CN106452593B - The construction method and device and nonlinear noise suppressing method and system of filter - Google Patents

Abstract

The invention discloses a filter construction method and device, and a nonlinear noise suppression method and system. The present invention is based on a Gaussian noise model (Gaussian noise model, GN), using the first-order perturbation theory to obtain the non-linear damage between channels caused by XPM in the optical fiber transmission system, and constructing and channel spacing according to the influence of channels at different frequencies on the central channel The channel compensation filter based on carrier correlation adaptation related to the transmission sequence of the interference channel can dynamically allocate the power of different channels in the fiber channel model, and compensate the nonlinear noise according to the principle of the digital reverse transmission algorithm. It is necessary to calculate the nonlinear influence of all interference channels on the central channel, so the complexity of the compensation DBP algorithm can be effectively reduced.

Description

Filter construction method and device, and nonlinear noise suppression method and system

technical field

The present invention relates to the field of optical transmission technology in the field of communication technology, in particular to a method for constructing a channel compensation filter based on carrier correlation adaptation, and a method and system for suppressing non-linear noise between channels.

Background technique

In recent years, with the rapid development of high-definition, 3D, ultra-high-definition and other video technologies, the explosive growth of business demand for big data, cloud computing, and cloud storage has put forward higher requirements for the transmission distance and capacity of optical fiber systems. Therefore, ultra-high-speed long-distance optical fiber Transmission has become one of the domestic research hotspots, and people have been moving towards the goal of faster speed and longer distance.

Every breakthrough in transmission capacity and transmission distance always comes from the adoption of new technologies and the overcoming of key problems, but it also introduces new problems, which limit the further development of optical fiber transmission systems. From the early intermodal dispersion and loss limitation, to the later group velocity dispersion limitation, to today's optical fiber nonlinearity and dispersion comprehensive limitation, with the increase of transmission rate and the increase of transmission distance, the problems faced by the optical fiber transmission system are also constantly change.

In large-capacity long-distance optical fiber transmission systems, multi-span cascading, multi-channel coexistence, and increased fiber interaction length make the accumulation of ASE noise, dispersion and nonlinear effects more serious, limiting large-capacity long-distance optical transmission systems performance. In recent years, many researchers at home and abroad have studied the dispersion and nonlinear effects and compensation methods in large-capacity long-distance optical transmission systems, mainly focusing on analyzing the impact of various nonlinear effects in optical fiber transmission systems, Interactions and compensation methods for nonlinear damage.

The current nonlinear damage compensation methods mainly include two categories: optical domain compensation and electrical domain compensation. With the development of large-scale integrated circuits, it is possible to use DSP technology to compensate the dispersion and nonlinearity of the system, which not only has strong flexibility, but also has low cost, making it possible for commercial use. In electrical domain compensation, the most commonly used is the reverse transmission algorithm, through the reverse digital transmission link of the analog optical signal, to achieve the purpose of eliminating the dispersion and nonlinear effects of the optical signal during transmission. The DBP algorithm needs to first estimate and predict the nonlinear noise in the channel. At present, the commonly used methods include the time-domain Gaussian noise model (GN model) and the frequency-domain logarithmic perturbation model (FRLP model). However, due to the complexity of the DBP algorithm, the compensation effect is not good.

Contents of the invention

The purpose of the embodiments of the present invention is to provide a method and device for constructing a channel compensation filter based on carrier-dependent adaptation, and a method and system for suppressing nonlinear noise between channels, so as to realize dynamic compensation for nonlinear noise, thereby effectively reducing channel noise. bit error rate and improve system performance. The specific technical scheme is as follows:

In the first aspect, the embodiment of the present invention discloses a filter construction method, including the following steps:

S1) The transmitting end sends the check sequence, and the data signal is modulated by the MZ modulator and then multiplexed into the optical fiber channel, and then demultiplexed and coherently received after being transmitted across the M span to obtain a coherent detection data signal;

S2) Use the DBP algorithm to establish a reverse virtual optical fiber link according to the principle of "first in, last out", perform dispersion compensation and nonlinear compensation on the coherent detection data signal, and add an optical attenuator to attenuate the optical signal before each span compensation ;

S3) Repeat the above steps S1) and S2) to obtain the influence coefficient of different interference channels on the target channel, including the influence coefficient of self-phase modulation on the signal and the noise influence coefficient caused by cross-phase modulation;

