WO2023123651A1

WO2023123651A1 - Multi-core fiber optic crosstalk detection method and apparatus, and storage medium

Info

Publication number: WO2023123651A1
Application number: PCT/CN2022/078322
Authority: WO
Inventors: 向练; 潘洪峰
Original assignee: 苏州大学
Priority date: 2021-12-27
Filing date: 2022-02-28
Publication date: 2023-07-06
Also published as: CN114707104A

Abstract

A multi-core fiber optic crosstalk detection method, device and apparatus, and a computer storage medium. The multi-core fiber optic crosstalk detection method comprises: introducing a Kerr nonlinear effect to redefine a linear coupled-mode equation, so as to obtain a coupled-mode equation including a nonlinear influence (S101); calculating the total average value of electric field analytical solutions of a coupled optical fiber by using fiber optic parameters and by means of the coupled-mode equation (S102); rewriting the total average value of the electric field analytical solutions of the coupled optical fiber, so as to obtain a coupled power equation including the nonlinear influence (S103); calculating a coupled power of the coupled optical fiber by using the coupled power equation including the nonlinear influence (S104); and calculating, by using a transmission power, and the coupled power of the coupled optical fiber, a multi-core fiber optic crosstalk value including the nonlinear influence (S105). By means of the method, a coupled power equation, to which a nonlinear influence is added, is derived again, and on this basis, a brand-new nonlinear crosstalk estimation is obtained, and the nonlinear crosstalk estimation is more suitable for an actual fiber optic laying situation.

Description

A multi-core optical fiber crosstalk detection method, device and storage medium

technical field

The invention relates to the technical field of optical fiber manufacturing, in particular to a multi-core optical fiber crosstalk detection method, equipment, device and computer storage medium.

Background technique

With the birth of optical fiber in 1966, after more than 40 years of development, it has become the cornerstone of information exchange in the world. From single-mode fiber to multi-mode fiber, from single-wavelength to multi-wavelength fiber, the development of optical fiber communication is advancing steadily. With the advent of wavelength division multiplexing (WDM), especially dense wavelength division multiplexing (DWDM) technology, the transmission capacity of optical fiber has increased several times to dozens of times compared with before, and optical fiber communication has entered the high-speed and large-capacity optical fiber communication. stage of development. However, with the development of technologies such as cloud computing, Internet of Things, and big data, business demands such as video conferencing, remote monitoring, and remote fault diagnosis are increasing day by day. The full use of single-core fiber (SM-SCF) in physical dimensions such as time, frequency, wavelength, and polarization has gradually approached the transmission limit of 100Tbit/s in the nonlinear Shannon theory. Nowadays, information acquisition methods are increasing explosively, and network data traffic is increasing continuously. It is expected that there will be a capacity crunch in the near future, which puts forward new requirements for optical fiber communication capacity.

In order to go beyond the limitation of Shannon's limit capacity and achieve higher traffic data throughput, the focus of research can only be shifted to the dimension that has not been utilized, the spatial dimension. Physically speaking, the utilization of spatial dimension is the only means to increase the capacity of optical fiber communication. There are three main ways to apply space division multiplexing technology to optical fibers: multi-core fiber (MCF), few-mode fiber (FMF) and few-mode multi-core fiber (FM-MCF). Among them, MCF contains multiple cores in one cladding layer, so that the transmission capacity of the optical fiber doubles with the increase of the number of optical fiber cores. MCF has a good application prospect, and it is slowly developing now. However, placing multiple fiber cores in the limited cladding space will result in a small distance between the fiber cores, so that the optical signal transmitted in the fiber core will be slow. It affects other adjacent fiber cores, resulting in coupling phenomenon and crosstalk, which affects the quality of optical fiber communication. Therefore, how to suppress the crosstalk between adjacent cores is a problem worthy of attention when studying the MCF process. Most of the research on crosstalk nowadays is based on coupled mode theory and coupled power theory. Under this theory, MCF transmission is linear transmission without considering the influence of nonlinear effects. However, in actual optical fiber transmission, under high power conditions, nonlinear effects will reduce the number of phase matching points, thereby reducing fiber crosstalk. Therefore, it is necessary to add nonlinear effects to the original coupled mode equations, and then derive nonlinear coupled power equations to analyze the effects of crosstalk.

