Abstract: A wavelength dispersion compensation control method determining whether a clock component is contained in an optical signal received from an optical transmission path and, if a clock component if contained in the optical signal, extracting the clock component, and stopping control of a variable wavelength dispersion compensator when no clock component is extracted.

Abstract: An optical receiver is disclosed in which the error rate for the received data may be effectively reduced even for the non-linear optical transmission system that provides a directly modulate laser diode as the optical transmitter and the single mode fiber inevitably accompanying with the dispersion as the transmission medium. The optical receiver includes a photodiode (PD), a low-pass filter (LPF) and a maximum likelihood sequence estimator (MLSE) carrying out the Viterbi algorithm. The LPF in front of the MLSE effectively suppresses the ringing appeared in the received signal to generate a replica data with good reproducibility.

Abstract: Certain aspects of a method and system for optimum channel equalization between a host Serializer-Deserializer (SerDes) and an optical module may compensate and reduce dispersion loss along an electrical transmit path of a transmitter and an optical transmit path coupled to the transmitter via pre-emphasis. The data degradation as a result of the dispersion loss along the electrical transmit path of the transmitter and the optical transmit path coupled to the transmitter may be recovered by equalizing signals received via an electrical receive path of a receiver communicatively coupled to the transmitter.

Abstract: An optical communications system for conveying traffic through an optical link between transmitting and receiving nodes. The system comprises, for each node, respective legacy and bypass paths coupled in parallel between the optical link and the node. The legacy path of each node includes an optical dispersion compensation block for compensating a respective portion of dispersion of the link. Thus the present invention provides a system architecture by which an optical communications system can be constructed using conventional modulation and optical dispersion compensation technologies. Once installed, system growth can be accommodated using next generation transmitters (with electronic compensation) without stranding the legacy equipment. Legacy channels can also be upgraded to electronic compensation, as desired.

Abstract: An optical homodyne communication system and method in which a side carrier is transmitted along with data bands in an optical data signal, and upon reception, the side carrier is boosted, shifted to the center of the data bands, and its polarization state is matched to the polarization state of the respective data bands to compensate for polarization mode dispersion during transmission. By shifting a boosted side carrier to the center of the data bands, and by simultaneously compensating for the effects of polarization mode dispersion, the provided system and method simulate the advantages of homodyne reception using a local oscillator. The deleterious effects of chromatic dispersion on the data signals within the data bands are also compensated for by applying a corrective function to the data signals which precisely counteracts the effects of chromatic dispersion.

Abstract: In a wavelength division multiplexing optical transmission system, in order to know an influence amount of a temperature dependency of a dispersion slope, a method of monitoring a dispersion variation amount in two or more of wavelength channels is provided. Further, a method of compensating a wavelength dependency of a temperature dependency of the dispersion by providing an appropriate dispersion individually to the channels or summarizingly for all of bandwidths based on the monitored dispersion variation amounts is provided. According to the present invention, in the WDM optical transmission system, a deterioration in a transmission characteristic by influence of a temperature variation of the dispersion slope can be reduced.

Abstract: An optical transmission system that alleviates waveform distortions due to nonlinear effects in fibers. A transmitter sends WDM signals to a receiver over a dispersion-managed optical transmission line with in-line optical repeaters. The transmission line is divided into a plurality of dispersion compensation intervals each composed of a main segment and a compensation segment. Chromatic dispersion is managed such that the dispersion compensation intervals have a non-zero net dispersion at every boundary point between them, or such that the number of zero-dispersion boundary points is reduced. The main segment is a series of repeater sections with negative dispersion, while the compensation segment is a single repeater section with positive dispersion.

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: An optical node apparatus according to the present invention amplifies a WDM signal light input to an input port, and thereafter, branches the amplified WDM signal light by an optical branching coupler to send the branched lights to first and second optical paths, and selects the light propagated through the first optical path by an optical switch to amplify the selected light by a post-amplifier, thereby outputting the amplified light from an output port, when the optical node apparatus is operated as an optical amplification repeating node. When the operational state is upgraded to an optical add/drop multiplexing node, an OADM section is connected between a set of connecting ports on the second optical path, and the adjustment of the OADM section is performed utilizing the WDM signal light branched by the optical branching coupler, and thereafter, the switching of the optical switch is performed to select the light on the second optical path side.

