Optical fiber channel polarization rotation simulation method and system

Abstract

The invention belongs to the technical field of optical fiber communication, and relates to an optical fiber channel polarization rotation simulation method and system. The simulation method comprises the following steps: configuring a quadratic term and a cross term including a first polarization angle, a second polarization angle and a third polarization angle, and calculating to obtain a polarization state rotation average change rate; judging and finding out the correlation between the cross term of the first and second polarization angles, the cross term of the first and third polarization angles and the cross term of the second and third polarization angles in the cross terms and the polarization state rotation average change rate, and simplifying the polarization state rotation average change rate according to the correlation; values of a first polarization angle, a second polarization angle and a third polarization angle in a quadratic term are set to be coprime, the simplified polarization state rotation average change rate is fitted, and a fitting coefficient is obtained; and the fitting coefficient is simplified and substituted into the simplified polarization state rotation average change rate to obtain the polarization state rotation average change rate of the total optical fiber link. The accuracy and reliability of a data analysis result can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber communication, and particularly to a method and system for simulating polarization rotation of an optical fiber channel. Background Art

[0002] In an optical fiber communication system, polarization damage, as the core damage mechanism of high-speed optical signal transmission, has become a key bottleneck restricting the improvement of the transmission capacity and distance of single-mode optical fibers. Polarization damage mainly includes polarization mode dispersion (PMD), rotation of state of polarization (RSOP), and polarization dependent loss (PDL). Among them, RSOP refers to the change in the polarization state of the transmitted optical signal caused by the birefringence of the optical fiber due to its own and external environmental influences, such as vibration, bending, and even extreme weather conditions. Usually, the RSOP of an optical fiber link is at the krad / s level. However, under extreme conditions, such as thunderstorm weather, the RSOP generated by the strong electric and magnetic fields of lightning in the surrounding large-scale optical fibers can reach up to the Mrad / s level, resulting in signal reception failure or communication interruption. The reason for signal reception failure is that RSOP will cause a huge difference between the polarization state at the receiving end and the polarization state at the sending end. When polarization beam splitting is performed at the receiving end, the two signals are mixed and the modulated signal cannot be correctly demodulated. Before the optical signal enters the optical fiber, it is in a certain polarization state. Due to the action of random birefringence, the polarization state of the optical signal will change continuously during transmission. RSOP can be regarded as a rotation operation of the polarization state in the Stokes space (abbreviated as S space), and its effect on the polarization state of the optical signal is equivalent to the transformation between polarization states. The three-parameter RSOP description model changes with time, usually causing the polarization state of polarization (SOP) to change with time and simultaneously changing the direction of the main state of the vector.

[0003] In existing research, when the probability density distribution of RSOP follows a Rayleigh distribution, in most cases, it does not fit well with the numerical simulation results, and there are significant differences in terms of mathematical expectation, peak value, and probability density function (pdf). The fitting curve model of the probability density distribution of the RSOP change rate does not fit well with the numerical simulation results of the probability density distribution of the RSOP change rate. Therefore, correctly modeling RSOP is crucial for the receiving end to "predict" the change in the polarization state of the sending end after transmission. Summary of the Invention

[0004] The object of the present invention is to address the problem that the fitting of the probability density distribution of the polarization state rotation change rate in the prior art is not ideal, and a fiber optic channel polarization rotation simulation method and system are proposed. By updating the Rayleigh distribution coefficient proposed for the statistical distribution of the polarization state rotation, the statistical distribution of the total output polarization state, that is, the average change rate of the polarization state rotation of the total fiber optic link, is obtained, so that the statistical distribution of the total output polarization state is perfectly fitted with the Rayleigh distribution curve; effectively improving the accuracy and reliability of the data analysis results, that is, being more appropriate for actual simulation fitting.

[0005] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a fiber optic channel polarization rotation simulation method, which includes the following steps: Configure the quadratic terms and cross terms including the first polarization angle, the second polarization angle, and the third polarization angle, and obtain the average change rate of the polarization state rotation through calculation; Simplify the average change rate of the polarization state rotation; Set the values of the first polarization angle, the second polarization angle, and the third polarization angle in the quadratic terms to be relatively prime and fit the simplified average change rate of the polarization state rotation to obtain the fitting coefficient; Simplify the fitting coefficient and substitute it into the simplified average change rate of the polarization state rotation to obtain the average change rate of the polarization state rotation of the total fiber optic link.