Contents of the invention

For this reason, the technical problem to be solved by the present invention is to overcome the problem in the prior art that the nonlinear influence of the fiber is not considered.

In order to solve the above technical problems, the present invention provides a multi-core optical fiber crosstalk detection method, equipment, device and computer storage medium, including:

Introduce the Kerr nonlinear effect to redefine the linear coupled mode equation, and obtain the coupled mode equation including nonlinear effects:

Among them, j is the imaginary number unit, A _m (z) and A _n (z) are the slow-varying complex amplitudes of the electric field of the coupling fiber m and the incident fiber n, respectively, γ _m is the self-coupling coefficient for nonlinear effects, and N is the core Quantity, C _mn is the mode coupling coefficient from the incident fiber n to the coupling fiber m, δf(z) is a phase function describing fiber bending and twist, Δβ′ _mn (z)=β′ _m (z)- β' _n (z) is the equivalent propagation constant difference, wherein β' _m (z) and β' _n (z) are respectively the equivalent propagation constants of the coupling fiber m and the incident fiber n;

Using the fiber parameters to calculate the total average value of the coupled fiber electric field analytical solution through the coupled mode equation;

rewriting the total average value of the analytical solution of the coupling fiber electric field to obtain a coupling power equation including nonlinear effects;

Using the coupling power equation that includes nonlinear effects to calculate the coupled fiber coupling power;

The multi-core optical fiber crosstalk value including nonlinear influence is calculated by using the transmitting power and the coupling power of the coupling optical fiber.

Preferably, the calculation of the total average value of the coupled fiber electric field analytical solution by using the fiber parameters through the coupled mode equation includes:

Assuming that the phase function δf(z) is a stationary random variable, in the case of <f(z)>=0, z>>D, the analytical solution A _m (0) of the coupling fiber electric field is calculated at the initial point of the optical waveguide;

Where z is the transmission length of the wave amplitude, and D is the correlation length of the phase function;

The total average value of the coupled optical fiber electric field analytical solution is calculated by using the obtained coupled optical fiber electric field analytical solution.

Preferably, the total average value of the coupled optical fiber electric field analytical solution is:

where * denotes conjugation, and c.c. denotes the complex conjugate term of the remainder on the right side of the above formula.

Preferably, the rewriting the total average value of the analytical solution of the coupling optical fiber electric field to obtain the coupling power equation including nonlinear effects includes:

In the case of weak coupling, the electric field analytical solution at the initial point of the optical waveguide is similar to the electric field analytical solution at any point of the optical waveguide, and A _n (0) and A _m (0) in the total average value of the coupled optical fiber electric field analytical solution are replaced by are A _n (z) and A _m (z);

because

and P _n ＝<|A _n | ² >, and then

replaced by P _m (z),

Replaced by P _n (z) to obtain the coupled power equation including nonlinear effects:

Preferably, the calculation of the coupling power of the coupling fiber by using the coupling power equation including nonlinear effects includes:

Under the dual-core fiber system, the coupling power of the coupling fiber is obtained as:

Preferably, the calculation of multi-core fiber crosstalk estimation including nonlinear effects by using the transmitting power and the coupling power of the coupling fiber includes:

The formula for calculating crosstalk between multi-core cores is as follows:

XT _NL =P _m (z)/P _n (z)

Assuming that in the case of weak coupling and low crosstalk, the approximate point z of the optical waveguide is:

P _n (z)-P _m (z)≈P _n (z)≈P _L

Using the multi-core inter-core crosstalk calculation formula to obtain the multi-core optical fiber crosstalk estimation including nonlinear effects is:

XT _NL ＝XT _N +XT _L

Among them, nonlinear intercore crosstalk

linear intercore crosstalk

γ _n is the self-coupling coefficient of the nonlinear influence, _PL is the transmission power, and z is the transmission length of the wave amplitude.

