Abstract: The invention relates to an optical receiving station, an optical communication system, and a dispersion controlling method for precisely controlling chromatic dispersion in an optical transmission line or chromatic dispersion in an optical transmission line that varies with time. An optical receiving station is provided with a dispersion compensating section for receiving, via an optical transmission line, an optical signal modulated according to an optical duo-binary modulation method and for changing a dispersion value to be used for compensating for chromatic dispersion in an optical transmission line, an intensity detecting section for detecting the intensity of a specific frequency component of the optical signal output from the dispersion compensating section, and a controlling section for adjusting the dispersion value of the dispersion compensating section so that the output of the intensity detecting section has a predetermined extreme value.

Abstract: In a wavelength division multiplexed optical transmission system wherein the zero dispersion wavelength of the optical fiber transmission path 224 is in the 1550 nm region, among multiplexed optical signals, the wavelengths of either of at least two optical signals are allocated between 1450 nm and 1530 nm, or between 1570 nm and 1650 nm.

Abstract: The present invention has an object to provide an optical communication system which keeps the confidentiality of information at the optical level to ensure the high safety. To this end, the optical communication system according to the present invention comprises: a PMD providing apparatus that gives the polarization-mode dispersion (PMD) which is changed in accordance with a variable pattern previously determined between an optical sender and an optical receiver to an optical signal output from the optical sender; to send the optical signal to an optical line network; and a PMD restoring apparatus that gives the PMD negating the PMD provided by the PMD providing apparatus to the optical signal propagated through the optical line network and restores the optical signal to the state at the transmission time, to send it to the optical receiver.

Abstract: The present invention provides an optical demultiplexer and an optical multi-/demultiplexer at low cost without reducing performance capabilities. The optical demultiplexer includes a multi-mode waveguide having such an optical path length as to cause a difference between first and second wavelengths with respect to a phase difference between zero- and first-order modes to become an integral multiple of ?, an input waveguide optically connected to the input side of the multi-mode waveguide such that the optical axis thereof is offset from the center line of the multi-mode waveguide, and two output waveguides optically coupled to the multi-mode waveguide at different positions of the output side of the multi-mode waveguide. The two output waveguides are located in such a manner as to maximize the extinction ratio.

Abstract: A dispersion compensator having relatively uniform transmission characteristics over the bandwidth of a communication channel. The compensator is designed to process an optical signal corresponding to the communication channel by decomposing that signal into spectral components, routing different components along different optical paths that impart relative delays between the components, and recombining the delayed components spatially and directionally to generate a processed optical signal with reduced chromatic dispersion. In one embodiment, the compensator includes a diffraction grating optically coupled to a mirror array, in which different mirrors receive light corresponding to different communication channels. For each channel, a desired group delay value is produced by selecting the curvature of the corresponding mirror. A compensator employing independently addressable, variable-curvature mirrors enables generation of variable, channel-specific group delays.

Abstract: A chromatic dispersion compensator comprises a beam delay element, such as one or more Gires-Tournois etalon (GTEs); a beam director, such as a polarizing beam splitter (PBS), a prism polarizer, a dielectric polarizer or a crystal polarizer; and a polarization changer, such as one or more quarter-wave plates. The beam director directs an inbound optical beam based on its polarization toward the beam delay element whereat a first unit of group delay is induced. The optical beam traverses the beam delay element and enters a polarization changer whereat the optical beam obtains a new polarization. The optical beam traverses the polarization changer and re-enters the beam director whereupon a path change is induced on the optical beam based on its new polarization and the optical beam is redirected toward the beam delay element whereat a second unit of group delay is induced.

