CN103179060B - The coefficient updating device of equalizer and method - Google Patents

Abstract

The embodiment of the present invention provides a kind of coefficient updating device and method of equalizer, and wherein, described updating device comprises: the first computing unit, and it calculates this equalizer according to the output of equalizer and eliminates the psk signal after making an uproar mutually; Second computing unit, its according to described in eliminate the coefficient residual quantity that the psk signal after making an uproar mutually and this decision signal eliminating the psk signal after making an uproar mutually calculate described equalizer, so that equalizer is according to described coefficient residual quantity renewal equalizer coefficients.By the method and apparatus of the embodiment of the present invention, eliminate the coupling between phase recovery and equilibrium, thus overcome traditional decision-aided LMSE method (DDLMS) needs the result feedback of phase recovery in equalizer, cause receiver structure complicated, and on hardware, realize the shortcoming of parallelization inconvenience.

Description

The coefficient updating device of equalizer and method

Technical field

The present invention relates to digital coherent optical communication technique, particularly relate to a kind of coefficient updating device and method of equalizer.

Background technology

Digital coherent optical communication technique is the developing direction of following high speed, Large Copacity optical communication technique.In coherent optical communication system, various modulation format can be used, as amplitude keying (ASK, AmplitudeShiftKeying), phase shift keying (PSK, PhaseShiftKeying), quadrature amplitude modulation (QAM, QuadratureAmplitudeModulation) etc.Wherein, mPSK is a kind of phase-only modulation, and it represents the information (m >=2) that will transmit by the phase place of signal.A symbol s of mPSK _ncan be expressed as: s _n=e ^{j2k π/m}, k=0,1 ... m-1.Common BPSK (BinaryPhaseShiftKeying, two-phase PSK), QPSK (QuaternaryPhaseShiftKeying, 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, DigitalSignalProcessing) technology to resist the various damages of optical channel.Because crosstalk (inter-symbolinterference between optical channel meeting created symbol, ISI), in coherent optical heterodyne communicatio, usual employing eliminates ISI (document 1) based on the adaptive equalization technique of finite impulse response (FIR, FiniteImpulseResponse) filter.In order to the overhead improving the availability of frequency spectrum He avoid training sequence to bring, it is desirable to use equalization methods that is blind or decision-aided.Conventional blind equalization algorithm CMA (ConstantModulusAlgorithm, constant modulus algorithm) is only applicable to the mPSK signal of m > 2, to bpsk signal inapplicable (document 2); And decision-aided LMSE method (Decision-DirectedLeast-Mean-Square, DDLMS) all mPSK signals are applicable to, and there is the advantage fast to channel variation tracking velocity, therefore, DDLMS method, in existing coherent optical communication system, obtains and uses widely.

But inventor, realizing finding in process of the present invention, in coherent optical communication system, because phase recovery carries out after the equalization, when using traditional DDLMS, needs the result feedback of phase recovery to (document 3) in equalizer.This not only allows receiver structure become complicated, is also unfavorable for that this algorithm realizes parallelization on hardware.

Following is a list for understanding the present invention and the useful document of routine techniques, incorporating them into by reference herein, as illustrated completely in this article.

Document 1:EzraIpandJosephM.Kahn, Digitalequalizationofchromaticdispersionandpolarizationm odedispersion.JournalofLightwaveTechnology, vol.25, no.8,2007.

Document 2:C.B.Papadias, OntheexistenceofundesirableglobalminimumofGodardequalize rs.Acoustics, SpeechandSignalProcessing, vol.5,1997.

Document 3:S.J.Savoryetal, Transmissionof42.8Gb/spolarizationmultiplexedNRZ-QPSKove r6400kmofstandardfiberwithnoopticaldispersioncompensatio n.OTuA1, OFC2007.

Document 4:SimonHaykin, AdaptiveFilterTheory.3rdedition, PrenticeHall, 1998.

Document 5:LeiLietal, Apparatusandmethodforestimationoffrequencyoffsetinoptica lcoherentreceiver, patent200710166788.3.

Above it should be noted that, just conveniently to technical scheme of the present invention, clear, complete explanation is carried out to the introduction of technical background, and facilitate the understanding of those skilled in the art to set forth.Only can not think that technique scheme is conventionally known to one of skill in the art because these schemes have carried out setting forth in background technology part of the present invention.

Summary of the invention

The object of the embodiment of the present invention is the coefficient updating device and the method that provide a kind 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, provide a kind of coefficient updating device of equalizer, wherein, described updating device comprises:

First computing unit, it calculates this equalizer according to the output of equalizer and eliminates the phase shift keying after making an uproar mutually (PSK) signal;

Second computing unit, its according to described in eliminate the coefficient residual quantity that the psk signal after making an uproar mutually and this decision signal eliminating the psk signal after making an uproar mutually calculate described equalizer, so that equalizer is according to described coefficient residual quantity renewal equalizer coefficients.

According to another aspect of the embodiment of the present invention, additionally provide a kind of receiver, described receiver comprises: equalizer, frequency difference estimation unit, phase estimation unit and decision device, and wherein, described receiver also comprises:

Equalizer coefficients updating device, it is 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, additionally provide a kind of single polarized systems, wherein, described system comprises aforesaid receiver.

