CN100592666C - Method for higher-order dispersion compensation - Google Patents
Method for higher-order dispersion compensation Download PDFInfo
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- CN100592666C CN100592666C CN02826396A CN02826396A CN100592666C CN 100592666 C CN100592666 C CN 100592666C CN 02826396 A CN02826396 A CN 02826396A CN 02826396 A CN02826396 A CN 02826396A CN 100592666 C CN100592666 C CN 100592666C
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/27—Optical coupling means with polarisation selective and adjusting means
- G02B6/2753—Optical coupling means with polarisation selective and adjusting means characterised by their function or use, i.e. of the complete device
- G02B6/278—Controlling polarisation mode dispersion [PMD], e.g. PMD compensation or emulation
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29304—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating
- G02B6/29305—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating as bulk element, i.e. free space arrangement external to a light guide
- G02B6/2931—Diffractive element operating in reflection
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29304—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating
- G02B6/29305—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating as bulk element, i.e. free space arrangement external to a light guide
- G02B6/29311—Diffractive element operating in transmission
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/34—Optical coupling means utilising prism or grating
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
- H04B10/2513—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion
- H04B10/2519—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion using Bragg gratings
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
- H04B10/2569—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to polarisation mode dispersion [PMD]
Abstract
A method for compensating for higher-order dispersion of an incoming optical communications signal in accordance with the present invention includes the steps of compensating the signal for first order polarization mode dispersion; compensating the signal for second order polarization mode dispersion; and compensating the signal for variable chromatic dispersion. Additionally, the method may include the steps of compensation for fixed chromatic dispersion and controlling the polarization of the incoming signal. The signal may be monitored after the compensating steps and the degree of compensation may be tuned based on the monitoring. The step of compensating the signal for first order polarization mode dispersion may include the steps of controlling the polarization of the signal; splitting the signal into a first and a second orthogonal polarization components; reflecting the first polarization component in a fixed linearly chirped grating; reflecting the second polarization component in a tuned linearly chirped grating; and recombining the first and the second polarization components.
Description
Technical field
The present invention relates to be used for the method and system of signal chromatic dispersion compensation.Specifically, the present invention relates to a kind of method that is used for higher-order dispersion compensation, this method adopts Prague (Bragg) grating of at least two high-frequency impulses, with the pip of decomposed two polarization signals of selectively harmonizing, causes and variable higher-order delay associated.
Current telecommunications systems need transmit light signal on very long distance.In the signal of an optical communication, data are sent with a series of light pulse.Signal pulse is made up of the distribution of light wavelength and polarization, and each pulse is with its feature velocity transmission.This variation on speed causes pulse stretching, thereby makes signal degradation.Degenerating of causing owing to speed is relevant with wavelength is referred to as coloured chromatic dispersion, because relevant with polarization degenerating of causing then is referred to as polarization mode dispersion (PMD).
On mathematics, the light velocity ν in waveguide is provided by following formula:
C is the light beam in the free space in the formula, and n is the effective refractive index in waveguide.
Under normal situation, the effective refractive index n of optical media, relevant with the wavelength of light component.Therefore, the component with light of different wave length will be propagated with different speed.
Effective refractive index in waveguide also can be relevant with the polarization of light signal except with wavelength is relevant.Even in " single mode " optical fiber, keeping two vertical polarised lights, and, existing under the birefringent situation, these two polarised lights are propagated with different speed.Birefringence in optical fiber may be due to and comprises and make changing and the two many reasons of the environmental factor relevant with the time.Speed difference causes the propagation time relevant with polarization between two different polarization patterns in birefringence fiber, i.e. " differential group delay " (differential group delay) (DGD).In the fibre system of reality, the orientation of birefringent size and birefringence axis is all different everywhere along optical fiber.So just cause more complicated effect on light signal, it is to be that the notion of PSP is represented its feature by " the basic attitude of polarization ".PSP is defined as being subjected to two polarization states of maximum relevant DGD, and their unique instantaneous states that characterizes this system.
When signal is propagated by the different portions section of optical communication system, by the statistics of two polarized component distinct group speed and the distortion that causes the time, measure polarization mode dispersion (PMD).PMD comprises single order PMD and higher-order PMD, and is indecisive.On a given wavelength, single order PMD is a differential polarization group delay.The instantaneous value of long optical fibers can for a long time at interval and the interval of short time change on the two, the former is owing to cause such as changing slowly of temperature drift, and the latter is owing to vibrate the polarization fluctuating of inducting such as mechanics and cause.Describe single order PMD mean value coefficient can to the poor PMD optical fiber of performance greater than 2ps/km
1/2Change to the reasonable PMD optical fiber of performance less than 0.1ps/km
1/2
Second order PMD is mainly caused by two reasons: (i) the single order PMD that becomes with wavelength; (ii) the orientation of the PSP of system (the basic attitude of polarization) is with the change of wavelength, and it causes PMD with wavelength change.Second order PMD causes the group delay relevant with wavelength, in fact, is of equal value to variable coloured chromatic dispersion, and can have or negative or positive symbol.Speed that rises and falls and the fluctuating velocity of single order PMD are on same magnitude.
The coloured chromatic dispersion of two classes is arranged: conclusive and variable.Decisive chromatic dispersion is the fixedly chromatic dispersion that has on the fixed refraction waveguide unit length.To one group of given environmental condition, decisive chromatic dispersion is relatively fixing (for example, to standard single-mode fiber～17ps/nmkm).For example, 17ps/nmkm refers to (10km) system of 10 kms, and dedicated bandwidth is 0.1 nanometer (nm) when carrying data, will often arrive the chromatic dispersion of about 17 picoseconds (ps).
Variable coloured chromatic dispersion is by owing to for example add or remove optical fiber that channel causes and connect the change of length and cause by tensile stress and/or temperature fluctuation.The prediction of the amount that will change coloured chromatic dispersion, reasonably value be arrive at-500ps/nm+scope of 500ps/nm in.
