Nonlinear compensation method and device for ultra-long single-span optical communication system

Abstract

The invention provides a nonlinear compensation method and device for an ultra-long single-span optical communication system, and the method comprises the steps: obtaining a receiving end signal at a receiving end position, and obtaining a longitudinal power distribution curve on a communication optical fiber according to the receiving end signal; according to the longitudinal power distribution curve and the parameters of the communication optical fiber, reverse calculation from a receiving end to a transmitting end is carried out on a receiving end signal, so that nonlinear compensation calculation is carried out on the receiving end signal, and signal light information of a corresponding position on the communication optical fiber after nonlinear compensation is obtained; by acquiring the longitudinal power distribution curve of the communication optical fiber, the power information of each position on the communication optical fiber is relatively accurately obtained, so that each reckoning coefficient corresponding to the communication optical fiber is relatively accurately obtained, nonlinear compensation calculation is performed, and more accurate compensated signal light information is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical signal transmission, in particular to a nonlinear compensation method and device for an ultra-long single-span optical communication system. BACKGROUND

[0002] In a distributed Raman amplification optical path, the nonlinear compensation signal light information at the transmitting end is usually obtained by reverse calculation of the receiving end signal through a digital back propagation model, but the effectiveness of the digital back propagation model highly depends on the accurate modeling of the optical fiber parameters, which requires accurate acquisition of the loss coefficient, nonlinear coefficient, dispersion characteristics and Raman gain coefficient. However, in the absence of prior knowledge (i.e. lack of accurate system parameter measurement or modeling), the above parameters are difficult to accurately obtain, so it is difficult to accurately model the optical fiber parameters, resulting in a significant decline in the compensation performance of the digital back propagation model, making it difficult to more accurately compensate the signal light and affecting the signal quality.

[0003] Therefore, it is urgent to overcome the defects of the prior art in the technical field. SUMMARY

[0004] The technical problem to be solved by the present application is how to improve the accuracy of signal light compensation in a distributed Raman amplification optical path.

[0005] The present application adopts the following technical solutions: In a first aspect, a nonlinear compensation method for an ultra-long single-span optical communication system is provided, comprising: obtaining a receiving end signal of a receiving end 7, and obtaining a longitudinal power distribution curve on a communication optical fiber 4 according to the receiving end signal; obtaining a calculation coefficient according to the longitudinal power distribution curve and the parameters of the communication optical fiber 4; performing reverse calculation of the receiving end signal from the receiving end 7 to the transmitting end direction according to the calculation coefficient, to perform nonlinear compensation calculation on the receiving end signal, and to obtain nonlinearly compensated signal light information at the corresponding position on the communication optical fiber 4.

[0006] Preferably, the calculation coefficient is obtained according to the longitudinal power distribution curve and the parameters of the communication optical fiber 4, and the reverse calculation of the receiving end signal from the receiving end 7 to the transmitting end direction is performed according to the calculation coefficient, to perform nonlinear compensation calculation on the receiving end signal, and to obtain nonlinearly compensated signal light information at the corresponding position on the communication optical fiber 4, specifically comprising: obtaining a distributed gain coefficient on the communication optical fiber 4 according to the longitudinal power distribution curve; obtaining a dispersion coefficient, a loss coefficient and a nonlinear coefficient according to the parameters of the communication optical fiber 4; The distributed gain coefficient, dispersion coefficient, loss coefficient, and nonlinear coefficient are used together as estimation coefficients. Based on the received signal and the estimation coefficients, the nonlinear Schrödinger equation is calculated in reverse. The received signal is nonlinearly compensated along the direction from the receiver 7 to the transmitter to obtain the nonlinearly compensated signal light information at the corresponding position on the communication optical fiber 4.

[0007] Preferably, obtaining the distributed gain coefficient on the communication optical fiber 4 based on the longitudinal power distribution curve specifically includes: The optical power information corresponding to each position of the communication optical fiber 4 is obtained based on the longitudinal power distribution curve. The optical power gain at each position of the communication fiber 4 is obtained based on the optical power information at each position of the communication fiber 4. The gain coefficients corresponding to each position of the communication optical fiber 4 are obtained based on the optical power gain at each position, and then the distributed gain coefficients on the communication optical fiber 4 are obtained. The expression for obtaining the distributed gain coefficient is: ; in, for Location-based optical power information for Location-based optical power information The loss coefficient is... for Location and Distance between locations for Distributed gain coefficient at location.