The present invention also provides a multi-core optical fiber crosstalk detection device, including:

The nonlinear influence introduction module is used to introduce the Kerr nonlinear effect to redefine the linear coupled mode equation, and obtain the coupled mode equation including nonlinear influence:

The total average value calculation module of the electric field is used to calculate the total average value of the coupled optical fiber electric field analytical solution by using the fiber parameters through the coupled mode equation;

The coupled power equation rewriting module is used to rewrite the total average value of the coupled optical fiber electric field analytical solution to obtain a coupled power equation that includes nonlinear effects;

A coupling power calculation module, configured to calculate the coupling power of the coupled fiber by using the coupling power equation including nonlinear effects;

The multi-core fiber crosstalk calculation module is used to calculate the multi-core fiber crosstalk estimation including nonlinear influence by using the transmitting power and the coupling power of the coupling fiber.

memory for storing computer programs;

The processor is configured to implement the steps of a multi-core optical fiber crosstalk detection method according to any one of claims 1 to 7 when executing the computer program.

The present invention also provides a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium. The steps of the calculation method of core fiber nonlinear crosstalk.

The above technical solution of the present invention has the following advantages compared with the prior art:

The multi-core optical fiber crosstalk detection method of the present invention includes: introducing the Kerr nonlinear effect to redefine the linear coupled mode equation, obtaining the coupled mode equation including the nonlinear effect, and calculating the electric field of the coupled optical fiber through the coupled mode equation by using the fiber parameters The total average value of the analytical solution is rewritten to obtain the coupling power equation including the nonlinear influence by rewriting the total average value of the analytical solution of the coupled optical fiber electric field; The coupling mode equation of influence has obtained the coupling power equation that comprises nonlinear influence; Utilizes the coupling power equation that comprises nonlinear influence to calculate coupling fiber coupling power, utilizes launch power and described coupling fiber coupling power to calculate the multiple that comprises nonlinear influence Core Fiber Crosstalk Estimation. The present invention obtains a brand-new crosstalk estimation including nonlinear influence on the basis of nonlinear influence, which is more suitable for actual fiber laying conditions and has a wider application range than the crosstalk estimation without nonlinear influence. It is equally applicable in the linear field and the nonlinear field. On this basis, the characteristics of crosstalk in different communication systems can be studied, and the theoretical method for reducing inter-core crosstalk can be studied according to the relationship between crosstalk and optical fiber parameters.

Description of drawings

In order to make the content of the present invention more easily understood, the present invention will be described in further detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

Fig. 1 is the realization flowchart of multi-core crosstalk calculation provided by the present invention;

Fig. 2 is the block diagram of simulation calculation;

Figure 3 is a schematic diagram of bending and twisting of a seven-core optical fiber;

Figure 4 is a 7-core optical fiber crosstalk measurement experimental device;

Figure 5 is a graph showing the variation of nonlinear crosstalk with power;

Figure 6 is a graph showing the variation of linear and nonlinear crosstalk with bending radius at different refractive indices;

Figure 7 is a graph showing linear and nonlinear crosstalk as a function of core spacing;

Figure 8 is a graph showing linear and nonlinear crosstalk as a function of optical wavelength;

FIG. 9 is a structural block diagram of a multi-core optical fiber crosstalk detection device provided by an embodiment of the present invention.

Detailed ways

The core of the present invention is to provide a method, device, equipment and computer storage medium for multi-core crosstalk calculation. Based on the nonlinear influence, a brand-new crosstalk estimation including nonlinear influence is obtained. The crosstalk estimation influenced by the crosstalk effect is more suitable for the actual fiber laying situation.

In order to enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. Apparently, the described embodiments are only some of the embodiments of the present invention, but not all of them. 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.