S4) using the influence coefficient of different interference channels on the target channel to obtain the XPM phase noise and variance thereof caused by different interference channels to the target channel;

S5) using the XPM phase noise and variance thereof caused by different interference channels to the target channel to obtain the autocorrelation coefficient of the XPM phase noise of the different interference channels to the target channel;

S6) Utilize the autocorrelation coefficient of the XPM phase noise of different interfering channels to the target channel to obtain the influence of the channels of different frequencies on the XPM effect of the central channel;

S7) Using the influence of channels of different frequencies on the XPM effect of the center channel, a channel compensation filter based on carrier correlation adaptation related to the channel spacing and the interference channel transmission sequence is obtained.

Further, in step S4), the channel compensation filter based on carrier correlation adaptation is expressed as:

in, is the XPM phase noise caused by different interference channels to the target channel, ω _k -ω _s is the channel spacing, {b ₀ } is the transmission sequence of the interference channel, L is the transmission distance, γ is the nonlinear coefficient, and β ₂ is the second-order dispersion parameter .

Further, in the step S11), the optical fiber channel is modeled using a fixed-step symmetric step-wise Fourier algorithm, the step size is h, and within the step size h, the linear operator and the nonlinear operator are independent of each other, and each span The segment is compensated N times, and a total of M spans are transmitted, and an optical amplifier is connected after each span to amplify the optical signal.

Further, in the step S2), the nonlinear compensation is performed at the middle position of each span, and the filter used for compensation is:

Further, in the step S2), the dispersion compensation uses a frequency domain filter, and the filter used for compensation is expressed as:

Among them, λ-carrier wavelength, ω-carrier frequency, S-dispersion slope, c-speed of light.

Further, in the nonlinear compensation, the optical signal of each channel uses the XPM module to calculate the influence of the cross-phase modulation of other channels on the channel, wherein the calculation formula of the XPM module of the qth channel is:

Among them, E _out - output light field.

In the second aspect, the embodiment of the present invention discloses a device for constructing a filter, including:

The coherent detection signal acquisition module is used for the transmitting end to send the inspection sequence. The data signal is modulated by the MZ modulator and then multiplexed into the optical fiber channel. After the M span transmission, it is demultiplexed and coherently received to obtain the coherent detection data signal;

The coherent detection signal compensation module is used to use the DBP algorithm to establish a reverse virtual optical fiber link according to the principle of "first in, last out", to perform dispersion compensation and nonlinear compensation on the coherent detection data signal, and to add optical attenuation before each span compensation The device attenuates the optical signal;

The DSP processing module is used to obtain the influence coefficient of different interference channels on the target channel through the multiple processing of the coherent detection signal acquisition module and the coherent detection signal compensation module, including the influence coefficient of the self-phase modulation on the signal and the cross-phase modulation. noise influence coefficient;

The XPM phase noise acquisition module is used to obtain the XPM phase noise and variance thereof caused by different interference channels to the target channel by using the influence coefficient of different interference channels on the target channel;

The XPM autocorrelation coefficient acquisition module is used to obtain the autocorrelation coefficient of the XPM phase noise of different interference channels to the target channel by using the XPM phase noise and variance thereof caused by different interference channels to the target channel;

The XPM effect acquisition module of different interference channels is used for utilizing the autocorrelation coefficient of the XPM phase noise of different interference channels to the target channel to obtain the influence of the channels of different frequencies on the central channel XPM effect;

The channel compensation filter acquisition module is used to obtain a channel compensation filter based on carrier correlation adaptation related to channel spacing and interference channel transmission sequence by using the influence of channels of different frequencies on the XPM effect of the center channel.

In the third aspect, the embodiment of the present invention discloses a nonlinear noise suppression method, including:

Use the DBP algorithm to establish a reverse virtual optical fiber link according to the principle of "first in, last out";

In the reverse virtual optical fiber link, the channel compensation filter based on carrier correlation adaptation is used to calculate the XPM phase noise compensation value under different channels for the coherent detection data signal;

The XPM phase noise in the target channel is compensated according to the XPM phase noise compensation values in different channels.

Further, the channel compensation filter based on carrier correlation adaptation is:

in, is the XPM phase noise caused by different interference channels to the target channel, ω _k -ω _s is the channel spacing, {b ₀ } is the transmission sequence of the interference channel, L is the transmission distance, γ is the nonlinear coefficient, and β ₂ is the second-order dispersion parameter .