[0008] Preferably, the expression for the nonlinear Schrödinger equation is: ; Where z is the length of the communication optical fiber 4 from the transmitting end to the specified position, A(z,t) is the signal light information at length z of the communication optical fiber 4, α is the loss coefficient, g(z) is the gain coefficient at length z of the communication optical fiber 4, i is the imaginary unit, β is the dispersion coefficient, and γ is the nonlinear coefficient.

[0009] Preferably, the step of performing a reverse calculation of the received signal from the receiver 7 to the transmitter based on the calculated coefficients, in order to perform nonlinear compensation calculation on the received signal, specifically includes: The communication optical fiber is divided into multiple segments of equal length. Starting from the segment closest to the receiving end 7, the receiving signal is substituted into the nonlinear Schrödinger equation for reverse recursive calculation. Following the order from receiver 7 to transmitter, for all adjacent fiber segments in communication fiber 4, the linear and nonlinear terms in the nonlinear Schrödinger equation are calculated alternately to obtain the nonlinear compensation signal light information for each fiber segment.

[0010] Secondly, a nonlinear compensation device for an ultra-long single-span optical communication system is provided, for applying the aforementioned nonlinear compensation method for the ultra-long single-span optical communication system, comprising: a laser 1, a first wavelength division multiplexer 2, a forward Raman amplification unit 3, a communication optical fiber 4, a second wavelength division multiplexer 5, a backward Raman amplification unit 6, and a receiver 7, wherein: The first wavelength division multiplexer 2 receives signal light from laser 1 and forward pump light from forward Raman amplification unit 3, respectively. The forward pump light amplifies the signal light forward, and the forward-amplified signal light is transmitted to the second wavelength division multiplexer 5 through communication optical fiber 4. The second wavelength division multiplexer 5 receives signal light and back pump light from back Raman amplification unit 6, respectively. The back pump light amplifies the signal light backward, and the receiving end 7 receives the back-amplified signal light as the receiving end signal. The receiving end 7 is used to obtain the longitudinal power distribution curve on the communication optical fiber 4 based on the receiving end signal; Based on the longitudinal power distribution curve and the parameters of the communication optical fiber 4, the receiving signal is reverse-calculated to perform nonlinear compensation calculation on the receiving signal, thereby obtaining the nonlinearly compensated signal light information at the corresponding position on the communication optical fiber 4.

[0011] Preferably, the receiving end 7 is used to obtain the longitudinal power distribution curve on the communication optical fiber 4 based on the receiving end signal, specifically including: The received signal is subjected to bus distortion compensation to obtain the bus-compensated signal optical information; The bus-compensated signal light information is processed to obtain lossless signal light information at the transmitting end position. The bus-linearly compensated signal optical information is loaded with bus-linear distortion on the communication optical fiber 4 to obtain signal optical information with complete linear distortion. According to each position on the communication optical fiber 4, the signal light information with complete linear distortion is compensated for partial linear distortion from the corresponding position to the receiving end 7, so as to obtain the signal light information with partial linear compensation at each position of the communication optical fiber 4. Nonlinear probe processing is performed on the partially linearly compensated signal light information at each position to subtract the nonlinear distortion at the corresponding position, and residual linear compensation is performed to obtain the signal light information with nonlinear information at each position. By correlating the nonlinear signal light information at each location with the lossless signal light information at the originating location, the longitudinal power distribution curve on the communication optical fiber 4 is obtained.

[0012] Preferably, the nonlinear compensation device for the ultra-long single-span optical communication system further includes a modulator 8, a first amplifier 9, a second amplifier 10, and a coherent receiver 11, wherein: The modulator 8 and the first amplifier 9 are sequentially disposed in the optical path between the laser 1 and the first wavelength division multiplexer 2; the modulator 8 is used to modulate the optical signal emitted from the laser 1, and the first amplifier 9 is used to amplify the modulated optical signal. The second amplifier 10 and the coherent receiver 11 are sequentially disposed on the optical path between the second wavelength division multiplexer 5 and the receiver 7; the second amplifier 10 is used to amplify the signal light from the second wavelength division multiplexer 5, and the coherent receiver 11 is used to acquire the phase information in the signal light.