Abstract: An optical fiber comprises a core region extending along a predetermined axis X, and a cladding region surrounding the core region. The cladding region 14 comprises first to (N+1)-th regions such that the first region surrounds the core region, and the (k+1)-th region surrounds the k-th region (k=1, 2, . . . , N). At least one of the first to (N+1)-th regions includes, in a main medium having a predetermined refractive index, a sub-region made of an auxiliary medium having a refractive index different from that of the main medium. Letting n[0] be the average refractive index of the core region, and n[k] (k=1, 2, . . . , N+1) be the average refractive index of the k-th region, this optical fiber satisfies the relationship of n[0]>n[1], and n[i]>n[i+1] (?i=h, h+1, . . . , h+m; where h and m are natural numbers).

Abstract: An exemplary embodiment of the invention is a dispersion compensation module for compensating dispersion in a communications network. The dispersion compensation module includes dispersion compensating fiber having a dispersion coefficient that varies with wavelength. A thermal regulator adjusts the temperature of the dispersion compensating fiber to adjust the dispersion characteristic of the dispersion compensating fiber. Alternate embodiments of the invention include a communications system using the dispersion compensation module and a method for compensating dispersion.

Abstract: Methods and apparatus are contemplated for multiplexing and de-multiplexing modulated optical signals using dispersion. Optical signals comprising a wavelength-multiplexed plurality of modulated spectra may be additionally multiplexed and de-multiplexed using dispersion. Dispersion multiplexing may be used in the simultaneous two-way propagation of optical signals over a waveguide.

Abstract: The present invention relates to an optical communication system including a structure for suppressing deterioration of transmission characteristics of signals added at each of nodes arranged in an optical transmission line, and a method of assigning signal channels. The optical communication system includes the optical transmission line for transmitting signals of plural channels between a transmitter and a receiver, and one or more nodes are arranged at predetermined positions of the optical transmission line. Each of the nodes includes an ADM for adding signals of a predetermined channel to the optical transmission line, and a signal channel at which the absolute value of accumulated-dispersion up to the receiver becomes smallest among signal channels which can be added is assigned to each of the nodes in advance or dynamically.

Abstract: A technique for PMD mitigation in an optical communications system that utilizes a plurality of polarization rotators in an optical fiber to continuously rotate the polarization state of at least one optical signal that propagates through the fiber. The optical fiber is segregated into a plurality of sections and the polarization rotators are disposed between adjacent sections of the fiber. The polarization state of at least one optical signal received from the first of a pair of adjacent sections is continuously rotated by the polarization rotator prior to being transmitted to the second of the pair of adjacent sections. The rotated optical signals are collected at a receiver and corrected for errors using, for example, forward error correction.

Abstract: An approach for automatic Raman gain and tilt control for a WDM (Wavelength Division Multiplexing) optical communication systems is disclosed. An optical fiber carries a plurality of optical signals, in which at least one of the optical signals are reference signals. An optical gain unit (e.g., Raman pump unit) couples to the optical fiber and adjusts the reference signals to compensate, in part, for losses associated with the optical fiber and gain tilt accumulation. Upon detecting and analyzing the reference signals, a controller controls the optical gain unit and outputs a control signal to the optical gain unit based upon the analyzed reference signals. An optical amplifier is connected to the optical fiber and amplifies the optical signals. The optical gain unit provides a nearly constant power per channel at an input of the optical amplifier.

Abstract: To generate light with the degree of polarization zeroed and the spread of an optical spectrum suppressed even with temporal overlapping between optical pulses each of which is polarized orthogonally to the succeeding pulse, a polarization scrambler includes an optical pulse generator that generates optical pulses with an intensity waveform repetition period T/2 and an electrical field repetition period T in which the same intensity waveform is repeated every repetition period T/2 and in which phase is inverted every repetition period T/2, and an orthogonal polarization delay unit which receives each of the optical pulses, separates the optical pulse into two optical pulses with orthogonal states of polarization, and relatively shifts the temporal position of one of the two optical pulses from that of the other optical pulse by (2n?1)T/4 (n is a natural number) to generate light in which each pulse is polarized orthogonally to a succeeding pulse.

