CN105262707A - Self-adaptive equalization method and device of high-speed optical transmission system - Google Patents

Abstract

The invention relates to a self-adaptive equalization method and device of a high-speed optical transmission system. The method comprises the following steps: configuring a tap initializing coefficient of a self-adaptive equalizer; driving the self-adaptive equalizer to carry out self-adaptive convergence according to the tap initializing coefficient; and when the self-adaptive equalizer can converge, carrying out initialization control on a convergence coefficient output by the self-adaptive equalizer to locate the convergence coefficient at a central position of a tap of the self-adaptive equalizer. According to the self-adaptive equalization method provided by the invention, the system is controlled at the central position of the tap initially to effectively utilize the tap coefficient.

Description

Method and device for self-adaptive equalization of high-speed optical transmission system

Technical Field

The present invention relates to the field of communications technologies, and in particular, to a method and an apparatus for adaptive equalization in a high-speed optical transmission system.

Background

Currently, in a high-speed optical transmission system, a coherent receiver needs to compensate for various impairments in an optical channel, such as Polarization Mode Dispersion (PMD), Chromatic Dispersion (CD), and Polarization Dependent Loss (PDL).

As shown in fig. 1, the coherent receiver mainly includes modules of dispersion compensation, clock recovery, adaptive equalization, and frequency offset estimation and phase offset estimation (wherein H, V represents each input). The dispersion compensation function is to compensate chromatic dispersion in a channel, the clock recovery function is to solve the clock synchronization problem between a transmitter and a receiver, the adaptive equalization function is to compensate PMD, residual CD, PDL and polarization mode demultiplexing, and the frequency offset estimation and phase offset estimation functions are to correct frequency and phase offset existing between a transmitting laser and a local oscillator laser.

The adaptive equalizer plays a role in starting and stopping in a coherent receiver, and the adaptive equalizer adaptively tracks the characteristics of a channel through a Digital Signal Processing (DSP) technology to achieve the effect of compensating various damages in the channel. The adaptive equalizer is composed of several Finite Impulse Response (FIR) filters and a blind equalization algorithm (e.g., Constant Modulus Algorithm (CMA)) unit for generating coefficients required for FIR computation.

In the initial working stage of the system, because the blind equalization algorithm needs a certain time to train out the channel characteristics, the center of the initial coefficient of the FIR configuration of the general adaptive equalizer is 1, and the others are all 0. Such disadvantages are: on the one hand, the range of the available tap coefficients of the FIR is not fully utilized. On the other hand, according to such an initialization configuration, after the adaptive equalizer converges, according to the characteristics of the blind equalization algorithm, the tap center position of the coefficient may concentrate a part of the main energy, and another part of the main energy may concentrate on the left side or the right side of the tap center position of the coefficient, so that the energy of the coefficient of the adaptive equalizer may deviate from the tap center position, and the adaptive equalizer may not converge to a better working state.

Disclosure of Invention

The main purpose of the present invention is to provide a method and apparatus for adaptive equalization in a high-speed optical transmission system, which aims to improve the effective utilization of tap coefficients and to initially control the coefficients at the tap center position.

In order to achieve the above object, the present invention provides a method for adaptive equalization in a high-speed optical transmission system, including:

configuring a tap initialization coefficient of the adaptive equalizer;

the adaptive equalizer is subjected to adaptive convergence according to the tap initialization coefficient;

when the self-adaptive equalizer can be converged, the convergence coefficient output by the self-adaptive equalizer is initialized and controlled, so that the convergence coefficient is positioned in the center of a tap of the self-adaptive equalizer.

Preferably, the step of adaptively converging the adaptive equalizer according to the tap initialization coefficient further comprises:

reconfiguring the tap initialization coefficients when the adaptive equalizer fails to converge;

the adaptive equalizer is subjected to adaptive convergence again according to the reconfigured tap initialization coefficient; until the adaptive equalizer can converge.

Preferably, when the adaptive equalizer can converge, the step of performing initial control on the convergence coefficient output by the adaptive equalizer so that the convergence coefficient is located at the tap center position of the adaptive equalizer includes:

when the self-adaptive equalizer can be converged, acquiring a convergence coefficient output by the self-adaptive equalizer;

estimating the size of the system DGD according to the convergence coefficient;

converting the minimum number of taps N required for resisting the DGD;

and configuring the convergence coefficient according to the minimum tap number N, so that the convergence coefficient is positioned in the tap center position of the self-adaptive equalizer.

Preferably, the step of estimating the magnitude of the system DGD according to the convergence coefficient comprises:

carrying out PMD detection according to the convergence coefficient;

and obtaining the DGD size according to the PMD detection result.

Preferably, the method further comprises:

and performing initial orthogonality conversion on the convergence coefficient after the initialization control.