Please refer to Fig. 1, Fig. 1 is the realization flowchart of multi-core crosstalk calculation provided by the present invention; The specific operation steps are as follows:

S101: Introducing the Kerr nonlinear effect to redefine the linear coupled mode equation to obtain a coupled mode equation including nonlinear effects;

The coupled mode equation that includes nonlinear effects is:

Among them, j is the imaginary number unit, A _m (z) and A _n (z) are the slow-varying complex amplitudes of the electric field of the coupling fiber m and the incident fiber n, respectively, γ _m is the self-coupling coefficient for nonlinear effects, and N is the core Quantity, C _mn is the mode coupling coefficient from the incident fiber n to the coupling fiber m, δf(z) is a phase function describing fiber bending and twist, Δβ′ _mn (z)=β′ _m (z)- β′ _n (z) is the equivalent propagation constant difference, wherein β′ _m (z) and β′ _n (z) are respectively the equivalent propagation constants of the coupling fiber m and the incident fiber n, and β′ _m ( z) can be expressed as:

β′ _m (z)≈β _c [R _b +rcosθ(z)]/R _b

Among them, β _c is the undisturbed core propagation constant, β _c = n _eff 2π/λ, n _eff is the effective refractive index of the fundamental mode, λ is the wavelength of the light wave, θ _n (z) is the core n at a transmission distance of The phase at z, r is the torsion rate.

S102: Calculate the total average value of the coupled optical fiber electric field analytical solution by using the optical fiber parameters through the coupled mode equation;

Assuming that the phase function δf(z) is a stationary random variable, in the case of <f(z)>=0, z>>D, the analytical solution A _m (0) of the coupling fiber electric field is calculated at the initial point of the optical waveguide, where z is the transmission length of the wave amplitude, and D is the autocorrelation length of the phase function:

Calculate the total average value of the coupled optical fiber electric field analytical solution by using the obtained coupled optical fiber electric field analytical solution;

Substitute (1) into

, where <> represents the overall average value, we get:

The solution of formula (2) is obtained based on the first-order perturbation theory, which is applicable to the case of very weak coupling. Substituting (2) into (3) and ignoring the higher-order items above the second order in C _mn , we can get:

Where cc represents the complex conjugate term of the remaining part on the right side of the above formula, since <f(z)>=0, the first-order term of C _mn is 0, assuming that f(z) is a stationary random variable, its autocorrelation function is Gaussian autocorrelation function, so:

<f(z)f(zu)>=σ ² exp[-(u/D) ² ]

where u is the autocorrelation function variable;

Since z>>D, and the variance ^σ2 is small enough to ensure the accuracy of the approximate solution of formula (2), it can be obtained:

Wherein is a real function independent of z, let F(D,Δβ' _mn )=F, put formula (5) into formula (4) to obtain the total average value of the analytical solution of the coupled optical fiber electric field:

S103: rewrite the total average value of the coupled optical fiber electric field analytical solution to obtain a coupling power equation including nonlinear effects;

In the case of weak coupling, d _mn > 2R ₀ , where d _mn is the distance between the coupling fiber m and the incident fiber n, R ₀ is the large core radius, and the electric field analytical solution at the initial point of the optical waveguide is approximate to any point of the optical waveguide The electric field analytical solution of described coupled optical fiber electric field analytical solution total average value An (0) and A _m (0) are replaced by _{A n} ₍ z) and A _m (z);

Since P _m ＝<|A _m | ² > and P _n ＝<|A _n | ² >, then the

Replaced by Pm(z),

Replaced by Pn(z) to obtain the coupled power equation containing nonlinear effects:

S104: Calculate the coupling power of the coupling fiber by using the coupling power equation including nonlinear effects;

Under the dual-core optical fiber system, the incident power is injected from the N core, not from the M core, and the first-order approximate solution of formula (6) is obtained, that is, the coupling power of the coupling fiber is:

where the first part on the right side of the equation represents linear mutual coupling, and the second part represents nonlinear self-coupling;

S105: Calculate the multi-core optical fiber crosstalk value including the nonlinear effect by using the transmitting power and the coupling power of the coupling optical fiber.