According to another aspect of the embodiment of the present invention, additionally provide a kind of polarization diversity receiver, described polarization diversity receiver comprises: for recovering the first equalizer, the first offset estimation unit, first phase estimation unit, first decision device of h circuit-switched data, with the second equalizer for recovering v circuit-switched data, the second offset estimation unit, second phase estimation unit, the second decision device, wherein, described polarization diversity receiver also comprises:

First equalizer coefficients updating device, it is for calculating the coefficient residual quantity of described first equalizer, so that described first equalizer upgrades its coefficient according to the coefficient residual quantity of described first equalizer;

Second equalizer coefficients updating device, it is for calculating the coefficient residual quantity of described second equalizer, so that described second equalizer upgrades its coefficient according to the coefficient residual quantity of described second equalizer;

Wherein, described first equalizer coefficients updating device and described second equalizer coefficients updating device are realized by aforesaid equalizer coefficients updating device.

According to another aspect of the embodiment of the present invention, additionally provide a kind of polarisation multiplex system, wherein, described system comprises aforesaid polarization diversity receiver.

According to another aspect of the embodiment of the present invention, additionally provide a kind of adaptive equilibrium method of psk signal, wherein, described method comprises:

Calculate described equalizer according to the output of equalizer and eliminate the psk signal after making an uproar mutually;

The coefficient residual quantity that the psk signal after making an uproar mutually and the described decision signal eliminating the psk signal after making an uproar mutually calculate described equalizer is eliminated according to described;

The coefficient of described equalizer is upgraded according to described coefficient residual quantity.

The beneficial effect of the embodiment of the present invention is, by the method and apparatus of the embodiment of the present invention, eliminate the coupling between phase recovery and equilibrium, thus overcome traditional decision-aided LMSE method (DDLMS) needs the result feedback of phase recovery in equalizer, cause receiver structure complicated, and on hardware, realize the shortcoming of parallelization inconvenience.

With reference to explanation hereinafter and accompanying drawing, disclose in detail particular implementation of the present invention, specifying principle of the present invention can adopted mode.Should be appreciated that, thus embodiments of the present invention are not restricted in scope.In the spirit of claims and the scope of clause, embodiments of the present invention comprise many changes, amendment and are equal to.

The feature described for a kind of execution mode and/or illustrate can use in one or more other execution mode in same or similar mode, combined with the feature in other execution mode, or substitutes the feature in other execution mode.

Should emphasize, term " comprises/comprises " existence referring to feature, one integral piece, step or assembly when using herein, but does not get rid of the existence or additional of one or more further feature, one integral piece, step or assembly.

Accompanying drawing explanation

Included accompanying drawing is used to provide further understanding of the invention, which constitute a part for specification, exemplified with 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 for the judgement schematic diagram of the common mPSK signal of m=4;

Fig. 4 is the composition schematic diagram of the receiver of the coefficient updating device comprising Fig. 2;

Fig. 5 is the composition schematic diagram of single polarization coherent optical communication system of the receiver comprising Fig. 4;

Fig. 6 is the composition schematic diagram of the polarization diversity receiver of the coefficient updating device comprising Fig. 2;

Fig. 7 is the composition schematic diagram of the palarization multiplexing coherent optical communication system of the polarization diversity receiver comprising 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 specification below, 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 for the adaptive equalizer of receiver end and is described, but be appreciated that the embodiment of the present invention is not limited to said structure.

Different in order to outstanding adaptive equilibrium method of the present invention and traditional DDLMS method, first carry out brief description to the DDLMS method used in traditional coherent optical heterodyne communicatio below.

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 the coherent optical heterodyne communicatio that this is traditional, with x _nrepresent nT _ssignal (the T that reception arrives _sfor symbol period, n=0,1,2 ...), w _nrepresent nT _sthe FIR tap coefficient (coefficient hereinafter referred to as equalizer) of moment equalizer, x _nand w _nit is all m dimensional vector.NT _sthe output of moment equalizer is y _n=w _n ^tx _n( ^trepresent transposition).Traditional decision-aided least mean-square error (DDLMS) method utilizes 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 makes the c in above formula minimum, such as, known gradient descent method can be used to upgrade coefficient w _n(document 4).Cost function c is to w _ngradient be:

$\mathrm{\Δ}{w}_n=\frac{\∂c}{\∂w_n}=(y_n-t_n)x_n^{*}$

Wherein, () ^*represent conjugation, Δ w _nfor the coefficient residual quantity of this equalizer.

Corresponding coefficient update formula is:

w _n+1＝w _n-μ·Δw _n

Wherein, μ is coefficient update step-length, and can be a real number being greater than 0.

In the coherent optical communication system of reality, between emitting laser and local oscillator laser, usually there is certain frequency difference, also have certain live width separately.Signal, after equalizer, also just can will be adjudicated through frequency difference compensation and phase compensation.In order to give receiver structure training sequence, need the output signal of the equalizer providing expectation.Even if equalizer completely eliminates ISI, 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 also need the result (document 3) of frequency difference estimation and phase estimation.As shown in Figure 1, court verdict 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, the phase deviation that the phase noise of transmitting terminal and receiving terminal laser causes.