Preferably, the step of performing initial orthogonality conversion on the convergence coefficient after initialization control includes:

if the X polarization state and the Y polarization state of the convergence coefficient are detected to be converged together or converged simultaneously, carrying out coefficient orthogonality conversion on any one path of polarization state and then assigning the polarization state to the other path of polarization state;

if the X polarization state of the convergence coefficient is detected to be converged first, performing coefficient orthogonality conversion on the X polarization state and assigning the X polarization state to a Y polarization state;

and if the Y polarization state of the convergence coefficient is detected to be converged first, performing coefficient orthogonality conversion on the Y polarization state and assigning the Y polarization state to the X polarization state.

The embodiment of the present invention further provides a device for adaptive equalization of a high-speed optical transmission system, including:

an initial configuration module, which is used for configuring the tap initialization coefficient of the adaptive equalizer;

a convergence module, configured to perform adaptive convergence on the adaptive equalizer according to the tap initialization coefficient;

and the initialization control module is used for performing initialization control on the convergence coefficient output by the adaptive equalizer when the adaptive equalizer can converge so as to enable the convergence coefficient to be positioned at the center of a tap of the adaptive equalizer.

Preferably, the initial configuration module is further configured to reconfigure the tap initialization coefficients when the adaptive equalizer cannot converge;

the initialization control module is further used for enabling the self-adaptive equalizer to perform self-adaptive convergence again according to the reconfigured tap initialization coefficient; until the adaptive equalizer can converge.

Preferably, the initialization control module includes:

the acquisition unit is used for acquiring a convergence coefficient output by the adaptive equalizer when the adaptive equalizer can converge;

the estimation unit is used for estimating the size of the system DGD according to the convergence coefficient;

a conversion unit for converting the minimum number of taps N required to resist the DGD;

and the configuration unit is used for configuring the convergence coefficient according to the minimum tap number N so that the convergence coefficient is positioned at the tap center position of the self-adaptive equalizer.

Preferably, the estimating unit is further configured to perform PMD detection according to the convergence coefficient; and obtaining the DGD size according to the PMD detection result.

Preferably, the apparatus further comprises:

and the conversion module is used for carrying out initial orthogonality conversion on the convergence coefficient after the initialization control.

Preferably, the conversion module is further configured to, when it is detected that the X polarization state and the Y polarization state of the convergence coefficient converge together or converge at the same time, perform coefficient orthogonality conversion on any one path of polarization state and assign the result to the other path of polarization state; when the convergence coefficient X polarization state is detected to be converged first, performing coefficient orthogonality conversion on the X polarization state and assigning the X polarization state to a Y polarization state; and when the convergence coefficient Y polarization state is detected to be converged first, performing coefficient orthogonality conversion on the Y polarization state and assigning the Y polarization state to the X polarization state.

The embodiment of the invention provides a method and a device for self-adaptive equalization of a high-speed optical transmission system, which are characterized in that a tap initialization coefficient of a self-adaptive equalizer is configured; the adaptive equalizer is subjected to adaptive convergence according to the tap initialization coefficient; when the adaptive equalizer can converge, the convergence coefficient output by the adaptive equalizer is initialized and controlled, so that the convergence coefficient is positioned in the center of a tap of the adaptive equalizer, and the effective utilization of the tap coefficient is realized.

Drawings

Fig. 1 is a schematic structural diagram of a coherent receiver of a conventional high-speed optical transmission system;

FIG. 2 is a flow chart illustrating an embodiment of a method for adaptive equalization in a high speed optical transmission system according to the present invention;

FIG. 3 is a diagram illustrating an adaptive equalizer according to an embodiment of the present invention;

FIG. 4 is a diagram illustrating an example of an adaptive equalizer coefficient initialization process according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of an example of an adaptive equalizer coefficient initialization process in conjunction with PMD detection in an embodiment of the present invention;

FIG. 6 is a flow chart illustrating a method for adaptive equalization in a high speed optical transmission system according to another embodiment of the present invention;

FIG. 7 is a diagram illustrating an example of an initialization process of adaptive equalizer coefficients based on initial orthogonality according to an embodiment of the present invention;

FIG. 8 is a functional block diagram of an embodiment of an apparatus for adaptive equalization in a high speed optical transmission system according to the present invention;

FIG. 9 is a schematic structural diagram of an initialization control module in an embodiment of an apparatus for adaptive equalization in a high-speed optical transmission system according to the present invention;

fig. 10 is a functional block diagram of another embodiment of the apparatus for adaptive equalization in a high-speed optical transmission system according to the present invention.

In order to make the technical solution of the present invention clearer and clearer, the following detailed description is made with reference to the accompanying drawings.

Detailed Description

It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The solution of the embodiment of the invention is mainly as follows: initializing coefficients by configuring taps of the adaptive equalizer; the adaptive equalizer is subjected to adaptive convergence according to the tap initialization coefficient; when the adaptive equalizer can converge, the convergence coefficient output by the adaptive equalizer is initialized and controlled to be positioned at the center of the tap of the adaptive equalizer, and the effective utilization of the tap coefficient is realized.

