CN103179060A - Balancer coefficient updating device and method - Google Patents

Balancer coefficient updating device and method Download PDF

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CN103179060A
CN103179060A CN2011104418408A CN201110441840A CN103179060A CN 103179060 A CN103179060 A CN 103179060A CN 2011104418408 A CN2011104418408 A CN 2011104418408A CN 201110441840 A CN201110441840 A CN 201110441840A CN 103179060 A CN103179060 A CN 103179060A
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equalizer
making
eliminated
coefficient
updating device
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CN103179060B (en
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燕萌
陶振宁
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Fujitsu Ltd
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Abstract

An embodiment of the invention provides a balancer coefficient updating device and method. The balancer coefficient updating device comprises a first calculating unit and a second calculating unit. The fist calculating unit calculates Phase Shift Keying (PSK) signals of a balancer after phase noise removing according to outputs of the balancer. The second calculating unit calculates coefficient residual quantity of the balancer according to the PSK signals with removed phase noise and judgment signals of the PSK signals with removed phase noise so that the balancer can update the balancer coefficient according to the coefficient residual quantity conveniently. By adopting the balancer coefficient updating device and method, coupling between phase retrieval and balancing is removed, and the shortcomings that a receiver is complex in structure and parallelization is inconvenient to achieve on hardware which are caused by the fact that phase retrieval results are needed to be fed back into the balancer in the traditional Decision-Directed Least Mean Square (DDLMS) method are overcome.

Description

The coefficient updating device of equalizer and method
Technical field
The present invention relates to the digital coherent optical communication technique, relate in particular to a kind of coefficient updating device and method of equalizer.
Background technology
The digital coherent optical communication technique is the developing direction of following high speed, the large Capacity Optical communication technology.In coherent optical communication system, can use various modulation formats, as amplitude keying (ASK, Amplitude Shift Keying), phase shift keying (PSK, Phase Shift Keying), quadrature amplitude modulation (QAM, Quadrature Amplitude Modulation) etc.Wherein, mPSK is the position modulation of a kind of pure phase, the information that it indicates to transmit with the phase place of signal (m 〉=2).The symbol s of mPSK nCan be expressed as: s n=e J2k π/m, k=0,1 ... m-1.Common BPSK (Binary Phase Shift Keying, two-phase PSK), QPSK (Quaternary Phase Shift Keying, quarternary phase-shift keying (QPSK)) are the special cases of mPSK signal.
In coherent optical communication system, receiving terminal uses coherent optical heterodyne communicatio and Digital Signal Processing (DSP, Digital Signal Processing) technology to resist the various damages of optical channel.Because crosstalk (inter-symbol interference between optical channel meeting created symbol, ISI), in coherent optical heterodyne communicatio, usually adopt and eliminate ISI (document 1) based on the adaptive equalization technique of finite impulse response (FIR, Finite Impulse Response) filter.For the overhead that improves the availability of frequency spectrum and avoid training sequence to bring, wish to use blind or equalization methods decision-aided.Blind equalization algorithm CMA (Constant Modulus Algorithm, constant modulus algorithm) commonly used is only applicable to the mPSK signal of m＞2, to bpsk signal inapplicable (document 2); And decision-aided least mean-square error method (Decision-Directed Least-Mean-Square, DDLMS) be applicable to all mPSK signals, and have the advantage fast to the channel variation tracking velocity, therefore, the DDLMS method has obtained using widely in existing coherent optical communication system.
Yet the inventor finds in realizing process of the present invention, in coherent optical communication system, because the phase bit recovery carries out after equilibrium, and when using traditional DDLMS, need to be the result feedback of phase bit recovery in equalizer (document 3).This not only allows receiver structure become complicated, is unfavorable for that also this algorithm realizes parallelization on hardware.
The below has listed for understanding the useful document of the present invention and routine techniques, by reference they is incorporated herein, as having illustrated fully in this article.
Document 1:Ezra Ip and Joseph M.Kahn, Digital equalization of chromatic dispersion and polarization mode dispersion.Journal of Lightwave Technology, vol.25, no.8,2007.
Document 2:C.B.Papadias, On the existence of undesirable global minimum of Godard equalizers.Acoustics, Speech and Signal Processing, vol.5,1997.
Document 3:S.J.Savory et al, Transmission of 42.8Gb/s polarization multiplexed NRZ-QPSK over 6400km of standard fiber with no optical dispersion compensation.OTuA1, OFC 2007.
Document 4:Simon Haykin, Adaptive Filter Theory.3rd edition, Prentice Hall, 1998.
Document 5:Lei Li et al, Apparatus and method for estimation of frequency offset in optical coherent receiver, patent 200710166788.3.
Introduction to technical background above should be noted that is just carried out clear, complete explanation for convenient to technical scheme of the present invention, and facilitates those skilled in the art's understanding to set forth.Can not only partly carry out setting forth and thinking that technique scheme is conventionally known to one of skill in the art in background technology of the present invention because of these schemes.
Summary of the invention
The purpose of the embodiment of the present invention is to provide a kind of coefficient updating device and method of equalizer, to carry out the adaptive equalization of psk signal, overcomes the above-mentioned shortcoming of traditional DDLMS.
According to an aspect of the embodiment of the present invention, a kind of coefficient updating device of equalizer is provided, wherein, described updating device comprises:
The first computing unit, its output according to equalizer calculate this equalizer and have eliminated phase shift keying (PSK) signal afterwards of making an uproar mutually;
The second computing unit, it has eliminated the coefficient residual quantity of the described equalizer of decision signal calculating of the psk signal after making an uproar mutually according to the described psk signal of having eliminated after making an uproar mutually with this, so that equalizer upgrades equalizer coefficients according to described coefficient residual quantity.
Another aspect according to the embodiment of the present invention also provides a kind of receiver, and described receiver comprises: equalizer, frequency difference estimation unit, phase estimation unit and decision device, and wherein, described receiver also comprises:
The equalizer coefficients updating device, it is used for calculating the coefficient residual quantity of described equalizer, so that described equalizer upgrades its coefficient according to described coefficient residual quantity;
Wherein, described equalizer coefficients updating device is realized by aforesaid equalizer coefficients updating device.