Please refer to Fig. 1 again, computing unit 105 is according to training sequence t and the output y of equalizer and the coefficient residual quantity Δ w of above-mentioned formulae discovery equalizer.

The signal that traditional coherent optical heterodyne communicatio as shown in Figure 1 carries out the coefficient update of equalizer is known, owing to needing the result feedback of phase recovery and frequency difference estimation in equalizer, not only allow the structure of receiver become complicated, be also unfavorable for that the method realizes parallelization on hardware.

Below the coefficient updating device of the equalizer of the embodiment of the present invention and the adaptive equilibrium method of psk signal are described.

Embodiment 1

Embodiments provide 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:

First computing unit 201 calculates this equalizer according to the output of equalizer and eliminates the phase shift keying after making an uproar mutually (PSK) signal.

As shown in Figure 2, this first computing unit 201 calculates r according to the output y of equalizer, wherein, and can according to this equalizer at nT _sthe output valve in moment and at (n-a) T _soutput valve calculating r, the r in moment are and eliminate the psk signal after making an uproar mutually.

According to an execution mode of the present embodiment, this eliminates the psk signal after making an uproar mutually for this equalizer is at nT _smoment and (n-a) T _sthe conjugate product of the output valve in moment, also, with r _nrepresent that this eliminates the psk signal after making an uproar mutually, y _nrepresent that this equalizer is at nT _sthe output in moment, y _n-arepresent that this equalizer is at (n-a) T _sthe output in moment, then r _n=y _ny _n-a ^*( ^*represent conjugation).Wherein, a be more than or equal to 1 natural number, as a=1, then r _n=y _ny _n-1 ^*, it represents that the conjugation of adjacent two symbols is amassed; As a > 1, r _n=y _ny _n-a ^*, it represents that the conjugation of two not far symbols of being separated by is amassed.

Wherein, if transmission is mPSK signal, also namely x is mPSK signal, and when equalizer eliminates ISI, the output of equalizer is with frequency difference and the mPSK signal of making an uproar mutually.Because the symbol rate of optical communication system is generally in GHz magnitude, and laser linewidth is generally less than 1MHz, thus on two adjacent-symbols or two be separated by not far symbol, the phase value caused by making an uproar mutually can be thought and is also approximately equal a >=1.Wherein, as a=1, represent the phase value approximately equal that two adjacent-symbols cause by making an uproar mutually; As a > 1, represent the phase value approximately equal that two not far symbols of being separated by cause by making an uproar mutually.Therefore, according to r _n=y _ny _n-a ^*calculate r _ntime, 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 _nbe a cancellation the psk signal after making an uproar mutually.

It should be noted that, r _nrelevant with frequency difference, it is a mPSK signal with phase deviation Δ θ.Wherein Δ θ=θ _n-θ _n-a=2 π a Δ fT _sthe phase deviation that the frequency difference Δ f of transmitting and local oscillator laser causes at the n-th and n-th-a intersymbol.

According to the another one execution mode of the present embodiment, this eliminates the psk signal after making an uproar mutually for this equalizer is at nT _s(n-a) T _sthe business of the output valve in moment.Same, with r _nrepresent that this eliminates the psk signal after making an uproar mutually, y _nrepresent that this equalizer is at nT _sthe output in moment, y _n-arepresent that this equalizer is at (n-a) T _sthe output in moment, then r _n=y _n/ y _n-a.Wherein, a be more than or equal to 1 natural number, as a=1, then r _n=y _n/ y _n-1, it represents the business of adjacent two symbols; As a > 1, r _n=y _n/ y _n-a, it represents the business of two not far symbols of being separated by.

Wherein, with r _n=y _ny _n-a ^*situation similar, due on two adjacent-symbols or two be separated by not far symbol, the phase value caused by making an uproar mutually can think approximately equal.Therefore r is being passed through _n=y _n/ y _n-acalculate r _ntime, this public phase term has also been cancelled, therefore according to r _n=y _n/ y _n-acalculate the r obtained _nalso with make an uproar mutually irrelevant, also, this r _nbe a cancellation the psk signal after making an uproar mutually.Same, according to r _n=y _n/ y _n-acalculate the r obtained _nonly be a cancellation and make an uproar mutually, but it being still relevant with frequency difference, is a mPSK signal with phase deviation Δ θ.

In above two execution modes, the calculating eliminating the psk signal after making an uproar mutually is just illustrated; but the embodiment of the present invention is not in this, as restriction; calculated the scheme eliminating the psk signal after making an uproar mutually by other alternative modes, be all contained in the protection range of the embodiment of the present invention.

Second computing unit 202, its according to described in eliminate the coefficient residual quantity that the psk signal after making an uproar mutually and this decision signal eliminating the psk signal after making an uproar mutually calculate described equalizer, so that equalizer is according to described coefficient residual quantity renewal equalizer coefficients.

Wherein, updating device of the present invention also comprises decision unit 203, this decision unit 203 for eliminating to described the judgement that psk signal (r) after making an uproar mutually carries out psk signal, with the decision signal of the psk signal after making an uproar mutually that has been eliminated also namely this eliminates the decision value of the psk signal after making an uproar mutually.Thus, this second computing unit 202 can according to the r of the first computing unit 201 feeding and its decision value calculate the coefficient residual quantity Δ w of equalizer.