In the fourth aspect, the embodiment of the present invention discloses a nonlinear noise suppression system, including:

A reverse virtual optical fiber link establishment module is used to establish a reverse virtual optical fiber link according to the principle of "first in, last out" using the DBP algorithm;

The XPM phase noise compensation calculation module is used to calculate the XPM phase noise compensation value under different channels by using a channel compensation filter based on carrier correlation adaptation for the coherent detection data signal in the reverse virtual optical fiber link;

The XPM phase noise compensation module is configured to compensate the XPM phase noise in the target channel according to the XPM phase noise compensation values in different channels.

It can be seen from the above technical solution that the embodiment of the present invention receives the symbols of the target channel at the receiving end to obtain the uncompensated sequence {r _k }, which is obtained from {r _k } According to the influence of channels at different frequencies on the central channel, a channel compensation filter based on carrier correlation adaptation related to channel spacing and interference channel transmission sequences is constructed, and the power of different channels in the fiber channel model is dynamically allocated. And the nonlinear noise is compensated according to the principle of the digital reverse transmission algorithm. Since it is not necessary to calculate the nonlinear influence of all interfering channels on the center channel, the complexity of the existing DSP compensation algorithm can be effectively reduced.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is a schematic structural diagram of a large-capacity long-distance WDM optical transmission system according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a fiber channel model according to an embodiment of the present invention;

3 is a schematic diagram of a non-linear compensation processing flow in a WDM system according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a processing flow for performing nonlinear compensation on a received signal by using an inter-channel nonlinear noise suppression method based on carrier-dependent adaptation according to an embodiment of the present invention;

FIG. 5 is a schematic diagram showing the influence of different interference channels on the nonlinear effect of the center channel according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of frequency characteristics of the filter obtained according to FIG. 5 according to an embodiment of the present invention;

7 is a schematic diagram of the forward transmission of each span in the fiber channel according to the embodiment of the present invention;

FIG. 8 is a schematic diagram of reverse transmission in a virtual fiber link using a DBP algorithm for each span according to an embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Below first the function used in the embodiment of the present invention and its parameter are described:

E(z,t)-slowly varying envelope of light field;

E _in – input light field;

E _out – output light field;

γ - nonlinear coefficient;

G – the amplification gain of the amplifier;

H(ω) is the transfer function of the dispersion compensation filter, where:

λ-carrier wavelength ω-carrier frequency D-dispersion coefficient S-dispersion slope c-speed of light;

Δa _k - at the moment z=L, the received signal is affected by non-linear effects;

L – transmission distance;

Sh _,u,m - characterizes the contribution of self-phase modulation (SPM) to phase noise;

X _h,u,m - characterizes the contribution of cross-phase modulation (XPM) to phase noise;

θ - the XPM phase noise caused by the interference channel to the target channel;

- phase noise variance;

R _{k, s} (l) - the phase noise of different interference channels and the autocorrelation function of the same center channel;

ω _k -ω _s - channel spacing.

Aiming at the long-distance and large-capacity WDM optical fiber transmission system, the invention adopts a digital reverse transmission algorithm (DBP) to jointly compensate dispersion and nonlinearity. The entire transmission system is shown in Figure 1, the fiber channel modeling is shown in Figure 2, and the algorithm block diagram of the dispersion nonlinear joint compensation module in the WDM transmission system is shown in Figure 3.

Example 1

This embodiment discloses a method for constructing a filter, including the following steps:

S1) The transmitting end sends the check sequence, and the data signal is modulated by the MZ modulator and then multiplexed into the optical fiber channel, and then demultiplexed and coherently received after being transmitted across the M span to obtain a coherent detection data signal;

S2) Use the DBP algorithm to establish a reverse virtual optical fiber link according to the principle of "first in, last out", perform dispersion compensation and nonlinear compensation on the coherent detection data signal, and add an optical attenuator to attenuate the optical signal before each span compensation ; The block diagram of each span DBP algorithm is shown in Figure 8.