According to another aspect of the embodiment of the present invention, a kind of single polarized systems also is provided, wherein, described system comprises aforesaid receiver.
Another aspect according to the embodiment of the present invention, a kind of polarization diversity receiver also is provided, described polarization diversity receiver comprises: the first equalizer, the first estimation of deviation unit, the first phase place estimation unit, the first decision device that be used for to recover the h circuit-switched data, with the second equalizer that be used for to recover the v circuit-switched data, the second estimation of deviation unit, the second phase place estimation unit, the second decision device, wherein, described polarization diversity receiver also comprises:
The first equalizer coefficients updating device, it is used for calculating the coefficient residual quantity of described the first equalizer, so that described the first equalizer upgrades its coefficient according to the coefficient residual quantity of described the first equalizer;
The second equalizer coefficients updating device, it is used for calculating the coefficient residual quantity of described the second equalizer, so that described the second equalizer upgrades its coefficient according to the coefficient residual quantity of described the second equalizer;
Wherein, described the first equalizer coefficients updating device and described the second equalizer coefficients updating device are realized by aforesaid equalizer coefficients updating device.
Another aspect according to the embodiment of the present invention also provides a kind of polarisation multiplex system, and wherein, described system comprises aforesaid polarization diversity receiver.
According to another aspect of the embodiment of the present invention, a kind of adaptive equilibrium method of psk signal also is provided, wherein, described method comprises:
Calculate described equalizer according to the output of equalizer and eliminated the psk signal afterwards of making an uproar mutually;
According to the described psk signal and the described coefficient residual quantity of having eliminated the described equalizer of decision signal calculating of the psk signal after making an uproar mutually of having eliminated after making an uproar mutually;
Upgrade the coefficient of described equalizer according to described coefficient residual quantity.
The beneficial effect of the embodiment of the present invention is, method and apparatus by the embodiment of the present invention, removed the coupling between phase bit recovery and equilibrium, need to be the result feedback of phase bit recovery in equalizer thereby overcome traditional decision-aided least mean-square error method (DDLMS), cause receiver structure complicated, and realize the shortcoming of parallelization inconvenience on hardware.
Explanation and accompanying drawing with reference to hereinafter disclose specific implementations of the present invention in detail, and having indicated principle of the present invention can adopted mode.Should be appreciated that, embodiments of the present invention on scope not thereby be restricted.In the scope of the spirit of claims and clause, embodiments of the present invention comprise many changes, revise and are equal to.
Can use in one or more other execution mode in same or similar mode for the feature that a kind of execution mode is described and/or illustrated, combined with the feature in other execution mode, or the feature in alternative other execution mode.
Should emphasize, term " comprises/comprises " existence that refers to feature, whole, step or assembly when this paper uses, but does not get rid of the existence of one or more further feature, whole, step or assembly or additional.
Description of drawings
Included accompanying drawing is used to provide further understanding of the invention, it has consisted of the part of specification, illustration the preferred embodiment of the present invention, and be used for explaining principle of the present invention together with explanatory note, wherein for identical key element, represent with identical Reference numeral all the time.
In the accompanying drawings:
Fig. 1 is the schematic diagram of the DDLMS method used in traditional coherent optical heterodyne communicatio;
Fig. 2 is the composition schematic diagram of the coefficient updating device of the embodiment of the present invention;
Fig. 3 is the judgement schematic diagram of the common mPSK signal as an example of m=4 example;
Fig. 4 is the composition schematic diagram of receiver that comprises the coefficient updating device of Fig. 2;
Fig. 5 is the composition schematic diagram of single polarization coherent optical communication system that comprises the receiver of Fig. 4;
Fig. 6 is the composition schematic diagram of polarization diversity receiver that comprises the coefficient updating device of Fig. 2;
Fig. 7 is the composition schematic diagram of palarization multiplexing coherent optical communication system that comprises the polarization diversity receiver of Fig. 6;
Fig. 8 is the adaptive equilibrium method flow chart of the embodiment of the present invention.
Embodiment
With reference to accompanying drawing, by following specification, the aforementioned and further feature of the embodiment of the present invention will become obvious.These execution modes are exemplary, are not limitations of the present invention.In order to enable those skilled in the art to easily to understand principle of the present invention and execution mode, the embodiment of the present invention has m tap FIR structure take the adaptive equalizer of receiver end and describes as example, but be appreciated that the embodiment of the present invention is not limited to said structure.
Different for outstanding adaptive equilibrium method of the present invention and traditional DDLMS method below are first carried out brief description to the DDLMS method of using in traditional coherent optical heterodyne communicatio.
Fig. 1 is the schematic diagram of the DDLMS method used in traditional coherent optical heterodyne communicatio, as shown in Figure 1, in this coherent optical heterodyne communicatio, comprises equalizer 101, frequency difference estimation unit 102, phase estimation unit 103, decision device 104, computing unit 105 etc.Please refer to Fig. 1, in this traditional coherent optical heterodyne communicatio, with x nExpression nT sSignal (the T that constantly receives sBe symbol period, n=0,1,2 ...), w nExpression nT sThe FIR tap coefficient (hereinafter to be referred as the coefficient of equalizer) of moment equalizer, x nAnd w nIt is all the m dimensional vector.nT sEqualizer is output as y constantly n=w n Tx n( TThe expression transposition).Traditional decision-aided least mean-square error (DDLMS) method is utilized the output y of equalizer nDecision value structure training sequence t n, and with y nWith training sequence t nBetween mean square error be the coefficient update that cost function carries out equalizer, that is:
c＝E{|y n-t n| 2}
Wherein, optimization aim is to make the c in following formula minimum, for example, can come update coefficients w with known gradient descent method n(document 4).Cost function c is to w nGradient be:
Δ w n = ∂ c ∂ w n = ( y n - t n ) x n *
Wherein, () *The expression conjugation, Δ w nCoefficient residual quantity for this equalizer.
