks on the sub-mount for alignment, the composite optical prism can be mounted accurately on the sub-mount. In addition, the light receiving portions and the light emitting portion can be mounted accurately by using marks for alignment provided on the substrate and the sub-mount.

Abstract: An output light intensity monitor unit of an optical repeater monitors an output light of an output point of the optical repeater. A reflected light intensity monitor unit monitors a reflected light returning from an optical fiber to the output point, An optical fiber transmission line loss from the apparatus output point to an optical fiber open end and a light intensity emitted from the open end are estimated from a monitored reflected light intensity, and a reflection abnormality detection threshold for detecting the reflection abnormality if the light intensity emitted from the open end exceeds a reference light intensity is prescribed. An output light intensity lowering amount and a reflection abnormality recovery threshold are prescribed from an output light intensity monitored at the apparatus output point and the reflected light intensity so that an open end output light intensity may be lowered to the reference light intensity.

Abstract: A problem to be solved in an optical communication system for carrying out bidirectional transmission between communication nodes by wavelength-division-multiplexed optical signals is that a plurality of optical add-drop multiplexers installed in the communication nodes are required for each transmission direction, and therefore, the communication cost is increased. An optical circulator or an optical coupler is arranged at an input/output port of the optical add-drop multiplexer and the wavelength-division-multiplexed optical signals are assembled for each transmission direction, whereby optical signals transmitted bidirectionally can be handled by one optical add-drop multiplexer.

Abstract: A low-cost configuration of, and at the same time to control the variable dispersion compensator at a high speed in a variable dispersion compensator for compensating the wavelength dependent accumulated dispersion resulting from the wavelength dependency of the transmission fiber and fixed dispersion compensator in a long-distance high-speed WDM transmission system. In order to achieve the object mentioned above, the wavelength dependent representative characteristic of the transmission fibers 4-1 . . . n, and the wavelength dependent representative characteristic of the DCFs 13-1 . . . n are recorded and maintained in advance in the dispersion control circuit 5-1 . . .

Abstract: Part of an inputted optical add signal 118 is reflected by a mirror 117, and is thereby inputted into an optical wavelength multiplexer 105 in the reverse direction so that the optical add signal is returned to paths 115-1 through 115-16 corresponding to wavelengths ?1 through ?16. If the returned optical add signal is an optical add signal having a correct wavelength, the optical signal enters its corresponding backward direction optical detector 113-16. Accordingly, it is possible to check whether or not a wavelength of the optical add signal is correct.

Abstract: An optical transmission apparatus includes a demultiplexer for separating wavelength-division multiplexing light received from a first optical transmission line into signals of different wavelengths to transmit the signals to an outside and a multiplexer for multiplexing signals of different wavelengths received from the outside to transmit multiplexed signals to a second optical transmission line. An input check unit is provided for monitoring a power level of a signal separated by the demultiplexer and for providing an output indicative thereof. An output adjuster is provided for intercepting a signal from the outside so as to inhibit receipt of the signal from the outside by the multiplexer depending on the output of the input check unit.

Abstract: In a quaternary phase modulator including two phase modulators disposed in parallel and a phase adjuster that adjusts a phase difference when the outputs of the two phase modulators are combined, there are provided a second light source that introduces light propagated in a backward direction, a first controller that controls the bias of the two phase modulators so that the intensity of the backward light is a minimum on the input side of the quaternary phase modulator, and a second controller that controls the bias of the phase adjuster so that a result monitored by a photodiode having a bandwidth not exceeding the bit rate on the output side of the quaternary phase modulator is a minimum, the first controller being implemented after the second controller is implemented.

Abstract: A variable dispersion slope compensator with a high-accuracy and a low-cost structure for compensating the dispersion slope compensation error accompanying variations in the zero-dispersion wavelength in transmission fibers in long-distance, high-speed WDM (wavelength division multiplexing) transmission systems.