Abstract: A wide band dispersion-controlled fiber which comprises a core forming an optical signal transmission path and having a peak refractive index, and a cladding surrounding the core and having a peak refractive index lower than the peak refractive index of the core. The wide band dispersion-controlled fiber further comprises at least one dispersion control layer arranged between the core and the cladding and having a refractive index profile such that its refractive index increases from an inner periphery to an outer periphery. The minimum refractive index of the dispersion control layer is less than the peak refractive indices of the core and cladding.

Abstract: An apparatus for transporting an optical signal is provided. The apparatus includes sections of optical fiber span with at least one section negative dispersion, negative slope fiber positioned at a distance from the output. A pump light emitting device optically coupled to the optical fiber span near the output is provided for generating an amplification signal.

Abstract: An optical filter having at least one optical fiber component and a thermal compensation device which includes a first, second and third member in which the thermal compensation device has a first and a second fixing point, the first, second and third members are made from materials having first, second and third thermal expansion coefficients, the optical fiber component is attached to the thermal compensation device at the first and the second fixing points thus defining a composite thermal expansion. The optical filter is such that the composite thermal expansion compensates for thermal behavior of the optical fiber component.

Abstract: Systems and methods for controlling power of WDM channels in a WDM receiver. A preamplifier is provided prior to a demultiplexer in the WDM receiver chain. The gain of the preamplifier may be controlled based on power measurements made on individual WDM channels. A filter with controllable tilt may be employed to compensate for amplifier gain tilt and assure that all of the WDM channels remain within the dynamic range of the photodetector and receiver electronics. This provides improved bit error rate performance.

Abstract: A tunable optical structure and devices based thereon for the compensation of chromatic dispersion in a multi-channel light signal are provided. The optical structure includes a waveguide and a Bragg grating provided therein. The Bragg grating has a plurality of grating components, each associated with one or a few of the channels to be compensated. The period of each grating component is selected to allow compensation of chromatic dispersion experienced by this particular channel or these particular channels, thereby taking into account the wavelength-dependent dispersion slope of the light signal. Tuning means are also provided in order to adjust the dispersion of the grating components to the required values.

Abstract: A tunable dispersion compensator for the compensation of the chromatic dispersion experienced by a single-channel or multi-channel light signal. The compensator includes a plurality of optical structures such as chirped Bragg gratings or combinations thereof, each having a characteristic dispersion profile. An optical coupling arrangement successively propagates the light signal in each of these structures, so that it accumulates the dispersion compensation effect of each. A tuning device jointly tunes the dispersion profile of each optical structure by applying a same tuning force thereto, preferably a temperature gradient.

Abstract: A chromatic dispersion compensation device selectively delays a respective portion of spectral sections of each respective optical channel of an optical WDM input signal to compensate each optical channel for dispersion compensation, and includes a spatial light modulator having a micromirror device with a two-dimensional array of micromirrors. The micromirrors tilt or flip between first and second positions in a “digital” fashion in response to a control signal provided by a controller in accordance with a switching algorithm and an input command. A collimator, diffraction gratings, and Fourier lens collectively collimate, disperse and focus the optical input channels onto the array of micromirrors. Each optical channel is focused onto micromirrors of the micromirror device, which effectively pixelates the optical channels. To compensate an optical channel for chromatic dispersion, a portion of the spectral sections of each channel is delayed a desired time period by tilting an array of mirrors (i.e.

Abstract: Apparatuses and methods are provided for chromatic dispersion compensation of wavelength division multiplexed (WDM) optical signals within an optical add/drop multiplexer (OADM) and especially within a remotely reconfigurable add/drop multiplexer (RROADM). The arrangement is especially useful in metro or regional networks where RROADMs can be dynamically reconfigured to deliver signals from any node to any other node. A dispersion compensation module (DCM) is located in the multiplexed through path of the RROADM between the drop module and the add module such that only wavelengths passing through the RROADM are compensated and shorter optical paths traversing only one span between adjacent nodes are not compensated. This allows lower cost static DCMs to be used, allows more flexibility in DCM values and allows fewer DCMs to be used while maintaining dispersion limits.

