CN103109481B - Compensation of nonlinearity method, device and receiving system - Google Patents

Abstract

This and brightly belong to the communications field, especially provide a kind of compensation of nonlinearity method, Apparatus and system, the method comprises: calculate input signal R respectively _xand R _ymodulus value square, obtain | R _x| ²with | R _y| ²; According to R _x, R _y, | R _x| ²with | R _y| ²carry out filter factor calculating, obtain first-order filtering coefficient W _xyand W _yx; To W _xyand W _yxcarry out filtering, obtain filtered first-order filtering coefficient W ' _xywith W ' _yx; To input signal R _xand R _ycarry out delay process, obtain and W ' _xywith W ' _yxsynchronous signal R _xtand R _yt, then based on W ' _xywith W ' _yxto R _xtand R _ytcarry out filtering, finally exported R ' _xwith R ' _y.It is good that technical scheme of the present invention has signal quality, increases the advantage of the OSNR surplus of system.

Description

Compensation of nonlinearity method, device and receiving system

Technical field

The present invention relates to the communications field, particularly relate to a kind of compensation of nonlinearity method, device and receiving system.

Background technology

With seeing the day by day perfect of industrial chain, palarization multiplexing transmission system will be widely used in the high-speed optical transmission system in future.Digital Signal Processing (Digitalsignalprocess, DSP) development of technology greatly improves the chromatic dispersion (Chromadispersion of system, and polarization mode dispersion (Polarizationmodedispersion CD), PMD) tolerance limit, the principal element of restriction palarization multiplexing transmission system performance is the nonlinear tolerance of link at present.

In order to improve the nonlinear tolerance of system, prior art provides a kind of non-linear compensation method improving mission nonlinear tolerance limit, and as shown in Figure 1, X, Y road signal, through carrier phase recovery, obtains phase recovery output signal R to the flow process of the method _xinand R _yin, obtain the signal S after adjudicating respectively through judgement _xinand S _yin, then according to expression formula 1.1,1.2 and R _xin, R _yinwith the signal S after judgement _xin, S _yinobtain first-order filtering coefficient W _xyinand W _yxin.

$W_{\mathrm{xyin}}=\frac{R_{\mathrm{xin}}-S_{\mathrm{xin}}}{S_{\mathrm{yin}}}---1.1$

$W_{\mathrm{yxin}}=\frac{R_{\mathrm{yin}}-S_{\mathrm{yin}}}{S_{\mathrm{xin}}}---1.2$

Then, to filter factor W _xyinand W _yxincarry out filtering (namely the sliding window wherein in Fig. 1 is on average the one of filtering) and obtain filtered first-order filtering coefficient W ' _xyinwith W ' _yxin, to R _xin, R _yincarry out delay process, make itself and W ' _xyinwith W ' _yxinafter synchronous, then carry out filtering, obtain final output

R′ _xin＝R _xin-W′ _xyR _yin1.3

R′ _yin＝R _yin-W′ _yxR _xin1.4

The nonlinear compensation effect schematic diagram of the signal adopting said method finally to export as shown in Figure 2, wherein planisphere is split up into four cloud clusters, wherein, the periphery of cloud cluster is the signal that carrier phase recovery unit exports, frequency deviation and skew are eliminated, but also do not carry out nonlinear compensation, signal quality is poor; The middle part of cloud cluster is the signal after nonlinear compensation, has better signal quality.

Conventionally provided technical scheme, finds to there is following technical problem in prior art:

The technical scheme that prior art provides must eliminate carrier wave frequency deviation and difference by carrier phase recovery unit, signal can be adjudicated, but decision error can cause the decline of its performance, especially at low Optical Signal To Noise Ratio (Opticalsignaltonoiseratio, OSNR) time, decision error increases, and performance can sharply decline, and affects signal quality.

Summary of the invention

Object of the present invention provides a kind of compensation of nonlinearity method, and the method being intended to solve prior art is large to the decision error caused by signal decision, hydraulic performance decline, the problem that signal quality is low.

The embodiment of the present invention provides a kind of compensation of nonlinearity method, and described method comprises:

Calculate input signal R respectively _xand R _ymodulus value square, obtain | R _x| ²with | R _y| ²; Wherein, R _xbe specially the signal of telecommunication corresponding to X polarization state light signals in polarisation-multiplexed signal, R _ybe specially the signal of telecommunication corresponding to Y polarization state light signals in polarisation-multiplexed signal, X polarization state light signals and Y polarization state light signals are a pair mutually orthogonal light signals;

According to R _x, R _y, | R _x| ²with | R _y| ²carry out filter factor calculating, obtain first-order filtering coefficient W _xyand W _yx;

To W _xyand W _yxcarry out filtering, obtain filtered first-order filtering coefficient W ' _xywith W ' _yx;

To input signal R _xand R _ycarry out delay process respectively, obtain and W ' _xywith W ' _yxsignal R synchronous respectively _xtand R _yt, then based on W ' _xywith W ' _yx, to R _xtand R _ytcarry out filtering, finally exported R ' _xwith R ' _y.