Except the independent effect of PMD and coloured chromatic dispersion, also have that there is the higher-order dispersion cross term that causes simultaneously in the two owing to coloured chromatic dispersion and PMD.This cross term between coloured chromatic dispersion and the second order PMD to have be zero mean value, but root mean square (RMS) contribution of non-zero can be arranged.Be similar to second order PMD item, this RMS value can have the contribution of plus or minus.Be similar to second order PMD item, this RMS value can have the contribution of plus or minus.The contribution of RMS, according to the PMD coefficient of optical fiber can from less than 1% colouredly be dispersed into the magnitude identical with coloured chromatic dispersion.
Chromatic dispersion has applied strict restriction to transmission bandwidth, is particularly crossing on the long distance such such as transoceanic link.When higher bit rates, it is more important that chromatic dispersion problem becomes, and this spacing that is between light pulse is less, and short herein pulse causes the signal spectrum bandwidth of broad, increases the weight of coloured and effect higher-order PMD.In bit rate during, even to the optical fiber (≤0.1ps/km of " good " more than or equal to 40Gb/s
1/2The PMD coefficient), long length connects the dynamic compensation that need to be considered to higher-order.Because the position of additional light-electricity-light signal conversion needs,, perhaps limit total system length or improve system cost, the factor that chromatic dispersion may be become-suppress to allow the regeneration of the signal of telecommunication.
Higher-order dispersion is measured and explained to unsuitable understanding in the dispersion compensation device in the past.In the solution of higher-order dispersion compensation is provided, be important to the understanding of reason in the higher-order dispersion and factor.
(the PMD coefficient is 0.1ps/km to " good " optical fiber
1/2) exemplary calculated show:
| Coloured dispersion term | 17ps/nm·km |
| Single order PMD coefficient | 0.1ps/km 1/2 |
| Second order PMD coefficient | 0.006ps/nm·km |
| The size of cross term RMS | 0.37ps/nm·km |
To " difference " optical fiber (1ps/km
1/2) exemplary calculated show:
| Coloured dispersion term | 17ps/nm·km |
| Single order PMD coefficient | 1ps/km 1/2 |
| Second order PMD coefficient | 0.6ps/nm·km |
| The size of cross term RMS | 3.7ps/nm·km |
The second order coefficient of PMD can be according to " second order polarization mode dispersion: the influence in analog-and digital-transmission " literary composition (IEEE.of Lightwave Tech, JLT-16, NO 5 pp 757-771, May 1998) described in theory calculate, this article is combined in this by reference.
Second order PMD coefficient=(single order PMD coefficient)
2/ 1.73 (2)
Equation 2 is only taken into account the root mean square (RMS) of last coloured chromatic dispersion.The calculating cross term is:
Cross term=17
1/2* (single order PMD coefficient)
1/2* 1.16 (3)
So, can understand: for to having the optical fiber of high PMD coefficient, because when only adopting fixing coloured dispersion compensation by coloured chromatic dispersion of second order PMD item and cross term accumulation, PMD may cause a problem.Like this, become big or when bit rate reaches higher, will cause having the uncompensated chromatic dispersion of high value when the PMD of optical fiber coefficient.
Analyze from this, adopt the current best optical fiber of producing (to suppose～0.025ps/km even can calculate
1/2), eliminate under the situation of effect of second order PMD and cross term not carrying out dynamic coloured dispersion compensation, to 10Gb/s transmission, propagation distance be mostly be limited to≤(chromatic dispersion＜0.3 * 100ps) to 40Gb/s then is≤200km (chromatic dispersion＜0.3 * 25ps) 3000km.
Many document papers attempt to explain the problem of higher-order dispersion compensation.A method is to adopt multi-section section PMD compensator.A kind of like this method is expensive mostly, and also will be subject to the quantity of accessible variable coloured chromatic dispersion.Other method is selectively to add the various piece of special-purpose linear tuning pulse to pulse, and transmits this pulse by the high dispersion element with calibration marker and compress this pulse.A kind of like this method can be taken into account all types of chromatic dispersions.But a kind of like this method is owing to need clock recovery and phase modulated, thus be expensive mostly, and only can just can use at receiver terminal.And if residual dispersion is low, it could be worked.
The needs that Dispersion Compensation Systems is stayed not only will be to PMD, but also dynamic the adjusting done in coloured chromatic dispersion and the chromatic dispersion of higher-order look.The needs of the telecommunications systems that has improved, such as to temperature fluctuation compensation and soon with prospect not because the needs of the possibility of the variable path length that the interpolation/system of removing of light causes, require one dynamic and be the bucking-out system of reality on cost.
Summary of the invention
The present invention relates to a kind of higher order dispersion compensator, be used for tuning one and have the first polarization mode dispersion component, the signal of second order polarization mode dispersion component and variable coloured chromatic dispersion component.
This compensator comprises first tuned cell of the single order polarization mode dispersion component of regulating the Polarization Control signal and regulates second tuned cell of variable coloured dispersive components of second order polarization mode dispersion component and Polarization Control signal.This compensator also can comprise the Polarization Controller that the incident light of random polarization is changed into the Polarization Control signal with required polarization state.
In one embodiment, first tuned cell can comprise differential higher-order delay line, this line comprises the beam splitter/combiner that is coupled to the signal that receives Polarization Control, and this polarization beam splitter becomes first polarized component polarized component vertical with second to the Signal Separation of Polarization Control herein.Have be tuned to first waveguide of reflection first grating of this first polarized component and first reference reflection point be optically coupled to and receive this first polarization signal.Have be tuned to second grating of this second polarized component of reflection, and have second waveguide of second reference reflection point to be optically coupled to receive this second polarization signal.First waveguide have be tuned to reflect the first tuning pulse grating of this first polarization signal in first reference reflection point.Second waveguide is optically coupled and aligned to second delivery outlet of separator.Second waveguide have be tuned to the second frequency modulation on pulse grating of this second polarization signal of reflection, and second reference reflection point is arranged.According to this embodiment of the invention, the frequency modulation on pulse of grating can be linear, nonlinear, maybe can have complicated spatial relationship.Some is used, and the length of grating can be to be equal to or greater than 1 meter.
In this first one exemplary embodiment, two gratings all are the Bragg gratings of finishing single order PWD compensation and fixing coloured colour table compensation with linear tuning pulse.First tuner is such as come a grating in the tuning grating by making grating be in stress on mechanics.