[0006] As a possible implementation, obtaining the average change rate of the polarization state rotation through calculation is specifically: taking the square root after summing the quadratic terms and cross terms, and multiplying the square root result by the weighting coefficient to obtain the average change rate of the polarization state rotation.

[0007] As a possible implementation, the weighting coefficient is the square root of the number of fiber segments plus 1.

[0008] As a possible implementation, the value range of the number of fiber segments is greater than or equal to 200 and less than or equal to 5000.

[0009] As a possible implementation, simplifying the average change rate of the polarization state rotation is to judge and find the correlation between the cross terms of the first and second polarization angles, the cross terms of the first and third polarization angles, and the cross terms of the second and third polarization angles in the cross terms and the average change rate of the polarization state rotation, and simplify the average change rate of the polarization state rotation according to the correlation.

[0010] As a possible implementation, simplifying the average change rate of the polarization state rotation according to the correlation is specifically to set the term with the lowest correlation containing the negative diagonal phase difference angular frequency to 0.

[0011] As a possible implementation, the negative diagonal phase difference angular frequency terms, including: the second polarization angle quadratic configuration term, the cross terms of the first and second polarization angles, and the cross terms of the second and third polarization angles.

[0012] As a possible implementation, the fitting coefficients include the coefficients of the first polarization angle quadratic configuration term, the third polarization angle quadratic configuration term, and the cross term of the first and third polarization angles.

[0013] As a possible implementation, the fitting coefficients are simplified by setting to 0 the coefficient closest to 0 in the fitting coefficients.

[0014] In a second aspect, the present invention provides an optical fiber channel polarization rotation simulation system, which includes a quadratic term configuration unit, a cross term configuration unit, and a summation unit connected in sequence, and a square root unit respectively connected to the summation unit and a weighting unit; The quadratic term configuration unit is used to configure the first polarization angle quadratic term, the second polarization angle quadratic term, and the third polarization angle quadratic term; The cross term configuration unit is used to configure the cross terms of the first and second polarization angles, the cross terms of the first and third polarization angles, and the cross terms of the second and third polarization angles; The summation unit sums the quadratic term configuration unit and the cross term configuration unit; The weighting unit multiplies the output of the square root unit by a weighting coefficient.

[0015] Compared with the prior art, the beneficial effects produced by the present invention are as follows: An optical fiber channel polarization rotation simulation method and system proposed by the present invention can correctly evaluate the real impact of polarization damage on the system by simulating the dynamic change characteristics of signals in the optical fiber channel and then establishing a high-precision mathematical model, which helps to further design an adaptive equalization filter with the best performance. An optical fiber channel polarization rotation simulation method and system proposed by the present invention updates the Rayleigh distribution coefficient proposed for the statistical distribution of the polarization state rotation, obtains the statistical distribution of the total output polarization state, that is, the average change rate of the total optical fiber link polarization state rotation, so that the statistical distribution of the output total polarization state and the Rayleigh distribution curve are perfectly fitted; effectively improves the accuracy and reliability of the data analysis results, that is, it is more appropriate to fit with the actual simulation. An optical fiber channel polarization rotation simulation method and system proposed by the present invention obtain the average change rate of the total optical fiber link polarization state rotation by simplifying the average change rate of the polarization state rotation twice according to the correlation between the cross terms of the first and second polarization angles, the cross terms of the first and third polarization angles, the cross terms of the second and third polarization angles and the average change rate of the polarization state rotation, and the fitting coefficients, and can correctly evaluate the real impact of polarization damage on the system. Description of the Drawings The accompanying drawings described herein are used to provide a further understanding of the present invention and form a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 is a flowchart of a method for simulating polarization rotation in an optical fiber channel; Figure 2 is set to zero to simplify the average change rate of the polarization state rotation of the total optical fiber link the coefficient in the expression , , the fitting result; Figure 3 is the true and the calculated by the present invention between the fitting residuals; Figure 4 is the comparison result of the polarization state transformation rate density distribution output by the simulation, the polarization state rotation transformation rate fitting model in the existing literature and the polarization state rotation transformation rate fitting model of the present invention. Specific embodiments