As shown in fig. 2, an embodiment of the present invention provides a method for adaptive equalization in a high-speed optical transmission system, including:

step S101, configuring a tap initialization coefficient of the adaptive equalizer;

the hardware operating environment of the method relates to an adaptive equalizer in a high-speed optical transmission system, improves the effective utilization of the tap coefficient of the adaptive equalizer based on the control of the initialization of the coefficient of the adaptive equalizer, and controls the coefficient to be in the tap center position in the initialization.

Specifically, a specific schematic diagram of the adaptive equalizer of the present embodiment is shown in fig. 3. The coefficients required by the FIR filter are calculated by an adaptive blind equalization algorithm (for example, CMA algorithm) and filtered. And simultaneously, the coefficient initialization control module performs initialization control on the coefficient obtained by the blind equalization algorithm.

The FIR filter may be implemented in a time domain or a frequency domain, and the coefficient update may also be implemented in the time domain or the frequency domain.

To describe the method of this embodiment, the mathematical expression of the FIR filter in the adaptive equalizer is given as follows:

$x\left(n\right)=\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{c}_{\mathrm{xh}}\left(m\right)\×h(n-m)+\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{c}_{\mathrm{xv}}\left(m\right)\×v(n-m);$

$y\left(n\right)=\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{c}_{\mathrm{yh}}\left(m\right)\×h(n-m)+\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{c}_{\mathrm{yv}}\left(m\right)\×v(n-m);$

wherein M is the number of taps of the FIR filter. Coefficient c_xh(m)、c_xv(m)、c_yh(m) and c_yv(m) are generated by a blind equalization algorithm such as CMA. c. C_xh(m) denotes the coefficient of mapping of the input h onto the x polarization state, c_xv(m) refers to the coefficient of mapping of the output v onto the x polarization state, c_yh(m) denotes the coefficient of input h mapped onto the y polarization state, c_yv(m) refers to the coefficient that the output v maps onto the y polarization state.

The specific scheme of the embodiment is as follows:

firstly, in an initialization stage, the tap initialization coefficients of the adaptive equalizer are configured, and the coefficients are respectively set as:

c_xv(m)＝c_yh(m)＝0。

step S102, the adaptive equalizer is subjected to adaptive convergence according to the tap initialization coefficient;

step S103, judging whether the adaptive equalizer can be converged, and if so, entering step S104; if the convergence is not possible, the process proceeds to step S105;

the self-adaptive equalizer performs self-adaptive convergence according to the initialization coefficient, and the self-adaptive convergence is processed in two conditions: if the equalizer can be normally converged, the step S104 is entered; if the equalizer cannot converge normally, the process proceeds to step S105.

And step S104, when the self-adaptive equalizer can be converged, performing initialization control on the convergence coefficient output by the self-adaptive equalizer to enable the convergence coefficient to be positioned at the center of a tap of the self-adaptive equalizer.

When the self-adaptive equalizer can be converged, acquiring a convergence coefficient output by the self-adaptive equalizer; the magnitude of the system DGD (differential group delay between two polarizing films) is estimated from the convergence coefficient, wherein the magnitude of the DGD can be obtained from the result of PMD detection.

Then, converting the minimum tap number N required for resisting the DGD; and configuring the convergence coefficient according to the minimum tap number N, so that the convergence coefficient is positioned in the tap center position of the self-adaptive equalizer.

Step S105, when the adaptive equalizer can not converge, the tap initialization coefficient is reconfigured; entering step S106;

step S106, the adaptive equalizer is made to perform adaptive convergence again according to the reconfigured tap initialization coefficient; returning to step S103 until the adaptive equalizer can converge.

More specifically, if the equalizer cannot converge, the coefficients are set to:

${c_{\mathrm{xh}}}^{\′}\left(m\right)=\left\{\begin{array}{c}1,m=d1,d2\\ 0,\mathrm{otherwise}\end{array}\right.,{c_{\mathrm{yv}}}^{\′}\left(m\right)=\left\{\begin{array}{c}1,m=M-d2,M-d1\\ 0,\mathrm{otherwise}\end{array}\right.;$

c_xv'(m)＝c_yh'(m)＝0。

wherein,d2 and d1 have the value range of [1, M]Alternatively, otherwise means that m takes on other values.

Then, reconvergence is performed by the adaptive equalizer according to the reconfigured initialization coefficients.