The formula for calculating crosstalk between multi-core cores is as follows:

XT _NL =P _m (z)/P _n (z)

P _n (z)-P _m (z)≈P _n (z)≈P _L

Usually take the variance σ ² =1, and solve the quadratic equation of XT _NL in the above formula to get the crosstalk value of multi-core optical fiber:

linear intercore crosstalk

Since the nonlinear influence of the coupling fiber has very little influence on the crosstalk, it can be ignored, so the approximate solution of the multi-core fiber crosstalk can be obtained:

XT _NL ＝XT _L +2σ ² F|C _mn | ² γ _n P _L z (8)

γ _n is the self-coupling coefficient of the nonlinear influence, _PL is the transmission power, and z is the transmission length of the wave amplitude;

Therefore, when we know some parameters of the fiber and the transmission power, we can rely on formula (7) or formula (8) to calculate the crosstalk between the cores, so as to analyze the size distribution of crosstalk in different situations, so as to Designing low-crosstalk multi-core optical fibers has a good reference.

Please refer to Figure 2, Figure 2 is a simulation calculation block diagram, based on the above embodiments, this embodiment simulates and verifies the theoretical model for different transmission systems, compares the simulation results with the experimental results, and verifies the correctness and reliability of the theory The scope of application is as follows:

A core radius a ₀ = 4um, cladding refractive index n ₀ = 1.4381, core refractive index is about n ₁ = 1.452, bending radius is R _b = 180mm, twist rate γ = 2πrad/m, core spacing is D _nm =40um, the optical pulse wavelength is 1550nm, and the transmission distance is a weakly coupled multi-core fiber of z=10km, its schematic diagram is shown in Figure 3, the incident core is the central core n, and the coupling core is the external core m;

Please refer to Figure 4, Figure 4 is a diagram of the experimental device;

The accuracy of the theoretical model is verified by simulation and experiment. Figure 5 shows the variation of NICXT along the incident power according to formula (7). The theoretical model is in good agreement with the experimental data. When the incident power increases, there is a critical power. Before the critical power, the nonlinearity has no or little influence on the incident power; after the critical power, the nonlinearity has a greater influence on the incident power. In the nonlinear region, with the increase of single-core power emission level, the Kerr effect reduces the phase constant of the core mode, so that the uniform 7CF becomes non-uniform 7CF. As shown in Figure 5, the number of phase matching points for crosstalk decreases in the nonlinear range, and the crosstalk decreases from -31dBm to -35dBm.

Fig. 6 is a graph showing the crosstalk variation with bending radius of the discrete variation model (DCM), the linear crosstalk model and the nonlinear crosstalk model based on formula (7), and the incident power is 20dbm. The bend radius affects the equivalent propagation constant and thus the linear crosstalk in Equation (7). Simulations were performed in real homogeneous and inhomogeneous 7CFs with intrinsic effective refractive index differences Δn _eff of 0.012% and 0.046%. When the bending radius is large, the suppression effect of NICXT is consistent with the experimental results shown in Fig. 5, no matter whether the actual fiber is uniform or not. However, the inhibitory effect of NICXT is relatively weak near the critical bending radius.

We also performed other simulations based on the derived model. Figures 7 and 8 show DCM, linear crosstalk and nonlinear crosstalk as a function of core spacing and optical wavelength at different incident powers, respectively. As shown in Figure 7, whether it is linear or nonlinear, the crosstalk decreases as the core spacing increases. However, when the incident power is 20dbm, the magnitude of the decrease of nonlinear crosstalk with the increase of magnetic core spacing is greater than that of linear crosstalk. It can be seen from Figure 8 that both linear and nonlinear crosstalk increase with optical wavelength. However, compared with linear crosstalk, when the incident power is high power 20dbm, the larger the wavelength of light, the smaller the crosstalk difference between them. In Figure 7 and Figure 8, the nonlinear crosstalk with an incident power of 20dbm is smaller than the linear crosstalk without nonlinearity, which is consistent with our nonlinear crosstalk suppression theory.

The present invention can provide a fast and accurate crosstalk estimation calculation method for the actual multi-core optical fiber communication system, and its application range is wider. The model is not only applicable to the phase matching area, but also applicable to the non-phase matching area. For multicore fibers, the same model applies. This model takes into account the nonlinear effects of fiber transmission that were not considered in previous models, and also considers the disturbance of bending and torsion in actual fiber laying scenarios, so this model is more suitable for crosstalk estimation of actual fibers. Based on this model, we can more It is good to study the characteristics of crosstalk in multicore fiber.

