Method for realizing optical fiber link power portrait estimation only by using symbol rate data

Abstract

The invention provides a method for realizing optical fiber link power portrait estimation only by using symbol rate data, and belongs to the field of optical fiber communication. The method comprises the steps that a digital signal is divided into two paths after carrier phase recovery, the first path serves as a receiving signal A, the second path is judged firstly, a digital twin reference signal Aref is calculated for a symbol obtained after judgment according to a first-order regular perturbation model, and the reference signal Aref can be expressed as a product of a perturbation matrix G and a nonlinear parameter gamma '; according to the method, an error between a received signal A and a reference signal Aref is minimized by using a least square method, a nonlinear parameter gamma'reflecting a power change condition can be obtained, and finally, the nonlinear parameter gamma 'is calibrated according to a calibration method based on a matrix trace, so that link power portrait estimation is realized. According to the invention, link power monitoring is realized only by using the received signal, so that the monitoring and maintenance cost of the optical network is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber communications, and in particular to a method for estimating optical fiber link power profiles using only symbol rate data. Background Art

[0002] With the further development of the mobile communication environment, the increase in communication between data centers, and the growing demand for remote work, network traffic is expected to continue to grow. A large amount of traffic data in the core network of the metropolitan area and the network between data centers relies on optical fiber for transmission. At the same time, optical networks are large in scale, have many components, have a wide coverage area, and are dynamic. Once an optical fiber link fails, it will cause extremely serious consequences, such as large-scale data loss, large-scale computing interruption, and core information transmission blockage. Therefore, in order to reduce operating costs, ensure optimal resource utilization and guarantee the full operation and management of optical networks, it is necessary to be able to continuously monitor various network performance parameters. This type of optical performance monitoring technology is an indispensable part of the future development of intelligent optical networks.

[0003] Fiber link power profiling is one of the key technologies for optical performance monitoring, used to ensure the normal operation of communication links and improve the level of network automation.

[0004] Existing methods for estimating optical fiber link power profiles often use an optical time-domain reflectometer (OTDR) to measure the power profile. This method injects a probe light pulse into one end of the optical fiber. During its transmission along the fiber, the probe light pulse experiences both attenuation and Rayleigh backscattering. Rayleigh backscattering power is proportional to the incident power. Measuring the scattered power provides the attenuation of the optical power. The scattered signal power received at different times corresponds to the power at different locations on the fiber, and can therefore be used to measure the power profile of the link. However, this measurement method requires dedicated measurement equipment, can only perform cross-segment measurements, and requires stopping channel service transmission. In intelligent optical networks, it is desirable to achieve real-time channel-level monitoring without interrupting services and without the use of additional measurement equipment.

[0005] In summary, the above systems use additional dedicated measurement equipment to achieve power profile estimation of optical fiber links, which increases the complexity of the system, has high implementation costs, and cannot meet the needs of intelligent optical network monitoring. Summary of the Invention

[0006] The present invention provides a method for estimating optical fiber link power profiles using only symbol rate data, which can significantly reduce the maintenance cost of optical network systems. The technical solution is as follows:

[0007] An embodiment of the present invention provides a method for estimating a fiber link power profile using only symbol rate data, including:

[0008] After the digital signal undergoes dispersion compensation, matched filtering, adaptive equalization, frequency offset estimation, and carrier phase recovery, it is divided into two paths. The first path is used as the received signal A, and the second path is first judged. The symbols obtained after the judgment are used to calculate the reference signal A of the digital twin according to the first-order canonical perturbation model. ref ;

[0009] Reference signal A of digital twin ref It can be expressed as the product of the perturbation matrix G and the nonlinear parameter γ′, constructing a least squares problem, and minimizing the difference between the received signal A and the reference signal A of the digital twin by optimizing the nonlinear parameter γ′. ref The error between the received signal A and the reference signal A of the digital twin is minimized using the least squares method. ref The error between them is used to obtain the nonlinear parameter γ′ that reflects the power change;

[0010] The nonlinear parameters are calibrated according to a matrix trace-based calibration method to eliminate the errors introduced by using symbol rate data, thereby achieving link power profile estimation.

