Abstract: The present invention aims at realizing a dispersion compensating method capable of readily conducting automatic compensation of waveform degradation caused by dispersion characteristics of an optical transmission path, and at providing a dispersion compensating apparatus and an optical transmission system, of a smaller size at a reduced cost. To this end, the dispersion compensating apparatus of the present invention comprises: a variable dispersion compensator for compensating for the dispersion of optical signal input via an optical transmission path; a bit error information monitoring circuit for generating bit error information of a received signal output from the variable dispersion compensator via an optical receiving circuit; and a controlling circuit for optimally controlling a wavelength dispersion value of the variable dispersion compensator based on the bit error information from the bit error information monitoring circuit.

Abstract: A switch unit included in one optical node is configured by a plurality of switch circuits having ports the number of which is fewer than that of lines to be accommodated by the switch unit. Since the plurality of switch circuits are mutually independent as sub-switches of the switch unit, the entire switch unit does not become a complete group switch. Accordingly, the line that is accommodated by each of the sub-switches is determined by a service provided to a user accommodated by the line. The switch unit is configured by independent sub-switches as described above, whereby an optical node having a simple configuration can be implemented with small and inexpensive switches. Furthermore, a service provided by the optical node can be easily added by replacing a sub-switch.

Abstract: The present invention relates to an optical amplifier and an optical communication system applied to WDM (wavelength division multiplexing). The optical amplifier includes an optical amplifying medium to which WDM signal light obtained by wavelength division multiplexing a plurality of optical signals having different wavelengths is supplied, a pumping unit for pumping the optical amplifying medium such that the medium gives a gain to the WDM signal light, a feedback loop for controlling the pumping unit so that the gain is maintained constant, and an optical attenuator for giving a variable attenuation to the WDM signal light. Through the structure of the present invention, it becomes possible to provide an optical amplifier which can maintain constant the optical output level per channel of WDM and can maintain the gain characteristic constant.

Abstract: A first layer (2) and a second layer (3) are formed on a substrate (1). The first layer is made of a resist against a groove-sculpturing etchant used in etching the substrate while the second layer is made of an anti-corrosive material against dry etching. The second layer is at first patterned into a patterned second layer (3a) in the form of a groove-sculpturing mask pattern (8). With the patterned second layer used as a mask, the first layer is etched and patterned into a patterned first layer (2a) in the form of the above-mentioned mask pattern. With the patterned first layer used as a mask, the substrate is etched to form a groove (9).

Abstract: The invention provides an optical time division demultiplexing apparatus which can perform optical time division demultiplexing while compensating for an operating point drift of an optical time division multiplex signal. The optical time division demultiplexing apparatus includes a clock signal generation element for generating a clock signal for optical time division demultiplexing processing of a received optical signal, and an optical switch for time division demultiplexing the optical signal based on the clock signal from the clock signal generation element.

Abstract: A first layer (2) and a second layer (3) are formed on a substrate (1). The first layer is made of a resist against a groove-sculpturing etchant used in etching the substrate while the second layer is made of an anti-corrosive material against dry etching. The second layer is at first patterned into a patterned second layer (3a) in the form of a groove-sculpturing mask pattern (8). With the patterned second layer used as a mask, the first layer is etched and patterned into a patterned first layer (2a) in the form of the above-mentioned mask pattern. With the patterned first layer used as a mask, the substrate is etched to form a groove (9).

Abstract: The object of the present invention is to provide an optical amplifying apparatus for collectively amplifying wavelength-division multiplexed signal lights, which can perform amplification in response to input signal light, whose power level is within a wide input dynamic range, without saturating, and which suppresses the influence of the wavelength dependency of gain thereof. Thus, this optical amplifying apparatus is composed of: three optical amplifying portions connected in cascade; an optical attenuating portion for controlling the level of signal light output from the optical amplifying portion provided in the post-stage by regulating the power level of signal light input to the optical amplifying portion provided in the middle stage; and a dispersion compensation fiber provided between the middle stage and post stage optical amplifying. A gain of each of the optical amplifying portions is controlled to be constant by an AGC circuit.

