A method, device and storage medium for detecting crosstalk in a multi-core optical fiber

Abstract

The present invention relates to a multi-core optical fiber crosstalk detection method, device, apparatus and computer storage medium. The multi-core optical fiber crosstalk detection method provided by the present invention includes: introducing the Kerr nonlinear effect to redefine the linear coupled mode equation to obtain a coupled mode equation including nonlinear effects, calculating the total average value of the analytical solution of the coupled optical fiber electric field through the coupled mode equation using optical fiber parameters, rewriting the total average value of the analytical solution of the coupled optical fiber electric field to obtain a coupled power equation including nonlinear effects, calculating the coupled power of the coupled optical fiber using the coupled power equation including nonlinear effects, and calculating the multi-core optical fiber crosstalk value including nonlinear effects using the transmitted power and the coupled power of the coupled optical fiber. The present invention re-derives the coupled power equation with the addition of nonlinear effects, and on this basis, obtains a brand-new nonlinear crosstalk estimation, which is more in line with the actual optical fiber laying situation.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber manufacturing, and in particular to a method, device, apparatus and computer storage medium for detecting crosstalk in multi-core optical fibers. Background Art

[0002] Since the birth of optical fibers in 1966, after more than forty years of development, they have become the cornerstone of information interaction in this world. From single-mode optical fibers to multi-mode optical fibers, from single-wavelength to multi-wavelength optical fibers, the development of optical fiber communication has been advancing steadily. With the advent of wavelength division multiplexing (WDM) technology, especially dense wavelength division multiplexing (DWDM) technology, the transmission capacity of optical fibers has increased by several to dozens of times compared to before, and optical fiber communication has entered the stage of high-speed and large-capacity optical fiber communication. However, with the development of technologies such as cloud computing, the Internet of Things, and big data, the business demands for video conferencing, remote monitoring, and remote fault diagnosis are increasing day by day, and people's requirements for the capacity of communication networks are also getting higher and higher. The full utilization of conventional single-mode single-core optical fibers (SM-SCF) in physical dimensions such as time, frequency, wavelength, and polarization has gradually approached the transmission limit value of 100 Tbit / s of the non-linear Shannon theory. Nowadays, the ways of information acquisition are increasing explosively, and the continuous growth of network data traffic is expected to lead to a capacity crunch problem in the near future, thus posing new requirements for the capacity of optical fiber communication.

[0003] In order to exceed the limitation of the Shannon limit capacity and achieve higher throughput of traffic data, the focus of research can only be shifted to the dimension that has not been utilized yet, the spatial dimension. Physically speaking, the utilization of the spatial dimension is the only means to improve the capacity of optical fiber communication. Applying space division multiplexing technology to optical fibers can mainly be achieved through three methods: multi-core optical fibers (MCF), few-mode optical fibers (FMF), and few-mode multi-core optical fibers (FM-MCF). Among them, MCF contains multiple cores in a single cladding, so that the transmission capacity of the optical fiber increases multiplicatively with the increase in the number of fiber cores. MCF has good application prospects and is also slowly developing now. However, putting multiple cores in a limited cladding space results in a very small distance between the cores, causing the optical signals transmitted in the cores to affect adjacent cores, generating a coupling phenomenon and crosstalk, which affects the quality of optical fiber communication. Therefore, in the process of researching MCF, how to suppress the crosstalk between adjacent cores is a problem worthy of attention. Nowadays, most of the research on crosstalk is based on the coupled mode theory and the coupled power theory. Under this theory, the transmission of MCF is linear transmission, without considering the influence of non-linear effects. However, in actual optical fiber transmission, at high power levels, non-linear effects will reduce the number of phase matching points, thereby reducing optical fiber crosstalk. Therefore, it is necessary to add non-linear effects to the original coupled mode equation, and then derive the non-linear coupled power equation to analyze the influence of crosstalk. Summary of the Invention

[0004] To this end, the technical problem to be solved by the present invention is to overcome the problem in the prior art that the influence of fiber nonlinearity is not considered.