[0011] Furthermore, the least squares method is used to minimize the difference between the received signal A and the reference signal A of the digital twin. ref The error between them, the nonlinear parameter γ′ reflecting the power change also includes:

[0012] Compare the received signal A with the digital twin's reference signal A ref =Gγ′ to calculate the error function I, and the expression for finding the optimal nonlinear parameter γ′ is:

[0013] γ′=arg min I=arg min E[||AA ref || 2 ]

[0014] Among them, when the number of points of power profile estimation is K, γ′=[γ0,γ1,…,γ K ], that is, each power estimation point has a corresponding nonlinear parameter, and the last term is a linear term that does not reflect the signal power;

[0015] The least squares method is used to minimize the objective function and the expression for the optimal nonlinear parameter γ′ is:

[0016] γ′=(G H G) -1 G H A

[0017] Furthermore, the matrix trace-based calibration method can be used to calibrate the nonlinear parameter γ′ as follows:

[0018]

[0019] This allows the absolute power profile in the optical fiber link to be obtained.

[0020] Furthermore, the number of points K for power profile estimation is equal to L / Δz k , where L is the total length of the optical fiber link, Δz k is the accuracy of the absolute power profile estimation.

[0021] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0022] In the embodiment of the present invention, after the received signal undergoes dispersion compensation, matched filtering, adaptive equalization, frequency offset estimation, and carrier phase recovery, it is divided into two paths. The first path is used as the received signal, and the second path is first judged. The symbols obtained after the judgment are used to calculate the reference signal of the digital twin according to the first-order regular perturbation model. The reference signal can be expressed as the product of the perturbation matrix and the nonlinear parameter; a least squares problem is constructed, and the error between the received signal and the reference signal is minimized using the least squares method to obtain a nonlinear parameter reflecting the power change. Finally, the nonlinear parameter is calibrated according to the matrix trace-based calibration method to obtain a nonlinear parameter that can measure the absolute power profile in the system. The nonlinear parameter is divided by the nonlinear refractive index of the optical fiber. Without using additional dedicated measurement equipment and without interrupting communication services, the absolute power profile in the optical fiber link can be obtained. In this way, the absolute power profile of the optical fiber link can be obtained by processing only the digital signal of the coherent receiver, thereby greatly reducing the maintenance cost of the optical network system and realizing intelligent network monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 Schematic diagram of the process of generating a reference signal for a digital twin provided by an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of a process for realizing optical fiber link power profile estimation using only symbol rate data provided by an embodiment of the present invention;

[0026] Figure 3 A schematic diagram showing the effect of absolute power profile estimation of an optical fiber link provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0028] The technical problem to be solved by the embodiment of the present invention is to provide a novel method for estimating the optical fiber link power profile using only symbol rate data. Figure 1 To illustrate the generation process of the reference signal of the digital twin, according to the nonlinear Schrödinger equation describing the transmission of optical signals in optical fibers and the first-order canonical perturbation model, the reference signal A of the digital twin is ref It is the superposition of the linear term that only considers the dispersion effect and the nonlinear term that considers the nonlinear effect at different positions. If the nonlinear coefficient of each branch is extracted and considered separately, the reference signal of the generated digital twin can be expressed in matrix form, let Where k = 0, 1, K-1, is the symbol of 1 times sampling after judgment, corresponding to the nonlinear term, K represents the actual transmission link is divided into N blocks in the digital twin link, when k = K, Corresponding to the linear term, therefore, let G k =g(k) and γ′=[γ0,γ1,…,γ K ], and obtain the matrix form A of the reference signal of the digital twin ref =Gγ′. Therefore, in this embodiment, the received signal A and the reference signal A of the digital twin are minimized. ref The error between them can be used to obtain the nonlinear parameter γ′, and then the nonlinear parameter is calibrated according to the inverse convolution matrix to obtain the absolute power profile of the optical fiber link.

[0029] In this embodiment, the number of points K for power profile estimation is equal to L / Δz k , where L is the total length of the optical fiber link, Δz k is the accuracy of power profile estimation.

[0030] An embodiment of the present invention provides a method for estimating a fiber link power profile using only symbol rate data, which may specifically include the following steps:

[0031] S101, such as Figure 2 As shown in the figure, after the digital signal undergoes dispersion compensation, matched filtering, adaptive equalization, frequency offset estimation, and carrier phase recovery, it is divided into two paths. The first path is used as the received signal, and the second path is first judged. For the symbols obtained after the judgment, the reference signal of the digital twin is calculated according to the first-order canonical perturbation model.