Corresponding coefficient update formula is:
w n+1＝w n-μ·Δw n
Wherein, μ is the coefficient update step-length, and can be one greater than 0 real number.
In the coherent optical communication system of reality, between emitting laser and local oscillator laser, certain frequency difference is arranged usually, certain live width is also arranged separately.Signal also will just can be adjudicated through frequency difference compensation and phase compensation through after equalizer.For to equalizer structure training sequence, need to provide the output signal of the equalizer of expectation.Even equalizer has been eliminated ISI fully, its output y nBe still with frequency difference and the signal of making an uproar mutually.So structure training sequence t nNot only need court verdict
Figure BDA0000124905640000052
The result (document 3) that also needs frequency difference estimation and phase estimation.As shown in Figure 1, court verdict
Figure BDA0000124905640000053
Output multiplication with frequency difference estimation module 102 and phase estimation module 103 obtains training sequence t:
Wherein, θ is the phase deviation that the frequency difference between transmitting terminal and receiving terminal laser causes,
Figure BDA0000124905640000055
The phase deviation that the phase noise of transmitting terminal and receiving terminal laser causes.
Please refer to Fig. 1, computing unit 105 is according to the output y of training sequence t and equalizer and the coefficient residual quantity Δ w of above-mentioned formula computation balance device again.
Undertaken by traditional coherent optical heterodyne communicatio shown in Figure 1 equalizer coefficient update signal as can be known, due to need to be the result feedback of phase bit recovery and frequency difference estimation in equalizer, not only allow the structure of receiver become complicated, be unfavorable for that also the method realizes parallelization on hardware.
The below describes the coefficient updating device of the equalizer of the embodiment of the present invention and the adaptive equilibrium method of psk signal.
Embodiment 1
The embodiment of the present invention provides a kind of coefficient updating device of equalizer.Fig. 2 is the composition schematic diagram of this updating device, please refer to Fig. 2, and this updating device comprises the first computing unit 201 and the second computing unit 202, wherein:
The first computing unit 201 calculates this equalizer according to the output of equalizer and has eliminated phase shift keying (PSK) signal afterwards of making an uproar mutually.
As shown in Figure 2, this first computing unit 201 calculates r according to the output y of equalizer, wherein, and can be according to this equalizer at nT sOutput valve constantly and at (n-a) T sOutput valve is constantly calculated r, and r is the psk signal of having eliminated after making an uproar mutually.
According to an execution mode of the present embodiment, the psk signal after this has been eliminated and has made an uproar mutually is that this equalizer is at nT sConstantly and (n-a) T sThe conjugation product of output valve constantly, also, with r nRepresent that this has eliminated the psk signal after making an uproar mutually, y nRepresent that this equalizer is at nT sOutput constantly, y n-aRepresent that this equalizer is at (n-a) T sOutput constantly, r n=y ny n-a *( *The expression conjugation).Wherein, a is the natural number more than or equal to 1, when a=1, and r n=y ny n-1 *, the conjugation of its expression adjacent two symbols is long-pending; When a＞1, r n=y ny n-a *, the be separated by conjugation of two not far symbols of its expression is long-pending.
Wherein, if transmission is the mPSK signal, be also that x is the mPSK signal, when equalizer had been eliminated ISI, the output of equalizer was with frequency difference and the mPSK signal of making an uproar mutually.Because the symbol rate of optical communication system is generally in the GHz magnitude, and laser linewidth is generally less than 1MHz, so on two adjacent-symbols or on two not far symbols of being separated by, the phase value that causes by making an uproar mutually can be thought and is approximately equal also
Figure BDA0000124905640000061
A＞=1.Wherein, when a=1, represent two phase value approximately equals that adjacent-symbol causes by making an uproar mutually; When a＞1, represent the phase value approximately equal that causes by making an uproar mutually on two not far symbols of being separated by.Therefore, according to r n=y ny n-a *Calculate r nThe time, this public phase term has been cancelled, i.e. r n≈ e J (2k π/m+ Δ θ), k=0,1 ... m-1.Can see r nWith make an uproar mutually irrelevant, also i.e. this r nIt is the psk signal of having eliminated after making an uproar mutually.
Need to prove r nRelevant with frequency difference, it be one with the mPSK signal of phase deviation Δ θ.Δ θ=θ wherein n-θ n-a=2 π a Δ fT sThat the frequency difference Δ f of emission and local oscillator laser is n and n-a the phase deviation that intersymbol causes.
According to the another one execution mode of the present embodiment, the psk signal after this has been eliminated and has made an uproar mutually is that this equalizer is at nT s(n-a) T sThe business of output valve constantly.Same, with r nRepresent that this has eliminated the psk signal after making an uproar mutually, y nRepresent that this equalizer is at nT sOutput constantly, y n-aRepresent that this equalizer is at (n-a) T sOutput constantly, r n=y n/ y n-aWherein, a is the natural number more than or equal to 1, when a=1, and r n=y n/ y n-1, the business of its expression adjacent two symbols; When a＞1, r n=y n/ y n-a, the be separated by business of two not far symbols of its expression.
Wherein, with r n=y ny n-a *Situation similar, due on two adjacent-symbols or on two not far symbols of being separated by, the phase value that causes by making an uproar mutually can be thought approximately equal.Therefore passing through r n=y n/ y n-aCalculate r nThe time, this public phase term also has been cancelled, therefore according to r n=y n/ y n-aCalculate the r that obtains nAlso with make an uproar mutually irrelevant, also, this r nIt is the psk signal of having eliminated after making an uproar mutually.Same, according to r n=y n/ y n-aCalculate the r that obtains nJust has eliminated mutually and made an uproar, but it is still relevant with frequency difference, be one with the mPSK signal of phase deviation Δ θ.
Just illustrate for the calculating of having eliminated the psk signal after making an uproar mutually in above two execution modes; but the embodiment of the present invention not with this as restriction; calculate the scheme of having eliminated the psk signal after making an uproar mutually by other alternative modes, all be contained in the protection range of the embodiment of the present invention.