Abstract: An apparatus and method directed to testing and optimizing performance of an optical transmission system is disclosed, including at least one broadband dispersion compensation unit (DCU) or at least one depolarization device. The depolarization device may be used alone or in combination with the at least one broadband DCU. A method for optimizing performance of data channels in initial loading (IL) and full loading (FL) configurations of the optical transmission system is also disclosed.

Abstract: A chromatic dispersion compensator of present invention includes a high-refractive-index VIPA plate, a three-dimensional mirror, and a control unit. The high-refractive-index VIPA plate is made of a material such as silicon having a refractive index higher than that of optical glass and is able to output incident lights toward different directions according to wavelength. The three-dimensional mirror reflects the light of each wavelength emitted from the high-refractive-index VIPA plate, at a predetermined position and returns the light to the VIPA plate. The control unit controls a temperature of the high-refractive-index VIPA plate at a constant level while controlling the position of the three-dimensional mirror corresponding to a chromatic dispersion compensation amount. Thereby, larger chromatic dispersion can be compensated while a decrease in transmission bandwidth is suppressed.

Abstract: A dispersion determining apparatus comprises a received waveform monitoring part (1) and a dispersion amount determining part (4). The received waveform monitoring part (1) has a waveform monitoring circuit (2) that samples data from the received waveform of a received signal having propagated along a transmission path, and a histogram extracting circuit (3) that extracts, based on the sampled data obtained by the waveform monitoring circuit (2), a histogram data representative of the intensity distribution in the voltage direction of the received waveform. The dispersion amount determining part (4) has a polarized wave dispersion estimating circuit (7) that determines the horizontally asymmetric degree of a received eye-pattern waveform of the received waveform obtained by analyzing the histogram data extracted by the received waveform monitoring part (1) and then estimates, based on the determined asymmetric degree, a polarized wave dispersion amount in the transmission path.

Abstract: A timing jitter measurement system and method is provided that acquires the timing jitter in an all-optical fashion, by extracting the timing jitter probability distribution function using auto-correlation and cross-correlation data. This makes the system and method of the present invention particularly useful for ultra-high bit rates, where power spectrum analysis cannot be applied. The resolution of the timing jitter measurement system and method is higher than the actual pulse width, and depends on the time resolution of the correlator. The system and method of the present invention facilitates the identification of deterministic or random timing jitters or combinations thereof, and therefore can be used to identify the origins of timing jitters within the optical network and to provide feedback to the optical network that can be used to actively control the timing jitter.

Abstract: The present invention discloses an adaptive dispersion compensation system and a method used in optical communication network, comprising at least one performance detecting unit (20), for detecting the dispersion relevant performances; at least one control processing unit (30), for generating control information according to the detected information from the at least one performance detecting unit (20); at least one dispersion adjusting unit (40), for compensating dispersion according to the control information from the at least one control processing unit (30); and an information transmission unit (50) which is connected among the at least one performance detecting unit, the at least one control processing unit and the at least one dispersion adjusting unit which are located at different nodes, the information transmission unit is used for transmitting the detected information from the at least one performance detecting unit to the at least one control processing unit which is located at a different node, an

Abstract: Described are an optical communications system and a method that allow for compensation of chromatic dispersion and polarization mode dispersion imparted to a communications signal propagating through an optical link. The system is based on a cost-effective optical transport architecture that accommodates baud rates exceeding 15 Gbaud and eliminates the need for costly optical dispersion compensators. Compensation for polarization mode dispersion is performed at the receiver using nonlinear processing. Advantageously, direct detection modulation using inexpensive electro-optic system components can be used in place of more costly and complex coherent and differential modulation formats. Digital filtering can be performed at the transmitter and the input signal can be inverted based on the nonlinearity of the transmitter electro-optic components. Consequently, the bandwidth and linearity requirements for the transmitter electro-optic components are relaxed, and cost reductions are realized.

Abstract: A system includes a laser generator, and a signal distortion generator circuit inline with the laser generator modulation signal and configured to generate distortion vectors in any of four distortion vector quadrants.

Abstract: A method of recovering a clock signal from an optical signal received through an optical communications system. A digital sample stream is processed to generate a dispersion compensated signal. The dispersion compensated signal is then tapped to obtain upper side band and lower side band signals of each received polarization of the optical signal. The upper side band and lower side band signals are then processed to compensate polarization dependent impairments, and the clock recovered from the resulting optimized.