The embodiment of the present invention also provides a kind of compensation of nonlinearity unit, and described unit comprises:

Mould squaring module, for calculating input signal R respectively _xand R _ymodulus value square, obtain | R _x| ²with | R _y| ²; Wherein, R _xbe specially the signal of telecommunication corresponding to X polarization state light signals in polarisation-multiplexed signal, R _ybe specially the signal of telecommunication corresponding to Y polarization state light signals in polarisation-multiplexed signal, X polarization state light signals and Y polarization state light signals are a pair mutually orthogonal light signals;

Filter factor computing module, for according to R _x, R _y, | R _x| ²with | R _y| ²carry out filter factor calculating, obtain first-order filtering coefficient W _xyand W _yx;

First-order filtering module, for W _xyand W _yxcarry out filtering, obtain filtered first-order filtering coefficient W ' _xywith W ' _yx;

Time delay module, for input signal R _xand R _ycarry out delay process respectively, obtain and W ' _xywith W ' _yxsignal R synchronous respectively _xtand R _yt;

Filtration module, for based on W ' _xywith W ' _yx, to R _xtand R _ytcarry out filtering, finally exported R ' _xwith R ' _y.

The embodiment of the present invention also provides a kind of receiving system, described receiving system is positioned at the receiving terminal of palarization multiplexing transmission system, for the palarization multiplexing light signal that the transmitting terminal receiving palarization multiplexing transmission system sends, described receiving system comprises above-mentioned nonlinear compensating device.

The embodiment of the present invention also provides a kind of receiving system, described receiving system is positioned at the receiving terminal of palarization multiplexing transmission system, for the palarization multiplexing light signal that the transmitting terminal receiving palarization multiplexing transmission system sends, described receiving system comprises two above-mentioned nonlinear compensating devices, and described receiving system also comprises further: chromatic dispersion CD compensating module, clock recovery module, polarization mode dispersion PMD compensating module, carrier phase recovery module and decoder; wherein, described palarization multiplexing light signal converts digital signal to after treatment in described receiving system, described CD compensating module carries out CD compensation to described digital signal and outputs to described clock recovering module, described clock recovery module carries out clock recovery to the signal exported through described CD compensating module and outputs to described PMD compensating module, described PMD compensating module carries out PMD compensation to the signal that first described clock recovers module output and outputs to first described nonlinear compensating device, first described nonlinear compensating device carries out nonlinear compensation to the signal that described PMD compensating module exports and outputs to described carrier phase recovery module, described carrier phase recovery module carries out carrier phase recovery to the signal that first described nonlinear compensating device exports and outputs to second described nonlinear compensating device, second described nonlinear compensating device carries out nonlinear compensation to the signal that described carrier phase recovery module exports and outputs to decoder, described decoder carries out decoding process to the signal that second described nonlinear compensating device exports and exports decode results.

The embodiment of the present invention also provides a kind of receiving system, described receiving system is positioned at the receiving terminal of palarization multiplexing transmission system, for the palarization multiplexing light signal that the transmitting terminal receiving palarization multiplexing transmission system sends, described receiving system comprises two above-mentioned nonlinear compensating devices, and described device also comprises further: chromatic dispersion CD compensating module, clock recovery module, polarization mode dispersion PMD compensating module, carrier phase recovery module, maximum-likelihood sequence estimation module and decoder; wherein, described palarization multiplexing light signal converts digital signal to after treatment in described receiving system, described CD compensating module carries out CD compensation to described digital signal and outputs to described clock recovering module, described clock recovery module carries out clock recovery to the signal exported through described CD compensating module and outputs to described PMD compensating module, described PMD compensating module carries out PMD compensation to the signal that first described clock recovers module output and outputs to first described nonlinear compensating device, first nonlinear compensating device carries out nonlinear compensation to the signal that described PMD compensating module exports and outputs to described carrier phase recovery module, described carrier phase recovery module carries out carrier phase recovery to the signal that described nonlinear compensating device exports and outputs to second described nonlinear compensating device, second described nonlinear compensating device processes the signal that described carrier phase recovery module exports and outputs to described maximum-likelihood sequence estimation module, described maximum-likelihood sequence estimation module is carried out maximum-likelihood sequence estimation process to the signal that second described nonlinear compensating device exports and outputs to decoder, described decoder carries out decoding process to the signal that described maximum-likelihood sequence estimation module exports and exports decode results.

The present invention compared with prior art, beneficial effect is: what the present invention calculated modulus value square replaces judgement of the prior art, large with the decision error solved caused by judgement, hydraulic performance decline, the problem that signal quality is low, so method provided by the invention has the advantage improving signal quality.