The second computing unit 202, it has eliminated the coefficient residual quantity of the described equalizer of decision signal calculating of the psk signal after making an uproar mutually according to the described psk signal of having eliminated after making an uproar mutually with this, so that equalizer upgrades equalizer coefficients according to described coefficient residual quantity.
Wherein, updating device of the present invention also comprises decision unit 203, and this decision unit 203 is used for the described psk signal (r) of having eliminated after making an uproar mutually being carried out the judgement of psk signal, the decision signal of the psk signal after making an uproar mutually to be eliminated Also namely this has eliminated the decision value of the psk signal after making an uproar mutually.Thus, r and its decision value that can send into according to the first computing unit 201 of this second computing unit 202
Figure BDA0000124905640000072
The coefficient residual quantity Δ w of computation balance device.
Wherein, this decision unit 203 can also further be adjudicated the described psk signal of having eliminated after making an uproar mutually according to the frequency difference reference value Δ θ that receives.The frequency difference reference value here can be prior information, can be also the value that obtains by frequency difference estimation.
Wherein, concrete decision method can adopt existing means to realize.In one embodiment, decision unit 203 receives frequency difference reference value (as shown in phantom in Figure 2), with r nJudgement is an element in set D.This frequency difference reference value can be prior information or provide (document 5) by certain frequency difference estimation method.If there is no the frequency difference reference value, acquiescence Δ θ is 0.D is the set that all possible decision value consists of:
D＝{d k：d k＝e j(2kπ/m+Δθ)，k＝0，1，Km-1}
The decision method of decision unit 203 uses of the present embodiment can be described as:
a n＝mod(arg(r ne -jΔθ)，2π)
r ^ n = d k if ( 2 k - 1 ) &pi; m &le; a n < ( 2 k + 1 ) &pi; m
Wherein, d kK the element of expression D.Arg () is for getting the argument computing, and mod (, 2 π) expression is to 2 π deliverys, its codomain be [0,2 π).
Compare with traditional mPSK decision method, the said method of the present embodiment is just many takes advantage of e in the following formula -j Δ θStep, this signal that is equivalent to receive rotates an angle delta θ on complex plane, then adjudicate as conventional mPSK signal.(QPSK signal), be shown in dotted line the decision boundaries to the QPSK signal in Fig. 3 as an example of m=4 example.
If there is no the frequency difference reference value, acquiescence Δ θ=0, exp (j Δ θ)=1, at this moment it is exactly common mPSK decision device.
When frequency difference than I when ignoring, Δ θ ≈ 0, exp (j Δ θ) ≈ 1, at this moment it also is equivalent to common mPSK decision device.
Above-mentioned decision method just illustrates, the present embodiment not with this as restriction.
In one embodiment, the second computing unit 202 can utilize the coefficient residual quantity of following cost function calculation equalizer:
c = E { | r n - r ^ n | 2 }
Wherein, E () expression expectation.
For example, by minimizing above-mentioned cost function, also namely minimize r nWith its decision value Between mean square error, and calculate the coefficient residual quantity of this equalizer with known gradient descent method.
With r n=y ny n-1 *Be example, c is to w nGradient be:
&Delta; w n = &PartialD; c &PartialD; w n = ( r n - r ^ n ) y n - 1 x n * + ( r n - r ^ n ) * y n x n - 1 *
With r n=y n/ y n-1Be example, c is to w nGradient be:
&Delta; w n = &PartialD; c &PartialD; w n = ( r n - r ^ n ) ( x n * / y n - 1 * - x n - 1 * y n * / ( y n - 1 * ) 2 )
Thus, equalizer can upgrade the coefficient of equalizer according to following formula:
w n+1＝w n-μ·Δw n
Wherein, the meaning of each parameter as previously mentioned, in this description will be omitted.
In the present embodiment, the method for carrying out adaptive equalization by the structure of this coefficient updating device is applicable to all mPSK (m＞=2) signal, as BPSK, QPSK, 8PSK etc.
Coefficient updating device by the embodiment of the present invention carries out adaptive equalization, has removed the coupling between phase bit recovery and equilibrium, has overcome to adopt traditional DDLMS method to carry out the shortcoming of adaptive equalization.
Utilize the coefficient updating device of embodiment 1, the invention allows for following examples.
Embodiment 2
The embodiment of the present invention provides the receiver of the coefficient updating device of a kind of embodiment of use 1.Fig. 4 is the composition schematic diagram of this receiver, please refer to Fig. 4, and this receiver comprises:
Equalizer 401, it carries out adaptive equalization to input signal, the signal of output after equilibrium;
Frequency difference estimation unit 402, its signal to equalizer 401 outputs carries out frequency difference estimation, the result of output frequency difference estimation;
Phase estimation unit 403, its result to frequency difference estimation is carried out phase estimation, the result that output phase is estimated;
Decision device 404, its result to phase estimation is adjudicated, the output decision value.
Wherein, equalizer 401, frequency difference estimation unit 402, phase estimation unit 403 and decision device 404 can adopt the composition of existing receiver to realize, its identical function is incorporated in this, does not repeat them here.
In the present embodiment, this receiver also comprises:
Coefficient updating device 405, it is used for calculating the coefficient residual quantity of described equalizer 401, so that described equalizer 401 upgrades its coefficient according to described coefficient residual quantity.
Wherein, this coefficient updating device 405 can realize by the coefficient updating device of embodiment 1, and its concrete constitute and function describes in detail in embodiment 1, in this omission.
Wherein, after equalizer 401 converged to stable state, frequency difference estimation unit 402 can be for decision unit 203 provides the frequency difference reference value, as shown in the dotted line in Fig. 4.Wherein, the receiver of the embodiment of the present invention utilizes above structure to carry out adaptive equalization, goes for all mPSK signals (m 〉=2), as BPSK, QPSK, 8PSK etc.
Compare with traditional DDLMS, this adaptive equilibrium method that the receiver of the embodiment of the present invention adopts needn't generate training sequence according to the result of phase estimation, thereby has eliminated the inaccurate impact on equalizer of phase estimation.Because balanced and phase estimation can be carried out independently of one another, receiver structure is simplified, and also easilier realizes on DSP (Digital Signal Processing, Digital Signal Processing) hardware.