Abstract: A dispersion compensating method for carrying out automatic level control with the use of target output power and an ASE correction value corresponding to the number of wavelengths to multiplex and making output power of a wavelength multiplexed signal constant, comprising the steps of: switching into automatic gain control in which the output power of the wavelength multiplexed signal is made constant, to carry out increase/decrease of the wavelengths to multiplex; varying a dispersion compensating amount based on the increase/decrease of the wavelengths by the automatic gain control; calculating an ASE variation amount due to the change in the dispersion compensating amount; and reflecting the ASE variation amount on the ASE correction value and switching into the automatic level control.

Abstract: An apparatus and method for correcting for the polarization mode distortion of an optical signal is described. The optical data signal to be transmitted is processed by a switch configured to place the signal into a plurality of polarization states on a periodic basis. At the receiving end of the system, a portion to the signal is coupled to a polarimeter and the wavelength-dependent state of polarization (SOP) of the received signal determined for the plurality of polarization states imposed on the transmitted signal. The data for two of the transmitted polarization states is selected to be used as the basis for correcting the SOP so as to compensate for the wavelength dependence thereof. The corrections may be applied in an optical pulse shaper.

Abstract: A technique for improving optical cross-connections comprises placing a switch in front of a number of processing units. So configured, the units are no longer dedicated to a specific link or signal. When necessary, a unit is connected/disconnected to one or more optical links by the switch to carry out any number of processing functions, such as regeneration, Raman pumping, dispersion equalization/compensation or performance monitoring. Because the units are no longer dedicated to specific links the cost of the cross-connections and the network it is a part of can be reduced.

Abstract: A repeating apparatus disposed at an end point of each divisional repeating interval of a light transmission line performs a first dispersion compensation step, an optical add/drop multiplexing step and a second dispersion compensation step to perform repeating transmission. The ratio of an over compensation amount at the second dispersion compensation step to the sum of dispersion compensation amounts at the first and second dispersion compensation steps is set so as to gradually vary together with the transmission distance from the terminal apparatus for transmission at which the repeating apparatus is disposed on the light transmission line so that degradation of wavelengths to be received by the terminal apparatus for reception is suppressed while dispersion compensation is performed with a high degree of accuracy at each optical add/drop multiplexing point on the transmission line.

Abstract: A method, a system, and a device for setting up a wavelength connection are disclosed herein. The method includes obtaining a wavelength path from a source network node to a destination network node and wavelength impairment compensation information of the wavelength path; and setting up the wavelength connection from the source network node to the destination network node according to the wavelength path and performing impairment compensation for wavelength signals in an interface of each network node on the wavelength path according to the wavelength impairment compensation information during setting up the wavelength connection. The device disclosed herein includes a path calculation server, a network node device, and a control server. The system disclosed herein is a network communication system. The embodiments of the present disclosure set up an available wavelength connection efficiently, simply and quickly.

Abstract: An amount of change of a control signal applied to a polarization controller in a polarization mode dispersion compensator is determined for each feedback loop by evaluating degree of polarization response in past feedback loops.

Abstract: An optical signal transmission control apparatus that controls transmission of optical signals transmitted via a plurality of redundant routes. The optical signal transmission control apparatus includes a delay difference adjusting unit that adjusts a transmission delay difference between the optical signals of each route by converting a wavelength of the optical signal and making the optical signal with a converted wavelength pass through a waveguide in which a transmission delay of the optical signal changes continuously depending on the wavelength, and a waveform degradation compensating unit that compensates degradation of a waveform of the optical signal, while maintaining the transmission delay difference adjusted by the delay difference adjusting unit.

Abstract: A dispersion compensator (1) has a substrate (2) made of a resin, on which a conductor layer (3a), a dielectric layer (4a), a wiring layer (5a), a dielectric layer (4b), a wiring layer (5b), a dielectric layer (4c), and a conductor layer (3b) are provided in this order. A transmission line (6a) forming the wiring layer (5a) and a transmission line (6b) forming the wiring layer (5b) have identical shapes to each other and have equivalent dispersion characteristics to each other. The transmission lines (6a) and (6b) are formed in a meander shape and are arranged to overlap with each other as viewed in plan. Differential signals (14) and (15) are input to the transmission lines (6a) and (6b), respectively.