Abstract: A method and apparatus for providing controllable second-order polarization mode dispersion for fiber optic transmission systems are provided. A section of fixed high birefringent optical fiber, a polarization controller, and a variable differential group delay module are provided. The polarization controller is connected to the optical fiber section, and the variable differential group delay module is connected to the polarization controller. The variable differential group delay module is controlled to vary the second-order polarization mode dispersion values at an output of the high birefringent optical fiber section.

Abstract: The present invention relates to an optical waveguide type grating element and others in structure for decreasing absolute values of chromatic dispersion occurring in selective reflection of each of signal channels in a reflection band. The optical waveguide type grating element is provided with an optical waveguide in which signal light containing a plurality of signal channels spaced at a channel spacing ?i propagates, and a grating which is an index modulation formed over a predetermined range of the optical waveguide. Particularly, the optical waveguide type grating element has a transmittance of ?20 dB or less for each of the signal channels in the reflection band, and has a reflectance of ?20 dB or less for each of signal channels outside the reflection band. Furthermore, a deviation of a group delay time of each of the signal channels in the reflection band, which is caused by reflection in the grating, is 10 ps or less in a wavelength range of (?CH??i×0.375/2) or more but (?CH+?i×0.

Abstract: A suite of optical performance monitoring (OPM) methods, based on optical subcarrier multiplexing, are described by the invention. The strength of this approach lies in the simplicity of double sideband subcarrier signals and the fact that these signals travel the complete optical path with the baseband signal of interest. The subcarrier signals can be recovered using techniques described in the application and are immune to fiber dispersion induced fading.

Abstract: The object of the present invention is to provide a compact dispersion slope equalizer by which it is possible to simultaneously recover distorted waveforms of WDM signals by dispersion slope of DSF or NZ-DSF at 1.55 ?m band, and to compensate for the dispersion of various fiber transmission lines having various dispersion values and variation of dispersion value caused by the temperature change or the like. WDM signals distorted by the dispersion slope of the fiber are introduced into an input waveguide, and are demultiplexed by a wavelength demultiplexer into each wavelength component, and pass through lattice-form optical circuits, transversal-form optical circuits, or the combination of these circuits. The dispersion slope of the signals is compensated for by these circuits. The recovered signals are multiplexed by a wavelength multiplexer, and the multiplexed light is outputted at an output waveguide. Arrayed-waveguide gratings can be used as the wavelength demultiplexer and multiplexer.

Abstract: A method for compensating for polarization mode dispersion of an incoming optical communications signal including the step of orienting the state of polarization of the incoming optical communications signal with respect to the axes of a polarization splitter. The communications signal is split into a first and a second orthogonal states of polarization at a split point. The first of the polarization states is directed to a first birefringent optical waveguide having a first chirped grating having a first reference reflection point. The second of the polarization states is directed to a second birefringent optical waveguide having a second chirped grating having a chirp pattern substantially similar to that of the first chirped grating and having a second reference reflection point. The optical path length from the second reflection point to the split point is adjustably varied to compensate for polarization dispersion between the first and second states of polarization.

Abstract: A system and method for optical power transient control and prevention in communication networks. An optical signal propagating on a network is demultiplexed into individual spectral bands, e.g. at an OADM, and an optical power monitor point is included into each band. A separate idler laser is provided for each OADM band. The power output of each laser is adjusted such that it compensates for the signal power lost from each band. The wavelength of each laser is chosen to fall within the associated OADM spectral band, but outside of the window of individual signal wavelengths, so that it may propagate through the network without causing deleterious interference at the receiver.

Abstract: The present invention relates to a dispersion compensating module or the like having a simple and compact structure. The dispersion compensating module comprises a plurality of dispersion compensators between its input and output ends and at least one or more optical switches disposed between these dispersion compensators. Each of the optical switches acquires signals reached from its first port and is switching-controlled so that the signals are outputted from one of its second and third ports. The dispersion compensating module controls the port switching operation of at least one of the optical switches, thereby adjusting the propagation line of the signals, i.e., the dispersion compensation amount.