Embodiment 3
The embodiment of the present invention also provides a kind of coherent optical communication system of single polarization.Fig. 5 is the composition schematic diagram of this system, please refer to Fig. 5, and this system comprises:
Laser 501, modulator 502, optical channel 503, optical mixer unit 504, photodetector 505, analog to digital converter 506, digital receiver 507 and local oscillator laser 508.
In the present embodiment, at transmitting terminal, the laser that sends from laser is through becoming the light signal of PSK modulation after modulator, and transmission arrives receiving terminal through optical channel.Then the light signal elder generation and the mixing of local oscillator laser that receive are converted to the signal of telecommunication by photodetector, and this signal of telecommunication becomes digital signal through over-sampling and analog-to-digital conversion, enter at last digital receiver and carry out a series of Digital Signal Processing to recover to send data.
Wherein, laser 501, modulator 502, optical channel 503, optical mixer unit 504, photodetector 505, analog to digital converter 506 and local oscillator laser 508 can be realized by the composition of traditional single polarization coherent optical communication system, its identical function is incorporated in this, does not repeat them here.
Wherein, digital receiver 507 can realize by the receiver of embodiment 2, and its concrete constitute and function is identical with embodiment 2, in this description will be omitted.
The coherent optical communication system of single polarization of the present embodiment due to the receiver that has adopted embodiment 2, has overcome and has adopted traditional DDLMS method to carry out the shortcoming of adaptive equalization.
Embodiment 4
The embodiment of the present invention also provides the polarization diversity receiver of the coefficient updating device of a kind of embodiment of use 1.Fig. 6 is the composition schematic diagram of this polarization diversity receiver, please refer to Fig. 6, and this polarization diversity receiver comprises:
Be used for to recover the first equalizer 601, the first estimation of deviation unit 602, the first phase place estimation unit 603, first decision device 604 of h circuit-switched data, and be used for recovering the second equalizer 601 ', the second estimation of deviation unit 602 ', the second phase place estimation unit 603 ', second decision device 604 ' of v circuit-switched data.
Wherein, the polarization diversity receiver of the present embodiment also comprises:
The first equalizer coefficients updating device 605, it is used for calculating the coefficient residual quantity of described the first equalizer, so that described the first equalizer upgrades its coefficient according to the coefficient residual quantity of described the first equalizer; And
The second equalizer coefficients updating device 605 ', it is used for calculating the coefficient residual quantity of described the second equalizer, so that described the second equalizer upgrades its coefficient according to the coefficient residual quantity of described the second equalizer.
Wherein, described the first equalizer coefficients updating device 605 and described the second equalizer coefficients updating device 605 ' can be realized by the equalizer coefficients updating device of embodiment 1, its concrete constitute and function describes in detail in embodiment 1, in this omission.
In the present embodiment, coherent optical communication system often adopts palarization multiplexing, namely all transmits signal on the polarization state of two quadratures.This moment, receiving terminal used the coherent receiver of polarization diversity, as shown in Figure 6.This polarization diversity receiver has used the adaptive equilibrium method of the structure that proposes according to embodiment 1.Wherein, 4 FIR are arranged, w hhAnd w vhBe used for recovering h circuit-switched data, w as the first equalizer 601 hvAnd w vvBe used for recovering the v circuit-switched data as the second equalizer 601 '.In Fig. 6, comprised the structures of the coefficient updating device of two cover embodiment 1, also namely 201～203 and 201 '～203 ', be respectively used to the equilibrium of h road and v road signal.After stable state, decision unit 604, the input of 604 ' reference frequency difference can be provided by frequency difference estimation unit 602,602 ' when equalizer convergence.
Same, the polarization diversity receiver of the embodiment of the present invention utilizes above structure to carry out adaptive equalization, goes for all mPSK signals (m 〉=2), as BPSK, QPSK, 8PSK etc.
Compare with traditional DDLMS, this adaptive equilibrium method that the polarization diversity receiver of the embodiment of the present invention adopts needn't generate training sequence according to the result of phase estimation, thereby has eliminated the inaccurate impact on equalizer of phase estimation.Because balanced and phase estimation can be carried out independently of one another, the structure of polarization diversity receiver is simplified, and also easilier realizes on DSP (Digital Signal Processing, Digital Signal Processing) hardware.
Embodiment 5
The embodiment of the present invention also provides a kind of coherent optical communication system of palarization multiplexing.Fig. 7 is the composition schematic diagram of this system, please refer to Fig. 7, and this system comprises:
The digital receiver 710 of laser 701, polarization beam apparatus 702, modulator 703, modulator 704, polarization beam combiner 705, optical channel 706, optical mixer unit 707, photodetector 708, analog to digital converter 709, polarization diversity and local oscillator laser 711.
Same, in the present embodiment, at transmitting terminal, the laser that sends from laser first is polarized beam splitting, is polarized after each automodulation again and closes bundle, and transmission arrives receiving terminal through optical channel.The light signal elder generation and the mixing of local oscillator laser that receive, then be converted to the signal of telecommunication by photodetector, this signal of telecommunication becomes digital signal through over-sampling and analog-to-digital conversion, and the digital receiver that enters at last polarization diversity carries out a series of Digital Signal Processing to recover to send data.
Wherein, laser 701, polarization beam apparatus 702, modulator 703, modulator 704, polarization beam combiner 705, optical channel 706, optical mixer unit 707, photodetector 708, analog to digital converter 709 and local oscillator laser 711 can be by traditional palarization multiplexing the composition of coherent optical communication system realize, its identical function is incorporated in this, does not repeat them here.
Wherein, the digital receiver 710 of polarization diversity can realize by the polarization diversity receiver of embodiment 4, and its concrete constitute and function is identical with embodiment 4, in this description will be omitted.
The coherent optical communication system of the palarization multiplexing of the present embodiment due to the polarization diversity receiver that has adopted embodiment 4, has overcome and has adopted traditional DDLMS method to carry out the shortcoming of adaptive equalization.