[0013] Preferably, the step of performing a reverse calculation of the received signal from the receiver 7 to the transmitter based on the calculated coefficient, and performing nonlinear compensation calculation on the received signal to obtain the nonlinearly compensated signal light information at the corresponding position on the communication optical fiber 4, specifically includes: The receiving end 7 obtains the distributed gain coefficient on the communication optical fiber 4 according to the longitudinal power distribution curve; The receiving end 7 obtains the dispersion coefficient, loss coefficient, and nonlinear coefficient based on the parameters of the communication optical fiber 4. The receiving end 7 performs inverse calculation of the nonlinear Schrödinger equation based on the received signal, distributed gain coefficient, dispersion coefficient, loss coefficient, and nonlinear coefficient, and performs nonlinear compensation on the received signal along the direction from the receiving end 7 to the transmitting end to obtain the nonlinearly compensated signal light information at the corresponding position on the communication optical fiber 4.

[0014] Preferably, the step of performing inverse calculation of the nonlinear Schrödinger equation based on the received signal, distributed gain coefficient, dispersion coefficient, loss coefficient, and nonlinear coefficient, and performing nonlinear compensation on the received signal along the direction from the receiver 7 to the transmitter, specifically includes: The communication optical fiber is divided into multiple segments of equal length. Starting from the segment closest to the receiving end 7, the receiving signal is substituted into the nonlinear Schrödinger equation for reverse recursive calculation. Following the order from receiver 7 to transmitter, for all adjacent fiber segments in communication fiber 4, the linear and nonlinear terms in the nonlinear Schrödinger equation are calculated alternately to obtain the nonlinear compensation signal light information for each fiber segment.

[0015] Thirdly, a non-volatile computer storage medium is provided, the computer storage medium storing computer-executable instructions, which are executed by one or more processors to perform the aforementioned nonlinear compensation method for ultra-long single-span optical communication systems.

[0016] Unlike existing technologies, the present invention has at least the following beneficial effects: By obtaining the longitudinal power distribution curve on the communication optical fiber, the power information at each location on the communication optical fiber can be obtained relatively accurately. This allows for the more accurate acquisition of various calculated coefficients corresponding to the communication optical fiber, enabling nonlinear compensation calculations and the acquisition of more accurate compensated signal light information. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0018] Figure 1 This is a flowchart of a nonlinear compensation method for an ultra-long single-span optical communication system provided by an embodiment of the present invention; Figure 2 This is a flowchart of a nonlinear compensation method for an ultra-long single-span optical communication system provided by an embodiment of the present invention; Figure 3 This is a flowchart of a nonlinear compensation method for an ultra-long single-span optical communication system provided by an embodiment of the present invention; Figure 4 This is a schematic diagram of the reverse calculation in a nonlinear compensation method for an ultra-long single-span optical communication system provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of a nonlinear compensation device for an ultra-long single-span optical communication system provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of another nonlinear compensation device for an ultra-long single-span optical communication system provided in an embodiment of the present invention; Figure 7 This is a flowchart of a method for obtaining the longitudinal power distribution curve in a nonlinear compensation method for an ultra-long single-span optical communication system provided in an embodiment of the present invention; Figure 8 This is a schematic diagram illustrating the acquisition of the longitudinal power distribution curve in a nonlinear compensation method for an ultra-long single-span optical communication system provided in an embodiment of the present invention. The diagrams are numbered as follows: Laser 1; First wavelength division multiplexer 2; Forward Raman amplifier 3; Communication optical fiber 4; Second wavelength division multiplexer 5; Backward Raman amplifier 6; Receiver 7; Modulator 8; First amplifier 9; Second amplifier 10; Coherent receiver 11. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this disclosure.

[0021] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more. Furthermore, for example, the description may use the prefix "A" or "B" to describe the same type of nouns as two independent entities. In this case, the corresponding features defined with "A" and "B" are used only to distinguish between similar entities and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0022] As used in this invention, “about,” “approximately,” or “approximately” includes the stated value and the average value within an acceptable range of deviation from a particular value, wherein the acceptable range of deviation is determined by a person skilled in the art taking into account the measurement under discussion and the error associated with the measurement of the particular quantity, i.e., the limitations of the measurement system.