Abstract: An optical amplifier relates to WDM (wavelength division multiplexing). The optical amplifier includes an optical amplifying unit, an ALC (automatic output level control) circuit for controlling the unit based on the output level thereof, and AGC (automatic gain control) circuit for controlling the unit based on the input and output levels thereof. A selecting circuit alternatively selects and operates the ALC and AGC circuits in accordance with a predetermined rule. Accordingly, the inconvenience occurring in the case of performing only one of ALC and AGC can be eliminated.

Abstract: The invention provides a technique for optimizing transmission conditions to achieve large-capacity transmission, and also provides peripheral techniques for the practical implementation of optical multiplexing that makes large-capacity transmission possible. A transmission characteristic is measured in a transmission characteristic measuring section, and control of signal light wavelength in a tunable light source, control of the amount of prechirping, control of the amount of dispersion compensation, and/or control of optical power are performed to achieve the best transmission characteristic. Wavelength dispersion is deliberately introduced by a dispersion compensator, to reduce nonlinear effects. A tunable laser is used to optimize signal light wavelength for each optical amplification repeater section. Peripheral technique, such as drift compensation, clock extraction, optical signal channel identification, clock phase stabilization, etc., are provided for the implementation of optical multiplexing.

Abstract: A first layer (2) and a second layer (3) are formed on a substrate (1). The first layer is made of a resist against a groove-sculpturing etchant used in etching the substrate while the second layer is made of an anti-corrosive material against dry etching. The second layer is at first patterned into a patterned second layer (3a) in the form of a groove-sculpturing mask pattern (8). With the patterned second layer used as a mask, the first layer is etched and patterned into a patterned first layer (2a) in the form of the above-mentioned mask pattern. With the patterned first layer used as a mask, the substrate is etched to form a groove (9).

Abstract: An optical modulating method and an optical modulating device for optical time division multiplexing (OTDM). The optical modulating device comprises, for example, an optical switch for generating first and second optical clocks according to a carrier beam output from a light source, optical modulators for respectively switching on/off the optical clocks by data signals to thereby generate first and second signal beams, an optical multiplexer for combining the signal beams to generate an OTDM signal, and prechirp circuit for controlling, for example, the optical clocks so that the OTDM signal has a chirp parameter adapted to an optical transmission line. This optical modulation device is suitable for high-speed transmission and allows chromatic compensation.

Abstract: A device and a method for driving an electro-absorption optical modulator for receiving carrier light emitted from a light source and outputting signal light subjected to intensity modulation according to the absorption of the carrier light. A bias circuit generates a bias voltage determined so that the optical modulator has a given chirping parameter. A driving circuit generates a modulating signal corresponding to an input signal, superimposes the modulating signal on the bias voltage, and supplies the superimposed signal to the optical modulator. A control circuit controls at least one parameter selected from a parameter group including the amplitude and duty of the modulating signal and the power of the carrier light, based on the bias voltage. It can be possible to provide a method of and a device for driving an optical modulator capable of arbitrarily setting a chirping parameter.

Abstract: An optical time-division multiplexer in which the phase difference between two optical signals to be used for the synthesis of an output optical signal thereof is maintained at a constant value, regardless of variations in accuracy of the manufacture thereof. Thereby, stable output optical signals are obtained at all times. The optical time-division multiplexer includes first and second optical modulators to respectively output first and second optical modulation signals synchronized with a clock signal and corresponding to different time slots, respectively; an optical coupler for performing time-division multiplexing of the first and second optical modulation signals respectively outputted by the first and second optical modulators; and an optical-phase adjusting unit to receive at least one of the first and second optical modulation signals and to regulate an optical phase of the inputted optical signal.

Abstract: The invention provides a technique for optimizing transmission conditions to achieve large-capacity transmission, and also provides peripheral techniques for the practical implementation of optical multiplexing that makes large-capacity transmission possible. A transmission characteristic is measured in a transmission characteristic measuring section, and control of signal light wavelength in a tunable light source, control of the amount of prechirping, control of the amount of dispersion compensation, and/or control of optical power are performed to achieve the best transmission characteristic. Wavelength dispersion is deliberately introduced by a dispersion compensator, to reduce nonlinear effects. A tunable laser is used to optimize signal light wavelength for each optical amplification repeater section. Peripheral techniques, such as drift compensation, clock extraction, optical signal channel identification, clock phase stabilization, etc., are provided for the implementation of optical multiplexing.