In other embodiments, all available non-linear tuning pulse of two gratings is finished except these two compensation of fixing and variable coloured chromatic dispersion, also will finish the compensation of single order and second order PMD.In addition, can select more complicated tuning pulse pattern to finish more special is the compensation of higher-order (three, fourth class rank).
The two all can have substantially the same reflection external form and substantially the same tuning pulsation rate first grating and second grating; And first and second pip can be at substantially the same optical path length place.Perhaps, before regulating by tuner, in the grating reflection point a bit may than second pip from optical path length place that burble point is lacked.
Second tuned cell can comprise the 3rd waveguide of second tuner of Bragg grating with the 3rd non-linear tuning pulse and tuning the 3rd grating.The scope of the tuning pulse value in this 3rd nonlinear FM pulse Bragg grating can determine the respective range of variable coloured dispersion compensation.
This system also may comprise static coloured dispersion element, and it comprises the speed corresponding to the average tuning pulse of first and second gratings of fixing coloured dispersion measure to be compensated.
Can adopt circulator to come the route of regulation light signal.One embodiment comprises the circulator of four-way, this circulator has the input port that couples light to reception Polarization Control signal, couple light to and controller output signal is transferred to differential off-delay line and receives first belt again mouthful that this delay line is exported, the delay line output signal is transferred to second tuned cell and goes in ring again mouthful with coupling light to, and fill the delivery outlet that is coupled to the transmission final output signal to second of the second tuned cell output signal.
In another one exemplary embodiment, first tuned cell and second tuned cell comprise and are coupled to the polarization beam splitter that receives the signal be subjected to Polarization Control, here, this separator is being subjected to the Signal Separation of Polarization Control to become first polarized component polarized component vertical with second.First waveguide is optically coupled to and receives first polarization signal, this first waveguide have be tuned to this first polarization signal of reflection and the first non-linear tuning pulse grating with first reference reflection point.Second waveguide is optically coupled to and receives second polarization signal, this second waveguide have be tuned to this second polarization signal of reflection and the second non-linear tuning pulse grating with second reference reflection point.First tuner simultaneously tuning first and second gratings the two, second tuner then with irrespectively tuning second grating of first grating.Compensator can have static coloured dispersive compensation element, and wherein the speed of the average tuning pulse of first and second gratings is corresponding to the amount of fixing coloured chromatic dispersion to be compensated.
In this embodiment, single order polarization mode dispersion compensating element, comprises second tuner and second grating, and the single order polarization mode dispersion by obtain with the first grating tuning dividually second non-linear tuning pulse grating, second order polarization mode dispersion compensation and variable coloured dispersive compensation element comprise first and second gratings and first tuner, variable coloured dispersion compensation and the compensation of higher-order polarization mode dispersion then obtain by tuning first and second gratings as one man.
In also having another embodiment, higher order dispersion compensator comprises the coloured dispersion compensator that is coupled to receiving inputted signal; Couple light to the phase-modulator of this coloured dispersion compensator, wherein this phase-modulator sends the tuning pulse of part selectively; And the dynamic dispersion element that is coupled to this phase-modulator signal of reception.This is adjustable the dynamic dispersion element comprises have be tuned to reflection this be subjected to the first non-linear tuning pulse grating of the signal of Polarization Control, and have first waveguide of first reference reflector; And first tuner of tuning this first grating.
This compensator can comprise and couples light to judgement by the signal of optical grating reflection and the signal analyzer of control signal to tuner correspondingly is provided.This signal analyzer also can provide control signal to arrive phase-modulator.
This waveguide is exemplary optical fiber.In specific embodiment, this waveguide can be the optical fiber that the light single mode is kept polarization (PM), polarising (PZ) optical fiber, and/or make the optical fiber of certain shape.
This compensator will be being the compensator that adapts to, and it also comprises the signal analyzer that control signal one of is provided in the tuner at least.
This dispersion compensator can be at least partially integrated in the integrated optics chip such as lithium niobate.This waveguide can be a channel waveguide.Another tuner can be used acoustics, calorifics, electricity-optics, or the method for mechanics is come tuning grating.
A kind of being used for compensates single order polarization mode dispersion signal the compensation method of the higher-order dispersion of incident light signal of communication according to the present invention; The second order polarization mode dispersion signal is compensated; And can be variable coloured dispersion signal is made the step of compensation.In addition, this method can comprise the step of solid tame coloured chromatic dispersion being made the polarization of compensation and control incoming signal.After compensation process, can monitor this signal, and according to monitoring the degree of regulating compensation.
The step of single order polarization mode dispersion signal being done compensation can comprise the polarization of controlling this signal; This Signal Separation is become the first and second vertical polarization components; In fixing linear tuning pulse grating, reflect this first polarized component; In tuned linear tuning pulse grating, reflect this second polarized component; And the step that reconfigures this first and second polarized component.
The step of the signal of second order polarization mode dispersion being done compensation can be included in the step that reflects this signal in the tuned non-linear tuning pulse grating.
In a certain embodiments of the present invention, this method comprises the steps:
The step of the signal of second order polarization mode dispersion being done compensation can be included in the step that reflects this signal in the tuned non-linear tuning pulse grating.
In a certain embodiments of the present invention, this method comprises the steps:
● the inclined to one side note of regulating the communicate optical signal of incident makes the basic attitude of polarization of signal of communication be registered to the basic attitude of polarization of compensator system exactly;
● at burble point signal of communication is separated into the first and second vertical basic attitudes of polarization;
● first attitude of polarization state is transferred to first waveguide with first non-linear tuning pulse grating, and this grating has first reference reflection point;
● second attitude of polarization state is transferred to second waveguide with second non-linear tuning pulse grating, and this grating has the figure of the tuning pulse that is similar to the first tuning pulse grating substantially, and has second reference reflection point;
● by changing along the position of first and second pips of grating, adjustable ground changes coloured chromatic dispersion of first and second reflections;
● adjustable ground changes at the corresponding optical path length between first and second pip and the burble point and compensates polarization dispersion between the first and second vertical attitudes at polarization; And
● first and second polarization states are reassembled into output signal.