Abstract: An optical communication system has a configuration in which an optical transmission line is laid between a repeater (transmitter) and another repeater (receiver). The optical transmission line is formed by fusion-splicing a first optical fiber on the upstream side and a second optical fiber on the downstream side. The first optical fiber has a transmission loss of 0.25 dB or less, and an effective area of 80 ?m2 or above (preferably 100 ?m2 or above), at a wavelength of 1550 nm, which is the wavelength of signal light. The second optical fiber is connected to the downstream end of the first optical fiber and has positive dispersion regions and negative dispersion regions which are alternately arranged along the longitudinal direction and whose chromatic dispersions at a wavelength of 1550 nm are positive and negative, respectively.

Abstract: Various methods, systems, and apparatuses in which a chromatic dispersion compensation module includes an input fiber, an output fiber, a lens, and an etalon resonator. The input fiber has a first core with a center. The output fiber has a second core with a center. The input fiber is adjacent to the output fiber. The spacing between the center of the first core and the center of the second core is affixed to less than one hundred and twenty microns. The input fiber routes an optical signal to a lens. The lens routes the optical signal to the etalon resonator. The etalon resonator has reflectors with fixed reflectivity and a variable optical length to induce a wavelength-dependent delay into the optical signal. The etalon resonator routes the optical signal to the output fiber through the lens.

Abstract: The specification describes an improved optical fiber design in which the criteria for high performance in a Raman amplified optical system, such as moderate effective area, moderate dispersion, low dispersion slope, and selected zero dispersion wavelength, are simultaneously optimized. In preferred embodiments of the invention, the dispersion characteristics are deliberately made selectively dependent on the core radius. This allows manufacturing variability in the dispersion properties, introduced in the core-making process, to be mitigated during subsequent processing steps.

Abstract: A VIPA plate having a configuration where a translucent reflection film and a total reflection film are respectively arranged on one side and the other side of a transparent parallel plate can be used as a wavelength dispersion compensator by using a special mirror and a lens. However, the transparency characteristic of the wavelength dispersion compensator using such a VIPA plate is a periodical characteristic which is asymmetric with a central wavelength in a wavelength regime. Accordingly, not parallel light but converged or diverged light having angular dispersion is input to an etalon plate, so that a filter whose transparency characteristic is an asymmetric periodical characteristic which is reverse to the VIPA plate is configured for the central wavelength in the wavelength regime. With this filter, the transparency characteristic of the wavelength dispersion compensator using the VIPA plate is optimized.

Abstract: An optical fiber suitable for the WDM transmission in the wavelength bands of 1.31 ?m and 1.55 ?m is provided. An optical fiber is characterized by a zero dispersion wavelength of longer than 1330 nm and shorter than 1430 nm, a dispersion of not less than 6 ps/nm/km and not more than 15 ps/nm/km at a wavelength of 1550 nm, a ratio of a dispersion to a dispersion slope of not less than 200 nm and not mare than 400 nm at a wavelength of 1550 nm, a dispersion of not more than ?1 ps/nm/km and not less than?8 ps/mn/km at 1300 nm, and a cutoff wavelength of 1300 nm or shorter.

Abstract: A device is provided for detecting polarization mode dispersion of an optical data signal, wherein the device includes at least two filters, each of which is respectively followed by a power detector. A better compensation can ensue due to the combination of a large monotony range and great steepness in the employment of a number of filters.

Abstract: An interference-reducing optoelectronic device determines the value of a current data bit in an optical data stream. A receiver receives the optical data stream, which is converted to a series of samples by a D/A converter. A set of adaptive filters, each filter corresponding to a unique possible value for one or more prior data bits, filters the series of samples utilizing variable tap coefficients to generate filtered output values. The variable tap coefficients are at least partially different than the variable tap coefficients of another adaptive filter. Comparators compare the filtered output values against filter-specific adaptive threshold values to generate tentative values for the current data bit. A delay mechanism delays a determined value for the prior data bits, and a selection mechanism determines the value of the current data bit by selecting the tentative value corresponding to the delayed determined value of the prior data bits.