Abstract: An optical transmission apparatus that performs optical transmission by wavelength multiplexing includes a receiving unit that receives a first optical signal transmitted from a transmitting device; a wavelength determining unit that determines wavelength of the first optical signal received by the receiving unit; a transmitting unit that transmits a second optical signal of varying wavelength; and a control unit that, based on the wavelength determined by the wavelength determining unit, controls wavelength of the second optical signal transmitted by the transmitting unit.

Abstract: A method of initializing an optical communication link between nodes. Optical transmitters adapted to pre-compensate link impairments based upon an optical compensation parameters are utilized to establish an optical communications link. Pre-compensation parameter values are selected at a node for generating an optical signal. The value is selected until confirmation from the remote node is received that the optical signal transmission has been successful. The successful pre-compensation parameter value is then used to generate the optical signal for the communications link.

Abstract: An optical homodyne communication system and method in which a side carrier is transmitted along with data bands in an optical data signal, and upon reception, the side carrier is boosted, shifted to the center of the data bands, and its polarization state is matched to the polarization state of the respective data bands to compensate for polarization mode dispersion during transmission. By shifting a boosted side carrier to the center of the data bands, and by simultaneously compensating for the effects of polarization mode dispersion, the provided system and method simulate the advantages of homodyne reception using a local oscillator. The deleterious effects of chromatic dispersion on the data signals within the data bands are also compensated for by applying a corrective function to the data signals which precisely counteracts the effects of chromatic dispersion.

Abstract: A method and apparatus of compensating for compact digital domain chromatic dispersion. The distortion of an optical signal due to chromatic dispersion is compensated by a digital signal processing in the electrical domain, either prior to the optical transmitter or following the receiver. The circular coefficient approximation and sub-band processing reduce the amount of computations to execute a given level of chromatic dispersion compensation compared to a direct finite impulse response filter implementation.

Abstract: The present invention relates to a method and system for high-speed bandpass serial data communication. A driver receives at least one data signal and generates a bandpass data signal for transmission through a bandpass waveguide interconnect. The bandpass data signal is launched into the bandpass waveguide interconnect using a first adaptor and extracted therefrom after transmission using a second adaptor. A receiver connected to the second adaptor recovers the at least one data signal from the extracted bandpass data signal. A dispersion compensation circuit receives one of the at least one data signal and the bandpass data signal and information indicative of a phase response of the bandpass waveguide interconnect and dispersion compensates the one of the at least one data signal and the bandpass data signal by compensating the phase response of the bandpass waveguide interconnect.

Abstract: A method of communicating digital information over a dispersive optical channel includes encoding the digital information into a plurality of data blocks, each of which includes a number of bits of the information. A time-varying electrical signal is generated which corresponds with each of said data blocks. The time-varying electrical signal is applied to an optical transmitter (122) to generate an optical signal which includes an asymmetrically amplitude limited transmitted signal modulated onto an optical carrier. The optical signal is then transmitted over the dispersive optical channel (106). At a receiving apparatus (104) the optical signal is detected to produce an electrical signal which corresponds with the asymmetrically amplitude limited transmitted signal.

Abstract: A polarization scrambler has a polarization state rotating unit rotating the polarization state of a signal light, and a rotation speed controlling unit controlling the rotation speed of the polarization state in the polarization state rotating unit on the basis of the speed and scheme of modulation of the signal light, and the value of polarization mode dispersion of a transmission path on which the signal light is to be transmitted. Degradation of the transmission quality due to PMD is more mitigated than the known techniques.

Abstract: An apparatus and method are applied to characterizing an dispersion-affecting element for use in controlling chromatic dispersion in an optical communications link. Information regarding the behavior of the dispersion-affecting element is recorded and stored in a medium that is provided for deployment with the dispersion-affecting element to enable improved management and active control of the dispersion-affecting element. The suitability of the dispersion-affecting element for operating under different conditions may also be characterized.

Abstract: This device for optically regenerating pulses includes a synchronous intensity modulator to provide time synchronization for pulses passing through it and to stabilize intensity fluctuations in the pulses. In addition, it includes noise suppression circuitry in the form of a saturable absorber that is distinct from the synchronous intensity modulator and the intensity fluctuations stabilizer.