Accompanying drawing explanation

A kind of non-linear compensation method flow chart improving mission nonlinear that Fig. 1 provides for prior art;

The nonlinear compensation effect schematic diagram of the signal that the method that Fig. 2 provides for employing prior art exports;

A kind of compensation of nonlinearity method flow diagram that Fig. 3 provides for the embodiment of the present invention;

The structure chart of a kind of nonlinear compensating device that Fig. 4 provides for one embodiment of the invention;

Fig. 5 is for the compensation effect figure of the final output signal of the present invention of PDM-QPSK system displaying;

Fig. 6 is the compensation effect figure showing final output signal of the present invention for PDM-16QAM system;

The structure chart of a kind of nonlinear compensating device that Fig. 7 provides for further embodiment of this invention;

First structure chart of the receiving system that Fig. 8 provides for the embodiment of the present invention;

Second structure chart of the receiving system that Fig. 9 provides for the embodiment of the present invention;

3rd structure chart of the receiving system that Figure 10 provides for the embodiment of the present invention;

4th structure chart of the receiving system that Figure 11 provides for the embodiment of the present invention;

5th structure chart of the receiving system that Figure 12 provides for the embodiment of the present invention.

Embodiment

The invention provides a kind of compensation of nonlinearity method, the scene that realizes of the present invention is specifically as follows: method provided by the invention completes in the digital signal processor of the receiving end device of palarization multiplexing transmission system, the signal of the method process is X, the signal of Y road input (wherein, the signal of X road input corresponds to X polarization state light signals, the signal of Y road input corresponds to Y polarization state light signals, X polarization state light signals and Y polarization state light signals are the light signals that in palarization multiplexing light signal, a pair polarization state is mutually orthogonal, this palarization multiplexing light signal produced by the dispensing device of palarization multiplexing transmission system), for convenience of description, here called after: R _x, R _y.Palarization multiplexing light signal is after receiving terminal is by process such as coherent receptions, convert digital signal to, and then with digital signal processor, this digital signal is processed to recover the data that palarization multiplexing light signal carries, wherein, above-mentioned data signal processor specifically can comprise following module, CD compensation, clock recovery, PMD compensation, carrier phase recovery and decoder; Wherein, CD compensating module may be used for carrying out CD compensation to signal, clock recovery module may be used for carrying out clock recovery process to signal, PMD compensating module is used for carrying out PMD compensation to signal, carrier phase recovery module is used for carrying out carrier phase recovery to signal, and decoder is used for carrying out decoding process to signal.Nonlinear linear compensation method provided by the invention, as shown in Figure 3, the method comprises the steps: its flow process

S31, respectively calculating input signal R _xand R _ymodulus value square, obtain | R _x| ²with | R _y| ²;

S32, according to R _x, R _y, | R _x| ²with | R _y| ²carry out filter factor calculating, obtain first-order filtering coefficient W _xyand W _yx;

Wherein, filter factor calculation expression is specifically as follows:

$W_{\mathrm{xy}}=({\left|R_x\right|}^2-P_x)R_x{R}_y^{*}---1.5$

$W_{\mathrm{yx}}=({\left|R_y\right|}^2-P_y)R_y{R}_x^{*}---1.6$

Wherein, asterisk (*) representative gets complex conjugate, P _xand P _yr respectively _xdesired value, the R of modulus value square _ythe desired value of modulus value square.In one embodiment, the following two kinds mode can be had to obtain R _xdesired value, the R of modulus value square _ythe desired value of modulus value square: (1), calculate R _xthe average of modulus value square, and the R that will calculate _xthe average of modulus value square is as R _xthe desired value of modulus value square, calculates R _ythe average of modulus value square, and the R that will calculate _ythe average of modulus value square is as R _ythe desired value of modulus value square; (2), R is calculated _xmodulus value square and R _ymodulus value square and average, using the average that calculates as R _xdesired value, the R of modulus value square _ythe desired value of modulus value square.The specific embodiment of the invention does not limit to above-mentioned P _x, P _ythe acquisition methods of value.In addition, this P _x, P _yvalue can arrange accordingly according to different systems, such as: if the modulation system that the transmitting terminal of palarization multiplexing transmission system adopts is when being non-amplitude modulation(PAM) mode (such as, BPSK, QPSK, 8PSK), P _x, P _yvalue all only have one, can respectively by calculating R _xthe average of modulus value square and R _ythe average of modulus value square obtains; If when the modulation system that the transmitting terminal of palarization multiplexing transmission system adopts is amplitude modulation(PAM) mode (such as, 16QAM, 32QAM, 64QAM), P _x, P _yall there is multiple value, in amplitude modulation(PAM) mode, have N (N>=2) to plant amplitude range, P _x, P _yjust respectively there is N kind value (P _x1, P _x2..., P _xN; P _y1, P _y2..., P _yN).Calculate i-th respectively (i=1,2 ..., N) plant R corresponding to amplitude range _x, R _ythe average of modulus value square, obtain P _xt, P _yt.When above-mentioned formula application, if R _x, R _ycorresponding to i-th kind of amplitude range, correspondingly, P _x, P _yn kind is respectively had correspondingly to get P _xt, P _yt.