If the equalizer can converge, the system DGD is estimated according to the convergence coefficient, and the minimum number of taps N required for resisting the DGD is calculated. And setting: d4-d3 is N, the mean of d4 and d3 is near the tap center, and the two satisfy the following relationship:

the coefficients are configured to:

${c_{\mathrm{xh}}}^{\′\′}\left(m\right)=\left\{\begin{array}{c}1,m=d3,d4\\ 0,\mathrm{otherwise}\end{array}\right.,{c_{\mathrm{yv}}}^{\′\′}\left(m\right)=\left\{\begin{array}{c}1,m=M-d4,M-d3\\ 0,\mathrm{otherwise}\end{array}\right.$

c_xv″(m)＝c_yh″(m)＝0。

in the embodiment, through the above scheme, the coefficients are initialized by configuring the taps of the adaptive equalizer; the adaptive equalizer is subjected to adaptive convergence according to the tap initialization coefficient; when the adaptive equalizer can converge, the convergence coefficient output by the adaptive equalizer is initialized and controlled to be positioned at the center of the tap of the adaptive equalizer, and the effective utilization of the tap coefficient is realized.

The scheme of the embodiment is explained in detail by the following specific examples:

example one, adaptive equalizer coefficient initialization procedure:

taking the adaptive equalizer FIR tap number as 11(m is 11), the following description is made with reference to fig. 4:

step 1, in an initialization stage, setting coefficients as:

$c_{\mathrm{xh}}\left(m\right)=\left\{\begin{array}{c}1,m=6\\ 0,m\≠6\end{array}\right.=,c_{\mathrm{yv}}\left(m\right)=c_{\mathrm{xh}}\left(m\right),$

c_xv(m)＝c_yh(m)＝0。

step 2, the self-adaptive equalizer performs self-adaptive convergence according to the initialization coefficient, and the self-adaptive convergence is processed by the following two conditions:

and 2.1, if the equalizer can normally converge, entering the step 3.

Step 2.2, if the equalizer cannot be converged and the function problem of the non-equalizer is eliminated, the system PMD size may be larger than the PMD size that can be borne by the half tap number of the adaptive equalizer, and then the coefficients may be set to be:

${c_{\mathrm{xh}}}^{\′}\left(m\right)=\left\{\begin{array}{c}1,m=\mathrm{2,10}\\ 0,\mathrm{otherwise}\end{array}\right.,{c_{\mathrm{yv}}}^{\′}\left(m\right)=\left\{\begin{array}{c}1,m=\mathrm{2,10}\\ 0,\mathrm{otherwise}\end{array}\right.$

c_xv'(m)＝c_yh'(m)＝0。

step 4 is entered.

And 3, estimating the DGD size of the system according to the convergence coefficient, and converting to obtain the minimum tap number 3 required for resisting the DGD under the assumption that the DGD size is 150ps and the data baud rate of the self-adaptive equalizer is 50G. Because a part of the main energy of the coefficient is concentrated at the position of tap sequence 6 and another part of the main energy is concentrated at the position of tap sequence 3 or 9 according to the configuration initialization manner described in step 1, the energy of the coefficient is biased to the left or the right, and the adaptive equalizer does not work in a good state. In order for the converged adaptive equalizer to work better, the coefficients are configured as:

${c_{\mathrm{xh}}}^{\′\′}\left(m\right)=\left\{\begin{array}{c}1,m=\mathrm{4,7}\\ 0,\mathrm{otherwise}\end{array}\right.,{c_{\mathrm{yv}}}^{\′\′}\left(m\right)=\left\{\begin{array}{c}1,m=\mathrm{5,8}\\ 0,\mathrm{otherwise}\end{array}\right.$

c_xv″(m)＝c_yh″(m)＝0。

and 4, re-converging the self-adaptive equalizer according to the reconfigured initialization coefficient.

Example two, adaptive equalizer coefficient initialization procedure in conjunction with PMD detection:

the present embodiment takes into account: the high-speed optical transmission system needs to monitor the operation state of the system, including the parameters such as the sizes of the CD and the DGD. DGD is an important parameter for characterizing the size of PMD, and is obtained by performing certain mathematical transformation on coefficients obtained by an adaptive blind algorithm. The result of PMD detection may be incorporated to control the adaptive equalizer coefficient initialization process during operation of the adaptive equalizer.

For convenience of description, the adaptive equalizer FIR tap number is set to 11(m is 11), and the following description is given with reference to fig. 5:

step 1, in an initialization stage, setting coefficients as:

$c_{\mathrm{xh}}\left(m\right)=\left\{\begin{array}{c}1,m=6\\ 0,m\≠6\end{array}\right.,c_{\mathrm{yv}}\left(m\right)=c_{\mathrm{xh}}\left(m\right),$

c_xv(m)＝c_yh(m)＝0。

step 2, the self-adaptive equalizer performs self-adaptive convergence according to the initialization coefficient, and the self-adaptive convergence is processed by the following two conditions:

and 2.1, if the equalizer can normally converge, entering the step 3.