[0023] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as openly inclusive, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples; that is, although they may be incorporated into embodiments or examples using the above terms for reasons such as order and position, it does not limit them to be incorporated in combination by a single embodiment or example.

[0024] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] Example 1: This embodiment provides a nonlinear compensation method for an ultra-long single-span optical communication system, such as... Figure 1 and Figure 5 As shown, the method flow includes: In step 101, the receiving end signal of the receiving end 7 is obtained, and the longitudinal power distribution curve on the communication optical fiber 4 is obtained based on the receiving end signal.

[0026] The application scenario of the method provided in this embodiment is that the optical signal is output from the transmitter and transmitted to the receiver 7 through the communication optical fiber 4. In the scenario where the communication optical fiber 4 is long, the signal light is amplified by the forward pump light and the backward pump light to ensure the signal-to-noise ratio of the signal light. After the signal light reaches the receiver 7, the effective signal in the signal light can be effectively extracted to complete the long-distance transmission of the signal light.

[0027] The receiving signal is the signal light received by the receiving end 7 in the above scenario, transmitted through the long-distance communication optical fiber 4. After obtaining the receiving signal, corresponding dispersion compensation and adaptive equalization processing can be performed based on the receiving signal to compensate for the linear distortion of the receiving signal. Then, through partial dispersion loading processing, the signal light information at different positions of the communication optical fiber 4 is located, and nonlinear probe processing is performed on the signal light information at different positions. At the same time, the remaining dispersion loading processing is completed to obtain the signal light information with nonlinear information at each position of the communication optical fiber 4. In this embodiment, since the nonlinear phase shift at each position of the communication optical fiber 4 is positively correlated with the square of the optical power at the corresponding position, the optical power information at each position of the communication optical fiber 4 can be obtained based on the signal light information with nonlinear information at each position of the communication optical fiber 4, i.e., the information with nonlinear phase shift, thereby obtaining the longitudinal power distribution curve of the communication optical fiber 4. The relationship between the nonlinear phase shift and the optical power at the corresponding position is: φ=γ|P|^2, where φ is the nonlinear phase shift, γ is the nonlinear constant, and P is the optical power.

[0028] In step 102, the calculated coefficients are obtained based on the longitudinal power distribution curve and the parameters of the communication optical fiber 4.

[0029] In step 103, the receiving signal is reversed from the receiving end 7 to the transmitting end based on the calculation coefficient, so as to perform nonlinear compensation calculation on the receiving signal and obtain the nonlinearly compensated signal light information at the corresponding position on the communication optical fiber 4.

[0030] In this embodiment, the parameters of the communication optical fiber 4 are determined by the entire optical path structure and the model of each device. Those skilled in the art can obtain these parameters after the optical path structure is built, based on the model of each device and the system status. For example, the length, loss coefficient, dispersion coefficient, and nonlinear coefficient of the communication optical fiber 4 are obtained using conventional methods known in the art, and will not be described in detail here.

[0031] In this embodiment, since the transmission of signal light in the communication optical fiber 4 from the transmitting end to the receiving end 7 satisfies the nonlinear Schrödinger equation, the nonlinear Schrödinger equation is calculated in reverse to satisfy the calculation of signal light from the receiving end 7 to the transmitting end. When the receiving end signal is obtained, the receiving end signal is substituted into the nonlinear Schrödinger equation for final reverse calculation. The signal light information at each position of the communication optical fiber 4 is gradually calculated along the direction from the receiving end 7 to the transmitting end until the signal light information at the transmitting end position is obtained, thus obtaining the signal light information after nonlinear distortion compensation, achieving a high-performance nonlinear compensation effect for the communication optical fiber 4.

[0032] In this embodiment, the calculation of the nonlinear Schrödinger equation requires corresponding estimation coefficients, which include the amplification gain coefficients at various positions of the communication fiber 4 and optical path related parameters. In the existing digital back-transmission technology, since the gain of the pump light at various positions on the communication fiber is difficult to determine, the amplification gain coefficients at various positions of the communication fiber 4 are difficult to obtain, making it difficult to use the reverse calculation of the nonlinear Schrödinger equation to obtain the nonlinear compensation of the signal light.