In one embodiment, above-mentioned filter factor calculation expression can also be other modes, is specially:

$W_{\mathrm{xy}}=C_0(C_1{\left|R_x\right|}^2-1)R_x{R}_y^{*}---\mathrm{1.7.1}$

$W_{\mathrm{yx}}=C_0(C_1{\left|R_y\right|}^2-1)R_y{R}_x^{*}---\mathrm{1.7.2}$

Or $W_{\mathrm{xy}}=\frac{C_0(C_1{\left|R_x\right|}^2-1)R_x}{R_y}---\mathrm{1.8.1}$

$W_{\mathrm{yx}}=\frac{C_0(C_1{\left|R_y\right|}^2-1)R_y}{R_x}---\mathrm{1.8.2}$

Wherein, C ₀dynamic gene, C ₁power normalization coefficient, wherein C ₁be specifically as follows: as R _xaverage power normalization, then C ₁get 1, as there is no normalization, then C ₁be averaged the inverse of power.

S33, to W _xyand W _yxcarry out filtering, obtain filtered first-order filtering coefficient W ' _xywith W ' _yx;

It should be noted that, to W _xyand W _yxthe processing mode of filtering specifically can adopt W _xyand W _yxcarry out filtering (can be average for sliding window, also can be other filtering) process respectively, certainly can also to W _xyand W _yxcarry out filtering simultaneously, during filtering process simultaneously, W ' _xywith W ' _yxreal part of symbol contrary, the value of real part can be respectively specifically: (real (Wxy)-real (Wyx))/2 and-(real (Wxy)-real (Wyx))/2, W ' _xywith W ' _yxthe symbol of imaginary part identical, imaginary part can be: (imag (Wxy)+imag (Wyx))/2; Wherein real (.) and imag (.) represents real part and the imaginary part of signal respectively.

S34, to input signal R _xand R _ycarry out delay process, obtain and W ' _xywith W ' _yxsynchronous signal R _xtand R _yt, then based on W ' _xywith W ' _yx, to R _xtand R _ytcarry out filtering and finally exported R ' _xwith R ' _y.

It should be noted that, the filtering mode of S34 is specifically as follows: 2*2 first-order filtering;

The formula of above-mentioned 2*2 first-order filtering is specifically as follows:

R′ _x＝R _xt-W′ _xyR _yt1.9

R′ _y＝R _yt-W′ _yxR _xt1.10

Certainly in another embodiment, the formula of above-mentioned 2*2 first-order filtering also can adopt other formula, such as:

R′ _x＝R _xt+W′ _xyR _yt1.11

R′ _y＝R _yt+W′ _yxR _xt1.12

In addition, the W ' in formula 1.9-1.12 _xyr _y, W ' _yxr _ysymbol only depends on W ' _xywith W ' _yxsymbol choose.

The compensation effect figure of final output signal with the inventive method illustrates effect of the present invention below.

Fig. 5 is for the compensation effect figure of the final output signal of the present invention of PDM-QPSK system displaying, wherein, annular region 51 is the planispheres before compensating based on this nonlinear compensation scheme, annular region 52 is the planispheres after nonlinear compensation, it should be noted that, above-mentioned annular region 52 is positioned at annular region 51, and annular region 52 and annular region 51 are just superimposed upon in a width figure by the scope that the present invention conveniently shows annular region, and Fig. 6 and Fig. 5 is similar.As can be seen from planisphere, the planisphere after compensation converges to a narrower ring, has better signal quality, so it has better gain and robustness.In addition, because method provided by the invention directly carries out modulus value square process to signal, decision process (slicing) is not adopted, so do not have decision error to affect the quality of signal, so its performance is high, signal quality is good, and especially when low OSNR, effect is more obvious.

Fig. 6 is the compensation effect figure showing final output signal of the present invention for PDM-16QAM system.Distinguishingly with PMD-QPSK system be, the signal constellation (in digital modulation) figure of 16QAM modulation is positioned on three rings, wherein, annular region 61,62,63 is the planispheres before compensating based on this nonlinear compensation scheme, and annular region 64,65,66 is the planispheres after nonlinear compensation, it should be noted that, annular region 64 is positioned at annular region 61, annular region 65 is positioned at annular region 62, and annular region 63 is positioned at annular region 66.As can be seen from planisphere, the planisphere after compensation converges to three narrower rings, has better signal quality.

In addition, it should be noted that, the desired value P of modulus value square _x, P _ythree different desired values all can be got to reduce error (also can get identical desired value, performance can decline a little) to the constellation point on different rings.

The present invention also provides a kind of nonlinear compensating device, and this device concrete structure as shown in Figure 7, specifically comprises:

Mould squaring module 71, for calculating input signal R respectively _xand R _ymodulus value square, obtain | R _x| ²with | R _y| ²;

It should be noted that, above-mentioned R _xand R _yit can be the signal of X, Y road input.

Filter factor computing module 72, for according to R _x, R _y, | R _x| ²with | R _y| ²carry out filter factor calculating, obtain first-order filtering coefficient W _xyand W _yx;

First-order filtering module 73, for W _xyand W _yxcarry out filtering, obtain filtered first-order filtering coefficient W ' _xywith W ' _yx;

Time delay module 74, for input signal R _xand R _ycarry out delay process, obtain and W ' _xywith W ' _yxsynchronous signal R _xtand R _yt;

Filtration module 75, for based on W ' _xywith W ' _yxto R _xtand R _ytcarry out filtering, finally exported R ' _xwith R ' _y.