[0032] When the digital signal undergoes offline digital signal processing, dispersion compensation, matched filtering, adaptive equalization, frequency offset estimation and carrier phase recovery are used to equalize the damage to the signal. The signal is then divided into two paths, one path (i.e., the first path) is used as the received signal containing nonlinear damage; the other path (i.e., the second path) is first judged, and the symbols obtained after the judgment are used to calculate the reference signal of the digital twin according to the first-order canonical perturbation model.

[0033] S102, based on the symbol obtained by the judgment, the reference signal of the digital twin is calculated according to the first-order regular perturbation model;

[0034] In this embodiment, the reference signal A of the digital twin is obtained based on the first-order regular perturbation model for the judged symbol. ref =Gγ′, this digital twin reference signal is a digital domain simulation of the actual received signal (first channel).

[0035] S103, constructing a least squares problem using the received signal and the reference signal of the digital twin, and then solving it using the least squares method to obtain a nonlinear parameter that can measure the absolute power profile in the system. Then, calibrating the nonlinear parameter according to a calibration method based on matrix trace can obtain the absolute power profile in the optical fiber link. Specifically, the following steps may be included:

[0036] A1, the least squares problem consists of the received signal A and the digital twin reference signal A ref The matrix form of the reference signal of the digital twin is A ref =Gγ′, G is the perturbation matrix calculated according to the first-order regular perturbation model; the received signal and the reference signal A of the digital twin are used. ref The error function I is calculated, and its expression for finding the optimal nonlinear parameter is:

[0037] γ′=arg min I=arg min E[||AA ref || 2 ]

[0038] This can be regarded as a classic least squares problem, where when the number of power profile estimation points is K, γ′=[γ0,γ1,…,γ K ], that is, the position of each power estimation point has a nonlinear parameter corresponding to it.

[0039] A2, using the least squares method to solve the optimal nonlinear parameters, where the formula for solving the optimal nonlinear parameters is:

[0040] γ′=(G H G) -1 G H A

[0041] Where H represents the conjugate transpose operation.

[0042] A3, the nonlinear parameters are calibrated according to the matrix trace-based calibration method, and its expression is:

[0043]

[0044] Where tr(·) represents the trace of the matrix, T=(G H G) -1 is the deconvolution matrix, and the subscripts w and s represent the use of oversampled data and symbol rate data, respectively.

[0045] In this embodiment, obtaining an absolute power profile in the optical fiber link by using a nonlinear parameter value includes:

[0046] By dividing the calibrated nonlinear parameters by the nonlinear refractive index of the optical fiber, the absolute power profile in the optical fiber link can be obtained.

[0047] In this embodiment, after the received signal undergoes dispersion compensation, matched filtering, adaptive equalization, frequency offset estimation, and carrier phase recovery, it is divided into two paths. The first path is used as the received signal, and the second path is first judged. The symbols obtained after the judgment are used to calculate the reference signal of the digital twin according to the first-order regular perturbation model. The reference signal can be expressed as the product of the perturbation matrix and the nonlinear parameter; a least squares problem is constructed, and the error between the received signal and the reference signal is minimized using the least squares method to obtain a nonlinear parameter reflecting the power change. Finally, the nonlinear parameter is calibrated according to the calibration method based on the matrix trace to obtain a nonlinear parameter that can measure the absolute power portrait in the system. The nonlinear parameter is divided by the nonlinear refractive index of the optical fiber. The specific process is as follows: Figure 2 As shown; Figure 3 is the absolute power profile obtained in a test system, Figure 3 The accuracy of the medium power profile estimation is set to 1km, and the fiber transmission distance is 250km, so there are a total of 250 estimated power points. Figure 3 The real power profile of the link is shown for comparison. It can be clearly seen from the line chart that the power profile obtained by using only symbol rate data and performing matrix trace-based calibration is basically consistent with the real power profile, and the average absolute value error at the fiber input power is only 0.18dB, which proves the reliability of the proposed method in estimating the absolute power profile of the optical fiber link.