Abstract: The present invention provides a method for reducing spreading of a pulse in a transmission line, said spreading being as a result of polarization mode dispersion, comprising inducing predetermined polarization rotations of particle or wave components of the pulse in the transmission line.

Abstract: A dispersion compensation method and a fiber transmission system are disclosed, pertaining to the field of fiber communications. The dispersion compensation method includes: after performing electrical pre-compensation processing on a digital transmit signal, the transmitting end controls the electrical/optical converting module to output a distorted optical signal; after receiving the optical signal, the receiving end performs post-compensation processing after converting the optical signal into an electrical signal, or converts the optical signal into an electrical signal after performing post-compensation processing on the optical signal. The fiber transmission system includes: a pre-compensation signal processing module, an optical source, an electrical/optical converting module, a fiber transmission line, an optical/electrical converting module, and a post-compensation processing module.

Abstract: An optical communication system and a communication network are disclosed herein capable of transmitting optical signals with high optical launch power over unrepeatered optical fiber links. A method of transmitting optical signals is also disclosed herein which comprises transmitting optical signals at high optical launch power over unrepeatered links.

Abstract: An optical equalizer/dispersion compensator (E/CDC) comprises an input/output for receiving a multiplexed channel signal comprising a plurality of channel signals of different wavelengths. An optical amplifier may be coupled to receive, as an input/output, the multiplexed channel signals which amplifier may be a semiconductor optical amplifier (SOA) or a gain clamped-semiconductor optical amplifier (GC-SOA). A variable optical attenuator (VOA) is coupled to the optical amplifier and a chromatic dispersion compensator (CDC) is coupled to the variable optical attenuator. A mirror or Faraday rotator mirror (FRM) is coupled to the chromatic dispersion compensator to reflect the multiplexed channel signal back through these optical components The E/CDC components may be integrated in a photonic integrated circuit (PIC) chip.

Abstract: Repeaterless transmission of differential phase-shift keying (DPSK) at 10.7 Gb/s over at least 304 km of standard single-mode fiber is obtained through use of a coherent optical receiver including electronic dispersion compensation. High receiver sensitivity and high tolerance to nonlinearities of DPSK, allow overcoming a total link loss of 58 dB with a 3 dB system margin, through use in the receiver of heterodyne detection to preserve phase distortions resulting from chromatic dispersion, to permit electronic dispersion compensation to be used.

Abstract: Dispersion compensation values are set so as to be transmittable to any path groups in a WDM optical communication system having OADM nodes, which includes transmitting-end and receiving-end terminal nodes; a WDM optical communication transmission line including a plurality of spans each having an optical fiber, the plurality of spans joining the transmitting-end and receiving-end terminal nodes; and a plurality of add drop multiplexing (OADM) nodes disposed on the optical communication transmission line; wherein when taking as the reference a residual dispersion target value of between the transmitting-end terminal and receiving-end terminal nodes, a residual dispersion target value for a node segment between one of the terminal nodes and one of the add drop multiplexing (OADM) nodes and a residual dispersion target value for a node-to-node segment between two of the add drop multiplexing (OADM) nodes are set so as to be proportional to ratios of the span counts in the node segment and in the node-to-node se

Abstract: An apparatus and method for transmitting a signal for optical network applications with automatic chromatic dispersion compensation. The apparatus includes a first optical transmitter. The first optical transmitter includes a first light source configured to generate a first laser signal in response to a first laser drive signal, a first data modulator configured to receive the first laser signal and a first data drive signal and output a first chirped return-to-zero signal, and a first signal source configured to generate a first non-return-to-zero signal. Additionally, the apparatus includes a first clock and data recovery system, a first data driver, a first adjustment system, and a first control system.

Abstract: An optical signal transmission control apparatus that controls transmission of optical signals transmitted via a plurality of redundant routes. The optical signal transmission control apparatus includes a delay difference adjusting unit that adjusts a transmission delay difference between the optical signals of each route by converting a wavelength of the optical signal and making the optical signal with a converted wavelength pass through a waveguide in which a transmission delay of the optical signal changes continuously depending on the wavelength, and a waveform degradation compensating unit that compensates degradation of a waveform of the optical signal, while maintaining the transmission delay difference adjusted by the delay difference adjusting unit.