Wherein, this decision unit 203 can also eliminate the psk signal after making an uproar mutually according to the frequency difference reference value Δ θ that receives adjudicate described further.Here frequency difference reference value can be prior information, also can be the value obtained 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), by r _njudgement is an element in set D.This frequency difference reference value can be prior information or be provided (document 5) by certain frequency difference estimation method.If do not have frequency difference reference value, acquiescence Δ θ is 0.D is the set that all possible decision value is formed:

D＝{d _k：d _k＝e ^{j(2kπ/m+Δθ)}，k＝0，1，Km-1}

The decision method that then decision unit 203 of the present embodiment uses can be described as:

a _n＝mod(arg(r _ne ^-jΔθ)，2π)

${\hat{r}}_n=d_k$ if $\frac{(2k-1)\mathrm{\&pi;}}{m}\&le;a_n<\frac{(2k+1)\mathrm{\&pi;}}{m}$

Wherein, d _krepresent a kth element of D.Arg () is for getting argument computing, and mod (, 2 π) represents 2 π deliverys, its codomain be [0,2 π).

Compare with traditional mPSK decision method, in the said method of the present embodiment is just many above formula, take advantage of e ^{-j Δ θ}step, this is equivalent to the signal received to rotate an angle delta θ on a complex plane, then adjudicates as conventional mPSK signal.For m=4 (QPSK signal), in Fig. 3, dotted line shows the decision boundaries to QPSK signal.

If do not have 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 is less can ignore time, Δ θ ≈ 0, exp (j Δ θ) ≈ 1, at this moment it is also equivalent to common mPSK decision device.

Above-mentioned decision method just illustrates, the present embodiment is not in this, as restriction.

In one embodiment, the second computing unit 202 can utilize the coefficient residual quantity of following cost function calculation equalizer:

$c=E\left\{{|r_n-{\hat{r}}_n|}^2\right\}$

Wherein, E () represents expectation.

Such as, by minimizing above-mentioned cost function, also namely r is minimized _nwith its decision value between mean square error, and use known gradient descent method to calculate the coefficient residual quantity of this equalizer.

With r _n=y _ny _n-1 ^*for example, c is to w _ngradient be:

$\mathrm{\&Delta;}{w}_n=\frac{\&PartialD;c}{\&PartialD;w_n}=(r_n-{\hat{r}}_n)y_{n-1}{x}_n^{*}+{(r_n-{\hat{r}}_n)}^{*}{y}_n{x}_{n-1}^{*}$

With r _n=y _n/ y _n-1for example, c is to w _ngradient be:

$\mathrm{\&Delta;}{w}_n=\frac{\&PartialD;c}{\&PartialD;w_n}=(r_n-{\hat{r}}_n)(x_n^{*}/y_{n-1}^{*}-x_{n-1}^{*}{y}_n^{*}/{\left(y_{n-1}^{*}\right)}^2)$

Thus, equalizer, according to following formula, can upgrade the coefficient of equalizer:

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) signals, as BPSK, QPSK, 8PSK etc.

Carry out adaptive equalization by the coefficient updating device of the embodiment of the present invention, eliminate the coupling between phase recovery and equilibrium, overcome the shortcoming adopting traditional DDLMS method to carry out adaptive equalization.

Utilize the coefficient updating device of embodiment 1, the invention allows for following examples.

Embodiment 2

Embodiments provide a kind of receiver using the coefficient updating device of embodiment 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, exports the signal after equilibrium;

Frequency difference estimation unit 402, it carries out frequency difference estimation to the signal that equalizer 401 exports, and exports the result of frequency difference estimation;

Phase estimation unit 403, it carries out phase estimation to the result of frequency difference estimation, exports the result of phase estimation;

Decision device 404, it is adjudicated the result of phase estimation, exports 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, and 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 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 be realized by the coefficient updating device of embodiment 1, and its concrete constitute and function elaborates in embodiment 1, omits at this.

Wherein, after equalizer 401 converges to stable state, frequency difference estimation unit 402 can provide frequency difference reference value for decision unit 203, as shown in phantom in figure 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 need not generate training sequence according to the result of phase estimation, thus eliminates 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 (DigitalSignalProcessing, Digital Signal Processing) hardware.

Embodiment 3

The embodiment of the present invention additionally 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 sent from laser becomes the light signal of PSK modulation after modulator, arrives receiving terminal through optical channel transmission.The light signal elder generation received and the mixing of local oscillator laser, be then converted to the signal of telecommunication by photodetector, this signal of telecommunication becomes digital signal through over-sampling and analog-to-digital conversion, finally enters digital receiver and carries 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 be realized 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, owing to have employed the receiver of embodiment 2, overcomes the shortcoming adopting traditional DDLMS method to carry out adaptive equalization.