[0016] In order to clearly describe the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, terms such as "first" and "second" are used to distinguish the same items or similar items with basically the same functions and roles. For example, the first threshold and the second threshold are only used to distinguish different thresholds and do not limit their order. Those skilled in the art can understand that terms such as "first" and "second" do not limit the quantity and execution order, and terms such as "first" and "second" do not necessarily limit to be different.

[0017] It should be noted that in the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the present invention should not be construed as being more preferred or more advantageous than other embodiments or design solutions. Exactly speaking, using words such as "exemplary" or "for example" aims to present relevant concepts in a specific way.

[0018] In the present invention, "at least one" means one or more, and "a plurality" means two or more. "And / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, or B exists alone, where A and B may be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after. The following at least one (item) or its similar expression refers to any combination of these items, including any combination of single item (s) or plural item (s). For example, at least one (item) of a, b, or c may represent: a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b, and c, where a, b, and c may be single or multiple.

[0019] An embodiment of the present invention aims to provide a method and system for simulating the polarization rotation of an optical fiber channel to solve the problem that the prior art has an unsatisfactory fitting of the probability density distribution of the polarization state rotation change rate. The specific implementation is as follows: In a first aspect, an embodiment of the present invention provides a method for simulating the polarization rotation of an optical fiber channel. Refer to Figure 1 , the simulation method includes the following steps: Configure the quadratic terms and cross terms including the first polarization angle, the second polarization angle, and the third polarization angle; Exemplarily, the quadratic terms include the quadratic term of the first polarization angle, the quadratic term of the second polarization angle, and the quadratic term of the third polarization angle.

[0020] Exemplarily, the cross terms include the cross term of the first and second polarization angles, the cross term of the first and third polarization angles, and the cross term of the second and third polarization angles.

[0021] Obtain the average change rate of the polarization state rotation by calculation; As a possible implementation manner, obtaining the average change rate of the polarization state rotation by calculation is specifically: summing the quadratic terms and cross terms and then taking the square root, and multiplying the square root result by a weighting coefficient to obtain the average change rate of the polarization state rotation.

[0022] As a possible implementation manner, the weighting coefficient is the square root of the number of optical fiber segments plus 1.

[0023] As a possible implementation manner, the value range of the number of optical fiber segments is greater than or equal to 200 and less than or equal to 5000.

[0024] Simplify the average change rate of the polarization state rotation; As a possible implementation, simplifying the average change rate of polarization state rotation is achieved by determining and finding the cross terms of the first and second polarization angles, the cross terms of the first and third polarization angles, and the cross terms of the second and third polarization angles in the cross terms and simplifying the average change rate of polarization state rotation based on the correlation degree.

[0025] As a possible implementation, simplifying the average change rate of polarization state rotation according to the correlation degree specifically means setting the term with the lowest correlation degree containing the negative diagonal phase difference angular frequency to 0.

[0026] As a possible implementation, the term containing the negative diagonal phase difference angular frequency includes: the second polarization angle quadratic configuration term, the cross term of the first and second polarization angles, and the cross term of the second and third polarization angles.

[0027] Set the values of the first polarization angle, the second polarization angle, and the third polarization angle in the quadratic term to be relatively prime and fit the simplified average change rate of polarization state rotation to obtain the fitting coefficients; As a possible implementation, the fitting coefficients include the coefficients of the first polarization angle quadratic configuration term, the third polarization angle quadratic configuration term, and the cross term of the first and third polarization angles.

[0028] Exemplarily, the first polarization angle is the positive diagonal phase difference angular frequency , the second polarization angle is the negative diagonal phase difference angular frequency , and the third polarization angle is the polarization plane rotation angular frequency .