S3) Repeat the above steps S1) and S2) to obtain the influence coefficient of different interference channels on the target channel, including the influence coefficient of self-phase modulation on the signal and the noise influence coefficient caused by cross-phase modulation;

S4) using the influence coefficient of different interference channels on the target channel to obtain the XPM phase noise and variance thereof caused by different interference channels to the target channel;

S5) using the XPM phase noise and variance thereof caused by different interference channels to the target channel to obtain the autocorrelation coefficient of the XPM phase noise of the different interference channels to the target channel;

S6) Utilize the autocorrelation coefficient of different interference channels to the XPM phase noise of the target channel, and obtain the influence size of the channels of different frequencies on the central channel XPM effect according to the superposition principle;

S7) Using the influence of channels of different frequencies on the XPM effect of the center channel, a channel compensation filter based on carrier correlation adaptation related to the channel spacing and the interference channel transmission sequence is obtained.

Further, in the step S11), the fiber channel is modeled using a fixed step-size symmetric sub-step Fourier (SSF) algorithm (as shown in Figure 2), and within the step size h, the linear operator and nonlinear operators Independent. where α is the fiber loss coefficient, β ₂ is the fiber dispersion constant, β ₃ is the second-order group velocity dispersion slope, γ is the nonlinear coefficient, and A(z,t) is the optical field envelope. Assuming that the length of each span is L _span , the span is compensated N times, then the number of compensations is N=L _span /h, each span is followed by an optical amplifier to amplify the optical signal, and a total of M spans are transmitted, that is, the total The transmission length is L=M×L _span . The transmission block diagram of each span is shown in FIG. 7 .

Further, in the step S2), in the nonlinear compensation, the optical signal of each channel uses the XPM module to calculate the influence of the cross-phase modulation of other channels on the channel, wherein the calculation formula of the XPM module of the qth channel is :

Among them, E _out is the output light field.

Further, in the step S2), the symmetrical sub-step Fourier algorithm is adopted, and the nonlinear compensation is performed at the middle position of each span, and the filter used for compensation is:

It should be noted that the nonlinear damage compensation function filter in step S2) is used to eliminate the spontaneous emission (ASE) noise brought by the optical amplifier, and the filter is designed by using the window function method to suppress the bandwidth of the signal and limit the high-frequency noise component , when the window function is Gaussian, the expression is as follows:

Among them, f _c is the center frequency of the filter, B is the 3dB bandwidth of the filter, and m is the order number of the filter. The 3dB bandwidth parameter of the filter is properly selected so that the sidelobe attenuation is relatively large under the premise that the bandwidth meets the requirements, so as to achieve the purpose of effectively filtering out noise.

Further, in the step S2), the dispersion compensation uses a frequency domain filter, and the filter used for compensation is expressed as:

Further, in step S4), the channel compensation filter based on carrier correlation adaptation is expressed as:

in, is the XPM phase noise caused by different interference channels to the target channel, ω _k -ω _s is the channel spacing, {b ₀ } is the transmission sequence of the interference channel, L is the transmission distance, γ is the nonlinear coefficient, and β ₂ is the second-order dispersion parameter .

It should be noted that the specific methods of steps S4)-S7) are as follows:

Send a test sequence {a _k } on the target channel of the transmitter, and transmit the sequence {b _k } on the interference channel. According to the time-domain analysis model, the zero-order solution of the transmitted signal can be expressed as:

where g ⁽⁰⁾ (z,t)=Ψ(z)g(0,t), g(0,t) has an orthogonal property.

The first-order solution of the signal can be obtained by solving the nonlinear Schrödinger equation (NLSE):

Among them, f(z) represents the loss characteristic of the link, and the solution of equation (2) is shown as follows:

u(L,t)=u ⁽⁰⁾ (L,t)+u ⁽¹⁾ (L,t)(4)

After matched filtering at the receiving end, u ⁽⁰⁾ (L,t) has no contribution to nonlinear phase noise, and the contribution of u ⁽¹⁾ (L,t) to nonlinear noise can be expressed as:

Substituting formula (3) into formula (5), we can get:

Among them, Sh _{, k, m} represent the influence of self-phase modulation on the signal, and X _{h, k, m} represent the noise caused by cross-phase modulation.

When h=0, u=m, the phase noise caused by nonlinearity can be obtained, as shown in the following formula:

in, is the phase noise, and the variance is:

It should be noted that the present invention only considers the conditions of large cumulative dispersion value and no built-in dispersion compensation. Under this condition, X _0,m,m can be expressed as:

Therefore, the variance of the phase noise can be obtained as:

The autocorrelation function of the phase noise is:

Among them, [u] ⁺ ＝max{u,0}

This formula expresses the influence of channels of different frequencies on the XPM effect of the central channel. When the interference channel is far enough away from the central channel, its nonlinear influence on the central channel can be ignored.