Embodiment 4

The embodiment of the present invention additionally provides a kind of polarization diversity receiver using the coefficient updating device of embodiment 1.Fig. 6 is the composition schematic diagram of this polarization diversity receiver, please refer to Fig. 6, and this polarization diversity receiver comprises:

For recovering the first equalizer 601, first offset estimation unit 602, first phase estimation unit 603, first decision device 604 of h circuit-switched data, and the second equalizer 601 ', the second offset estimation unit 602 ', second phase estimation unit 603 ', second decision device 604 ' for recovering v circuit-switched data.

Wherein, the polarization diversity receiver of the present embodiment also comprises:

First equalizer coefficients updating device 605, it is for calculating the coefficient residual quantity of described first equalizer, so that described first equalizer upgrades its coefficient according to the coefficient residual quantity of described first equalizer; And

Second equalizer coefficients updating device 605 ', it is for calculating the coefficient residual quantity of described second equalizer, so that described second equalizer upgrades its coefficient according to the coefficient residual quantity of described second equalizer.

Wherein, described first equalizer coefficients updating device 605 and described second equalizer coefficients updating device 605 ' can be realized by the equalizer coefficients updating device of embodiment 1, its concrete constitute and function elaborates in embodiment 1, omits at this.

In the present embodiment, coherent optical communication system often adopts palarization multiplexing, i.e. all transmission signal in two orthogonal polarization states.Now receiving terminal uses the coherent receiver of polarization diversity, as shown in Figure 6.This polarization diversity receiver employs the adaptive equilibrium method of the structure proposed according to embodiment 1.Wherein, 4 FIR, w are had _hhand w _vhas the first equalizer 601 for recovering h circuit-switched data, w _hvand w _vvas the second equalizer 601 ' for recovering v circuit-switched data.In figure 6, contain the structure of the coefficient updating device of two cover embodiments 1, be also 201 ~ 203 and 201 ' ~ 203 ', be respectively used to the equilibrium of h road and v road signal.When after equalizer convergence to stable state, the reference frequency difference input of decision unit 604,604 ' can be provided by frequency difference estimation unit 602,602 '.

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 need not generate training sequence according to the result of phase estimation, thus eliminates 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 (DigitalSignalProcessing, Digital Signal Processing) hardware.

Embodiment 5

The embodiment of the present invention additionally 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 sent from laser is first polarized beam splitting, is polarized again and closes bundle after each automodulation, arrives receiving terminal through optical channel transmission.The light signal elder generation received and the mixing of local oscillator laser, then the signal of telecommunication is converted to by photodetector, this signal of telecommunication becomes digital signal through over-sampling and analog-to-digital conversion, and the digital receiver finally entering 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 realized by the composition of the coherent optical communication system of traditional palarization multiplexing, its identical function is incorporated in this, does not repeat them here.

Wherein, the digital receiver 710 of polarization diversity can be realized 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, owing to have employed the polarization diversity receiver of embodiment 4, overcomes the shortcoming adopting traditional DDLMS method to carry out adaptive equalization.

Embodiment 6

The embodiment of the present invention additionally 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 eliminate the psk signal after making an uproar mutually;

Step 802: eliminate the coefficient residual quantity that the psk signal after making an uproar mutually and the described decision signal eliminating the psk signal after making an uproar mutually calculate described equalizer according to described;

Step 803: the coefficient upgrading described equalizer according to described coefficient residual quantity.

In the present embodiment, after step 801, the method also comprises:

Step 804: eliminate the psk signal after making an uproar mutually adjudicate described, eliminate the decision signal of the psk signal after making an uproar mutually described in obtaining.

Wherein, this step 804 specifically can eliminate the psk signal after making an uproar mutually adjudicate described according to the frequency difference reference value received, and described frequency difference reference value is prior information or is obtained by frequency difference estimation.

In step 801, specifically can according to described equalizer at nT _sthe output valve in moment and at (n-a) T _sthe output valve in moment calculates and eliminates the psk signal after making an uproar mutually.

In one embodiment, this eliminates the psk signal after making an uproar mutually for this equalizer is at nT _smoment and (n-a) T _sthe conjugate product of the output valve in moment.In another embodiment, this eliminates the psk signal after making an uproar mutually for this equalizer is at nT _s(n-a) T _sthe business of the output valve in moment.Wherein, described a be more than or equal to 1 natural number, and wherein, for nT _smoment by the phase value caused of making an uproar mutually, for (n-a) T _smoment is by the phase value caused of making an uproar mutually.

In step 802, specifically cost function can be utilized calculate the coefficient residual quantity of this equalizer.Wherein, r _nthe psk signal after making an uproar mutually is eliminated for described, for the described decision signal eliminating the psk signal after making an uproar mutually, E () represents expectation.Such as, can by minimizing this cost function, and use traditional gradient descent method to calculate the coefficient residual quantity of this equalizer.

The coefficient updating device of the principle of dealing with problems due to the present embodiment and embodiment 1 is similar, and therefore, its concrete enforcement with reference to the enforcement of the coefficient updating device of embodiment 1, can repeat part and repeat no more.

In the present embodiment, this adaptive equilibrium method is applicable to all mPSK (m >=2) signals, as BPSK, QPSK, 8PSK etc.

By the adaptive equilibrium method of the present embodiment, eliminate the coupling between phase recovery and equilibrium, overcome the shortcoming adopting traditional DDLMS method to carry out adaptive equalization.