[0029] Exemplarily, the first polarization angle quadratic configuration term is the weighting of the square of the positive diagonal phase difference angular frequency ; the second polarization angle quadratic configuration term is the weighting of the square of the negative diagonal phase difference angular frequency ; the third polarization angle quadratic configuration term is the weighting of the square of the polarization plane rotation angular frequency ; the cross term of the first and second polarization angles is the weighting of the product of the positive diagonal phase difference angular frequency and the negative diagonal phase difference angular frequency ; the cross term of the first and third polarization angles is the weighting of the product of the polarization plane rotation angular frequency and the positive diagonal phase difference angular frequency ; the cross term of the second and third polarization angles is the weighting of the product of the polarization plane rotation angular frequency and the negative diagonal phase difference angular frequency .

[0030] Simplify the fitting coefficients and substitute them into the simplified average change rate of polarization state rotation to obtain the total average change rate of polarization state rotation of the optical fiber link; As a possible implementation method, the fitting coefficients are simplified, specifically by setting the coefficients closest to 0 in the fitting coefficients to 0.

[0031] For example, the average rate of change of polarization state rotation of the total optical fiber link is recorded as , the expression is:

[0032] in, is the number of fiber segments, is the angular frequency at which the polarization state changes rapidly, All are coefficients.

[0033] After extensive simulation verification, Setting it to zero does not affect the final Rayleigh distribution, so it is inferred that the average rate of change of the polarization state rotation of the total fiber link is No matter, Can be simplified to , the expression is:

[0034] Will Zero, research 、 Relationship with the average rate of change of polarization state rotation of the output total fiber link.

[0035] For example, the parameters are set as follows: N=1000, The value range of is from 100 krad / s to 2000 krad / s, set as x variable; The value range is from 111 krad / s to 2001 krad / s, set as y variable; 、 and The values are mutually prime, and the square of the average rate of change of the polarization state rotation of the total optical fiber link is set as the z variable; determine Coefficients in expressions , , , the fitting results are as follows Figure 2 As shown, the fitting residuals are Figure 3 .

[0036] At a confidence level of 95%, the coefficient The confidence interval is (2.142, 2.152), and the coefficient The confidence interval is (-0.072,-0.051), and the coefficient The confidence interval for is (2.132, 2.142), is the goodness of fit.

[0037] Exemplarily, according to the experimental results, and the coefficient before and are approximately equal. Taking and cross - multiplying the terms the average change rate of the polarization state rotation of the total optical fiber link is:

[0038] Exemplarily, set N = 1000. The numerical simulation graph is fitted with the set Rayleigh curve graph to obtain the fitting model of the present invention. Comparing this fitting model with the fitting models in the existing literature, as Figure 4 shown.

[0039] From Figure 4 it can be seen that compared with the polarization state rotation rate fitting model proposed in the existing literature, the actual polarization state rotation rate probability density statistics obtained by fitting the polarization state rotation rate fitting model proposed by the present invention is more ideal.

[0040] The average change rate of the polarization state rotation of the total optical fiber link is further used to evaluate the real impact of polarization damage on the system.

[0041] In a second aspect, the present invention provides an optical fiber channel polarization rotation simulation system, which includes a quadratic term configuration unit, a cross - term configuration unit and a summation unit connected in sequence, and a square - root unit respectively connected to the summation unit and a weighting unit; The quadratic term configuration unit is used to configure the quadratic term of the first polarization angle, the quadratic term of the second polarization angle, and the quadratic term of the third polarization angle; The cross - term configuration unit is used to configure the cross - term of the first and second polarization angles, the cross - term of the first and third polarization angles, and the cross - term of the second and third polarization angles; The summation unit sums the quadratic term configuration unit and the cross - term configuration unit; The weighting unit multiplies the output of the square - root unit by a weighting coefficient.

[0042] The optical fiber channel polarization rotation simulation method and system provided by the present invention update the Rayleigh distribution coefficient proposed for the statistical distribution of polarization state rotation, and obtain the statistical distribution of the total output polarization state, that is, the average change rate of the polarization state rotation of the total optical fiber link, so that the statistical distribution of the total output polarization state is perfectly fitted with the Rayleigh distribution curve; effectively improving the accuracy and reliability of the data analysis results, that is, being more fitting with the actual simulation.