Please refer to FIG. 9. FIG. 9 is a structural block diagram of a multi-core optical fiber crosstalk detection device provided by an embodiment of the present invention; the specific device may include:

The nonlinear introduction module 100 introduces the Kerr nonlinear effect to redefine the linear coupled mode equation, and obtains the coupled mode equation including nonlinear effects:

The total average value calculation module 200 of the electric field calculates the total average value of the coupled optical fiber electric field analytical solution by using the fiber parameters through the coupled mode equation;

The coupling power equation rewriting module 300 rewrites the total average value of the analytical solution of the coupled optical fiber electric field to obtain a coupling power equation including nonlinear effects;

The coupling power calculation module 400 is used to calculate the coupling power of the coupling fiber by using the coupling power equation including nonlinear effects;

The multi-core fiber crosstalk calculation module 500 calculates the multi-core fiber crosstalk value including nonlinear effects by using the transmit power and the coupling power of the coupling fiber.

The multi-core optical fiber crosstalk detection device of this embodiment is used to implement the aforementioned multi-core optical fiber crosstalk detection method, so the specific implementation of the multi-core optical fiber crosstalk detection device can be seen in the embodiment part of the multi-core optical fiber crosstalk detection method above, for example, The linear introduction module 100, the electric field total average value calculation module 200, the coupling power equation rewriting module 300, the coupling power calculation module 400 and the multi-core optical fiber crosstalk calculation module 500 are respectively used to implement steps S101 and S102 in the above multi-core optical fiber crosstalk detection method, S103, S104, and S105. Therefore, for their specific implementation manners, reference may be made to the descriptions of the corresponding partial embodiments, and details are not repeated here.

The specific embodiment of the present invention also provides a multi-core optical fiber crosstalk detection device, including: a memory for storing computer programs;

The processor is configured to implement the steps of the above-mentioned method for multi-core optical fiber crosstalk detection when executing the computer program.

A specific embodiment of the present invention also provides a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the above-mentioned multi-core optical fiber crosstalk detection method is implemented. step.

Those skilled in the art should understand that the embodiments of the present application may be provided as methods, systems, or computer program products. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowcharts and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow chart or blocks of the flowchart and/or the block or blocks of the block diagrams.

Apparently, the above-mentioned embodiments are only examples for clear description, and are not intended to limit the implementation. For those of ordinary skill in the art, on the basis of the above description, other changes or changes in various forms can also be made. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims

A multi-core optical fiber crosstalk detection method is characterized in that, comprising:

Introduce the Kerr nonlinear effect to redefine the linear coupled mode equation, and obtain the coupled mode equation including nonlinear effects:

Among them, j is the imaginary number unit, A m (z) and A n (z) are the slow-varying complex amplitudes of the electric field of the coupling fiber m and the incident fiber n, respectively, γ m is the self-coupling coefficient for nonlinear effects, and N is the core Quantity, C mn is the mode coupling coefficient from the incident fiber n to the coupling fiber m, δf(z) is a phase function describing fiber bending and twist, Δβ′ mn (z)=β′ m (z)- β' n (z) is the equivalent propagation constant difference, wherein β' m (z) and β' n (z) are respectively the equivalent propagation constants of the coupling fiber m and the incident fiber n;

Using the fiber parameters to calculate the total average value of the coupled fiber electric field analytical solution through the coupled mode equation;

rewriting the total average value of the analytical solution of the coupling fiber electric field to obtain a coupling power equation including nonlinear effects;

Using the coupling power equation that includes nonlinear effects to calculate the coupled fiber coupling power;

The multi-core optical fiber crosstalk value including nonlinear influence is calculated by using the transmitting power and the coupling power of the coupling optical fiber.
The multi-core optical fiber crosstalk detection method according to claim 1, wherein the calculation of the total average value of the coupled optical fiber electric field analytical solution by using the optical fiber parameters through the coupled mode equation includes:

Assuming that the phase function δf(z) is a stationary random variable, in the case of <f(z)>=0, z>>D, the analytical solution A m (0) of the coupling fiber electric field is calculated at the initial point of the optical waveguide;

Where z is the transmission length of the wave amplitude, and D is the correlation length of the phase function;

The total average value of the coupled optical fiber electric field analytical solution is calculated by using the obtained coupled optical fiber electric field analytical solution.
The multi-core optical fiber crosstalk detection method according to claim 2, wherein the total average value of the coupled optical fiber electric field analytical solution is:

where * denotes conjugation, and c.c. denotes the complex conjugate term of the remainder on the right side of the above formula.
The multi-core optical fiber crosstalk detection method according to claim 3, wherein said rewriting the total average value of the coupled optical fiber electric field analytical solution to obtain a coupling power equation including nonlinear effects includes:

In the case of weak coupling, the electric field analytical solution at the initial point of the optical waveguide is similar to the electric field analytical solution at any point of the optical waveguide, and A n (0) and A m (0) in the total average value of the coupled optical fiber electric field analytical solution are replaced by are A n (z) and A m (z);

because
and P n ＝<|A n | 2 >, and then
replaced by P m (z),
Replaced by P n (z) to obtain the coupled power equation including nonlinear effects:
The multi-core optical fiber crosstalk detection method according to claim 4, wherein the calculation of the coupled fiber coupling power by using the coupling power equation including nonlinear effects comprises:

Under the dual-core fiber system, the coupling power of the coupling fiber is obtained as:
The multi-core optical fiber crosstalk detection method according to claim 5, wherein the calculation of the multi-core optical fiber crosstalk estimation including nonlinear effects by using the transmitting power and the coupling power of the coupling fiber comprises:

The formula for calculating crosstalk between multi-core cores is as follows:

XT NL =P m (z)/P n (z)

Assuming that in the case of weak coupling and low crosstalk, the approximate point z of the optical waveguide is:

P n (z)-P m (z)≈P n (z)≈P L

Utilize the crosstalk calculation formula between the multi-core cores to obtain the multi-core optical fiber crosstalk estimation including nonlinear influence as:

XT NL ＝XT N +XT L

Among them, nonlinear intercore crosstalk

linear intercore crosstalk

PL is the transmission power, and z is the transmission length of the wave amplitude.
A multi-core optical fiber crosstalk detection device is characterized in that it comprises:

The nonlinear influence introduction module is used to introduce the Kerr nonlinear effect to redefine the linear coupled mode equation, and obtain the coupled mode equation including nonlinear influence:

Among them, j is the imaginary number unit, A m (z) and A n (z) are the slow-varying complex amplitudes of the electric field of the coupling fiber m and the incident fiber n, respectively, γ m is the self-coupling coefficient for nonlinear effects, and N is the core Quantity, C mn is the mode coupling coefficient from the incident fiber n to the coupling fiber m, δf(z) is a phase function describing fiber bending and twist, Δβ′ mn (z)=β′ m (z)- β' n (z) is the equivalent propagation constant difference, wherein β' m (z) and β' n (z) are respectively the equivalent propagation constants of the coupling fiber m and the incident fiber n;

The total average value calculation module of the electric field is used to calculate the total average value of the coupled optical fiber electric field analytical solution by using the fiber parameters through the coupled mode equation;

The coupled power equation rewriting module is used to rewrite the total average value of the coupled optical fiber electric field analytical solution to obtain a coupled power equation that includes nonlinear effects;

A coupling power calculation module, configured to calculate the coupling power of the coupled fiber by using the coupling power equation including nonlinear effects;

The multi-core fiber crosstalk calculation module is used to calculate the multi-core fiber crosstalk estimation including nonlinear influence by using the transmitting power and the coupling power of the coupling fiber.
A multi-core optical fiber crosstalk detection device is characterized in that it comprises:

memory for storing computer programs;

Processor, when being used to execute described computer program, realize the step of a kind of multi-core optical fiber crosstalk detection method as described in any one of claims 1 to 6.
A computer-readable storage medium, characterized in that a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the multi-core The steps of the calculation method of optical fiber nonlinear crosstalk.