More than describe the preferred embodiment of the present invention with reference to the accompanying drawings.Many feature and advantage of these execution modes are clearly according to this detailed description book, and therefore claims are intended to all these feature and advantage fallen in its true spirit and scope covering these execution modes.In addition, owing to those skilled in the art will find apparent that a lot of amendment and changing, therefore not embodiments of the present invention to be limited to precision architecture that is illustrated and that describe and operation, but can contain and fall into all suitable modifications within the scope of it and equivalent.

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, multiple step or method can with to store in memory and the software performed by suitable instruction execution system or firmware realize.Such as, if realized with hardware, the same in another embodiment, any one in the following technology can known altogether with this area or their combination realize: the discrete logic with the logic gates for realizing logic function to data-signal, there is the application-specific integrated circuit (ASIC) of suitable combinational logic gate circuit, programmable gate array (PGA), field programmable gate array (FPGA) etc.

To describe or frame can be understood in flow chart or in this any process otherwise described or method, represent and comprise one or more for realizing the module of the code of the executable instruction of the step in specific logical function or process, fragment or part, and the scope of the preferred embodiment of the present invention comprises other realization, wherein, can not according to order that is shown or that discuss, comprise according to involved function by the mode while of basic or by contrary order, carry out n-back test, this should those skilled in the art described by the present invention understand.

In flow charts represent or in this logic otherwise described and/or step, such as, the sequencing list of the executable instruction for realizing logic function can be considered to, may be embodied in any computer-readable medium, for instruction execution system, device or equipment (as computer based system, comprise the system of processor or other can from instruction execution system, device or equipment instruction fetch and perform the system of instruction) use, or to use in conjunction with these instruction execution systems, device or equipment.With regard to this specification, " computer-readable medium " can be anyly can to comprise, store, communicate, propagate or transmission procedure 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 such as but be not limited to electronics, magnetic, optical, electrical magnetic, infrared or semiconductor system, device, equipment or propagation medium.The example more specifically (non-exhaustive list) of computer-readable medium 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 suitable media that can print described program thereon, because can such as by carrying out optical scanner to paper or other media, then carry out editing, decipher or carry out process with other suitable method if desired and electronically obtain described program, be then stored in computer storage.

Above-mentioned explanatory note and accompanying drawing show various different feature of the present invention.Should be appreciated that those of ordinary skill in the art describe and each step illustrative and process in the accompanying drawings above can preparing suitable computer code to realize.It is also understood that above-described various terminal, computer, server, network etc. can be any types, and described computer code can be prepared according to disclosure and realize the present invention to utilize described device.

Particular implementation 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 in other circumstances.In fact, also there is 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 " for ... device " to quote be all the explaination that device in order to describe key element and claim adds function, and specifically do not use arbitrarily " for ... device " the key element quoted do not wish to be understood to that device adds the element of function, even if this claim includes the word of " device ".

Although illustrate and describe the present invention for certain preferred embodiments or multiple execution mode, obviously, those skilled in the art are reading and can expect the modification that is equal to and modified example when understanding specification and accompanying drawing.Especially for the various functions performed by above-mentioned key element (parts, assembly, device, form), unless otherwise noted, wish that (namely the term (comprising quoting of " device ") for describing these key elements corresponds to any key element of the concrete function performing described key element, function equivalent), even if this key element is structurally different from the open structure performing this function in illustrated illustrative embodiments of the present invention or multiple execution mode.In addition, although below in several illustrative execution mode only one or more describes specific features of the present invention, as required and from the viewpoint of to any given or embody rule is favourable, but this feature can be combined with one or more other features of other execution modes.

About the execution mode comprising above multiple embodiment, following remarks is also disclosed.

The coefficient updating device of remarks 1, a kind of equalizer, wherein, described updating device comprises:

First computing unit, it calculates this equalizer according to the output of equalizer and eliminates the phase shift keying after making an uproar mutually (PSK) signal;

Second computing unit, its according to described in eliminate the coefficient residual quantity that the psk signal after making an uproar mutually and this decision signal eliminating the psk signal after making an uproar mutually calculate described equalizer, so that equalizer is according to described coefficient residual quantity renewal equalizer coefficients.

Remarks 2, updating device according to remarks 1, wherein, described updating device also comprises:

Decision unit, it eliminates to described the judgement that psk signal after making an uproar mutually carries out psk signal, the decision signal of the psk signal after making an uproar mutually that has been eliminated.

Remarks 3, updating device according to remarks 2, wherein, described decision unit eliminates the psk signal after making an uproar mutually according to the frequency difference reference value that receives adjudicate described further, and described frequency difference reference value is prior information or is obtained by frequency difference estimation.

Remarks 4, updating device according to remarks 1, wherein, described first computing unit according to described equalizer at nT _sthe output valve in moment and at (n-a) T _sthe output valve in moment calculates and eliminates the psk signal after making an uproar mutually;

Wherein, the psk signal eliminated described in after making an uproar mutually is that described equalizer is at nT _smoment and (n-a) T _sthe conjugate product of the output valve in moment; Or, described in eliminate the psk signal after making an uproar mutually be that described equalizer is at nT _s(n-a) T _sthe business of the output valve in moment;

Wherein, described a be more than or equal to 1 natural number, and wherein, for nT _smoment by the phase value caused of making an uproar mutually, for (n-a) T _smoment is by the phase value caused of making an uproar mutually.