This method also comprises the step to the quality of output signals sampling.Adopt this quality reading, the present invention can comprise the steps:
● adapt to that the polarization state of incoming signal is regulated on ground and with respect to the optical path length of second pip of burble point, the quality of response output signal and the single order polarization mode dispersion is compensated, and/or
● adapt to ground and regulate with respect in first and second pips of burble point one or two, so that the chromatic dispersion in signal is compensated.
Changing before the step of the optical path length of second pip adjustablely, at least in the grating can regulate like this, makes that second pip is on a desirable point, for example, as first pip, from substantially the same optical path length of burble point or different optical path lengths.Its difference can be selected according to the polarization dispersion of an expectation between the first and second vertical polarization attitudes.
At another embodiment that is used for the higher-order dispersion of communicate optical signal is done the method for compensation according to the present invention, this method comprises the following steps:
● signal of communication is separated into the first and second vertical basic polarization states,
● first polarization state is transferred to the first high birefringence fiber waveguide with first linear tuning pulse grating, and this first fiber waveguide has first pip at the first optical path length place;
● second polarization state is transferred to the second adjustable high birefringence fiber waveguide with second linear tuning pulse grating, and this second fiber waveguide has second pip at the second optical path length place;
● this first and second polarization state is reassembled into output signal;
● this output signal is transferred to the 3rd high birefringence fiber waveguide with non-linear tuning pulse grating, and wherein this grating has a pip;
● adjustable ground changes second optical path length of the second linear tuning pulse grating, so that the polarization dispersion between the first and second vertical polarization attitudes is compensated; And
● the light path of adjustable ground change in the 3rd grating is to compensate the higher-order dispersion in output signal.
The second tuning pulse grating can have the tuning pulse pattern that is substantially similar to the first tuning pulse grating, and this second grating has the same with first pip basically at second pip on the identical optical path length of burble point.Again, can be to output signal sampling, the optical path length of the polarization state of incoming signal and second pip can respond the quality of output signal and regulate.
The accompanying drawing summary
Fig. 1 is to dynamic according to the present invention, the part schematic flow sheet of higher-order dispersion compensation method;
Fig. 2 is dynamic according to the present invention, the representative schematic diagram of first embodiment of higher-order dispersion compensation system;
Fig. 3 is dynamic according to the present invention, the representative schematic diagram of second embodiment of higher order dispersion compensator; And
Fig. 4 is dynamic according to the present invention, the representative schematic diagram of the 3rd embodiment of higher order dispersion compensator.
Specific implementation method
The objective of the invention is to be used for a kind of method and a kind of system of higher-order dispersion compensation (HDC), it can be to by coloured chromatic dispersion, polarization mode dispersion, the higher-order polarization mode dispersion, make compensation simultaneously with the higher-order dispersion effect that variable coloured chromatic dispersion is formed, and optical loss and equipment are on the whole reduced to minimum.Higher-order dispersion compensation be defined as comprise coloured, polarization mode, second order polarization mode and variable coloured dispersion compensation.
An one exemplary embodiment of the present invention relates to a kind of higher order dispersion compensator system of adaptation.This system comprises Polarization Controller, differential polarization delay unit, dynamic coloured dispersive compensation element and fixing coloured dispersion element.In various forms of the present invention, these work are by two, three, or four elements are finished.For example, in one embodiment, all these four work can be finished by the element that separates, and in another embodiment, all working except Polarization Control is finished by a compensating element.
Resemble the so tuning pulse-echo type grating of Bragg grating (FBG) and be used to generation time delay between vertical polarization.In an one exemplary embodiment of the present invention, between vertical polarization, come generation time to postpone with two tuning pulse Bragg gratings at least, comprise correcting value simultaneously according to coloured chromatic dispersion of the tuning level of the tuning pulse of grating and grating.A kind of signal analysis method is pointed out the level of specific chromatic dispersion component, or the level of all chromatic dispersion components, and a controlling schemes will adopt this signal analysis result to go to optimize this system.
Signal to be compensated can comprise the first polarization mode dispersion component, second order (and/or higher-order) the polarization mode dispersion component, variable (promptly dynamic) coloured chromatic dispersion component, and/or static (promptly fixing) coloured chromatic dispersion component, and/or static (promptly fixing) coloured chromatic dispersion component.Fig. 1 is the flow chart that is used for signal is provided all steps of one exemplary embodiment of higher-order dispersion compensation according to the present invention.Incoming signal 142 passes Polarization Controller 140, and it is transformed into the output signal that is controlled 144 with required polarization state to any incident polarized light.This controlled output signal is gone out through total pulse distortion being reduced to minimum fixing coloured dispersion compensator 112.To connect length relevant for bear look dispersion measure and the expectation of progressively leading to compensator introduced.To a plurality of embodiment that discussed, because the use of tuning pulse fiber Bragg grating, this function will be finished simultaneously with following step.
The output of signal sends by single order PMD compensator 114.Then, last signal sends by variable coloured dispersion compensator 116, and it also compensates any dynamic coloured chromatic dispersion the compensation except any residue second order PMD is done.At last, this final output signal that has compensated 148 is subjected to signal analyse block 120 monitoring by light signal tap 118, and this module outputs to control element such as Polarization Controller 140 and suitable dispersion compensating element, 110 to control signal 128.
To vacuum wavelength is that the grating periods lambda that the light signal of λ is made strong reflection is provided by following formula:
Λ=λ/2n (4) n in addition is the effective refractive index of waveguide.Therefore,, just can be controlled in the pip of signal pulse in the grating by control Λ (x), thus the may command propagation time.And, pass to from the cycle be the be reflected coloured chromatic dispersion of signal of the tuning pulse grating of Λ (x), (this cycle has corresponding cyclic gradient d Λ/dx or " tuning pulse " provided by following formula along this grating
By the periods lambda (x) of normal design and tuning this grating, people can be controlled in coloured chromatic dispersion of being subjected to by pulse in the grating and total delay the two.