Step 2.2, if the equalizer cannot be converged and the function problem of the non-equalizer is eliminated, the system PMD size may be larger than the PMD size that can be borne by the half tap number of the adaptive equalizer, and then the coefficients may be set to be:

${c_{\mathrm{xh}}}^{\′}\left(m\right)=\left\{\begin{array}{c}1,m=\mathrm{2,10}\\ 0,\mathrm{otherwise}\end{array}\right.,{c_{\mathrm{yv}}}^{\′}\left(m\right)=\left\{\begin{array}{c}1,m=\mathrm{2,10}\\ 0,\mathrm{otherwise}\end{array}\right.$

c_xv'(m)＝c_yh'(m)＝0。

step 4 is entered.

And 3, obtaining the DGD according to the PMD detection result, and converting to obtain the minimum tap number 4 required for resisting the DGD under the assumption that the DGD is 120ps and the data baud rate of the adaptive equalizer is 30G. Because a part of the main energy of the coefficient is concentrated at the position of tap sequence 6 and another part of the main energy is concentrated at the position of tap sequence 2 or 10 according to the configuration initialization manner described in step 1, the energy of the coefficient is biased to the left or the right, and the adaptive equalizer does not work in a good state. In order for the converged adaptive equalizer to work better, the coefficients are configured as:

${c_{\mathrm{xh}}}^{\text{\′\′}}\left(m\right)=\left\{\begin{array}{c}1,m=\mathrm{4,8}\\ 0,\mathrm{otherwise}\end{array}\right.,{c_{\mathrm{yv}}}^{\′\′}\left(m\right)=\left\{\begin{array}{c}1,m=\mathrm{4,8}\\ 0,\mathrm{otherwise}\end{array}\right.$

c_xv″(m)＝c_yh″(m)＝0。

and 4, re-converging the self-adaptive equalizer according to the reconfigured initialization coefficient.

As shown in fig. 6, another embodiment of the present invention provides a method for adaptive equalization in a high-speed optical transmission system, which, based on the embodiment shown in fig. 2, further includes, after the step S104:

in step S107, the convergence coefficient after the initialization control is subjected to initial orthogonality conversion.

The specific process is as follows:

if the X polarization state and the Y polarization state of the convergence coefficient are detected to be converged together or converged simultaneously, carrying out coefficient orthogonality conversion on any one path of polarization state and then assigning the polarization state to the other path of polarization state;

if the X polarization state of the convergence coefficient is detected to be converged first, performing coefficient orthogonality conversion on the X polarization state and assigning the X polarization state to a Y polarization state;

and if the Y polarization state of the convergence coefficient is detected to be converged first, performing coefficient orthogonality conversion on the Y polarization state and assigning the Y polarization state to the X polarization state.

The scheme of the embodiment is explained in detail by the following specific examples:

example three, adaptive equalizer coefficient initialization procedure based on initial orthogonality:

for convenience of description, the adaptive equalizer FIR tap number is set to 10(m is 10), and the following description is given with reference to fig. 7:

step 1, in an initialization stage, setting coefficients as:

$c_{\mathrm{xh}}\left(m\right)=\left\{\begin{array}{c}1,m=5\\ 0,m\≠5\end{array}\right.,c_{\mathrm{yv}}\left(m\right)=c_{\mathrm{xh}}\left(m\right),$

c_xv(m)＝c_yh(m)＝0。

step 2, the self-adaptive equalizer performs self-adaptive convergence according to the initialization coefficient, and the self-adaptive convergence is processed by the following two conditions:

and 2.1, if the equalizer can normally converge, entering the step 3.

Step 2.2, if the equalizer cannot be converged and the function problem of the non-equalizer is eliminated, the system PMD size may be larger than the PMD size that can be borne by the half tap number of the adaptive equalizer, and then the coefficients may be set to be:

${c_{\mathrm{xh}}}^{\′}\left(m\right)=\left\{\begin{array}{c}1,m=\mathrm{2,9}\\ 0,\mathrm{otherwise}\end{array}\right.,{c_{\mathrm{yv}}}^{\′}\left(m\right)=\left\{\begin{array}{c}1,m=\mathrm{2,9}\\ 0,\mathrm{otherwise}\end{array}\right.$

c_xv'(m)＝c_yh'(m)＝0。

step 4 is entered.

And 3, estimating the DGD size of the system according to the convergence coefficient, and converting to obtain the minimum tap number 2 required for resisting the DGD under the assumption that the DGD size is 120ps and the data baud rate of the self-adaptive equalizer is 40G. Because a part of the main energy of the coefficient is concentrated at the position of tap sequence 5 and another part of the main energy is concentrated at the position of tap sequence 3 or 7 according to the configuration initialization manner described in step 1, the energy of the coefficient is biased to the left or the right, and the adaptive equalizer does not work in a good state. In order for the converged adaptive equalizer to work better, the coefficients are configured as:

${c_{\mathrm{xh}}}^{\text{\′\′}}\left(m\right)=\left\{\begin{array}{c}1,m=4,7\\ 0,\mathrm{otherwise}\end{array}\right.,{c_{\mathrm{yv}}}^{\′\′}\left(m\right)=\left\{\begin{array}{c}1,m=\mathrm{4,7}\\ 0,\mathrm{otherwise}\end{array}\right.$

c_xv″(m)＝c_yh″(m)＝0。

and 4, re-converging the self-adaptive equalizer according to the reconfigured initialization coefficient.