Abstract: An optical signal, which is to become the subject of dispersion compensation, is split by optical combining/splitting unit 2, and each frequency component of the optical signal that is split is reflected by the corresponding reflective mirror 30 included in reflective mirror group 3 to apply a predetermined phase shift to the respective frequency components Each reflected frequency component is then combined using optical combining/splitting unit 2, to give dispersion compensated optical signal Furthermore, in regards to reflective mirror group 3, which is used to apply phase shift to each frequency component of an optical signal, each of the respective plurality of reflective mirrors 30 is made a movable mirror having a movable reflection position that reflects the frequency components. Through this, dispersion that develops in an optical signal may be compensated with favorable controllability and high accuracy.

Abstract: A waveform converter for altering the waveform and optical spectrum of an optical signal may comprise a nonlinear element having a nonlinear effect on optical pulses, a dispersion element having a dispersion effect on optical pulses, and a wavelength selecting element configured to select spectral components in a desired wavelength region.

Abstract: A semiconductor-based tunable optical dispersion compensation method and apparatus for multiple channels. In one aspect of the present invention, an apparatus according to an embodiment of the present invention includes a semiconductor material. An optical path through the semiconductor material is included. The optical path is optically coupled to receive an optical beam. A nonlinearly chirped Bragg grating is disposed in the semiconductor material. The optical path includes the nonlinearly chirped Bragg grating to substantially reduce chromatic dispersion in the optical beam.

Abstract: The system includes a receiver for receiving a bit stream; an error monitor for indicating a first error rate for a first set of data received in the bit stream; and an adjustable circuit for converting an incoming signal into the bit stream using a reference signal that is modulated using a control signal. The system also includes a subsystem for correlating the first error rate and the control signal to generate the reference signal. The control signal has an amplitude that is selected so that a second set of data received in the bit stream has a second error rate that is less than the first error rate.

Abstract: A polarization dispersion compensation apparatus includes a polarization controller, a polarization beam splitter, an optical delay circuit, and a polarization beam combiner. The polarization controller controls polarization of an optical signal so that the polarization axis of the input optical signal substantially coincides with the optical axis of an optical transmission line, and the polarization beam splitter section splits the optical signal into two polarized components perpendicular to each other. The optical delay circuit section causes a difference in delay between the two polarized components, and the polarization beam combiner section combines the two polarized components output from the optical delay circuit section.

Abstract: A system and method for programmable phase compensation of optical signals is disclosed. The systems and methods include the use of a polarization-independent spatial light modulator (PI-SLM), so that the state of polarization (SOP) of the incoming optical signal need not be known. The system includes a first dispersive module that spatially separates the optical signal into its frequency components. The frequency components are spread over the active area of the PI-SLM. The active area of the PI-SLM includes an array of independently programmable addressable regions capable of altering the phase of the light incident thereon. An exemplary application of the invention is chromatic dispersion compensation. By knowing the amount of chromatic dispersion in the optical signal, or alternatively, by knowing the amount of chromatic dispersion to be introduced into the optical signal downstream, the appropriate phase adjustments can be made to each frequency component of the signal.

Abstract: A dispersion compensator for the compensation of chromatic dispersion in a multi-channel light signal is provided. The compensator includes a pair of optical structures each having a waveguide and a Bragg grating provided therein. The Bragg grating has a plurality of grating components, each associated with one or a few of the channels to be compensated. An optical assembly propagates the light signal sequentially through both optical structures. The periods of the grating components are selected to allow compensation of chromatic dispersion experienced by this particular channel or these particular channels, thereby taking into account the dispersion slope of the light signal. Tuning means are also provided in order to adjust the dispersion of the grating components of each optical structures, and proper selection of the tuning parameters allows tuning independently both the dispersion and dispersion slope.