[0005] To solve the above technical problem, the present invention provides a multi-core fiber crosstalk detection method, device, apparatus and computer storage medium, including:

[0006] Introduce the Kerr nonlinear effect to redefine the linear coupled mode equation, and obtain the coupled mode equation including the nonlinear influence:

[0007]

[0008] where j is the imaginary unit, A m (z) and A n (z) are the slowly varying complex amplitudes of the electric fields of the coupled fiber m and the incident fiber n respectively, γ m is the self-coupling coefficient for the nonlinear influence, N is the number of fiber cores, C mn is the mode coupling coefficient from the incident fiber n to the coupled fiber m, δf(z) is the phase function describing the bending and torsion of the fiber, Δβ′ mn (z) = β′ m (z) - β n ′(z) is the equivalent propagation constant difference, where β′ m (z) and β n ′(z) are the equivalent propagation constants of the coupled fiber m and the incident fiber n respectively;

[0009] Use the fiber parameters to calculate the total average value of the analytical solution of the electric field of the coupled fiber through the coupled mode equation;

[0010] Rewrite the total average value of the analytical solution of the electric field of the coupled fiber to obtain a coupled power equation including the nonlinear influence;

[0011] Use the coupled power equation including the nonlinear influence to calculate the coupled power of the coupled fiber;

[0012] Use the transmitted power and the coupled power of the coupled fiber to calculate the multi-core fiber crosstalk value including the nonlinear influence.

[0013] Preferably, the step of using the fiber parameters to calculate the total average value of the analytical solution of the electric field of the coupled fiber through the coupled mode equation includes:

[0014] Assume that the phase function δf(z) is a stationary random variable. When <f(z)> = 0 and z >> D, calculate the analytical solution A of the electric field of the coupled fiber at the initial point of the optical waveguide m (0);

[0015] where z is the transmission length of the wave amplitude and D is the correlation length of the phase function;

[0016] Calculate the total average value of the analytical solution of the coupled optical fiber electric field by using the obtained analytical solution of the coupled optical fiber electric field.

[0017] Preferably, the total average value of the analytical solution of the coupled optical fiber electric field is:

[0018]

[0019] where * represents the conjugate, and c.c. represents the complex conjugate term of the remaining part on the right side of the above formula.

[0020] Preferably, the rewriting of the total average value of the analytical solution of the coupled optical fiber electric field to obtain the coupled power equation including the nonlinear effect includes:

[0021] In the case of weak coupling, the analytical solution of the electric field at the initial point of the optical waveguide is approximately the same as the analytical solution of the electric field at any point of the optical waveguide. Replace A n (0) and A m (0) in the total average value of the analytical solution of the coupled optical fiber electric field with A n (z) and A m (z);

[0022] Since and P n =<|A n | 2 >, and then replace with P m (z), replace with P n (z) to obtain the coupled power equation including the nonlinear effect:

[0023]

[0024] Preferably, the calculation of the coupled power of the coupled optical fiber by using the coupled power equation including the nonlinear effect includes:

[0025] In the dual-core optical fiber system, the coupled power of the coupled optical fiber is obtained as:

[0026]

[0027] Preferably, the calculation of the multi-core optical fiber crosstalk estimation including the nonlinear effect by using the launch power and the coupled power of the coupled optical fiber includes:

[0028] The formula for calculating the multi-core inter-core crosstalk is as follows:

[0029] XT NL =P m (z) / P n (z)

[0030] Assume that in the case of weak coupling and low crosstalk, at any point z of the optical waveguide, approximately there is:

[0031] P n (z) - P m (z) ≈ P n (z) ≈ P L

[0032] Using the multi-core inter-core crosstalk calculation formula described above, the estimated crosstalk of the multi-core optical fiber including the non-linear effect is obtained as:

[0033] XT NL = XT N + XT L

[0034] where the non-linear inter-core crosstalk

[0035] the linear inter-core crosstalk

[0036] γ n is the self-coupling coefficient for the non-linear effect, P L is the transmission power, and z is the wave amplitude transmission length.