And 5, performing coefficient initial orthogonality conversion so as to reduce the probability of convergence to the same polarization state of the initialized and controlled coefficients. The following cases are processed:

step 5.1, if the X polarization state and the Y polarization state are monitored to be converged together or converged simultaneously, carrying out coefficient orthogonality conversion on any one path of polarization state and then assigning a value to the other path of polarization state;

step 5.2, detecting that the X polarization state is converged, performing coefficient orthogonality conversion on the X polarization state, and assigning a value to the Y polarization state;

step 5.3, detecting that the Y polarization state is converged, performing coefficient orthogonality conversion on the Y polarization state, and assigning a value to the X polarization state;

taking the adjustment of the polarization state of Y as an example, the coefficient orthogonality conversion method is as follows:

c_yv(m)＝-c_xh ^*(M-m)、c_yh(m)＝c_xv ^*(M-M), wherein x is a conjugation operation.

In the embodiment, through the above scheme, the coefficients are initialized by configuring the taps of the adaptive equalizer; the adaptive equalizer is subjected to adaptive convergence according to the tap initialization coefficient; when the adaptive equalizer can converge, the convergence coefficient output by the adaptive equalizer is initialized and controlled to be positioned at the center of the tap of the adaptive equalizer, and the effective utilization of the tap coefficient is realized.

As shown in fig. 8, an embodiment of the present invention provides an apparatus for adaptive equalization in a high-speed optical transmission system, including: an initial configuration module 201, a convergence module 202, and an initialization control module 203, wherein:

an initial configuration module 201, configured to configure tap initialization coefficients of the adaptive equalizer;

a convergence module 202, configured to perform adaptive convergence on the adaptive equalizer according to the tap initialization coefficient;

and the initialization control module 203 is configured to perform initialization control on the convergence coefficient output by the adaptive equalizer when the adaptive equalizer can converge, so that the convergence coefficient is located at a tap center position of the adaptive equalizer.

Further, the initial configuration module 201 is further configured to reconfigure the tap initialization coefficients when the adaptive equalizer cannot converge;

the initialization control module 203 is further configured to make the adaptive equalizer perform adaptive convergence again according to the reconfigured tap initialization coefficient; until the adaptive equalizer can converge.

The present embodiment relates to an adaptive equalizer in a high-speed optical transmission system, which improves the effective utilization of the tap coefficients of the adaptive equalizer based on the control of the initialization of the coefficients of the adaptive equalizer, and controls the coefficients to the tap center position at the beginning.

Specifically, a specific schematic diagram of the adaptive equalizer of the present embodiment is shown in fig. 3. The coefficients required by the FIR filter are calculated by an adaptive blind equalization algorithm (for example, CMA algorithm) and filtered. And simultaneously, the coefficient initialization control module performs initialization control on the coefficient obtained by the blind equalization algorithm.

The FIR filter may be implemented in a time domain or a frequency domain, and the coefficient update may also be implemented in the time domain or the frequency domain.

To describe the scheme of this embodiment, the mathematical expression of the FIR filter in the adaptive equalizer is as follows:

$x\left(n\right)=\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{c}_{\mathrm{xh}}\left(m\right)\×h(n-m)+\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{c}_{\mathrm{xv}}\left(m\right)\×v(n-m);$

$y\left(n\right)=\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{c}_{\mathrm{yh}}\left(m\right)\×h(n-m)+\underset{m=0}{\overset{M}{\mathrm{\Σ}}}{c}_{\mathrm{yv}}\left(m\right)\×v(n-m);$

wherein M is the number of taps of the FIR filter. Coefficient c_xh(m)、c_xv(m)、c_yh(m) and c_yv(m) are generated by a blind equalization algorithm such as CMA. c. C_xh(m) denotes the coefficient of mapping of the input h onto the x polarization state, c_xv(m) refers to the coefficient of mapping of the output v onto the x polarization state, c_yh(m) denotes the coefficient of input h mapped onto the y polarization state, c_yv(m) refers to the coefficient that the output v maps onto the y polarization state.

The specific scheme of the embodiment is as follows:

firstly, in an initialization stage, the tap initialization coefficients of the adaptive equalizer are configured, and the coefficients are respectively set as:

c_xv(m)＝c_yh(m)＝0。

then, the adaptive equalizer performs adaptive convergence according to the initialized coefficient, and the adaptive convergence is processed in two cases:

when the self-adaptive equalizer can be converged, acquiring a convergence coefficient output by the self-adaptive equalizer; and estimating the system DGD according to the convergence coefficient, wherein the DGD can be obtained according to the PMD detection result.