[0043] Although the present invention has been described in connection with various embodiments, those skilled in the art will recognize other variations of the disclosed embodiments upon viewing the drawings, the disclosure, and the accompanying description. In the specification, the word "comprising" does not exclude other components or steps, and the singular "a" or "an" does not exclude a plurality. A single processor or other unit may implement several functions recited in the specification. Certain measures are recited in mutually different embodiments, but this does not mean that these measures cannot be combined to produce favorable results.

[0044] Although the present invention has been described in connection with specific features and their embodiments, it will be apparent that various modifications and combinations can be made without departing from the spirit and scope of the invention. Accordingly, the specification and drawings are merely exemplary of the invention and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the invention. Thus, if these modifications and variations of the present invention fall within the scope of the present invention and its equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. A method for simulating polarization rotation of an optical fiber channel, characterized in that It includes the following steps: Configure the quadratic terms and cross terms including the first polarization angle, the second polarization angle, and the third polarization angle, and obtain the average change rate of polarization state rotation through calculation; Simplify the average change rate of polarization state rotation; Set the values of the first polarization angle, the second polarization angle, and the third polarization angle in the quadratic terms to be relatively prime and fit the simplified average change rate of polarization state rotation to obtain the fitting coefficients; Simplify the fitting coefficients and substitute them into the simplified average change rate of polarization state rotation to obtain the average change rate of polarization state rotation of the total optical fiber link.

2. The optical fiber channel polarization rotation simulation method according to claim 1, wherein The obtaining of the average change rate of polarization state rotation through calculation is specifically: sum the quadratic terms and cross terms and then take the square root, and multiply the square root result by the weighting coefficient to obtain the average change rate of polarization state rotation.

3. The optical fiber channel polarization rotation simulation method according to claim 2, wherein The weighting coefficient is the square root of the number of optical fiber segments plus 1.

4. The method for simulating polarization rotation of an optical fiber channel according to claim 2 or 3, characterized in that The value range of the number of optical fiber segments is greater than or equal to 200 and less than or equal to 5000.

5. The fiber channel polarization rotation simulation method according to claim 1, characterized in that The simplification of the average change rate of polarization state rotation is to judge and find the correlation between the cross terms of the first and second polarization angles, the cross terms of the first and third polarization angles, and the cross terms of the second and third polarization angles in the cross terms and the average change rate of polarization state rotation, and simplify the average change rate of polarization state rotation according to the correlation.

6. The method for simulating polarization rotation of an optical fiber channel according to claim 5, wherein Simplifying the average rate of change of the polarization state rotation according to the relevance specifically means setting to zero the term with the lowest relevance and containing the angular frequency of the negative diagonal phase difference .

7. The method for simulating polarization rotation of an optical fiber channel according to claim 6, wherein The term containing the negative diagonal phase difference angular frequency includes: the second polarization angle quadratic configuration term, the cross terms of the first and second polarization angles, and the cross terms of the second and third polarization angles.

8. The optical fiber channel polarization rotation simulation method according to claim 1, characterized in that The fitting coefficients include the coefficients of the quadratic configuration term of the first polarization angle, the quadratic configuration term of the third polarization angle, and the cross term of the first and third polarization angles.

9. The method for simulating polarization rotation of an optical fiber channel according to claim 1, wherein The simplification of the fitting coefficients is specifically to set the coefficient closest to 0 in the fitting coefficients to 0.

10. An optical fiber channel polarization rotation simulation system, characterized in that, It includes a connected quadratic term configuration unit, a cross term configuration unit, and a summation unit, and a square root unit respectively connected to the summation unit and the weighting unit; The quadratic term configuration unit is used to configure the quadratic term of the first polarization angle, the quadratic term of the second polarization angle, and the quadratic term of the third polarization angle; The cross term configuration unit is used to configure the cross term of the first and second polarization angles, the cross term of the first and third polarization angles, and the cross term of the second and third polarization angles; The summation unit sums the quadratic term configuration unit and the cross term configuration unit; The weighting unit multiplies the output of the square root unit by the weighting coefficient.

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