Abstract: A system and method for transmission of data modulated spectrally enriched optical pulses via an error free propagation region of an optical fiber, in which the optical pulses generated by an optical transmitter have a spectrum that is substantially wider than the spectrum of Fourier-transform limit at an input of the error-free propagation region. The spectral width of the optical pulses gradually narrows while transmitting along this region and becomes comparable to the Fourier-transform limit at an output of this region. Linear and non-linear distortions are compensated within the error free propagation region respectively by deployment of dispersion compensating units and phase modulation of transmitted optical pulses for providing them with an appropriate frequency chirp having shape comparable with a frequency chirp induced by a self-phase modulation of the optical fiber but having opposite sign.

Abstract: An apparatus comprises an optical sublink including an operationally coupled optical fiber segments. The optical fiber segments are from a first optical fiber type, a second optical fiber type and a third optical fiber type. The first optical fiber type has a positive dispersion and a positive dispersion slope. The second optical fiber type has a negative dispersion and a negative dispersion slope. The third optical fiber type has one from the group of (1) a positive dispersion and a negative dispersion slope, and (2) a negative dispersion and a positive dispersion slope.

Abstract: A signal time-scaling arrangement utilises a known configuration comprising the use of a laser which has its wavelength varied over time, a modulator coupled to the laser and to a modulating analogue electrical source and a dispersion means coupled to the output of the modulator and providing at its output a signal which is a stretched version of the analogue modulating signal, but provides for the modulator to be a single-sideband modulator instead of double-sideband. The effect of this is to enable the use of a much simple laser-control system involving a CW laser output which is wavelength-ramped continuously between quite narrow wavelength limits, while allowing the use of a dispersion means having a wide dispersion characteristic in order to provide the required degree of time-scaling. The invention is application to an ADC system or to a Doppler system.

Abstract: A method and device is disclosed for relaying a narrow diameter collimated optical beam carrying optical communication signal channels between a multilayer interference filters and another reflective surface avoiding signal loss by routing the optical beam to compensate for beam broadening caused by the multilayer interference filter. The method and device are particularly applicable to dispersion compensating filters, especially those wherein one filter is tunable, in that a controllable amount of dispersion is introduced to offset or compensate dispersion. Preferably one of the filters is a tunable periodic device in the form of a multi-cavity etalon structure. In a preferred embodiment of the filters can be designed to provide various controllable but different constant amounts of dispersion.

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: This invention relates to an optical transmission system which allows high quality transmission of signal light where a plurality of signal channels are multiplexed, and has a configuration that is particularly suitable for CWDM optical transmission. In the optical transmission system, the plurality of signal channels propagating through the optical fiber transmission line are demultiplexed into a signal channel group in the first wavelength band ?1 and a signal channel group in the second wavelength band ?2. Then, each signal channel in the second wavelength band ?2 where the absolute value of chromatic dispersion is large is dispersion-compensated.

Abstract: An optical structure and devices based thereon for the compensation of chromatic dispersion in a multi-channel light signal are provided. The optical structure includes a waveguide and a Bragg grating provided therein. The Bragg grating has a plurality of grating components, each associated with one or a few of the channels to be compensated. The period of each grating component is selected to allow compensation of chromatic dispersion experienced by this particular channel or these particluar channels, thereby taking into account the wavelength-dependent dispersion slope of the light signal.

Abstract: The present invention provides devices and methods for dispersion compensation. According to one embodiment of the invention, a dispersion compensating device includes a negative dispersion fiber having an input configured to receive the optical signal, the negative dispersion fiber having a length and dispersion sufficient to remove any positive chirp from each wavelength channel of the optical signal, thereby outputting a negatively chirped optical signal; an amplifying device configured to amplify the negatively chirped optical signal; and a nonlinear positive dispersion fiber configured to receive the negatively chirped optical signal. The devices of the present invention provide broadband compensation for a systems having a wide range of variable residual dispersions.