[0037] The present invention also provides a multi-core optical fiber crosstalk detection device, including:

[0038] A non-linear effect introduction module, configured to introduce the Kerr non-linear effect to redefine the linear coupled mode equation, and obtain a coupled mode equation including the non-linear effect:

[0039]

[0040] where j is the imaginary unit, A m (z) and A n (z) are respectively the slowly varying complex amplitudes of the electric fields of the coupled optical fiber m and the incident optical fiber n, γ m is the self-coupling coefficient for the non-linear effect, N is the number of fiber cores, C mn is the mode coupling coefficient from the incident optical fiber n to the coupled optical fiber m, δf(z) is the phase function describing the bending and twisting of the optical fiber, Δβ′ mn (z) = β′ m (z) - β n ′(z) is the equivalent propagation constant difference, where β′ m (z) and β n ′(z) are respectively the equivalent propagation constants of the coupled optical fiber m and the incident optical fiber n;

[0041] An electric field total average value calculation module, configured to calculate the total average value of the analytical solution of the electric field of the coupled optical fiber through the coupled mode equation using the optical fiber parameters;

[0042] A coupled power equation rewriting module, configured to rewrite the total average value of the analytical solution of the coupled optical fiber electric field to obtain a coupled power equation including nonlinear effects;

[0043] A coupled power calculation module, configured to calculate the coupled power of the coupled optical fiber by using the coupled power equation including nonlinear effects;

[0044] A multi-core optical fiber crosstalk calculation module, configured to calculate an estimation of multi-core optical fiber crosstalk including nonlinear effects by using the transmitted power and the coupled power of the coupled optical fiber.

[0045] The present invention further provides a multi-core optical fiber crosstalk detection device, including:

[0046] A memory, configured to store a computer program;

[0047] A processor, configured to implement the steps of a multi-core optical fiber crosstalk detection method as described above when executing the computer program.

[0048] The present invention further provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of a multi-core optical fiber nonlinear crosstalk calculation method as described above are implemented.

[0049] The above technical solution of the present invention has the following advantages compared with the prior art:

[0050] 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 to obtain a coupled mode equation including nonlinear effects, calculating the total average value of the analytical solution of the coupled optical fiber electric field by using the optical fiber parameters through the coupled mode equation, and rewriting the total average value of the analytical solution of the coupled optical fiber electric field to obtain a coupled power equation including nonlinear effects; the present invention takes into account the nonlinear effects not considered in the previous optical fiber transmission, re-derives the coupled mode equation with the addition of nonlinear effects to obtain a coupled power equation including nonlinear effects; calculating the coupled power of the coupled optical fiber by using the coupled power equation including nonlinear effects, and calculating an estimation of multi-core optical fiber crosstalk including nonlinear effects by using the transmitted power and the coupled power of the coupled optical fiber. The present invention obtains a brand-new crosstalk estimation including nonlinear effects based on the nonlinear effects. Compared with the crosstalk estimation without the influence of the nonlinear effect, it is more in line with the actual optical fiber laying situation, and its application range is wider, and 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 according to the relationship between crosstalk and optical fiber parameters, the theoretical method of reducing crosstalk between cores can be further studied. Description of the Drawings

[0051] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0052] Figure 1 This is a flowchart for implementing the multi-core crosstalk calculation provided by the present invention;

[0053] Figure 2 This is the simulation calculation block diagram;

[0054] Figure 3 Schematic diagram of bending and twisting of seven-core optical fiber;

[0055] Figure 4 It is a 7-core optical fiber crosstalk measurement experimental device;

[0056] Figure 5 is the graph of nonlinear crosstalk changing with power;

[0057] Figure 6 The linear and nonlinear crosstalk are plotted against the bending radius at different refractive indices;

[0058] Figure 7 is the graph of linear and nonlinear crosstalk changing with core spacing;

[0059] Figure 8 is a graph showing the variation of linear and nonlinear crosstalk with optical wavelength;

[0060] Figure 9 This is a structural block diagram of a device for detecting multi-core optical fiber crosstalk provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0061] The core of the present invention is to provide a method, device, equipment and computer storage medium for multi-core crosstalk calculation. Based on nonlinear effects, a new crosstalk estimation that includes nonlinear effects is obtained. Compared with crosstalk estimation without nonlinear effects, it is more in line with the actual optical fiber laying situation.