Embodiment 6
The embodiment of the present invention also provides a kind of adaptive equilibrium method of psk signal.Fig. 8 is the flow chart of the method, please refer to Fig. 8, and the method comprises:
Step 801: calculate described equalizer according to the output of equalizer and eliminated the psk signal afterwards of making an uproar mutually;
Step 802: according to the described psk signal and the described coefficient residual quantity of having eliminated the described equalizer of decision signal calculating of the psk signal after making an uproar mutually of having eliminated after making an uproar mutually;
Step 803: the coefficient that upgrades described equalizer according to described coefficient residual quantity.
In the present embodiment, after step 801, the method also comprises:
Step 804: the described psk signal of having eliminated after making an uproar is mutually adjudicated, obtain the described decision signal of having eliminated the psk signal after making an uproar mutually.
Wherein, this step 804 specifically can be adjudicated the described psk signal of having eliminated after making an uproar mutually according to the frequency difference reference value that receives, and described frequency difference reference value is prior information or obtains by frequency difference estimation.
In step 801, specifically can be according to described equalizer at nT sOutput valve constantly and at (n-a) T sOutput valve is constantly calculated the psk signal of having eliminated after making an uproar mutually.
In one embodiment, the psk signal after this has been eliminated and has made an uproar mutually is that this equalizer is at nT sConstantly and (n-a) T sThe conjugation product of output valve constantly.In another embodiment, the psk signal after this has been eliminated and has made an uproar mutually is that this equalizer is at nT s(n-a) T sThe business of output valve constantly.Wherein, described a is the natural number more than or equal to 1, and
Figure BDA0000124905640000121
Wherein,
Figure BDA0000124905640000122
Be nT sConstantly by the phase value of making an uproar mutually and causing,
Figure BDA0000124905640000123
Be (n-a) T sConstantly by the phase value of making an uproar mutually and causing.
In step 802, specifically can utilize cost function
Figure BDA0000124905640000124
Calculate the coefficient residual quantity of this equalizer.Wherein, r nBe the described psk signal of having eliminated after making an uproar mutually,
Figure BDA0000124905640000125
Be the described decision signal of having eliminated the psk signal after making an uproar mutually, E () represents expectation.For example, can be by minimizing this cost function, and calculate the coefficient residual quantity of this equalizer with traditional gradient descent method.
The principle of dealing with problems due to the present embodiment and the coefficient updating device of embodiment 1 are similar, and therefore, its concrete enforcement can with reference to the enforcement of the coefficient updating device of embodiment 1, repeat part and repeat no more.
In the present embodiment, this adaptive equilibrium method is applicable to all mPSK (m＞=2) signal, as BPSK, QPSK, 8PSK etc.
By the adaptive equilibrium method of the present embodiment, removed the coupling between phase bit recovery and equilibrium, overcome and adopted traditional DDLMS method to carry out the shortcoming of adaptive equalization.
More than describe the preferred embodiment of the present invention with reference to the accompanying drawings.Many feature and advantage specification detailed according to this of these execution modes is clearly, so claims are intended to cover all these feature and advantage in its true spirit and scope of falling into of these execution modes.In addition, owing to those skilled in the art will find apparent that a lot of modifications and change, not therefore embodiments of the present invention to be limited to precision architecture and operation illustrated and that describe, but can contain all suitable modifications and the equivalent that falls in its scope.
Should be appreciated that each several part of the present invention can realize with hardware, software, firmware or their combination.In the above-described embodiment, a plurality of steps or method can realize with being stored in memory and by software or firmware that suitable instruction execution system is carried out.For example, if realize with hardware, the same in another embodiment, any one in the following technology that can know altogether with this area or their combination realize: have for data-signal being realized the discrete logic of the logic gates of logic function, application-specific integrated circuit (ASIC) with suitable combinational logic gate circuit, programmable gate array (PGA), field programmable gate array (FPGA) etc.
Describe or frame can be understood in flow chart or in this any process of otherwise describing or method, expression comprises module, fragment or the part of code of the executable instruction of the step that one or more is used for realizing specific logical function or process, and the scope of the preferred embodiment of the present invention comprises other realization, wherein, can be not according to order shown or that discuss, comprise according to related function by the mode of basic while or by opposite order, carry out function, this should those skilled in the art described by the present invention understand.
In flow chart the expression or in this logic of otherwise describing and/or step, for example, can be considered to the sequencing list be used to the executable instruction that realizes logic function, may be embodied in any computer-readable medium, use for instruction execution system, device or equipment (as the computer based system, comprise that the system of processor or other can and carry out the system of instruction from instruction execution system, device or equipment instruction fetch), or use in conjunction with these instruction execution systems, device or equipment.With regard to this specification, " computer-readable medium " can be anyly can comprise, storage, communication, propagation or transmission procedure be for instruction execution system, device or equipment or the device that uses in conjunction with these instruction execution systems, device or equipment.Computer-readable medium can be for example but be not limited to electronics, magnetic, light, electromagnetism, infrared or semiconductor system, device, equipment or propagation medium.The example more specifically of computer-readable medium (non-exhaustive list) comprises following: the electrical connection section (electronic installation) with one or more wiring, portable computer diskette box (magnetic device), random access memory (RAM) (electronic installation), read-only memory (ROM) (electronic installation), Erasable Programmable Read Only Memory EPROM (EPROM or flash memory) (electronic installation), optical fiber (electro-optical device), and portable optic disk read-only memory (CDROM) (Optical devices).In addition, computer-readable medium can be even paper or other the suitable medium that can print described program thereon, because can be for example by paper or other media be carried out optical scanner, then edit, decipher or process in the electronics mode with other suitable method in case of necessity and obtain described program, then it is stored in computer storage.
Above-mentioned explanatory note and accompanying drawing show various feature of the present invention.Should be appreciated that those of ordinary skills can prepare that suitable computer code is described above realizing and illustrative each step and process in the accompanying drawings.It is also understood that above-described various terminal, computer, server, network etc. can be any types, and can prepare described computer code to utilize described device to realize the present invention according to disclosure.