Type that the chromatic dispersion measurement technology is used and number can according to circumstances change.Fig. 1 illustrates the three kinds of technology that adopted: DOP mensuration 122, subharmonic filtering 124, and/or frequency modulation(FM) 126.To adopting two kinds or more may be advantageous simultaneously such as the measuring technique of the subfrequency filtering of polarization monitoring degree and electricity.But, may increase the cost of compensator like this, thereby wish only to adopt a kind of technology.The modification technology of shown other measuring technique or these technology may be advantageous.Some example is: laterally filtering; The DOP mensuration that has scanning filter; Or the direct inspectional analysis or the digital communication analyzer of use bit error rate tester.The two all can be used for analytic signal suitably feedforward and rear feed measuring technique.
Can combine to obtain extra functionality with various feed forward methods or with the phase modulated compensation method from some compensating element, of embodiment shown in Fig. 1.
Fig. 2 is the schematic diagram of first embodiment of higher-order bucking-out system 200 according to the present invention, and 2nd order chromatic dispersion herein is to do compensation by the compensating element, that separates with 1st order chromatic dispersion.Signal of communication 242 enters this system by Polarization Controller 240, and wherein the polarization state of incoming signal 242 was corrected.
Then, final controller output signal 244 is gone out by first circulator 250.Circulator 250 has the input port of being coupled to reception controller output signal 244, couple light to controller output signal is transferred to and comprise, (in this example), the going in ring again mouthful of the single order PMD of differential delay line 260 and fixing coloured dispersive compensation element (and return path is provided for this reflected signal), and be coupled to the delivery outlet that reflected signal 246 is transferred to another circulator 252.
Differential delay line 260 comprises beam splitter/combiner 262, the first fixed delay element 270, and the second adjustable delay element 280.Polarization beam splitter 262 is separated into two vertical polarized components to controller output signal.A polarized component is transferred to first fixed delay element downwards, and it exemplarily comprises first waveguide 272 of aiming at first linear tuning pulse Bragg grating 274.The second polarization component is transferred to second delay element 280 downwards, and it exemplarily comprises second waveguide 282 with second linear tuning pulse Bragg grating 284.Can select more complicated tuning pulse pattern to finish is the compensation of higher-order (three rank, quadravalence etc.) more specifically.Waveguide can be birefringent, thereby is suppressed at the coupling of two polarization modes between each.Differential delay element comprises first waveguide and second waveguide.This waveguide and separator delivery outlet be optical coupling and aim at by the fibre core and the polarization axle that mate them.
Signal is being reflected corresponding to the grating 274 of signal wavelength and the pip place of 284 inside.This o'clock, available tuner 286 tuning gratings 284 in second waveguide 282 changed.
Tuner 286 can be by changing optical grating element effective period regulate optical path length changeably with the reference reflection point that changes signal with respect to one or two reference point of burble point.The device that is used for the tuned light grid cycle can comprise: apply axial mechanics tension force to uphold or the compression grating, apply electric field electricity consumption-light and control grating index, apply heat and control grating index with heat-light, or adopt other known in the art tuner such as method (for example, by upholding or the compression grating) with acoustics and/or mechanics.
Waveguide 272 and 282 is exemplary optical fiber.In specific embodiment, waveguide 272 and 282 can be the light single mode keep polarization (PM) optical fiber, polarising (PZ) optical fiber, and/or make the optical fiber of certain shape is such as generally having, U. S. application the 09/515th in waiting to examine, No. 187 and United States Patent (USP) the 6th, 459, described in No. 838, this two literary composition all is combined in this by reference.
After reflection, when signal is got back to circulator 250, the optical path difference between these two optical grating reflection points will compensate single order PMD this moment, and because these two gratings have the predetermined tuning pulsation rate corresponding to fixing coloured dispersion measure to be compensated, so fixing coloured chromatic dispersion is compensated.Therefore, the amount of the fixing coloured dispersion compensation of average tuning pulsation rate decision of first grating 274 and second grating 284.
In this one exemplary embodiment, first grating and second grating the two all have substantially the same reflection to distribute and substantially the same tuning pulsation rate; And first and second reference reflection point be at identical optical path length place basically.
Perhaps, before regulating by first tuner, first pip of first grating can than second pip on the short or long optical path length of the burble point of beam splitter.With respect to the initial position (that is, the optical path length of this section) of first and second reference reflection point of burble point, can should be as finishing to specific.In the application of the expectation DGD that is no more than the tuner scope, the one the second reference reflection point can be at the optical path length place substantially the same with respect to burble point.Perhaps, a certain reference reflection point can be departed from (can have different optical path lengths) so that single order PMD all or part is made compensation.
The parts that the present invention is different can be integrated into such as lithium niobate (LiNbO
3) one on the chip comprise the integrated optical device of birefringent waveguide.In one embodiment, Polarization Controller and differential delay are integrated into single LiNbO
3Chip on.In another embodiment, can be integrated into single LiNbO to polarization dispersion compensator in wavelength division multiplexing (WDM) system from adjacent channel
3Chip on.Obviously, also can adopt integrated optical device based on other material system.
So signal 246 comes out by second circulator 252, it is to from variable coloured, and the signal after 264 reflections of higher-order pmd compensator provides the path of recurrence.Compensator 264 comprises the 3rd delay element 290, and it comprises the waveguide 292 that contains the 3rd tuned grating 294.In this example, grating 294 is by non-linearly tuning.
Exemplarily, waveguide 272,282 and 292 is the optical fiber of single mode.In an one exemplary embodiment, these optical fiber are the optical fiber of keeping polarization.By using tuner 296 tuning gratings 294 suitably, (such as by applying tension force or temperature gradient) will the two all does dynamic compensation to variable coloured and higher-order polarization mode dispersion.Must consider that average coloured chromatic dispersion of being inducted by non-linear tuning pulse grating 294 is adjusted in the tuning pulsed quantity of linear tuning pulse grating 274 and 284 in the section of back.So the scope of tuning pulse value will determine the relevant range of variable coloured dispersion compensation in non-linear tuning impulse wave guide grating.
Because flexibility in the grating that writes different tuning pulses and bandwidth, shown in three optical grating constructions can make PMD, coloured and variable have the amount of dispersion compensation that a scope is very flexibly arranged, and don't change configuration.