[0062] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0063] Please refer to Figure 1 , Figure 1 This is a flowchart for implementing the multi-core crosstalk calculation provided by the present invention; the specific operation steps are as follows:

[0064] S101: Redefine the linear coupled mode equation by introducing the Kerr nonlinear effect to obtain a coupled mode equation including nonlinear effects;

[0065] The coupled mode equation including nonlinear effects is as follows:

[0066]

[0067] where \(j\) is the imaginary unit, \(A\) m (z) and \(A\) n (z) are the slowly varying complex amplitudes of the electric fields of the coupled optical fiber \(m\) and the incident optical fiber \(n\) respectively, \(\gamma\) m is the self - coupling coefficient for nonlinear effects, \(N\) is the number of cores, \(C\) mn is the mode coupling coefficient from the incident optical fiber \(n\) to the coupled optical fiber \(m\), \(\delta f(z)\) is the phase function describing the bending and twisting of the optical fiber, \(\Delta\beta'\) mn (z)=\(\beta'\) m (z)-\(\beta\) n '(z) is the equivalent propagation constant difference, where \(\beta'\) m (z) and \(\beta\) n '(z) are the equivalent propagation constants of the coupled optical fiber \(m\) and the incident optical fiber \(n\) respectively, \(\beta'\) m (z) can be expressed as:

[0068] \(\beta'\) m (z)\(\approx\)\(\beta\) c [R b +\(r\cos\theta(z)\)] / \(R\) b

[0069] where \(\beta\) c is the core propagation constant without perturbation, \(\beta\) c =\(n\) eff 2\pi / \(\lambda\), \(n\) eff is the effective refractive index of the fundamental mode, \(\lambda\) is the optical wave wavelength, \(\theta\) n (z) is the phase of the core \(n\) at the transmission distance \(z\), and \(r\) is the twisting rate.

[0070] S102: Calculate the total average value of the analytical solution of the electric field of the coupled optical fiber through the coupled mode equation using optical fiber parameters;

[0071] Assume that the phase function \(\delta f(z)\) is a stationary random variable. When \(\langle f(z)\rangle = 0\) and \(z\gg D\), the analytical solution \(A\) of the electric field of the coupled optical fiber is calculated at the initial point of the optical waveguide m (0), where \(z\) is the transmission length of the wave amplitude and \(D\) is the autocorrelation length of the phase function:

[0072]

[0073] Calculating a total average value of the coupled optical fiber electric field analytical solution using the obtained coupled optical fiber electric field analytical solution;

[0074] Substitute (1) into , where < > represents the overall average value, we get:

[0075]

[0076] The solution of Equation (2) is based on the first-order perturbation theory, which is applicable to the case of very weak coupling. Substituting (2) into (3) and ignoring C mn For higher-order terms above the second order, we can get:

[0077]

[0078] Where cc represents the complex conjugate term of the remaining part on the right side of the above formula, since<f(z)> =0, C mn The first-order term is 0. Assuming f(z) is a stationary random variable, its autocorrelation function is a Gaussian autocorrelation function, so:

[0079] <f(z)f(z-u)> =σ 2 exp[-(u / D) 2 ]

[0080] Where u is the autocorrelation function variable;

[0081] Since z>>D, and the variance σ 2 is small enough to ensure the accuracy of the approximate solution of formula (2), so we can get:

[0082]

[0083] Where is a real function independent of z, let F(D,Δβ' mn )=F, and substituting formula (5) into formula (4) yields the total average value of the analytical solution of the coupled optical fiber electric field:

[0084]

[0085] S103: rewriting the total average value of the coupled optical fiber electric field analytical solution to obtain a coupled power equation including nonlinear effects;

[0086] In the weak coupling case, d mn >2R0, where d mn is the distance between the coupling fiber m and the incident fiber n, R0 is the maximum core radius, the electric field analytical solution at the initial point of the optical waveguide is approximately the electric field analytical solution at any point of the optical waveguide, and the A in the total average value of the coupling fiber electric field analytical solution is n (0) and A m (0) Replaced by A n(z) and A m (z);

[0087] Because P m =<|A m | 2 > and P n =<|A n | 2 >, and then Replace with P m (z), Replace with P n (z) Obtaining the coupled power equation including nonlinear effects:

[0088]

[0089] S104: Calculating the coupled optical fiber coupling power using the coupled power equation including nonlinear effects;

[0090] In a dual-core fiber system, the incident power is injected from the N core, not from the M core, and the first-order approximate solution of equation (6) is obtained, that is, the coupling power of the coupling fiber is:

[0091]

[0092] The first part of the right side of the equation represents linear mutual coupling, and the second part represents nonlinear self-coupling;

[0093] S105: Calculate a multi-core optical fiber crosstalk value including nonlinear effects using the emission power and the coupling optical fiber coupling power.