Specific implementations of the present invention is disclosed at this.Those of ordinary skill in the art will readily appreciate that, the present invention has other application under other environment.In fact, also there are many execution modes and realization.Claims are absolutely not in order to limit the scope of the present invention to above-mentioned embodiment.In addition, arbitrarily for " be used for ... device " to quote be all to add the explaination of function for the device of describing key element and claim, and specifically use arbitrarily " be used for ... device " the key element of quoting do not wish to be understood to that device adds the element of function, even this claim has comprised the word of " device ".
Although illustrate and described the present invention for certain preferred embodiments or a plurality of execution mode, obviously, those skilled in the art can expect the modification and the modified example that are equal to when reading and understanding specification and accompanying drawing.Especially for the various functions of being carried out by above-mentioned key element (parts, assembly, device, form etc.), unless otherwise noted, the term (comprising quoting of " device ") of wish to be used for describing these key elements corresponding to any key element of the concrete function of the described key element of execution (namely, function equivalent), even this key element structurally is different from the open structure of carrying out this function in illustrated illustrative embodiments of the present invention or a plurality of execution mode.In addition, although below in several illustrative execution modes only one or more has described specific features of the present invention, but can be as required and to any given or specifically use favourable aspect and consider, this feature is combined with one or more other features of other execution modes.
About comprising the execution mode of above a plurality of embodiment, following remarks is also disclosed.
The coefficient updating device of remarks 1, a kind of equalizer, wherein, described updating device comprises:
The first computing unit, its output according to equalizer calculate this equalizer and have eliminated phase shift keying (PSK) signal afterwards of making an uproar mutually;
The second computing unit, it has eliminated the coefficient residual quantity of the described equalizer of decision signal calculating of the psk signal after making an uproar mutually according to the described psk signal of having eliminated after making an uproar mutually with this, so that equalizer upgrades equalizer coefficients according to described coefficient residual quantity.
Remarks 2, updating device described according to remarks 1, wherein, described updating device also comprises:
Decision unit, it carries out the judgement of psk signal to the described psk signal of having eliminated after making an uproar mutually, the decision signal of the psk signal after making an uproar mutually that has been eliminated.
Remarks 3, updating device described according to remarks 2, wherein, described decision unit is further adjudicated the described psk signal of having eliminated after making an uproar mutually according to the frequency difference reference value that receives, and described frequency difference reference value is prior information or obtains by frequency difference estimation.
Remarks 4, updating device described according to remarks 1, wherein, described the first computing unit according to described equalizer at nT sOutput valve constantly and at (n-a) T sOutput valve is constantly calculated the psk signal of having eliminated after making an uproar mutually;
Wherein, the described psk signal of having eliminated after making an uproar mutually is that described equalizer is at nT sConstantly and (n-a) T sThe conjugation product of output valve constantly; Perhaps, the described psk signal of having eliminated after making an uproar mutually is that described equalizer is at nT s(n-a) T sThe business of output valve constantly;
Wherein, described a is the natural number more than or equal to 1, and
Figure BDA0000124905640000151
Wherein,
Figure BDA0000124905640000152
Be nT sConstantly by the phase value of making an uproar mutually and causing,
Figure BDA0000124905640000153
Be (n-a) T sConstantly by the phase value of making an uproar mutually and causing.
Remarks 5, updating device described according to remarks 1, wherein, described the second computing unit utilizes the coefficient residual quantity of the described equalizer of following cost function calculation:
c = E { | r n - r ^ n | 2 }
Wherein, r nBe the described psk signal of having eliminated after making an uproar mutually,
Figure BDA0000124905640000155
Be the described decision signal of having eliminated the psk signal after making an uproar mutually, E () represents expectation.
Remarks 6, a kind of receiver, described receiver comprises: equalizer, frequency difference estimation unit, phase estimation unit and decision device, wherein, described receiver also comprises:
The equalizer coefficients updating device, it is used for calculating the coefficient residual quantity of described equalizer, so that described equalizer upgrades its coefficient according to described coefficient residual quantity;
Wherein, described equalizer coefficients updating device is realized by the described equalizer coefficients updating device of remarks 1-5 any one.
Remarks 7, a kind of single polarized systems, wherein, described system comprises the described receiver of remarks 6.
Remarks 8, a kind of polarization diversity receiver, described polarization diversity receiver comprises: the first equalizer, the first estimation of deviation unit, the first phase place estimation unit, the first decision device that be used for to recover the h circuit-switched data, with the second equalizer that be used for to recover the v circuit-switched data, the second estimation of deviation unit, the second phase place estimation unit, the second decision device, wherein, described polarization diversity receiver also comprises:
The first equalizer coefficients updating device, it is used for calculating the coefficient residual quantity of described the first equalizer, so that described the first equalizer upgrades its coefficient according to the coefficient residual quantity of described the first equalizer;
The second equalizer coefficients updating device, it is used for calculating the coefficient residual quantity of described the second equalizer, so that described the second equalizer upgrades its coefficient according to the coefficient residual quantity of described the second equalizer;
Wherein, described the first equalizer coefficients updating device and described the second equalizer coefficients updating device are realized by the described equalizer coefficients updating device of remarks 1-5 any one.
Remarks 9, a kind of polarisation multiplex system, wherein, described system comprises the described polarization diversity receiver of remarks 8.
The adaptive equilibrium method of remarks 10, a kind of psk signal, wherein, described method comprises:
Calculate described equalizer according to the output of equalizer and eliminated the psk signal afterwards of making an uproar mutually;
According to the described psk signal and the described coefficient residual quantity of having eliminated the described equalizer of decision signal calculating of the psk signal after making an uproar mutually of having eliminated after making an uproar mutually;
Upgrade the coefficient of described equalizer according to described coefficient residual quantity.
Remarks 11, method described according to remarks 10, wherein, described method also comprises:
The described psk signal of having eliminated after making an uproar is mutually adjudicated, obtain the described decision signal of having eliminated the psk signal after making an uproar mutually.
Remarks 12, method described according to remarks 11 wherein, are adjudicated the described psk signal of having eliminated after making an uproar mutually, comprising:
According to the frequency difference reference value that receives, the described psk signal of having eliminated after making an uproar is mutually adjudicated, described frequency difference reference value is prior information or obtains by frequency difference estimation.