Abstract: An optical interconnection circuit structure includes a substrate, an optical waveguide path, a semiconductor optical element, and a supporting base. The supporting base may be the same material as that for the optical waveguide path, as that for the substrate, or as that for the semiconductor optical element. The supporting base has an appropriately shaped surface or surfaces which abut the semiconductor optical element and a fixing material may be used depending on the shapes of the abutting surfaces. The supporting base thus formed ensures that the semiconductor optical element is stably mounted thereon and securely fixed thereto thereby establishing optical interconnection between the optical waveguide and the semiconductor optical element in a highly efficient and very reliable manner.

Abstract: The invention provides a technique for optimizing transmission conditions to achieve large-capacity transmission, and also provides peripheral techniques for the practical implementation of optical multiplexing that makes large-capacity transmission possible. A transmission characteristic is measured in a transmission characteristic measuring section, and control of signal light wavelength in a tunable light source, control of the amount of prechirping, control of the amount of dispersion compensation, and/or control of optical power are performed to achieve the best transmission characteristic. Wavelength dispersion is deliberately introduced by a dispersion compensator, to reduce nonlinear effects. A tunable laser is used to optimize signal light wavelength for each optical amplification repeater section. Peripheral techniques, such as drift compensation, clock extraction, optical signal channel identification, clock phase stabilization, etc., are provided for the implementation of optical multiplexing.

Abstract: The invention provides a technique for optimizing transmission conditions to achieve large-capacity transmission, and also provides peripheral techniques for the practical implementation of optical multiplexing that makes large-capacity transmission possible. A transmission characteristic is measured in a transmission characteristic measuring section, and control of signal light wavelength in a tunable light source, control of the amount of prechirping, control of the amount of dispersion compensation, and/or control of optical power are performed to achieve the best transmission characteristic. Wavelength dispersion is deliberately introduced by a dispersion compensator, to reduce nonlinear effects. A tunable laser is used to optimize signal light wavelength for each optical amplification repeater section. Peripheral techniques, such as drift compensation, clock extraction, optical signal channel identification, clock phase stabilization, etc., are provided for the implementation of optical multiplexing.

Abstract: The invention provides a technique for optimizing transmission conditions to achieve large-capacity transmission, and also provides peripheral techniques for the practical implementation of optical multiplexing that makes large-capacity transmission possible. A transmission characteristic is measured in a transmission characteristic measuring section, and control of signal light wavelength in a tunable light source, control of the amount of prechirping, control of the amount of dispersion compensation, and/or control of optical power are performed to achieve the best transmission characteristic. Wavelength dispersion is deliberately introduced by a dispersion compensator, to reduce nonlinear effects. A tunable laser is used to optimize signal light wavelength for each optical amplification repeater section. Peripheral techniques, such as drift compensation, clock extraction, optical signal channel identification, clock phase stabilization, etc., are provided for the implementation of optical multiplexing.

Abstract: A control unit for controlling an optically modulating apparatus in an optical transmitter, including plural optical modulators producing an optical output signal consisting of a series of optical pulses for transmitting data under OTDM or WDM, so that pre-chirping magnitudes of the modulators are changed together with drift compensation, for preventing waveform deterioration due to an optical transmission line from occurring. The pre-chirping magnitudes are changed by shifting operating points of modulators only concerning pre-chirping, without affecting other transmitting characteristics of the optical output signal.

Abstract: An optical, transmitter with a stabilized operating point for an optical transmitter, especially for that including a Mach-Zehnder optical modulator, is disclosed. An optical modulator is provided which modulates a light beam from a light source according to a driving voltage from a drive circuit. An operating point stabilizing circuit is provided which detects a drift in the characteristic curve from the optical modulator and controls the optical modulator to bring the operating point to a specified position. Deterioration in the waveform of the output optical signal due to the operating point drift is thereby prevented without depending on the input signal. Further, by performing an operating point shift under specific conditions, deterioration in the waveform due to wavelength dispersion can be effectively prevented, whether the sign of the wavelength dispersion is positive or negative.