[0094] The calculation formula for multi-core crosstalk is as follows:

[0095] XT NL =P m (z) / P n (z)

[0096] Assuming weak coupling and low crosstalk, the approximate z point of the optical waveguide is:

[0097] P n (z)-P m (z)≈P n (z)≈P L

[0098] The multi-core optical fiber crosstalk including nonlinear effects is estimated using the multi-core inter-core crosstalk calculation formula as follows:

[0099]

[0100] Usually the variance σ 2 =1, solve the above formula about XT NLFor a quadratic equation of one variable, the crosstalk value of the multi-core optical fiber can be obtained:

[0101]

[0102] Linear inter-core crosstalk

[0103] Since the influence of the nonlinear effect of the coupled optical fiber on crosstalk is very small and can be ignored, an approximate solution of the multi-core optical fiber crosstalk can be obtained:

[0104] XT NL = XT L + 2σ 2 F|C mn | 2 γ n P L z (8)

[0105] γ n is the self-coupling coefficient for the nonlinear effect, P L is the transmission power, and z is the wave amplitude transmission length;

[0106] Therefore, when we know some parameters of the optical fiber and the transmission power, we can rely on Equation (7) or Equation (8) to calculate the crosstalk between the cores, so as to analyze the magnitude distribution of crosstalk under different conditions, which has a good reference for designing low-crosstalk multi-core optical fibers.

[0107] The multi-core optical fiber crosstalk detection method described in the present invention includes: introducing the Kerr nonlinear effect to redefine the linear coupled mode equation to obtain a coupled mode equation including the nonlinear effect, calculating the total average value of the analytical solution of the coupled optical fiber electric field through the coupled mode equation using the optical fiber parameters, and rewriting the total average value of the analytical solution of the coupled optical fiber electric field to obtain a coupled power equation including the nonlinear effect; the present invention takes into account the nonlinear effect that has not been considered in the previous optical fiber transmission, and re-derives the coupled mode equation with the nonlinear effect to obtain a coupled power equation including the nonlinear effect; calculating the coupled power of the coupled optical fiber using the coupled power equation including the nonlinear effect, and calculating the multi-core optical fiber crosstalk estimate including the nonlinear effect using the transmission power and the coupled power of the coupled optical fiber. The present invention obtains a brand-new crosstalk estimate including the nonlinear effect based on the nonlinear effect. Compared with the crosstalk estimate without the influence of the nonlinear effect, it is more in line with the actual optical fiber laying situation, and its application range is wider, and 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 according to the relationship between crosstalk and optical fiber parameters, the theoretical method of reducing inter-core crosstalk can be further studied.

[0108] Please refer to Figure 2 , Figure 2It is a simulation calculation block diagram. Based on the above embodiments, in this embodiment, the theoretical model is simulated and verified for different transmission systems, and the simulation results are compared with the experimental results to verify the correctness and applicable scope of the theory, which are specifically as follows:

[0109] A weakly coupled multi-core optical fiber with a core radius a0 = 4um, a cladding refractive index n0 = 1.4381, a core refractive index of approximately n1 = 1.452, a bending radius of R b = 180mm, a twist rate γ = 2πrad / m, a core pitch of D nm = 40um, an optical pulse wavelength of 1550nm, and a transmission distance of z = 10km. Its schematic diagram is as Figure 3 shown, where the incident core is the central core n and the coupled core is the outer core m;

[0110] Please refer to Figure 4 , Figure 4 for the experimental setup diagram;

[0111] The accuracy of the theoretical model is verified through simulation and experiment. Figure 5 According to Equation (7), the variation of NICXT with the incident power is given. 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 effect on the incident power; after the critical power, the nonlinearity has a greater effect on the incident power. In the nonlinear region, as the single-core power emission level increases, the Kerr effect reduces the phase constant of the core mode, thus changing the uniform 7CF into a non-uniform 7CF. As Figure 5 shown, within the nonlinear range, the number of phase matching points of crosstalk decreases, and the crosstalk decreases from -31dBm to -35dBm.