Then, converting the minimum tap number N required for resisting the DGD; and configuring the convergence coefficient according to the minimum tap number N, so that the convergence coefficient is positioned in the tap center position of the self-adaptive equalizer.

If the equalizer cannot converge, reconfiguring the tap initialization coefficients; the adaptive equalizer is subjected to adaptive convergence again according to the reconfigured tap initialization coefficient; until the adaptive equalizer can converge.

More specifically, if the equalizer cannot converge, the coefficients are set to:

${c_{\mathrm{xh}}}^{\′}\left(m\right)=\left\{\begin{array}{c}1,m=d1,d2\\ 0,\mathrm{otherwise}\end{array}\right.,{c_{\mathrm{yv}}}^{\′}\left(m\right)=\left\{\begin{array}{c}1,m=M-d2,M-d1\\ 0,\mathrm{otherwise}\end{array}\right.;$

c_xv'(m)＝c_yh'(m)＝0。

wherein,d2 and d1 have the value range of [1, M]Alternatively, otherwise means that m takes on other values.

Then, reconvergence is performed by the adaptive equalizer according to the reconfigured initialization coefficients.

If the equalizer can converge, the system DGD is estimated according to the convergence coefficient, and the minimum number of taps N required for resisting the DGD is calculated. And setting: d4-d3 is N, the mean of d4 and d3 is near the tap center, and the two satisfy the following relationship:

the coefficients are configured to:

${c_{\mathrm{xh}}}^{\′\′}\left(m\right)=\left\{\begin{array}{c}1,m=d3,d4\\ 0,\mathrm{otherwise}\end{array}\right.,{c_{\mathrm{yv}}}^{\′\′}\left(m\right)=\left\{\begin{array}{c}1,m=M-d4,M-d3\\ 0,\mathrm{otherwise}\end{array}\right.$

c_xv″(m)＝c_yh″(m)＝0。

in the embodiment, through the above scheme, the coefficients are initialized by configuring the taps of the adaptive equalizer; the adaptive equalizer is subjected to adaptive convergence according to the tap initialization coefficient; when the adaptive equalizer can converge, the convergence coefficient output by the adaptive equalizer is initialized and controlled to be positioned at the center of the tap of the adaptive equalizer, and the effective utilization of the tap coefficient is realized.

In a specific implementation, as shown in fig. 9, the initialization control module 203 includes: an acquisition unit 2031, an estimation unit 2032, a scaling unit 2033, and a configuration unit 2034, wherein:

an obtaining unit 2031, configured to obtain a convergence coefficient output by the adaptive equalizer when the adaptive equalizer is capable of converging;

an estimating unit 2032, configured to estimate the system DGD size according to the convergence coefficient;

a conversion unit 2033 configured to convert the minimum number N of taps required to resist the DGD;

a configuring unit 2034, configured to configure the convergence coefficient according to the minimum tap number N, so that the convergence coefficient is located at a tap center position of the adaptive equalizer.

Further, the estimating unit 2032 is further configured to perform PMD detection according to the convergence coefficient; and obtaining the DGD size according to the PMD detection result.

For a specific example of the adaptive equalizer coefficient initialization process of this embodiment, please refer to the above method embodiment, which is not described herein again.

As shown in fig. 10, a second embodiment of the present invention provides an apparatus for adaptive equalization in a high-speed optical transmission system, which, based on the first embodiment shown in fig. 8, further includes:

a conversion module 204, configured to perform initial orthogonality conversion on the initialized and controlled convergence coefficient.

The specific process is as follows:

when the convergence coefficient is detected to converge together or simultaneously, carrying out coefficient orthogonality conversion on any one path of polarization state and then assigning the polarization state to the other path of polarization state; when the convergence coefficient X polarization state is detected to be converged first, performing coefficient orthogonality conversion on the X polarization state and assigning the X polarization state to a Y polarization state; and when the convergence coefficient Y polarization state is detected to be converged first, performing coefficient orthogonality conversion on the Y polarization state and assigning the Y polarization state to the X polarization state.

For a specific example of the adaptive equalizer coefficient initialization process of this embodiment, please refer to the above method embodiment, which is not described herein again.

The embodiment of the invention discloses a method and a device for self-adaptive equalization of a high-speed optical transmission system, which are characterized in that a tap initialization coefficient of a self-adaptive equalizer is configured; the adaptive equalizer is subjected to adaptive convergence according to the tap initialization coefficient; when the adaptive equalizer can converge, the convergence coefficient output by the adaptive equalizer is initialized and controlled to be positioned at the center of the tap of the adaptive equalizer, and the effective utilization of the tap coefficient is realized.