Remarks 5, updating device according to remarks 1, wherein, described second computing unit utilizes the coefficient residual quantity of equalizer described in following cost function calculation:

$c=E\left\{{|r_n-{\hat{r}}_n|}^2\right\}$

Wherein, r _nthe psk signal after making an uproar mutually is eliminated for described, for the described decision signal eliminating 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, and wherein, described receiver also comprises:

Equalizer coefficients updating device, it is 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 equalizer coefficients updating device described in any one of remarks 1-5.

Remarks 7, a kind of single polarized systems, wherein, described system comprises the receiver described in remarks 6.

Remarks 8, a kind of polarization diversity receiver, described polarization diversity receiver comprises: for recovering the first equalizer, the first offset estimation unit, first phase estimation unit, first decision device of h circuit-switched data, with the second equalizer for recovering v circuit-switched data, the second offset estimation unit, second phase estimation unit, the second decision device, wherein, described polarization diversity receiver also comprises:

First equalizer coefficients updating device, it is for calculating the coefficient residual quantity of described first equalizer, so that described first equalizer upgrades its coefficient according to the coefficient residual quantity of described first equalizer;

Second equalizer coefficients updating device, it is for calculating the coefficient residual quantity of described second equalizer, so that described second equalizer upgrades its coefficient according to the coefficient residual quantity of described second equalizer;

Wherein, described first equalizer coefficients updating device and described second equalizer coefficients updating device are realized by the equalizer coefficients updating device described in any one of remarks 1-5.

Remarks 9, a kind of polarisation multiplex system, wherein, described system comprises the polarization diversity receiver described in 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 eliminate the psk signal after making an uproar mutually;

The coefficient residual quantity that the psk signal after making an uproar mutually and the described decision signal eliminating the psk signal after making an uproar mutually calculate described equalizer is eliminated according to described;

The coefficient of described equalizer is upgraded according to described coefficient residual quantity.

Remarks 11, method according to remarks 10, wherein, described method also comprises:

Eliminate the psk signal after making an uproar mutually adjudicate described, described in obtaining, eliminate the decision signal of the psk signal after making an uproar mutually.

Remarks 12, method according to remarks 11, wherein, eliminate the psk signal after making an uproar mutually adjudicate described, comprising:

Eliminate the psk signal after making an uproar mutually according to the frequency difference reference value received adjudicate described, described frequency difference reference value is prior information or is obtained by frequency difference estimation.

Remarks 13, method according to remarks 10, wherein, calculate described equalizer according to the output of equalizer and eliminate the psk signal after making an uproar mutually, comprising:

According to described equalizer at nT _sthe output valve in moment and at (n-a) T _sthe output valve in moment calculates and eliminates the psk signal after making an uproar mutually;

Wherein, the psk signal eliminated described in after making an uproar mutually is that this equalizer is at nT _smoment and (n-a) T _sthe conjugate product of the output valve in moment; Or, described in eliminate the psk signal after making an uproar mutually for this equalizer at nT _s(n-a) T _sthe business of the output valve in moment;

Wherein, described a be more than or equal to 1 natural number, and wherein, for nT _smoment by the phase value caused of making an uproar mutually, for (n-a) T _smoment is by the phase value caused of making an uproar mutually.

Remarks 14, method according to remarks 10, wherein, calculate the coefficient residual quantity of described equalizer, comprising:

Utilize the coefficient residual quantity of equalizer described in following cost function calculation:

Wherein, r _nthe psk signal after making an uproar mutually is eliminated for described, for the described decision signal eliminating the psk signal after making an uproar mutually, E () represents expectation.

Remarks 15, a kind of computer-readable program, wherein when performing this program in the equalizer at coherent optical heterodyne communicatio, this program makes computer in described equalizer, perform method described in remarks 10-14.

Remarks 16, a kind of storage medium storing computer-readable program, wherein this computer-readable program makes computer in the equalizer of coherent optical heterodyne communicatio, perform method described in remarks 10-14.

Claims (8)

1. a coefficient updating device for equalizer, wherein, described updating device comprises:

First computing unit, its according to equalizer at nT _sthe output valve in moment and at (n-a) T _sthe output valve in moment calculates this equalizer and eliminates the phase shift keying after making an uproar mutually (PSK) signal; Wherein, the psk signal eliminated described in after making an uproar mutually is that described equalizer is at nT _smoment and (n-a) T _sthe conjugate product of the output valve in moment; Or, described in eliminate the psk signal after making an uproar mutually be that described equalizer is at nT _s(n-a) T _sthe business of the output valve in moment; Described a be more than or equal to 1 natural number, and wherein, for nT _smoment by the phase value caused of making an uproar mutually, for (n-a) T _smoment is by the phase value caused of making an uproar mutually;

Second computing unit, its according to described in eliminate the coefficient residual quantity that the psk signal after making an uproar mutually and this decision signal eliminating the psk signal after making an uproar mutually calculate described equalizer so that equalizer is according to described coefficient residual quantity renewal equalizer coefficients,