[0048] The method for estimating the power profile of an optical fiber link using only symbol rate data described in an embodiment of the present invention is as follows: after the received signal undergoes dispersion compensation, matched filtering, adaptive equalization, frequency offset estimation, and carrier phase recovery, it is divided into two paths. The first path is used as the received signal, and the second path is first judged. For the symbols obtained after the judgment, the reference signal of the digital twin is calculated according to the first-order regular perturbation model. The reference signal can be expressed as the product of the perturbation matrix and the nonlinear parameter; a least squares problem is constructed, and the error between the received signal and the reference signal is minimized using the least squares method to obtain a nonlinear parameter reflecting the power change. Finally, the nonlinear parameter is calibrated according to a calibration method based on matrix trace to obtain a nonlinear parameter that can measure the absolute power profile in the system. The nonlinear parameter is divided by the nonlinear refractive index of the optical fiber. Without using additional dedicated measurement equipment and without interrupting communication services, the absolute power profile in the optical fiber link can be obtained. In this way, the absolute power profile of the optical fiber link can be obtained by processing only the digital signal of the coherent receiver, thereby greatly reducing the maintenance cost of the optical network system and realizing intelligent network monitoring.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for estimating optical fiber link power profile using only symbol rate data, characterized in that: include: After the digital signal undergoes dispersion compensation, matched filtering, adaptive equalization, frequency offset estimation, and carrier phase recovery, it is divided into two paths. The first path is used as the received signal A, and the second path is first judged. The symbols obtained after the judgment are used to calculate the reference signal A of the digital twin according to the first-order canonical perturbation model. ref ; Reference signal A ref It can be expressed as the product of the perturbation matrix G and the nonlinear parameter γ′, constructing a least squares problem, and minimizing the difference between the received signal A and the reference signal A of the digital twin by optimizing the nonlinear parameter γ′. ref The error between Use the least squares method to minimize the difference between the received signal A and the digital twin reference signal A ref The error between them is used to obtain the nonlinear parameter γ′ that reflects the power change; The nonlinear parameter γ′ is calibrated using a matrix trace-based calibration method to eliminate the error introduced by using symbol rate data, thereby achieving link power profile estimation. Among them, the reference signal A of the digital twin is calculated according to the first-order regular perturbation model ref The expression is: in, is the dispersion operation process, is a nonlinear operation process, K is the number of steps for power profile estimation, is the symbol obtained after the judgment; Reference signal A ref It can be expressed as the product of the perturbation matrix G and the nonlinear parameter γ′, and its expression is: A ref =Gγ′ Among them, the kth column of the perturbation matrix γ′=[γ0,γ1,...,γ K ] is the nonlinear parameter to be optimized; The least squares problem is constructed to minimize the difference between the received signal A and the reference signal A of the digital twin. ref The error expression between them is: γ′=argminI=argminE[||AA ref || 2 ] Use the least squares method to minimize the difference between the received signal A and the digital twin reference signal A ref The error between , the expression of the nonlinear parameter γ′ reflecting the signal power is obtained as: γ′=(G H G) -1 G H A Where H represents the conjugate transpose operation; The nonlinear parameter γ′ is calibrated according to the matrix trace-based calibration method, and its expression is: Where tr(·) represents the trace of the matrix, T=(G H G) -1 is the deconvolution matrix, subscripts w and s represent the use of oversampled data and symbol rate data respectively; The nonlinear parameter γ′ can give the power variation of the link and realize power profile estimation.

2. The method for estimating optical fiber link power profile using only symbol rate data according to claim 1, characterized in that: The number of points K for power profile estimation is equal to L / Δz k , where L is the total length of the optical fiber link, Δz k is the accuracy of power profile estimation.

3. The method for estimating optical fiber link power profile using only symbol rate data according to claim 1, characterized in that: The overall implementation uses only symbol-rate data.

4. The method for estimating optical fiber link power profile using only symbol rate data according to claim 1, wherein: A matrix-based trace calibration method is used to remove the errors introduced by using symbol rate data.

5. The method for estimating optical fiber link power profile using only symbol rate data according to claim 1, wherein: The nonlinear parameter γ′ after matrix trace calibration can give the absolute power variation of the link and realize absolute power profile estimation.

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