[0033] In this embodiment, after obtaining the longitudinal power distribution curve of the communication optical fiber 4, the gain coefficients at different positions on the communication optical fiber 4 can be obtained based on the optical power information at different positions on the communication optical fiber 4. The nonlinear Schrödinger equation can then be calculated in reverse using the gain coefficients and the coefficients related to the parameters of the communication optical fiber 4.

[0034] Furthermore, in this embodiment, after obtaining the longitudinal power distribution curve of the communication optical fiber 4, it is necessary to perform nonlinear compensation calculation on the receiving signal based on the longitudinal power distribution curve and the parameters of the communication optical fiber 4. The corresponding method is designed as follows.

[0035] The method involves performing a reverse calculation of the receiving signal from the receiving end 7 to the transmitting end based on the longitudinal power distribution curve and the parameters of the communication optical fiber 4, to perform nonlinear compensation calculation on the receiving signal, thereby obtaining the nonlinearly compensated signal light information at the corresponding position on the communication optical fiber 4, such as... Figure 2 As shown, the method flow is as follows.

[0036] In step 201, the distributed gain coefficient on the communication optical fiber 4 is obtained based on the longitudinal power distribution curve.

[0037] In this embodiment, the power information corresponding to different positions on the communication optical fiber 4 can be obtained through the longitudinal power distribution curve of the communication optical fiber 4. By comparing the optical power information at different positions, the amplification factor of the optical power at the corresponding position can be obtained, and then the Raman gain coefficient of the optical signal at different positions on the communication optical fiber 4 can be obtained, that is, the distributed gain coefficient.

[0038] The expression for obtaining the distributed gain coefficient is: ; in, for Location-based optical power information for Location-based optical power information The loss coefficient is... for Location and Distance between locations for Distributed gain coefficient at location.

[0039] The specific steps are as follows: obtain the optical power information corresponding to each position of the communication optical fiber 4 according to the longitudinal power distribution curve; obtain the optical power gain corresponding to each position of the communication optical fiber 4 according to the optical power information corresponding to each position of the communication optical fiber 4; obtain the gain coefficient corresponding to each position of the communication optical fiber 4 according to the optical power gain corresponding to each position of the communication optical fiber 4, and then obtain the distributed gain coefficient on the communication optical fiber 4.

[0040] In step 202, the dispersion coefficient, loss coefficient, and nonlinear coefficient are obtained based on the parameters of the communication optical fiber 4.

[0041] In this embodiment, the dispersion coefficient, loss coefficient, and nonlinear coefficient are related to the optical path configuration. Once the optical path configuration is determined, the dispersion coefficient, loss coefficient, and nonlinear coefficient will hardly change.

[0042] In step 203, the distributed gain coefficient, dispersion coefficient, loss coefficient, and nonlinear coefficient are used together as estimation coefficients. Based on the received signal and the estimation coefficients, the nonlinear Schrödinger equation is calculated in reverse. The received signal is nonlinearly compensated along the direction from the receiver 7 to the transmitter to obtain the nonlinearly compensated signal light information at the corresponding position on the communication optical fiber 4.

[0043] The expression for the nonlinear Schrödinger equation is as follows.

[0044] ; Where A(z,t) is the signal light information at position z from the transmitting end on the communication optical fiber 4, z is the length from the transmitting end to the specified position on the communication optical fiber 4, α is the loss coefficient, g(z) is the gain coefficient at position z from the transmitting end on the communication optical fiber 4, i is the imaginary unit, β is the dispersion coefficient, and γ is the nonlinear coefficient.

[0045] In this embodiment, based on the known distributed gain coefficient, dispersion coefficient, loss coefficient, and nonlinear coefficient, the receiving signal is substituted into the nonlinear Schrödinger equation for inverse solution. The signal light information at each position of the communication optical fiber 4 is gradually calculated along the direction from the receiving end 7 to the transmitting end until the signal light information A(0,t) at the transmitting end position is obtained, which is the signal light information after nonlinear compensation.

[0046] Furthermore, since the aforementioned nonlinear Schrödinger equation contains both linear and nonlinear terms, it cannot be solved directly with an exact solution. Therefore, in this embodiment, the corresponding equation can be solved by finding an approximate solution. The corresponding method is designed as follows.