Abstract: An optical access network system having a function of correcting upstream signal waveform distortions occurring in the PON section, wherein a central office side apparatus comprises a main controller to notify each subscriber connection apparatus of a transmission grant period, an equalizer of a tap gain adaptive control type to correct waveform distortions of signals received from the subscriber connection apparatuses, an equalizer controller, and a parameter table for storing, for each subscriber connection apparatus, the initial values of tap gains to be set for the equalizer. The main controller issues a switchover request for switching the equalization characteristic to the equalizer controller each time notifying a subscriber connection apparatus of a transmission grant period, and the equalizer controller retrieves the initial values of the tap gains for the subscriber connection apparatus from the parameter table in response to the switchover request, and sets these values to the equalizer.

Abstract: A data transmission system comprising a transmitter and a receiver. The transmitter comprises a phase encoder for partitioning consecutive bit data to be input in data in units of X bits; and converting a 2x value indicated by the data of X bits in unique association with an (N/2-1)Y value of a Y symbol, and for confining use of signal points, from among the signal points of N-ary phase, only to a signal point P1 (at a phase angle 0) and N/2-2 signal points P(2n+2) (where 1?n<N/2-2). The receiver comprises a phase decoder for notifying an error detection when a signal point other than a signal point that are permitted to be used is received, and performing an error correction by changing the signal point to a signal point which has a smaller hamming distance.

Abstract: A variable dispersion slope compensator with a high-accuracy and a low-cost structure for compensating the dispersion slope compensation error accompanying variations in the zero-dispersion wavelength in transmission fibers in long-distance, high-speed WDM (wavelength division multiplexing) transmission systems.

Abstract: In the variable gain compensating apparatus, input power of optical amplifiers employed in respective optical repeaters is monitored, and the monitored input power is transferred to a down-stream side by using supervisor (SV) light. In a repeater equipped with a variable gain tilt compensator, input power monitor information of the optical amplifiers employed in the respective repeaters provided on the upper stream side is acquired from a supervisor signal. While utilizing a linear relationship established between a gain tilt of an optical amplifier and input power of the optical amplifier, the acquired input power monitor information is compared with a reference power value so as to calculate gain tilt amounts of the respective optical amplifiers. Then, the optimum gain tilt compensation amount of the variable gain tilt compensator is determined based upon the calculated gain tilt amounts.

Abstract: A low-cost configuration of, and at the same time to control the variable dispersion compensator at a high speed in a variable dispersion compensator for compensating the wavelength dependent accumulated dispersion resulting from the wavelength dependency of the transmission fiber and fixed dispersion compensator in a long-distance high-speed WDM transmission system. In order to achieve the object mentioned above, the wavelength dependent representative characteristic of the transmission fibers 4-1 . . . n, and the wavelength dependent representative characteristic of the DCFs 13-1 . . . n are recorded and maintained in advance in the dispersion control circuit 5-1 . . .

Abstract: To provide an optical transceiver module comprising an optical prism for optical communications which has mounting portions, a light emitting portion, light receiving portions, a substrate and a sub-mount that are used as the basis of the optical transceiver module, whose configuration is compact with reduced components which are accurately mounted. A sub-mount is provided on the substrate. The composite optical prism is formed with an optical lens provided with mounting supports and a wavelength division film in an integrated fashion. By using marks on the sub-mount for alignment, the composite optical prism can be mounted accurately on the sub-mount. In addition, the light receiving portions and the light emitting portion can be mounted accurately by using marks for alignment provided on the substrate and the sub-mount.

Abstract: An optical access network system having a function of correcting upstream signal waveform distortions occurring in the PON section, wherein a central office side apparatus comprises a main controller to notify each subscriber connection apparatus of a transmission grant period, an equalizer of a tap gain adaptive control type to correct waveform distortions of signals received from the subscriber connection apparatuses, an equalizer controller, and a parameter table for storing, for each subscriber connection apparatus, the initial values of tap gains to be set for the equalizer. The main controller issues a switchover request for switching the equalization characteristic to the equalizer controller each time notifying a subscriber connection apparatus of a transmission grant period, and the equalizer controller retrieves the initial values of the tap gains for the subscriber connection apparatus from the parameter table in response to the switchover request, and sets these values to the equalizer.