[0112] Figure 6 It is a graph of crosstalk versus bending radius for the discrete change model (DCM), the linear crosstalk model, and the nonlinear crosstalk model based on Equation (7), with an incident power of 20dbm. The bending radius affects the equivalent propagation constant, thus affecting the linear crosstalk in Equation (7). Simulations are carried out in real uniform and non-uniform 7CFs with an intrinsic effective refractive index difference Δn eff of 0.012% and 0.046%. When the bending radius is large, regardless of whether the actual optical fiber is uniform, the suppression effect of NICXT is consistent with Figure 5 the experimental results shown. However, the suppression effect of NICXT is relatively weak near the critical bending radius.

[0113] We also made other simulations based on the derived model. Figure 7 and Figure 8 respectively show the relationships between DCM, linear crosstalk, and nonlinear crosstalk and the core pitch and optical wavelength under different incident powers. AsFigure 7 As shown, whether linear or non-linear, crosstalk decreases as the core spacing increases. When the incident power is 20 dbm, the non-linear crosstalk decreases more significantly with the increase of core spacing than the linear crosstalk. From Figure 8 it can be seen that both linear and non-linear crosstalk increase with the increase of optical wavelength. However, compared with linear crosstalk, when the incident power is 20 dbm (high power), the larger the optical wavelength, the smaller the crosstalk difference between them. In Figure 7 and Figure 8 , the non-linear crosstalk with an incident power of 20 dbm is less than the linear crosstalk without non-linearity, which is consistent with our non-linear crosstalk suppression theory.

[0114] The present invention can provide a fast and accurate crosstalk estimation calculation method for practical multi-core optical fiber communication systems, with a wider application range. This model is applicable not only to the phase matching region but also to the non-phase matching region, and is equally applicable to homogeneous and heterogeneous multi-core optical fibers. This model takes into account the non-linear effect of optical fiber transmission that previous models did not consider, as well as the perturbations of bending and torsion in the actual optical fiber laying scenario. Therefore, this model is more suitable for crosstalk estimation of actual optical fibers. Based on this model, we can better study the characteristics of crosstalk in multi-core optical fibers.

[0115] Please refer to Figure 9 , Figure 9 which is the structural block diagram of a device for detecting crosstalk in multi-core optical fibers provided by an embodiment of the present invention; the specific device may include:

[0116] A non-linearity introduction module 100 that redefines the linear coupled mode equation by introducing the Kerr non-linearity effect to obtain a coupled mode equation including non-linear effects:

[0117]

[0118] where j is the imaginary unit, A m (z) and A n (z) are the slowly varying complex amplitudes of the electric fields of the coupled optical fiber m and the incident optical fiber n respectively, γ m is the self-coupling coefficient for non-linear effects, N is the number of cores, C mn is the mode coupling coefficient from the incident optical fiber n to the coupled optical fiber m, δf(z) is the phase function describing the bending and torsion of the optical fiber, and Δβ′ mn (z) = β′ m (z) - β n ′(z) is the equivalent propagation constant difference, where β′ m (z) and β n ′(z) are the equivalent propagation constants of the coupled optical fiber m and the incident optical fiber n respectively;

[0119] The total average value calculation module 200 of the electric field calculates the total average value of the analytical solution of the coupled optical fiber electric field by using the optical fiber parameters through the coupled mode equation;

[0120] The coupled power equation rewriting module 300 rewrites the total average value of the analytical solution of the coupled optical fiber electric field to obtain a coupled power equation including the influence of nonlinearity;

[0121] The coupled power calculation module 400 calculates the coupled power of the coupled optical fiber by using the coupled power equation including the influence of nonlinearity;

[0122] The multi-core optical fiber crosstalk calculation module 500 calculates the multi-core optical fiber crosstalk value including the influence of nonlinearity by using the transmitted power and the coupled power of the coupled optical fiber.