Optionally, the computing formula of filter factor computing module 72 specifically comprises:

$W_{\mathrm{xy}}=({\left|R_x\right|}^2-P_x)R_x{R}_y^{*},$ $W_{\mathrm{yx}}=({\left|R_y\right|}^2-P_y)R_y{R}_x^{*};$

Or $W_{\mathrm{xy}}=C_0(C_1{\left|R_x\right|}^2-1)R_x{R}_y^{*},$ $W_{\mathrm{yx}}=C_0(C_1{\left|R_y\right|}^2-1)R_y{R}_x^{*};$

Or $W_{\mathrm{xy}}=\frac{C_0(C_1{\left|R_x\right|}^2-1)R_x}{R_y},$ $W_{\mathrm{yx}}=\frac{C_0(C_1{\left|R_y\right|}^2-1)R_y}{R_x};$

Wherein, * representative gets complex conjugate, P _xand P _yr respectively _xdesired value, the R of modulus value square _ythe desired value of modulus value square, C ₀dynamic gene, C ₁it is power normalization coefficient; Wherein P _xand P _ythe mode of specifically choosing of value see the explanation in embodiment of the method, can repeat no more here.

Optionally, the filtering of filtration module 75 is specifically as follows 2*2 first-order filtering, and 2*2 first-order filtering formula is specifically as follows:

R′ _x＝R _xt-W′ _xyR _yt、R′ _y＝R _yt-W′ _yxR _xt；

Or R ' _x=R _xt+ W ' _xyr _yt, R ' _y=R _yt+ W ' _yxr _xt

In addition, it should be noted that, the W ' in formula 1.9-1.12 _xyr _ysymbol only depends on W ' _xywith W ' _yxsymbol choose.

A kind of concrete structure of the nonlinear compensating device that Fig. 4 provides for the embodiment of the present invention, in the figure " || ²" represent square process signal being input to this module being carried out to modulus value, represent adder, represent multiplier, in this structure, the process of other parts see the associated description in embodiment above, can repeat no more herein.

Nonlinear compensating device provided by the invention exports the signal after compensating after carrying out nonlinear compensation to input signal, known according to the planisphere (as Fig. 5,6) of the signal after compensation, signal after compensation has good signal quality, has the advantage of the OSNR surplus of increase system.

The present invention also provides a kind of receiving system, and it is positioned at the receiving terminal of palarization multiplexing transmission system, the palarization multiplexing light signal that the transmitting terminal for receiving this palarization multiplexing transmission system sends, and this receiving system comprises above-mentioned nonlinear compensating device.The palarization multiplexing light signal that this receiving system is received is by converting analog electrical signal to after coherent reception process, and then convert analog electrical signal to digital signal by analog-to-digital conversion, then adopt Digital Signal Processing process above-mentioned digital signal thus recover the data that palarization multiplexing light signal carries.Wherein, the process that the nonlinear compensating device in the present invention carries out is exactly a link in above-mentioned Digital Signal Processing, and after its process, the quality of signal is improved, thus makes the data recovered have the less error rate.

It should be noted that, receiving system provided by the invention does not limit nonlinear compensating device at intrasystem particular location, the particular location of nonlinear compensating device is described below by specific embodiment, and this nonlinear compensating device can be positioned at the digital signal processor of described receiving system.

For convenience of description, below specific embodiment by nonlinear compensating device referred to as NLC (Nonlinearcompensation).

The invention provides an embodiment, the present embodiment provides a kind of receiving system, and this receiving system comprises the nonlinear compensating device described in embodiment above, its concrete structure as shown in Figure 8, wherein, before NLC can be positioned at carrier phase recovery module.The receiving system that the present embodiment provides, except comprising NLC, also specifically can comprise: chromatic dispersion CD compensating module, for carrying out CD compensation to signal; Clock recovery module, for carrying out clock recovery process to signal; PMD compensating module, for the PMD of compensating signal; Carrier phase recovery module, for the carrier phase of restoring signal; Decoder, carries out decoding process for carrying out to signal.Wherein, the annexation of above-mentioned each module as shown in Figure 8, the output of CD compensating module is the input of clock recovery module, the output of clock recovery module is the input of PMD compensating module, the output of PMD compensating module is the input of NLC, the output of NLC is the input of carrier phase recovery module, and the output of carrier phase recovery module is the input of decoder.

The system that the present embodiment provides, owing to have employed NLC, so it has the advantage improving signal quality, namely has the advantage of the OSNR surplus of increase system.

The invention provides another embodiment, the present embodiment provides a kind of receiving system, this receiving system comprises the nonlinear compensating device described in embodiment above, its concrete structure as shown in Figure 9, be from the different of receiving system of structure shown in Fig. 8, after carrier phase recovery is adjusted in the position of NLC, after namely NLC can be positioned at carrier phase recovery.In the present embodiment, the annexation of modules as shown in Figure 9, the output of CD compensating module is the input of clock recovery module, the output of clock recovery module is the input of PMD compensating module, the output of PMD compensating module is the input of carrier phase recovery module, the output of carrier phase recovery module is the input of NLC, and the output of NLC is the input of decoder.