Example 2

The embodiment of the present invention discloses a device for constructing a filter using the method of Embodiment 1, including:

The coherent detection signal acquisition module is used for the transmitting end to send the inspection sequence. The data signal is modulated by the MZ modulator and then multiplexed into the optical fiber channel. After the M span transmission, it is demultiplexed and coherently received to obtain the coherent detection data signal;

The coherent detection signal compensation module is used to use the DBP algorithm to establish a reverse virtual optical fiber link according to the principle of "first in, last out", to perform dispersion compensation and nonlinear compensation on the coherent detection data signal, and to add optical attenuation before each span compensation The device attenuates the optical signal;

The DSP processing module is used to obtain the influence coefficient of different interference channels on the target channel through the multiple processing of the coherent detection signal acquisition module and the coherent detection signal compensation module, including the influence coefficient of the self-phase modulation on the signal and the cross-phase modulation. noise influence factor.

The XPM phase noise acquisition module is used to obtain the XPM phase noise and variance thereof caused by different interference channels to the target channel by using the influence coefficient of different interference channels on the target channel;

The XPM autocorrelation coefficient acquisition module is used to obtain the autocorrelation coefficient of the XPM phase noise of different interference channels to the target channel by using the XPM phase noise and variance thereof caused by different interference channels to the target channel;

The XPM effect acquisition module of different interference channels is used for utilizing the autocorrelation coefficient of the XPM phase noise of different interference channels to the target channel to obtain the influence of the channels of different frequencies on the central channel XPM effect;

The channel compensation filter acquisition module is used to obtain a channel compensation filter based on carrier correlation adaptation related to channel spacing and interference channel transmission sequence by using the influence of channels of different frequencies on the XPM effect of the central channel.

Example 3

The embodiment of the present invention discloses a nonlinear noise suppression method using the filter construction method of Embodiment 1, including:

The DBP algorithm is used to establish a reverse virtual optical fiber link according to the principle of "first in, last out". For the coherent detection data signal, the channel compensation filter based on carrier correlation adaptation is used to calculate the XPM phase noise compensation value under different channels. The XPM phase noise is compensated.

Further, the channel compensation filter based on carrier correlation adaptation is:

in, is the XPM phase noise caused by different interference channels to the target channel, ω _k -ω _s is the channel spacing, {b ₀ } is the transmission sequence of the interference channel, L is the transmission distance, γ is the nonlinear coefficient, and β ₂ is the second-order dispersion parameter .

Specifically, before optical signal transmission, a check sequence is sent first to obtain the influence coefficient of different interference channels on the central channel, and the coefficient is used to construct an inter-channel nonlinear noise suppression filter R-filter based on carrier correlation adaptation. This filter performs nonlinear compensation to the received signal, and the calculation process is shown in Figure 4. In an optical fiber link with large dispersion accumulation and no dispersion management, when the modulation format of the transmitted signal is 16QAM, R _θ (l ) is shown in Figure 5, and the frequency characteristics of the filter frequency R-filter obtained according to this curve are shown in Figure 6. The curve in Figure 5 represents the influence of different interference channels on the nonlinear effect of the center channel. According to this curve, a power selective filter is constructed to compensate the nonlinear noise. It can be seen from the figure that when the distance between the interference channel and the center channel is sufficient When the distance is far, the influence of interference channel noise can be neglected, so the complexity of the DBP algorithm can be greatly reduced within the allowable range of the error.

Example 4

The embodiment of the present invention discloses a nonlinear noise suppression system adopting the method of embodiment 3, including:

A reverse virtual optical fiber link establishment module is used to establish a reverse virtual optical fiber link according to the principle of "first in, last out" using the DBP algorithm;

The XPM phase noise compensation calculation module is used to calculate the XPM phase noise compensation value under different channels by using a channel compensation filter based on carrier correlation adaptation for the coherent detection data signal in the reverse virtual optical fiber link;

The XPM phase noise compensation module is configured to compensate the XPM phase noise in the target channel according to the XPM phase noise compensation values in different channels.

Example 5

The specific application process of the multi-channel dispersion nonlinear joint compensation algorithm in the long-distance and large-capacity WDM optical fiber transmission system is as follows:

S1. The transmitter adopts 16QAM modulation, the symbol mapping method is Gray code mapping, and the pulse shaping filter is selected as Gaussian pulse, which satisfies the following relationship:

S2. After the data signal is modulated by the MZ modulator, it enters the optical fiber channel through multiplexing. The channel model adopts the symmetrical step-by-step Fourier algorithm. After the M-span transmission, it undergoes demultiplexing and coherent reception, and then enters the DSP processing module.