[0123] The multi-core optical fiber crosstalk detection device of this embodiment is used to implement the foregoing multi-core optical fiber crosstalk detection method. Therefore, the specific implementation manners in the multi-core optical fiber crosstalk detection device can be seen in the embodiment part of the foregoing multi-core optical fiber crosstalk detection method. For example, the nonlinear introduction module 100, the total average value calculation module 200 of the electric field, the coupled power equation rewriting module 300, the coupled power calculation module 400, and the multi-core optical fiber crosstalk calculation module 500 are respectively used to implement steps S101, S102, S103, S104, and S105 in the foregoing multi-core optical fiber crosstalk detection method. Therefore, the specific implementation manners can refer to the descriptions of the corresponding respective part embodiments and will not be elaborated here.

[0124] A specific embodiment of the present invention further provides a device for detecting multi-core optical fiber crosstalk, including: a memory for storing a computer program;

[0125] A processor for implementing the steps of the foregoing method for detecting multi-core optical fiber crosstalk when executing the computer program.

[0126] A specific embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored, and the computer program implements the steps of the foregoing method for detecting multi-core optical fiber crosstalk when being executed by a processor.

[0127] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program codes.

[0128] This application is described with reference to the 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 flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing device produce means for implementing the functions specified in the Figure 1 one or more flows and / or blocks Figure 1 one or more blocks.

[0129] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including instruction means that implement the functions specified in the Figure 1 one or more flows and / or blocks Figure 1 one or more blocks.

[0130] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operational steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in the Figure 1 one or more flows and / or blocks Figure 1 one or more blocks.

[0131] Obviously, the above embodiments are merely examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for detecting crosstalk in a multi-core optical fiber, characterized in that, Including: Redefine the linear coupled mode equation by introducing the Kerr nonlinear effect to obtain a coupled mode equation including nonlinear effects; Calculate the total average value of the analytical solution of the coupled optical fiber electric field through the coupled mode equation using fiber parameters; Rewrite the total average value of the analytical solution of the coupled optical fiber electric field to obtain a coupled power equation including nonlinear effects; Calculate the coupled power of the coupled optical fiber using the coupled power equation including nonlinear effects; Calculate the crosstalk value of the multi-core optical fiber including nonlinear effects using the transmitted power and the coupled power of the coupled optical fiber; Specifically including: The formula for calculating the crosstalk between multi-core cores is as follows: XT NL = P m (z) / P n (z) Assume that in the case of weak coupling and low crosstalk, at any z point of the optical waveguide, approximately: P n (z)-P m (z)≈P n (z)≈P L Use the formula for calculating the crosstalk between multi-core cores to obtain the estimated crosstalk of the multi-core optical fiber including nonlinear effects as: XT NL = XT N + XT L Among them, the non-linear crosstalk between cores Linear inter-core crosstalk P L is the said launch power, z is the wave amplitude transmission length, P m (z) represents the coupled power of the coupled optical fiber m, C mn is the mode coupling coefficient from the incident optical fiber n to the coupled optical fiber m, Δβ′ mn (z) = β′ m (z) - β n ′(z) is the equivalent propagation constant difference, where β′ m (z) and β n ′(z) are respectively the equivalent propagation constants of the said coupled optical fiber m and the said incident optical fiber n, D is the correlation length of the phase function, * represents conjugate; P n (z) represents the coupled power of the incident optical fiber n; σ 2 represents variance; γ * represents the conjugate of the twist rate γ; γ n represents the self - coupling coefficient for the nonlinear effect.

2. The multi-core optical fiber crosstalk detection method according to claim 1, characterized in that The coupled mode equation including nonlinear effects is: where j is the imaginary unit, A m (z) and A n (z) are the slowly varying complex amplitudes of the electric fields of the coupled fiber m and the incident fiber n, respectively. γ m is the self-coupling coefficient for the nonlinear effect, N is the number of cores, C mn is the mode coupling coefficient from the incident fiber n to the coupled fiber m, and Δβ′ mn (z) = β′ m (z) - β n ′(z) is the equivalent propagation constant difference, where β′ m (z) and β n ′(z) are the equivalent propagation constants of the coupled fiber m and the incident fiber n, respectively.