The invention provides another embodiment, the present embodiment provides a kind of receiving system, this receiving system comprises two nonlinear compensating devices described in embodiment above, its concrete structure as shown in Figure 10, be from the different of receiving system of structure shown in Fig. 8, a NLC is also add, after being namely positioned at carrier phase and respectively have a NLC before after carrier phase recovery.In the present embodiment, the annexation of modules as shown in Figure 10, the output of CD compensating module is the input of clock recovery module, the output of clock recovery module is the input of PMD compensating module, the output of PMD compensating module is the input of a NLC, the output of the one NLC is the input of carrier phase recovery module, and the output of carrier phase recovery module is the input of the 2nd NLC, and the output of the 2nd NLC is the input of decoder.

The invention provides next embodiment, the present embodiment provides a kind of receiving system, this receiving system comprises two nonlinear compensating devices described in embodiment above, its concrete structure as shown in figure 11, be from the different of receiving system of structure shown in Figure 10, can by NLC and maximum-likelihood sequence estimation (Maximumlikelihoodsequenceestimation, MLSE) module combines, namely, on the basis of the receiving system of structure shown in Figure 10, after a rear NLC, MLSE is increased.In the present embodiment, the annexation of modules as shown in figure 11, the output of CD compensating module is the input of clock recovery module, the output of clock recovery module is the input of PMD compensating module, the output of PMD compensating module is the input of a NLC, and the output of a NLC is the input of carrier phase recovery module, and the output of carrier phase recovery module is the input of the 2nd NLC, the output of the 2nd NLC is the input of MLSE module, and the output of MLSE module is the input of decoder.Wherein, MLSE module carries out maximum-likelihood sequence estimation process to the signal that a NLC exports, this process can compensating signal experience linear damage, nonlinear impairments, device narrow-band filtering damage etc.

An embodiment after the invention provides, the present embodiment provides a kind of receiving system, this receiving system comprises the nonlinear compensating device described in embodiment above, its concrete structure as shown in figure 12, be from the different of receiving system of structure shown in Fig. 8, the receiving system in the present embodiment does not have carrier phase recovery module.Signal reception can be realized, to improve the non-linear of CPEfree system when CPEfree (carrierfree phase recovery unit).In the present embodiment, as shown in figure 12, the output of CD compensating module is the input of clock recovery module to the annexation of modules, and the output of clock recovery module is the input of PMD compensating module, the output of PMD compensating module is the input of NLC, and the output of NLC is the input of decoder.

Modules in structure shown in Fig. 8-12 all can be positioned at digital signal processor.In said apparatus and system embodiment, included modules or unit just carry out dividing according to function logic, but are not limited to above-mentioned division, as long as can realize corresponding function; In addition, the concrete title of each functional module, also just for the ease of mutual differentiation, is not limited to protection scope of the present invention.The chromatic dispersion compensating module described in embodiment above, clock recovery module, polarization mode dispersion (PMD) compensation module, carrier phase recovery module, maximum-likelihood sequence estimation module and decoder all can adopt prior art to realize, therefore repeat no more in this application.

It will be understood by those skilled in the art that in the compensation of nonlinearity method that the embodiment of the present invention provides, its all or part of step can have been come by the hardware that program command is relevant.Such as can be come by computer runs programs.This program can be stored in read/write memory medium, such as, and random asccess memory, disk, CD etc.

Claims (14)

1. a compensation of nonlinearity method, is characterized in that, described method comprises:

Calculate input signal R respectively _xand R _ymodulus value square, obtain | R _x| ²with | R _y| ²; Wherein, R _xbe specially the signal of telecommunication corresponding to X polarization state light signals in palarization multiplexing light signal, R _ybe specially the signal of telecommunication corresponding to Y polarization state light signals in polarisation-multiplexed signal, X polarization state light signals and Y polarization state light signals are a pair mutually orthogonal light signals;

According to R _x, R _y, | R _x| ²with | R _y| ²carry out filter factor calculating, obtain first-order filtering coefficient W _xyand W _yx;

To W _xyand W _yxcarry out filtering, obtain filtered first-order filtering coefficient W ' _xywith W ' _yx;

To input signal R _xand R _ycarry out delay process respectively, obtain and W ' _xywith W ' _yxsignal R synchronous respectively _xtand R _yt, then based on W ' _xywith W ' _yx, to R _xtand R _ytcarry out filtering, finally exported R ' _xwith R ' _y.

2. method according to claim 1, is characterized in that, described filter factor calculates and specifically comprises:

$W_{\mathrm{xy}}=({\left|R_x\right|}^2-P_x)R_x{R}_y^{*},W_{\mathrm{yx}}=({\left|R_y\right|}^2-P_y)R_y{R}_x^{*};$

Or $W_{\mathrm{xy}}=C_0(C_1{\left|R_x\right|}^2-1)R_x{R}_y^{*},W_{\mathrm{yx}}=C_0(C_1{\left|R_y\right|}^2-1)R_y{R}_x^{*};$

Or $W_{\mathrm{xy}}=\frac{C_0(C_1{\left|R_x\right|}^2-1)R_x}{R_y},W_{\mathrm{yx}}=\frac{C_0(C_1{\left|R_y\right|}^2-1)R_y}{R_x};$

Wherein, * representative gets complex conjugate, P _xr _xthe desired value of modulus value square, P _yr _ythe desired value of modulus value square, C ₀dynamic gene, C ₁it is power normalization coefficient.