S3. In the DSP processing module, use the digital reverse transmission algorithm to jointly compensate the dispersion and nonlinearity of the signal, establish a reverse virtual optical fiber link according to the principle of "first in, last out", and add an optical attenuator before each span compensation Attenuate the optical signal. in,

The formula for the optical attenuator is

Specifically, in the linear compensation unit, the dispersion compensation of the signal is implemented through a frequency domain filter method. In the nonlinear compensation unit, the optical signal of each channel passes through the XPM module to calculate the influence of the cross-phase modulation of other channels on the channel.

S4. In order to further optimize the compensation effect of the algorithm, before optical signal transmission, a test sequence is sent to obtain the influence coefficient of different interference channels on the central channel, and the coefficient is used to construct nonlinear noise suppression between channels based on carrier correlation adaptation Filter R-filter, use this filter to perform nonlinear compensation on the received signal, the calculation process is shown in Figure 4, in the optical fiber link with large dispersion accumulation and no dispersion management, the modulation format of the transmitted signal is 16QAM , the influence curve of R _k,s (l) is shown in Figure 5, and the frequency characteristics of the filter frequency R-filter obtained according to this curve are shown in Figure 6.

According to the above embodiment, it can be seen that the symbols of the target channel are received at the receiving end to obtain the uncompensated sequence {r _k }, and the value of R _k,s (l) is obtained from {r _k }, according to the channel pairs at different frequencies The size of the center channel influence constructs a filter with frequency selection function, dynamically allocates the power of different channels in the fiber channel model, and compensates the nonlinear noise according to the principle of the digital reverse transmission algorithm, because it is not necessary to calculate all interfering channels Non-linear influence on the center channel, so the complexity of the compensation algorithm can be effectively reduced.

It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is a relationship between these entities or operations. There is no such actual relationship or order between them. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or device. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

Each embodiment in this specification is described in a related manner, the same and similar parts of each embodiment can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and for relevant parts, refer to part of the description of the method embodiment.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims (10)

1. The construction method of the filter is characterized by comprising the following steps:

s1) the transmitting end sends a check sequence, the data signal enters an optical fiber channel through multiplexing after being modulated by an MZ modulator, and is subjected to demultiplexing and coherent receiving after being transmitted by an M span, so as to obtain a coherent detection data signal;

s2) establishing a reverse virtual optical fiber link by using a DBP algorithm according to a 'first-in last-out' principle, performing dispersion compensation and nonlinear compensation on coherent detection data signals, and adding an optical attenuator to attenuate the optical signals before each span compensation;

s3) repeating the steps S1) and S2) to obtain the influence coefficients of different interference channels on the target channel, including the influence coefficient of self-phase modulation on the signal and the influence coefficient of noise caused by cross-phase modulation;

s4) obtaining XPM phase noise and variance thereof caused by different interference channels to a target channel by utilizing the influence coefficients of the different interference channels to the target channel;

s5) obtaining the autocorrelation coefficients of the XPM phase noises of the target channels caused by different interference channels by using the XPM phase noises and the variances thereof of the different interference channels;

s6) obtaining the influence of channels with different frequencies on the XPM effect of the center channel by utilizing the autocorrelation coefficients of the XPM phase noise of different interference channels on the target channel;

s7) obtaining a channel compensation filter which is related to the channel interval and the interference channel transmitting sequence and is based on carrier correlation adaptation by utilizing the influence of channels with different frequencies on the XPM effect of the central channel.

2. The method according to claim 1, wherein in step S4), the channel compensation filter based on carrier-dependent adaptation is represented as:

wherein R is_k,s(l) Is the autocorrelation function of the phase noise of different interference channels with the central channel, l is the channel interval after normalization, T is the time constant,XPM phase noise, omega, caused for different interference channels on a target channel_k-ω_sFor channel spacing, { b₀the sequence is transmitted by interference channel, L is transmission distance, gamma is nonlinear coefficient, beta₂Is a second order dispersion parameter.