Get back to reference to figure 2, can be coupled to the delivery outlet of circulator to optical axis head coupler so that the sampling of output signal is provided to analyzer 220.The quality of 220 pairs of delay line output signals of analyzer is assessed, and control signal offered compiles shake controller and differential polarization delay unit.Control signal 228 from the signal analyse block 220 that output signal 248 is sampled passes to Polarization Controller 240, is used for the tuner of linear tuning impulse wave guide grating 284 and tuned non-linear frequency-modulated wave guide grating 294.As above-mentioned, preferable detection method can according to circumstances be decided.
The configuration of the dispersive compensation element in Fig. 2 is exemplary.For example, people can variable coloured/higher-order PMD compensator 264 is placed on before the fixing coloured dispersion compensator 260 of single order PMD/.If this tuned non-linear tuning impulse wave guide grating is to have write the Fiber Bragg Grating FBG (FBG) of keeping polarization fiber (PMF), because the single order PMD that added compensation, people also can variable coloured/use the second Polarization Controller (not shown) to reach higher functionality before the higher-order PMD compensator 264.Also have, the circulator of available single four ports replaces the circulator 250 and 252 of two three ports, can save an element.
Another compensator 300 shown in Figure 3, it can finish dynamic higher-order dispersion compensation.In compensator 300, signal at first passes through fixedly dispersion compensator 312, makes and has only single order PMD and higher-order dispersion component (second order PMD and variable coloured chromatic dispersion) keeping.So it is gone out through single order and second order PMD and dynamic coloured dispersion compensator that comprises phase-modulator 380 and the waveguide 392 that comprises non-linear tuning pulse Bragg grating 394.Phase-modulator 380 is added to part signal to tuning pulse [ps/nm] on time selectively.Phase correction module 382 provides control signal 327 for phase-modulator.The purpose of phase correction module 382 is the phase place of the tuning pulse that is provided by this module and cycle and incoming signal suitable phase place and cycle are aimed at, for example the signal of a nrz encoding.So this tuning pulse signal is gone out through circulator 350, and enters the waveguide 392 that comprises non-linear tuning pulse Bragg grating 394.Non-linear tuning pulse Bragg grating 392 is tuning by tuner 396, makes it have normal chromatic dispersion [ps/nm] level.The combination of the chromatic dispersion that is applied to the tuning pulse of part signal and is given by tuned grating 394 will have the effect at compression pulse edge on time, thereby any remaining and/or higher-order dispersion component is compensated.
After Bragg grating 394 returns, signal 348 leaves circulator 350 for belt again mouthful by an output, and is taken a sample by signal analyse block 320.Signal analyse block 320 supplies to tuner 396 to suitable control signal to adapt to the tuning non-linear tuning pulse grating 394 in ground.Because the combination of the element (non-linear tuning pulse FBG) of phase-modulator and chromatic dispersion is made compensation to all types of chromatic dispersions, so be the subharmonic filter to the exemplary candidate of signal analysis.Equally, be receiving terminal to the example location of this penalty method, from the electrical representation signal tap to occurring here at attachment.Down, will be a receiver after circulator 350 on this occasion, make that signal 348 will be the signal of telecommunication rather than light signal.
This method can be used in conjunction with other element.For example, can connect together use to single order PMD compensator and compensator 300 to reduce polarization dispersion to be compensated.This should be very favorable connecting together when reducing the necessary compensation range of dynamic higher order dispersion compensator with high PMD.
Another interchangeable embodiment of Fig. 3, the two optimizes the composite behaviour that is added to chromatic dispersion in the tuning pulse of signal and that be subjected to by tuner in grating will to have signal analyse block 320 to control tuned grating 392 and phase correction module 380.
Another one exemplary embodiment will not fixed coloured dispersive compensation element 312 or be adopted one basically to the suitable value more or less of the fixed compensation of fixing coloured dispersive compensation element 312.If like this, can be adjusted to normal level to the relevant range of adjustable chromatic dispersion element 394 so that all dispersion term are compensated.In other words, can be adjusted to adjustable chromatic dispersion element 394 the fixing coloured chromatic dispersion with variable is compensated, and can be transferred to phase-modulator 380 phase place of having added and the combination of dispersion element 394 can be compensated the chromatic dispersion of remainder.This may give whole bucking-out systems with many more flexibility and scope in compensation program.
Another one exemplary embodiment will have the non-linear tuning grating 394 in the high birefringence waveguide that has been written to the optical fiber of for example keeping polarization, and comprise that also Polarization Controller enters the polarization of the signal of non-linear tuning pulse grating 394 with control.This embodiment may be implemented a kind of usefulness in previously described two kinds of methods or need not fix coloured dispersive compensation element 312.The fixing coloured dispersive compensation element 312 that occurs under the occasion of Polarization Control and the combination of non-linear tuning pulse Xi Lage grating can be used to all or part single order polarization mode dispersion are compensated.Fixing coloured dispersion element 312 will compensate the fixing coloured chromatic dispersion that occurs in incoming signal.So the combination of the instantaneous value of phase-modulator and chromatic dispersion can compensate by optimised next chromatic dispersion component to remainder.Under fixing coloured dispersive compensation element 312 absent variable occasions, also will comprise fixing coloured dispersion term to remaining item to be compensated by phase modulated and dispersion element combination.
Fig. 4 illustrates another embodiment of the bucking-out system 400 according to the present invention.System 400 is convenient to make the higher-order dispersion compensation notion integrated with less level.Input signal 442 enters system 400 by Polarization Controller 440, and this controller converts the signal state of polarization of incident to the signal 444 with required polarization state.After signal 444 was gone out by the mouth that goes in ring again of circulator 450, it was optically coupled to the beam splitter/combiner 462 of Delay Element 460.This Delay Element also comprises first delay element 470 and second delay element 480.Signal 444 is separated into its vertical component, and each component is transferred to the delivery outlet of splitter/combiner 462.These two signals crossed first delay element 470 and second delay element 480 simultaneously, first delay element comprises that first waveguide 472 that comprises the first non-linear tuning pulse grating 474 then comprises second waveguide 482 that comprises the second non-linear tuning pulse grating 484 with second waveguide, 482, the second delay cells 480 that comprise the second non-linear tuning pulse grating 484.