Wherein, described second computing unit utilizes the coefficient residual quantity of equalizer described in following cost function calculation:

$c=E\left\{\right|r_n-{\hat{r}}_n{|}^2\}$

Wherein, r _nthe psk signal after making an uproar mutually is eliminated for described, for the described decision signal eliminating the psk signal after making an uproar mutually, E () represents expectation,

Work as r _n=y _ny _n-1 ^*time, described coefficient residual quantity Δ w _nfor:

Wherein, x _nand x _n-1represent nT _s(n-1) T _sthe signal that reception arrives, T _sfor symbol period, n=0,1,2 ..., w _nrepresent nT _sthe equalizer coefficients in moment, y _nand y _n-1represent nT _s(n-1) T _sthe output of moment equalizer, () ^*represent conjugation, or

Work as r _n=y _n/ y _n-1time, described coefficient residual quantity Δ w _nfor:

Wherein, x _nand x _n-1represent nT _s(n-1) T _sthe signal that reception arrives, T _sfor symbol period, n=0,1,2 ..., w _nrepresent nT _sthe equalizer coefficients in moment, y _nand y _n-1represent nT _s(n-1) T _sthe output of moment equalizer, () ^*represent conjugation.

2. updating device according to claim 1, wherein, described updating device also comprises:

Decision unit, it eliminates to described the judgement that psk signal after making an uproar mutually carries out psk signal, 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 eliminates the psk signal after making an uproar mutually according to the frequency difference reference value that receives adjudicate described further, and described frequency difference reference value is prior information or is obtained by frequency difference estimation.

4. a receiver, described receiver comprises: equalizer, frequency difference estimation unit, phase estimation unit and decision device, and wherein, described receiver also comprises:

Equalizer coefficients updating device, it is 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 equalizer coefficients updating device described in any one of claim 1-3.

5. a single polarized systems, wherein, described system comprises receiver according to claim 4.

6. a polarization diversity receiver, described polarization diversity receiver comprises: for recovering the first equalizer, the first offset estimation unit, first phase estimation unit, first decision device of h circuit-switched data, with the second equalizer for recovering v circuit-switched data, the second offset estimation unit, second phase estimation unit, the second decision device, wherein, described polarization diversity receiver also comprises:

First equalizer coefficients updating device, it is for calculating the coefficient residual quantity of described first equalizer, so that described first equalizer upgrades its coefficient according to the coefficient residual quantity of described first equalizer;

Second equalizer coefficients updating device, it is for calculating the coefficient residual quantity of described second equalizer, so that described second equalizer upgrades its coefficient according to the coefficient residual quantity of described second equalizer;

Wherein, described first equalizer coefficients updating device and described second equalizer coefficients updating device are realized by the equalizer coefficients updating device described in any one of claim 1-3.

7. a polarisation multiplex system, wherein, described system comprises polarization diversity receiver according to claim 6.

8. an adaptive equilibrium method for psk signal, wherein, described method comprises:

According to equalizer at nT _sthe output valve in moment and at (n-a) T _sthe output valve in moment calculates this equalizer and eliminates the phase shift keying after making an uproar mutually (PSK) signal; Wherein, the psk signal eliminated described in after making an uproar mutually is that described equalizer is at nT _smoment and (n-a) T _sthe conjugate product of the output valve in moment; Or, described in eliminate the psk signal after making an uproar mutually be that described equalizer is at nT _s(n-a) T _sthe business of the output valve in moment; Described a be more than or equal to 1 natural number, and wherein, for nT _smoment by the phase value caused of making an uproar mutually, for (n-a) T _smoment is by the phase value caused of making an uproar mutually;

The coefficient residual quantity that the psk signal after making an uproar mutually and the described decision signal eliminating the psk signal after making an uproar mutually calculate described equalizer is eliminated according to described;

The coefficient of described equalizer is upgraded according to described coefficient residual quantity,

Wherein, the coefficient residual quantity of described equalizer is obtained by following cost function calculation:

$c=E\left\{\right|r_n-{\hat{r}}_n{|}^2\}$

Wherein, r _nthe psk signal after making an uproar mutually is eliminated for described, for the described decision signal eliminating the psk signal after making an uproar mutually, E () represents expectation,

Work as r _n=y _ny _n-1 ^*time, described coefficient residual quantity Δ w _nfor:

Wherein, x _nand x _n-1represent nT _s(n-1) T _sthe signal that reception arrives, T _sfor symbol period, n=0,1,2 ..., w _nrepresent nT _sthe equalizer coefficients in moment, y _nand y _n-1represent nT _s(n-1) T _sthe output of moment equalizer, () ^*represent conjugation, or

Work as r _n=y _n/ y _n-1time, described coefficient residual quantity Δ w _nfor:

Wherein, x _nand x _n-1represent nT _s(n-1) T _sthe signal that reception arrives, T _sfor symbol period, n=0,1,2 ..., w _nrepresent nT _sthe equalizer coefficients in moment, y _nand y _n-1represent nT _s(n-1) T _sthe output of moment equalizer, () ^*represent conjugation.