[0047] The nonlinear Schrödinger equation is calculated in reverse based on the received signal, distributed gain coefficient, dispersion coefficient, loss coefficient, and nonlinear coefficient. Nonlinear compensation is then applied to the received signal along the direction from receiver 7 to transmitter 7. Figure 3 As shown, the method flow is as follows.

[0048] In step 301, the communication optical fiber 4 is divided into multiple segments of equal length. Starting from the segment closest to the receiving end 7, the receiving end signal is substituted into the nonlinear Schrödinger equation for reverse recursive calculation.

[0049] In step 302, following the order from receiver 7 to transmitter, for all adjacent fiber segments in communication fiber 4, the linear and nonlinear terms in the nonlinear Schrödinger equation are calculated alternately to obtain the nonlinear compensation signal light information for each fiber segment.

[0050] In this embodiment, the linear term in the nonlinear Schrödinger equation is: and The nonlinear term is In this embodiment, to improve the accuracy of the obtained approximate solution, it is necessary to ensure that the length of each segment of optical fiber is as short as possible. Furthermore, when solving for the signal light information corresponding to each segment of optical fiber, for two adjacent segments, one communication optical fiber 4 is solved using the linear term of the nonlinear Schrödinger equation, while the other communication optical fiber 4 is solved using the nonlinear term of the nonlinear Schrödinger equation. When using the linear term of the nonlinear Schrödinger equation, the nonlinear term is treated as 0, and the corresponding parameters are substituted into the linear term to obtain the signal light information corresponding to the corresponding position.

[0051] To illustrate the above solution method more intuitively, the following example is used: For instance, the communication fiber 4 is divided into 10 segments of equal length. From the transmitter to the receiver 7, all segments are numbered sequentially from 1 to 10. Starting with the 10th segment, which is closest to the receiver 7, the 10th segment is solved using nonlinear terms. The 9th segment is solved using linear terms, and the 8th segment of the communication fiber 4 is solved using nonlinear terms. The solutions for adjacent segments of the communication fiber 4 are performed alternately using nonlinear and linear terms until the solution is reached for the 1st segment of the communication fiber 4, thus obtaining the signal light information at the transmitter position.

[0052] like Figure 4The diagram shown illustrates the solution of the nonlinear Schrödinger equation by the receiver 7 after receiving the signal from the receiver.

[0053] During the transmission of signal light through communication fiber 4, linear and nonlinear distortions accumulate simultaneously. Therefore, when the received signal is reversed from the receiver 7 to the transmitter, nonlinear and linear distortions are compensated simultaneously. When the transmission position is reached, most of the linear and nonlinear distortions can be compensated. Finally, through adaptive equalization, the remaining uncompensated linear distortions are compensated again, resulting in signal light information where both linear and nonlinear distortions are basically compensated.

[0054] Example 2: This embodiment provides a nonlinear compensation device for an ultra-long single-span optical communication system based on Embodiment 1, which is used to apply the nonlinear compensation method for the ultra-long single-span optical communication system described in Embodiment 1.

[0055] The nonlinear compensation device for the ultra-long single-span optical communication system, such as Figure 5 As shown, it includes: a laser 1, a first wavelength division multiplexer 2, a forward Raman amplification unit 3, a communication optical fiber 4, a second wavelength division multiplexer 5, a backward Raman amplification unit 6, and a receiver 7, wherein: the laser 1, the first wavelength division multiplexer 2, the communication optical fiber 4, the second wavelength division multiplexer 5, and the receiver 7 are connected in sequence; the output terminal of the forward Raman amplification unit 3 is connected to the first wavelength division multiplexer 2, the input terminal of the forward Raman amplification unit 3 is connected to the receiver 7; the output terminal of the backward Raman amplification unit 6 is connected to the second wavelength division multiplexer 5, and the input terminal of the backward Raman amplification unit 6 is connected to the receiver 7.

[0056] The first wavelength division multiplexer 2 receives signal light from laser 1 and forward pump light from forward Raman amplification unit 3, respectively. The forward pump light amplifies the signal light forward, and the amplified signal light is transmitted to the second wavelength division multiplexer 5 through communication optical fiber 4. The second wavelength division multiplexer 5 receives signal light and back pump light from back Raman amplification unit 6, respectively. The back pump light amplifies the signal light backward, and the receiving end 7 receives the back amplified signal light as the receiving end signal.