The above description is only for the preferred embodiment of the present invention and is not intended to limit the scope of the present invention, and all equivalent structures or flow transformations made by the present specification and drawings, or applied directly or indirectly to other related arts, are included in the scope of the present invention.

Claims (12)

1. A method for adaptive equalization in a high speed optical transmission system, comprising:

configuring a tap initialization coefficient of the adaptive equalizer;

the adaptive equalizer is subjected to adaptive convergence according to the tap initialization coefficient;

when the self-adaptive equalizer can be converged, the convergence coefficient output by the self-adaptive equalizer is initialized and controlled, so that the convergence coefficient is positioned in the center of a tap of the self-adaptive equalizer.

2. The method of claim 1, wherein said step of adaptively converging said adaptive equalizer based on tap initialization coefficients further comprises:

reconfiguring the tap initialization coefficients when the adaptive equalizer fails to converge;

the adaptive equalizer is subjected to adaptive convergence again according to the reconfigured tap initialization coefficient; until the adaptive equalizer can converge.

3. The method of claim 1, wherein when the adaptive equalizer can converge, initially controlling the convergence coefficient output by the adaptive equalizer such that the convergence coefficient is located at a tap center of the adaptive equalizer comprises:

when the self-adaptive equalizer can be converged, acquiring a convergence coefficient output by the self-adaptive equalizer;

estimating the DGD of the differential group delay of the system according to the convergence coefficient;

converting the minimum number of taps N required for resisting the DGD;

and configuring the convergence coefficient according to the minimum tap number N, so that the convergence coefficient is positioned in the tap center position of the self-adaptive equalizer.

4. The method of claim 1, wherein the step of estimating the magnitude of the system DGD based on the convergence factor comprises:

carrying out polarization film dispersion PMD detection according to the convergence coefficient;

and obtaining the DGD size according to the PMD detection result.

5. The method according to any one of claims 1-4, further comprising:

and performing initial orthogonality conversion on the convergence coefficient after the initialization control.

6. The method of claim 5, wherein the step of performing initial orthogonality conversion on the convergence coefficients after initialization control comprises:

if the X polarization state and the Y polarization state of the convergence coefficient are detected to be converged together or converged simultaneously, carrying out coefficient orthogonality conversion on any one path of polarization state and then assigning the polarization state to the other path of polarization state;

if the X polarization state of the convergence coefficient is detected to be converged first, performing coefficient orthogonality conversion on the X polarization state and assigning the X polarization state to a Y polarization state;

and if the Y polarization state of the convergence coefficient is detected to be converged first, performing coefficient orthogonality conversion on the Y polarization state and assigning the Y polarization state to the X polarization state.

7. An apparatus for adaptive equalization in a high speed optical transmission system, comprising:

an initial configuration module, which is used for configuring the tap initialization coefficient of the adaptive equalizer;

a convergence module, configured to perform adaptive convergence on the adaptive equalizer according to the tap initialization coefficient;

and the initialization control module is used for performing initialization control on the convergence coefficient output by the adaptive equalizer when the adaptive equalizer can converge so as to enable the convergence coefficient to be positioned at the center of a tap of the adaptive equalizer.

8. The apparatus of claim 7,

the initial configuration module is further configured to reconfigure the tap initialization coefficients when the adaptive equalizer is unable to converge;

the initialization control module is further used for enabling the self-adaptive equalizer to perform self-adaptive convergence again according to the reconfigured tap initialization coefficient; until the adaptive equalizer can converge.

9. The apparatus of claim 7, wherein the initialization control module comprises:

the acquisition unit is used for acquiring a convergence coefficient output by the adaptive equalizer when the adaptive equalizer can converge;

the estimation unit is used for estimating the size of the system DGD according to the convergence coefficient;

a conversion unit for converting the minimum number of taps N required to resist the DGD;

and the configuration unit is used for configuring the convergence coefficient according to the minimum tap number N so that the convergence coefficient is positioned at the tap center position of the self-adaptive equalizer.

10. The apparatus of claim 9,

the estimation unit is also used for carrying out PMD detection according to the convergence coefficient; and obtaining the DGD size according to the PMD detection result.

11. The apparatus of any one of claims 7-10, further comprising:

and the conversion module is used for carrying out initial orthogonality conversion on the convergence coefficient after the initialization control.

12. The apparatus of claim 11,

the conversion module is further configured to, when it is detected that the X polarization state and the Y polarization state of the convergence coefficient converge together or converge at the same time, perform coefficient orthogonality conversion on any one path of polarization state and assign a value to the other path of polarization state; when the convergence coefficient X polarization state is detected to be converged first, performing coefficient orthogonality conversion on the X polarization state and assigning the X polarization state to a Y polarization state; and when the convergence coefficient Y polarization state is detected to be converged first, performing coefficient orthogonality conversion on the Y polarization state and assigning the Y polarization state to the X polarization state.