3. The multi-core optical fiber crosstalk detection method according to claim 1, wherein The step of calculating the total average value of the analytical solution of the coupled optical fiber electric field through the coupled mode equation using fiber parameters includes: Assume that the phase function δf(z) is a stationary random variable. When <f(z)> = 0 and z >> D, the analytical solution A of the coupled optical fiber electric field is calculated at the initial point of the optical waveguide. m (0); Where z is the transmission length of the wave amplitude, and D is the correlation length of the phase function; Calculate the total average value of the analytical solution of the coupled optical fiber electric field using the obtained analytical solution of the coupled optical fiber electric field.

4. The multi-core optical fiber crosstalk detection method according to claim 3, characterized in that, The total average value of the analytical solution of the coupled optical fiber electric field is: where * represents the conjugate, and c.c. represents the complex conjugate term of the remaining part on the right side of the above formula; N represents the number of cores; A n (0) represents the analytical solution of the electric field of the incident optical fiber n; j represents the imaginary unit.

5. The multi-core optical fiber crosstalk detection method according to claim 4, wherein The step of rewriting the total average value of the analytical solution of the coupled optical fiber electric field to obtain a coupled power equation including nonlinear effects includes: In the case of weak coupling, the analytical solution of the electric field at the initial point of the optical waveguide is approximated to the analytical solution of the electric field at any point of the optical waveguide, and A n (0) and A m (0) are replaced by A n (z) and A m (z); Due to and P n = <A n | 2 >, and further replace with P m (z), replace with P n (z) to obtain the coupled power equation including the nonlinear effect:

6. The multi-core optical fiber crosstalk detection method according to claim 5, characterized in that The step of calculating the coupled power of the coupled optical fiber using the coupled power equation including nonlinear effects includes: In a dual-core optical fiber system, obtain the coupled power of the coupled optical fiber as:

7. A multi-core optical fiber crosstalk detection device, characterized in that, Including: A nonlinear effect introduction module for redefining the linear coupled mode equation by introducing the Kerr nonlinear effect to obtain a coupled mode equation including nonlinear effects; An electric field total average value calculation module for calculating the total average value of the analytical solution of the coupled optical fiber electric field through the coupled mode equation using fiber parameters; A coupled power equation rewriting module for rewriting the total average value of the analytical solution of the coupled optical fiber electric field to obtain a coupled power equation including nonlinear effects; A coupled power calculation module for calculating the coupled power of the coupled optical fiber using the coupled power equation including nonlinear effects; A multi-core optical fiber crosstalk calculation module for calculating the estimated crosstalk of the multi-core optical fiber including nonlinear effects using the transmitted power and the coupled power of the coupled optical fiber; Specifically including: The formula for calculating the crosstalk between multi-core cores is as follows: XT NL = P m (z) / P n (z) Assume that in the case of weak coupling and low crosstalk, at any z point of the optical waveguide, approximately: P n (z)-P m (z)≈P n (z)≈P L Use the formula for calculating the crosstalk between multi-core cores to obtain the estimated crosstalk of the multi-core optical fiber including nonlinear effects as: XT NL = XT N + XT L Among them, the non-linear crosstalk between cores Linear inter-core crosstalk P L is the transmission power, z is the wave amplitude transmission length, P m (z) represents the coupling power of the coupling optical fiber m, C mn is the mode coupling coefficient from the incident optical fiber n to the coupling optical fiber m, Δβ′ mn (z) = β′ m (z) - β n ′(z) is the equivalent propagation constant difference, where β′ m (z) and β n ′(z) are the equivalent propagation constants of the coupling optical fiber m and the incident optical fiber n respectively, D is the correlation length of the phase function, * represents the conjugate; P n (z) represents the coupling power of the incident optical fiber n; σ 2 represents the variance; γ * represents the conjugate of the twist rate γ; γ n represents the self-coupling coefficient for the nonlinear effect.

8. A multi-core optical fiber crosstalk detection device, characterized in that Including: A memory for storing computer programs; A processor for implementing the steps of a method for detecting crosstalk in a multi-core optical fiber as described in any one of claims 1 to 6 when executing the computer program.

9. 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 the processor, the steps of a method for detecting crosstalk in a multi-core optical fiber as described in any one of claims 1 to 6 are implemented.

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