3. method according to claim 2, is characterized in that, described P _xbe specially R _xthe average of modulus value square, P _ybe specially R _ythe average of modulus value square; Or,

Described P _xand P _yall be specially R _xmodulus value square and R _ymodulus value square and average.

4. according to the method in claim 2 or 3, it is characterized in that, if described palarization multiplexing light signal is specially the am signals of palarization multiplexing, and when described am signals has a N kind amplitude range, described P _xand P _yall there is N kind value, based on the R corresponding to i-th kind of amplitude range _x, R _y, obtain P _xand P _ycorresponding to the value of i-th kind of amplitude range, wherein, N be more than or equal to 2 integer, i=1,2 ... N.

5. method according to claim 1, is characterized in that, described based on W ' _xywith W ' _yx, to R _xtand R _ytcarry out filtering and finally exported R ' _xwith R ' _ybe specially:

R′ _x＝R _xt-W′ _xyR _yt、R′ _y＝R _yt-W′ _yxR _xt；

Or R ' _x=R _xt+ W ' _xyr _yt, R ' _y=R _yt+ W ' _yxr _xt.

6. a nonlinear compensating device, is characterized in that, described device comprises:

Mould squaring module, for calculating input signal R respectively _xand R _ymodulus value square, obtain | R _x| ²with | R _y| ²; Wherein, R _xbe specially the signal of telecommunication corresponding to X polarization state light signals in polarisation-multiplexed signal, R _ybe specially the signal of telecommunication corresponding to Y polarization state light signals in polarisation-multiplexed signal, X polarization state light signals and Y polarization state light signals are a pair mutually orthogonal light signals;

Filter factor computing module, for according to R _x, R _y, | R _x| ²with | R _y| ²carry out filter factor calculating, obtain first-order filtering coefficient W _xyand W _yx;

First-order filtering module, for W _xyand W _yxcarry out filtering, obtain filtered first-order filtering coefficient W ' _xywith W ' _yx;

Time delay module, for input signal R _xand R _ycarry out delay process respectively, obtain and W ' _xywith W ' _yxsignal R synchronous respectively _xtand R _yt;

Filtration module, for based on W ' _xywith W ' _yx, to R _xtand R _ytcarry out filtering, finally exported R ' _xwith R ' _y.

7. device according to claim 6, is characterized in that, the formula that described filter factor computing module carries out filter factor calculating specifically comprises:

$W_{\mathrm{xy}}=({\left|R_x\right|}^2-P_x)R_x{R}_y^{*},W_{\mathrm{yx}}=({\left|R_y\right|}^2-P_y)R_y{R}_x^{*};$

Or $W_{\mathrm{xy}}=C_0(C_1{\left|R_x\right|}^2-1)R_x{R}_y^{*},W_{\mathrm{yx}}=C_0(C_1{\left|R_y\right|}^2-1)R_y{R}_x^{*};$

Or $W_{\mathrm{xy}}=\frac{C_0(C_1{\left|R_x\right|}^2-1)R_x}{R_y},W_{\mathrm{yx}}=\frac{C_0(C_1{\left|R_y\right|}^2-1)R_y}{R_x};$

Wherein, * representative gets complex conjugate, P _xr _xthe desired value of modulus value square, P _yr _ythe desired value of modulus value square, C ₀dynamic gene, C ₁it is power normalization coefficient.

8. the device according to claim 6 or 7, is characterized in that, described filtration module is specifically for W ' _xywith W ' _yxand R _xtand R _ytcarry out filtering and finally exported R ' _xwith R ' _y, the formula of this filtering is specially:

R′ _x＝R _xt-W′ _xyR _yt、R′ _y＝R _yt-W′ _yxR _xt；

Or R ' _x=R _xt+ W ' _xyr _yt, R ' _y=R _yt+ W ' _yxr _xt.

9. a receiving system, it is characterized in that, described receiving system is positioned at the receiving terminal of palarization multiplexing transmission system, for receive palarization multiplexing transmission system transmitting terminal send palarization multiplexing light signal, described receiving system comprise as arbitrary in claim 6-8 as described in nonlinear compensating device.

10. receiving system according to claim 9, is characterized in that, described receiving system also comprises further: chromatic dispersion CD compensating module, clock recovery module, polarization mode dispersion PMD compensating module, carrier phase recovery module and decoder, wherein, described palarization multiplexing light signal converts digital signal to after treatment in described receiving system, described CD compensating module carries out CD compensation to described digital signal and outputs to described clock recovering module, described clock recovery module carries out clock recovery to the signal exported through described CD compensating module and outputs to described PMD compensating module, described PMD compensating module carries out PMD compensation to the signal that described clock recovers module output and outputs to described carrier phase recovery module, described carrier phase recovery module carries out carrier phase recovery to the signal that described PMD compensating module exports and outputs to described nonlinear compensating device, described nonlinear compensating device carries out nonlinear compensation to the signal that described carrier phase recovery module exports and outputs to decoder, described decoder carries out decoding process to the signal that described nonlinear compensating device exports and exports decode results.