Remarks 13, method described according to remarks 10 wherein, are calculated described equalizer according to the output of equalizer and have been eliminated the psk signal afterwards of making an uproar mutually, comprising:
According to described equalizer at nT sOutput valve constantly and at (n-a) T sOutput valve is constantly calculated the psk signal of having eliminated after making an uproar mutually;
Wherein, the described psk signal of having eliminated after making an uproar mutually is that this equalizer is at nT sConstantly and (n-a) T sThe conjugation product of output valve constantly; Perhaps, the described psk signal of having eliminated after making an uproar mutually is that this equalizer is at nT s(n-a) T sThe business of output valve constantly;
Wherein, described a is the natural number more than or equal to 1, and
Figure BDA0000124905640000161
Wherein,
Figure BDA0000124905640000162
Be nT sConstantly by the phase value of making an uproar mutually and causing,
Figure BDA0000124905640000163
Be (n-a) T sConstantly by the phase value of making an uproar mutually and causing.
Remarks 14, method described according to remarks 10 wherein, are calculated the coefficient residual quantity of described equalizer, comprising:
Utilize the coefficient residual quantity of the described equalizer of following cost function calculation:
Figure BDA0000124905640000164
Wherein, r nBe the described psk signal of having eliminated after making an uproar mutually,
Figure BDA0000124905640000165
Be the described decision signal of having eliminated the psk signal after making an uproar mutually, E () represents expectation.
Remarks 15, a kind of computer-readable program, wherein when carrying out this program in the equalizer at coherent optical heterodyne communicatio, this program makes computer carry out the described method of remarks 10-14 in described equalizer.
Remarks 16, a kind of storage medium that stores computer-readable program, wherein this computer-readable program makes computer carry out the described method of remarks 10-14 in the equalizer of coherent optical heterodyne communicatio.

Claims (10)

1. the coefficient updating device of an equalizer, wherein, described updating device comprises:
The first computing unit, its output according to equalizer calculate this equalizer and have eliminated phase shift keying (PSK) signal afterwards of making an uproar mutually;
The second computing unit, it has eliminated the coefficient residual quantity of the described equalizer of decision signal calculating of the psk signal after making an uproar mutually according to the described psk signal of having eliminated after making an uproar mutually with this, so that equalizer upgrades equalizer coefficients according to described coefficient residual quantity.
2. updating device according to claim 1, wherein, described updating device also comprises:
Decision unit, it carries out the judgement of psk signal to the described psk signal of having eliminated after making an uproar mutually, the decision signal of the psk signal after making an uproar mutually that has been eliminated.
3. updating device according to claim 2, wherein, described decision unit is further adjudicated the described psk signal of having eliminated after making an uproar mutually according to the frequency difference reference value that receives, and described frequency difference reference value is prior information or obtains by frequency difference estimation.
4. updating device according to claim 1, wherein, described the first computing unit according to described equalizer at nT sOutput valve constantly and at (n-a) T sOutput valve is constantly calculated the psk signal of having eliminated after making an uproar mutually;
Wherein, the described psk signal of having eliminated after making an uproar mutually is that described equalizer is at nT sConstantly and (n-a) T sThe conjugation product of output valve constantly; Perhaps, the described psk signal of having eliminated after making an uproar mutually is that described equalizer is at nT s(n-a) T sThe business of output valve constantly;
Wherein, described a is the natural number more than or equal to 1, and
Figure FDA0000124905630000011
Wherein,
Figure FDA0000124905630000012
Be nT sConstantly by the phase value of making an uproar mutually and causing,
Figure FDA0000124905630000013
Be (n-a) T sConstantly by the phase value of making an uproar mutually and causing.
5. updating device according to claim 1, wherein, described the second computing unit utilizes the coefficient residual quantity of the described equalizer of following cost function calculation:
c = E { | r n - r ^ n | 2 }
Wherein, r nBe the described psk signal of having eliminated after making an uproar mutually,
Figure FDA0000124905630000015
Be the described decision signal of having eliminated the psk signal after making an uproar mutually, E () represents expectation.
6. receiver, described receiver comprises: equalizer, frequency difference estimation unit, phase estimation unit and decision device, wherein, described receiver also comprises:
The equalizer coefficients updating device, it is used for calculating the coefficient residual quantity of described equalizer, so that described equalizer upgrades its coefficient according to described coefficient residual quantity;
Wherein, described equalizer coefficients updating device is realized by the described equalizer coefficients updating device of claim 1-5 any one.
7. single polarized systems, wherein, described system comprises receiver claimed in claim 6.
8. polarization diversity receiver, described polarization diversity receiver comprises: the first equalizer, the first estimation of deviation unit, the first phase place estimation unit, the first decision device that be used for to recover the h circuit-switched data, with the second equalizer that be used for to recover the v circuit-switched data, the second estimation of deviation unit, the second phase place estimation unit, the second decision device, wherein, described polarization diversity receiver also comprises:
The first equalizer coefficients updating device, it is used for calculating the coefficient residual quantity of described the first equalizer, so that described the first equalizer upgrades its coefficient according to the coefficient residual quantity of described the first equalizer;
The second equalizer coefficients updating device, it is used for calculating the coefficient residual quantity of described the second equalizer, so that described the second equalizer upgrades its coefficient according to the coefficient residual quantity of described the second equalizer;
Wherein, described the first equalizer coefficients updating device and described the second equalizer coefficients updating device are realized by the described equalizer coefficients updating device of claim 1-5 any one.
9. polarisation multiplex system, wherein, described system comprises polarization diversity receiver claimed in claim 8.
10. the adaptive equilibrium method of a psk signal, wherein, described method comprises:
Calculate described equalizer according to the output of equalizer and eliminated the psk signal afterwards of making an uproar mutually;
According to the described psk signal and the described coefficient residual quantity of having eliminated the described equalizer of decision signal calculating of the psk signal after making an uproar mutually of having eliminated after making an uproar mutually;
Upgrade the coefficient of described equalizer according to described coefficient residual quantity.
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