Abstract: The invention relates to an optical transmission system which allows high quality transmission of signal light, and has a configuration that is suitable particularly for CWDM optical transmission. In the optical transmission system, signal channels outputted from non-temperature controlled direct modulation light sources are multiplexed by a multiplexer, transmitted through an optical fiber transmission line, and demultiplexed into a first wavelength band ?1 and second wavelength band ?2 by a demultiplexer. The signal channel group in the second wavelength band ?2 of which the absolute value of chromatic dispersion is large is dispersion-compensated for by a non-temperature controlled dispersion compensator. The chromatic dispersion of the signal channels in the second wavelength band ?2 after passing through the dispersion compensator is set to be negative over a temperature range of 0° C. to 60° C.

Abstract: The present invention relates to an automatic dispersion compensating optical link system. Carrier suppressed RZ encoded optical signals generated using carrier suppressing means and binary NRZ code or partial response code, or carrier suppressed clock signals generated using carrier suppressing means and clock signals are transmitted on an optical transmission line. Two bands of the carrier suppressed RZ encoded optical signals or carrier suppressed clock signals transmitted on the optical transmission line are each divided into bands and are received. Phase information of the respective basebands is extracted from the binary NRZ code components or partial response code components or clock signals in each band and the relative phase difference thereof is detected. The chromatic dispersion value of the optical transmission line is then calculated from the relative phase difference.

Abstract: An apparatus and method directed to testing and optimizing performance of an optical transmission system is disclosed, including at least one broadband dispersion compensation unit (DCU) or at least one depolarization device. The depolarization device may be used alone or in combination with the at least one broadband DCU. A method for optimizing performance of data channels in initial loading (IL) and full loading (FL) configurations of the optical transmission system is also disclosed.

Abstract: An all optical network for optical signal traffic has at least a first ring with at least one transmitter and one receiver. The first ring includes a plurality of network nodes. At least a first add/drop broadband coupler is coupled to the first ring. The broadband coupler includes an add port and a drop port to add and drop wavelengths to and or from the first ring, a pass-through direction and an add/drop direction. The first add/drop broadband coupler is configured to minimize a pass-through loss in the first ring and is positioned on the first ring.

Abstract: Disclosed is a wavelength division multiplexing (WDM) optical transmission system including: an optical transmitter for transmitting, to an optical fiber transmission path, a WDM signal obtained by multiplexing a plurality of optical signals on the optical fiber transmission path in terms of wavelength, the plurality of optical signals respectively having negative chirps; an optical receiver for receiving the WDM signal from the optical fiber transmission path; and at least one relay node which is provided between the optical transmitter and the optical receiver. Each of the relay node and the optical receiver includes a dispersion compensator for compensating a chromatic dispersion suffered in the optical fiber in the immediately preceding transmission span. Moreover, a dispersion adder for beforehand adding a predetermined positive dispersion amount to the WDM signal before transmission is included in the optical transmitter or at least one relay node.

Abstract: A bidirectional communication system is disclosed. A single optical line amplifier is used to amplify signals in both the east and west directions. Additionally, a single dispersion compensation module is used to compensate for fiber dispersion in both directions. Using a single optical line amplifier and a single dispersion compensation module for both directions allows for reduction in the number of optical line amplifiers used in a given network.

Abstract: An optical fiber system comprising: (i) a dispersion pre-compensator including dispersion compensating fiber DCF characterized by the overall dispersion value DDCF at the operating wavelength ?; and (ii) a passive optical network (PON) including a plurality of transmission paths provided by a plurality of optical fibers, said plurality of transmission paths having a minimum and maximum dispersion value DMIN and DMAX; wherein the dispersion pre-compensator includes an output port operatively coupled to an input port of the a passive optical network and ?DMAX<DDCF<?DMIN.

Abstract: A dispersion compensator is applicable to a WDM optical transmission system and features low loss, wideband usage, and minimum ripple. The dispersion compensator is constructed so that the light emitted from a collimator will be reflected from an etalon of a 100% single-side reflectance by arranging the etalon and a mirror in parallel or with a slight angle and then enter another collimator. Elements for achieving variable dispersion compensation by changing temperature using a heater, for example, are also provided. In addition, these dispersion compensating elements are provided in multi-stage form and the angle of the mirror and the reflectance of the etalon are optimized. Thus, it becomes possible to realize a dispersion compensator applicable to a WDM optical transmission system and featuring low loss, wideband usage, and minimum ripple.