11. receiving systems according to claim 9, is characterized in that, described receiving system also comprises further: chromatic dispersion CD compensating module, clock recovery module, polarization mode dispersion PMD compensating module, carrier phase recovery module and decoder, wherein, described palarization multiplexing light signal converts digital signal to after treatment in described receiving system, described CD compensating module carries out CD compensation to described digital signal and outputs to described clock recovering module, described clock recovery module carries out clock recovery to the signal exported through described CD compensating module and outputs to described PMD compensating module, described PMD compensating module carries out PMD compensation to the signal that described clock recovers module output and outputs to described nonlinear compensating device, described nonlinear compensating device carries out nonlinear compensation to the signal that described PMD compensating module exports and outputs to described carrier phase recovery module, described carrier phase recovery module carries out carrier phase recovery to the signal that described nonlinear compensating device exports and outputs to described decoder, described decoder carries out decoding process to the signal that described decoder exports and exports decode results.

12. receiving systems according to claim 9, is characterized in that, described receiving system also comprises further: chromatic dispersion CD compensating module, clock recovery module, polarization mode dispersion PMD compensating module and decoder, wherein, described palarization multiplexing light signal converts digital signal to after treatment in described receiving system, described CD compensating module carries out CD compensation to described digital signal and outputs to described clock recovering module, described clock recovery module carries out clock recovery to the signal exported through described CD compensating module and outputs to described PMD compensating module, described PMD compensating module carries out PMD compensation to the signal that described clock recovers module output and outputs to described nonlinear compensating device, described nonlinear compensating device carries out nonlinear compensation to the signal that described PMD compensating module exports and outputs to decoder, described decoder carries out decoding process to the signal that described nonlinear compensating device exports and exports decode results.

13. 1 kinds of receiving systems, it is characterized in that, described receiving system is positioned at the receiving terminal of palarization multiplexing transmission system, for the palarization multiplexing light signal that the transmitting terminal receiving palarization multiplexing transmission system sends, described receiving system comprise two as arbitrary in claim 6-8 as described in nonlinear compensating device, described receiving system also comprises further: chromatic dispersion CD compensating module, clock recovery module, polarization mode dispersion PMD compensating module, carrier phase recovery module and decoder; wherein, described palarization multiplexing light signal converts digital signal to after treatment in described receiving system, described CD compensating module carries out CD compensation to described digital signal and outputs to described clock recovering module, described clock recovery module carries out clock recovery to the signal exported through described CD compensating module and outputs to described PMD compensating module, described PMD compensating module carries out PMD compensation to the signal that first described clock recovers module output and outputs to first described nonlinear compensating device, first described nonlinear compensating device carries out nonlinear compensation to the signal that described PMD compensating module exports and outputs to described carrier phase recovery module, described carrier phase recovery module carries out carrier phase recovery to the signal that first described nonlinear compensating device exports and outputs to second described nonlinear compensating device, second described nonlinear compensating device carries out nonlinear compensation to the signal that described carrier phase recovery module exports and outputs to decoder, described decoder carries out decoding process to the signal that second described nonlinear compensating device exports and exports decode results.

14. 1 kinds of receiving systems, it is characterized in that, described receiving system is positioned at the receiving terminal of palarization multiplexing transmission system, for the palarization multiplexing light signal that the transmitting terminal receiving palarization multiplexing transmission system sends, described receiving system comprise two as arbitrary in claim 6-8 as described in nonlinear compensating device, described device also comprises further: chromatic dispersion CD compensating module, clock recovery module, polarization mode dispersion PMD compensating module, carrier phase recovery module, maximum-likelihood sequence estimation module and decoder; wherein, described palarization multiplexing light signal converts digital signal to after treatment in described receiving system, described CD compensating module carries out CD compensation to described digital signal and outputs to described clock recovering module, described clock recovery module carries out clock recovery to the signal exported through described CD compensating module and outputs to described PMD compensating module, described PMD compensating module carries out PMD compensation to the signal that first described clock recovers module output and outputs to first described nonlinear compensating device, first nonlinear compensating device carries out nonlinear compensation to the signal that described PMD compensating module exports and outputs to described carrier phase recovery module, described carrier phase recovery module carries out carrier phase recovery to the signal that described nonlinear compensating device exports and outputs to second described nonlinear compensating device, second described nonlinear compensating device processes the signal that described carrier phase recovery module exports and outputs to described maximum-likelihood sequence estimation module, described maximum-likelihood sequence estimation module is carried out maximum-likelihood sequence estimation process to the signal that second described nonlinear compensating device exports and outputs to decoder, described decoder carries out decoding process to the signal that described maximum-likelihood sequence estimation module exports and exports decode results.