First grating 474 and second grating 484 have the tuner 490 of controlling these two gratings simultaneously.Second grating 484 has the additional tuner 492 of independent tuning grating 484.Fixing coloured dispersion compensation is to finish by the correct mean value of tuning pulse being write non-linear tuning impulse wave guide grating 474 and 484.Variable coloured dispersion compensation and higher-order PMD compensation is by as one man tuning 474 and 484, and for example, the temperature of both same amounts that changes them only obtains.Single order PMD compensation is by the tuning second non-linear tuning pulse grating 484 dividually, for example by making it be in that stress obtains.Can adopt tuning type to be not limited to temperature or stressed tuning, and each all can be used for a harmonic tuning or separately tuning.
After optical grating reflection, the signal 446 that has compensated is reconfigured by polarization separator combiner 462, and continues to turn back to the delivery outlet of this circulator by circulator 450 at once.It comprises light tap coupler 452 one exemplary embodiment of the present invention, and in the signal analyse block 420 of circulator 450 back.According to selected detection method with whether adopt the feedforward or the algorithm of rear feed, tap coupler 452 can be placed on the different place of system.Signal analyse block 420 is provided to tuner 490 and 492 to control signal 428, and to Polarization Controller 440.
A small amount of residue that above-mentioned method and system may cause inducting between two polarized components of signal is fixed coloured chromatic dispersion.For a spot of single order PMD, this is receptible mostly, as based on shown in below the calculating in the example system of Fiber Bragg Grating FBG.
| Fixing coloured dispersion measure: | 700ps/nm |
| Variable coloured dispersion measure: | -500ps/nm arrives+500ps/nm |
| The actual tuning pulsating sphere of grating: | 200ps/nm is to 1200ps/nm (or 50pm/mm is to the tuning pulse of 8.33pm/mm cycle) |
| Grating length (example): | 1 meter |
| The tuning impulse speed of unit length changes: | The every cm of 10ps/nm |
| DGD scope (example): | 100ps (or the 1cm pip changes) |
| The tuning impulse speed of grating changes every DGD maximum magnitude | 10ps/nm |
In an example system, if (PMD (DGD) is that maximum expected value is 100ps to the incident single order, and then the grating of above-mentioned design can preferentially add the coloured chromatic dispersion of residue of 10ps/nm between two vertical polarization components of signal.Because Mike's Si prestige that PMD has in time distributes, if make that maximum expected value is 100ps, the actual amount branch that most of time is seen is less, so this amount should be low more usually.And, increase grating length or change design, otherwise can further reduce this quantity.Above structure will cause being used for making a kind of very flexible, the low-loss method of compensation to any kind chromatic dispersion or in tight any combination of the factor chromatic dispersion type of mode.
In the one exemplary embodiment of Fig. 4, waveguide 472 and 482 is to be made by the optical fiber of keeping polarization.In an interchangeable embodiment, can be integrated in this waveguide on the integrated optics chip such as lithium niobate chip.In addition, being attached in the integrated optics chip, may be good such as more bucking-out system parts such as more bucking-out system device/combiner 462 such as polarization splitter/combiner 462 and Polarization Controller 440 and Polarization Controllers 440.Can be placed on Polarization Controller 440 on the position between circulator 450 and the polarization splitter/combiner 462 the interchangeable configuration of Fig. 4.This will make things convenient for certain or all these parts to integrate on the optical chip together.For example, an one exemplary embodiment can be Polarization Controller 440, and polarization splitter/combiner 462 and waveguide 472 and 482 are integrated in a substrate.
Technical staff in the art will understand the present invention and can be used in all optical application that need the higher-order compensation.Although the present invention has used the reference of preferable all embodiment is described, the present invention can realize with other concrete form in the case without departing from the scope of the present invention.Therefore, it only is exemplary will be appreciated that here all embodiment that describe and illustrate of institute, can not be thinking limitation of the scope of the invention.Can make other variation and modification according to the scope of the invention.
Claims (7)
1. one kind the communicate optical signal higher-order dispersion of incident made the method for compensation, it is characterized in that this method comprises following step:
A) polarization state of the communicate optical signal of adjusting incident makes the basic attitude of polarization of the basic attitude alignment compensation of the polarization device system of signal of communication exactly;
B), signal of communication is separated into the first and second vertical basic attitudes of polarization at burble point;
C) first attitude of polarization state is propagated into first waveguide with first non-linear tuning pulse grating, this first grating has first reference reflection point;
D) second attitude of polarization state is propagated into second waveguide with second non-linear tuning pulse grating, this second grating has and first this similar tuning figure of tuning pulsed light grid base, and has second reference reflection point;
E) the correct mean value with tuning pulse writes the first and second non-linear tuning pulse gratings to compensate fixing coloured chromatic dispersion;
F) come adjustable ground to compensate the variable coloured chromatic dispersion and the high-order polarization mode dispersion of first and second pips by as one man changing along the position of first and second pips of grating;
G) adjustable ground changes the relative optical path length between second pip and burble point, thereby the single order polarization dispersion between the first and second polarization orthogonal attitudes is compensated; And
H) reconfigure first and second polarization states and become output signal.
2. the method for claim 1, it is characterized in that, the step that this method also comprises is: change at adjustable ground before the step of the relative optical path length between first pip and the burble point, the optical path length of a grating in the tuning grating at least makes second pip from burble point identical optical path length be arranged as first pip basically.
3. the method for claim 1, it is characterized in that, the step that this method also comprises is, changed before step at adjustable ground with respect to the optical path length of second pip of burble point, the optical path length of a grating in the tuning grating at least, make second pip shorter than first pip from the optical path length of burble point, wherein the difference in optical path length will postpone to come selected according to the expectation polarization dispersion between the first and second vertical polarization states.
4. method that is used for the communicate optical signal higher-order dispersion is done compensation is characterized in that this method comprises following step:
A) signal of communication is separated into the first and second vertical basic polarization states;
B) first polarization state is propagated into the first high birefringence fiber waveguide with first linear tuning pulse grating, first fiber waveguide has first pip at the first optical path length place;
C) second polarization state is propagated into the second adjustable high birefringence fiber waveguide with second linear tuning pulse grating, second fiber waveguide has second pip at the second optical path length place;
D) reconfigure first and second polarization states and become output signal;
E) output signal is propagated into the 3rd high birefringence fiber waveguide with the non-linear tuning pulse grating that has pip;
F) change second optical path length of the second linear tuning pulse grating, so that the single order polarization dispersion between the first and second vertical polarization states is compensated adjustablely; And
G) adjustable ground changes the light path in the 3rd grating, so that variable coloured chromatic dispersion in output signal and higher-order polarization dispersion are compensated.