3. The method according to claim 1, wherein in step S1), the optical fiber channel is modeled by a fixed-step symmetric step-by-step fourier algorithm, the step size is h, in the step size h, the linear operator and the nonlinear operator are independent from each other, each span is compensated for N times, M spans are transmitted in total, and an optical amplifier is connected after each span to amplify the optical signal.

4. The method according to claim 1, wherein in step S2), the nonlinear compensation is performed at each mid-span, and the filter for compensation is:

5. the method according to claim 1, wherein in step S2), the dispersion compensation employs a frequency-domain filter, and the filter for compensation is represented as:

wherein H (omega) is the transfer function of the dispersion compensation filter, D is the dispersion coefficient, H is the selected step length, lambda-carrier wavelength, omega-carrier frequency, S-dispersion slope, c-speed of light.

6. The method of claim 1, wherein in the nonlinear compensation, the XPM module is used to calculate the effect of the cross-phase modulation of each channel on the channel, and the XPM module of the q-th channel has the following calculation formula:

wherein E is_out-outputting the light field.

7. A filter construction apparatus using the method of claim 1, comprising:

the coherent detection signal acquisition module is used for transmitting an inspection sequence by a transmitting end, modulating a data signal by an MZ modulator, then multiplexing the data signal into an optical fiber channel, and after M span transmission, demultiplexing and coherent reception the data signal to obtain a coherent detection data signal;

the coherent detection signal compensation module is used for establishing a reverse virtual optical fiber link according to a 'first-in and last-out' principle by utilizing a DBP algorithm, performing dispersion compensation and nonlinear compensation on a coherent detection data signal, and adding an optical attenuator to attenuate the optical signal before each span compensation;

the DSP processing module is used for obtaining the influence coefficients of different interference channels on a target channel through multiple processing of the coherent detection signal acquisition module and the coherent detection signal compensation module, wherein the influence coefficients comprise the influence coefficients of self-phase modulation on signals and the influence coefficients of noise caused by cross phase modulation;

the XPM phase noise acquisition module is used for acquiring XPM phase noise and variance thereof caused by different interference channels to a target channel by utilizing the influence coefficients of the different interference channels to the target channel;

the XPM autocorrelation coefficient acquisition module is used for acquiring the autocorrelation coefficients of the XPM phase noise of different interference channels to the target channel by utilizing the XPM phase noise and the variance thereof caused by the different interference channels to the target channel;

the system comprises an XPM effect acquisition module of different interference channels, a central channel XPM effect acquisition module and a central channel XPM effect acquisition module, wherein the XPM effect acquisition module is used for acquiring the influence of channels with different frequencies on the XPM phase noise of a target channel by using the autocorrelation coefficients of the XPM phase noise of the different interference channels;

and the channel compensation filter acquisition module is used for acquiring a carrier correlation adaptation-based channel compensation filter related to the channel interval and the interference channel transmission sequence by utilizing the influence of channels with different frequencies on the XPM effect of the central channel.

8. A method of nonlinear noise suppression using the filter of claim 1, comprising:

establishing a reverse virtual optical fiber link by utilizing a DBP algorithm according to a 'first-in and last-out' principle;

in a reverse virtual optical fiber link, calculating XPM phase noise compensation values under different channels for coherent detection data signals by adopting a channel compensation filter based on carrier correlation adaptation;

and compensating the XPM phase noise in the target channel according to the XPM phase noise compensation values under different channels.

9. The method of claim 8, wherein the channel compensation filter based on carrier-dependent adaptation is:

wherein R is_k,s(l) The method comprises the steps of taking the autocorrelation function of phase noise of different interference channels and a central channel, wherein l is channel interval after normalization, and T is a time constant;XPM phase noise, omega, caused for different interference channels on a target channel_k-ω_sFor channel spacing, { b₀the sequence is transmitted by interference channel, L is transmission distance, gamma is nonlinear coefficient, beta₂Is a second order dispersion parameter.

10. A nonlinear noise suppression system employing the method of claim 8, comprising:

the reverse virtual optical fiber link establishing module is used for establishing a reverse virtual optical fiber link according to a 'first-in-last-out' principle by utilizing a DBP algorithm;

the XPM phase noise compensation calculation module is used for calculating XPM phase noise compensation values under different channels for coherent detection data signals in a reverse virtual optical fiber link by adopting a channel compensation filter based on carrier correlation adaptation;

and the XPM phase noise compensation module is used for compensating the XPM phase noise in the target channel according to the XPM phase noise compensation values under different channels.