5. method as claimed in claim 4, it is characterized in that, the described second tuning pulse grating has basically the similar tuning figure with the first tuning pulse, second grating have basically as first pip at second pip from the same optical path length of burble point.
6. method as claimed in claim 4 is characterized in that, this method also comprises following step:
A) to output signal sampling;
B) quality of response output signal is regulated second pip with respect to burble point with adapting in second grating.
7. method as claimed in claim 4 is characterized in that, this method also comprises following step:
A) to output signal sampling,
The quality of response output signal is carried out following steps:
B) adapt to the polarization state that incoming signal is regulated on ground;
C) adapt to second pip of ground adjusting with respect to second grating of burble point, and
D) adapt to the 3rd pip that the 3rd grating is regulated on ground.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US34496501P | 2001-12-31 | 2001-12-31 | |
| US60/344,965 | 2001-12-31 | ||
| US10/323,280 US7062123B2 (en) | 2001-12-31 | 2002-12-18 | System for higher-order dispersion compensation |
| US10/323,301 US6829409B2 (en) | 2001-12-31 | 2002-12-18 | Method for higher-order dispersion compensation |
| US10/323,280 | 2002-12-18 | ||
| US10/323,301 | 2002-12-18 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1611022A CN1611022A (en) | 2005-04-27 |
| CN100592666C true CN100592666C (en) | 2010-02-24 |
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| Application Number | Title | Priority Date | Filing Date |
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| CNA028264290A Pending CN1611023A (en) | 2001-12-31 | 2002-12-19 | System for higher-order dispersion compensation |
| CN02826396A Expired - Fee Related CN100592666C (en) | 2001-12-31 | 2002-12-19 | Method for higher-order dispersion compensation |
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| CNA028264290A Pending CN1611023A (en) | 2001-12-31 | 2002-12-19 | System for higher-order dispersion compensation |
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| KR (1) | KR20040068607A (en) |
| CN (2) | CN1611023A (en) |
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| DE102006045133A1 (en) * | 2006-09-25 | 2008-04-10 | Nokia Siemens Networks Gmbh & Co.Kg | Arrangement for setting and compensating polarization mode dispersion of first and second order |
| CN102047150B (en) * | 2008-05-30 | 2013-11-06 | 皇家飞利浦电子股份有限公司 | A higher order dispersion compensation device |
| CN101630978A (en) * | 2008-07-14 | 2010-01-20 | 北京大学 | Method, device and system for realizing polarization mode dispersion compensation |
| ES2396784B2 (en) * | 2011-03-15 | 2014-07-23 | Medlumics, S.L. | INTEGRABLE ACTIVE EQUALIZATION SYSTEM OF CHROMATIC DISPERSION. |
| CN103312414B (en) * | 2012-03-16 | 2016-03-30 | 富士通株式会社 | A kind of inverse channel device and comprise the transmitter of this device, receiver and system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| DE19717457A1 (en) * | 1997-04-25 | 1998-10-29 | Ernst Dr Brinkmeyer | Variable optical delay line |
| US6647180B2 (en) * | 2000-09-21 | 2003-11-11 | Teraxion Inc. | Tunable optical dispersion by using two fiber Bragg gratings with nonlinear group delays |
| US6271952B1 (en) * | 1998-08-18 | 2001-08-07 | Nortel Networks Limited | Polarization mode dispersion compensation |
| GB9818941D0 (en) * | 1998-08-28 | 1998-10-21 | Northern Telecom Ltd | Polarisation mode dispersion compensation |
| US6275629B1 (en) * | 1998-09-11 | 2001-08-14 | Lucent Technologies Inc. | Optical grating devices with adjustable chirp |
| DE19903523A1 (en) * | 1999-01-29 | 2000-08-03 | Ernst Brinkmeyer | Delay system for an optical transmission system includes Bragg grating with variable positioning |
| US6658215B1 (en) * | 1999-09-24 | 2003-12-02 | Fitel Usa Corp. | Arrangement for mitigating first order and second-order polarization mode dispersion in optical fiber communication systems |
| US20010028760A1 (en) * | 2000-03-03 | 2001-10-11 | Yaffe Henry H. | Methods and apparatus for compensating chromatic and polarization mode dispersion |
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2002
- 2002-12-19 WO PCT/US2002/041025 patent/WO2003058858A2/en not_active Application Discontinuation
- 2002-12-19 WO PCT/US2002/040958 patent/WO2003058311A2/en not_active Application Discontinuation
- 2002-12-19 CN CNA028264290A patent/CN1611023A/en active Pending
- 2002-12-19 CN CN02826396A patent/CN100592666C/en not_active Expired - Fee Related
- 2002-12-19 EP EP02792496A patent/EP1461879A2/en not_active Withdrawn
- 2002-12-19 AU AU2002358258A patent/AU2002358258A1/en not_active Abandoned
- 2002-12-19 EP EP02806197A patent/EP1461881A2/en not_active Withdrawn
- 2002-12-19 KR KR10-2004-7010320A patent/KR20040068607A/en not_active Application Discontinuation
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|---|---|
| WO2003058311A2 (en) | 2003-07-17 |
| CN1611022A (en) | 2005-04-27 |
| CN1611023A (en) | 2005-04-27 |
| AU2002367358A1 (en) | 2003-07-24 |
| WO2003058311A3 (en) | 2003-10-16 |
| EP1461881A2 (en) | 2004-09-29 |
| WO2003058858A2 (en) | 2003-07-17 |
| WO2003058858A3 (en) | 2003-11-27 |
| EP1461879A2 (en) | 2004-09-29 |
| KR20040068607A (en) | 2004-07-31 |
| AU2002358258A1 (en) | 2003-07-24 |
| AU2002367358A8 (en) | 2003-07-24 |
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