[0057] In this embodiment, the communication optical fiber 4 is the transmission medium. In practical applications, the communication optical fiber 4 is often quite long. If the signal light is not amplified by pump light before being transmitted to the communication optical fiber 4, the signal-to-noise ratio of the signal light will become extremely low after long-distance transmission to the other end. Even if amplified by back-pump light, both the effective signal and noise signal in the signal light will be amplified. Given the already low signal-to-noise ratio, the effective signal will be overwhelmed, making it impossible to read the effective signal. Correspondingly, if forward pump light amplification is performed before the signal light is transmitted to the communication optical fiber 4, both the effective signal and noise signal in the signal light will be amplified. At this time, because the signal-to-noise ratio is high, the effective signal accounts for a large proportion of the signal light. After amplification, the amount of effective signal will become even larger. Although some of the effective signal will be lost and some of the noise signal will accumulate after long-distance loss through the communication optical fiber 4, the effective signal still accounts for a certain proportion of the signal light. After back-pump light amplification, the effective signal in the signal light can be effectively extracted, completing the long-distance transmission of the signal light.

[0058] The receiving end 7 is used to obtain the longitudinal power distribution curve on the communication optical fiber 4 based on the receiving end signal; and to perform nonlinear compensation calculation on the receiving end signal based on the longitudinal power distribution curve and the parameters of the communication optical fiber 4 to obtain the nonlinearly compensated signal light information at the corresponding position on the communication optical fiber 4.

[0059] In this embodiment, the longitudinal power distribution curve is the distribution curve formed by the power values ​​at different locations of the communication optical fiber 4.

[0060] It should be noted that, in this embodiment, the nonlinear compensation device for the ultra-long single-span optical communication system also requires the following basic components to meet basic functional requirements, such as... Figure 6 As shown below: The nonlinear compensation device for the ultra-long single-span optical communication system further includes a modulator 8, a first amplifier 9, a second amplifier 10, and a coherent receiver 11, wherein: the modulator 8 and the first amplifier 9 are sequentially disposed on the optical path between the laser 1 and the first wavelength division multiplexer 2; the modulator 8 is used to modulate the optical signal emitted from the laser 1, and the first amplifier 9 is used to amplify the modulated optical signal; the second amplifier 10 and the coherent receiver 11 are sequentially disposed on the optical path between the second wavelength division multiplexer 5 and the receiver 7; the second amplifier 10 is used to amplify the signal light from the second wavelength division multiplexer 5, and the coherent receiver 11 is used to acquire the phase information in the signal light.

[0061] Furthermore, in this embodiment, since the receiver 7 can only obtain the optical power of the receiver 7 when it receives the signal light, and it is difficult to directly obtain the optical power at different locations of the communication optical fiber 4 through the signal light, this embodiment also involves the following design: The receiver 7 is used to obtain the longitudinal power distribution curve on the communication optical fiber 4 based on the received signal light, such as... Figure 7 As shown, the method flow includes: In step 401, the received signal light is subjected to bus distortion compensation to obtain the signal light information after bus distortion compensation.

[0062] In this embodiment, the signal light is received by receiver 7 after passing through the device and the optical fiber link. The received signal light has linear distortion caused by dispersion and nonlinear distortion caused by nonlinearity. Both linear and nonlinear distortions are accumulated on the communication optical fiber 4. The bus linear distortion compensation is to compensate for all the linear distortions accumulated on the communication optical fiber 4. The bus linear distortion compensation process includes dispersion compensation and adaptive equalization. The dispersion compensation is used to compensate for most of the linear distortion on the communication optical fiber 4. The adaptive equalization is used to compensate for the residual linear distortion after dispersion compensation. The linear distortion in the signal light information after bus linear compensation is close to that of the signal light emitted by laser 1. The signal light information includes the amplitude and phase of the signal light. The purpose of step 101 is to restore the signal light received by receiver 7 at the angle of linear distortion to the state of the signal light at the transmitting end.

[0063] In step 402, the bus-compensated signal light information is processed to obtain lossless signal light information at the transmitting end position.

[0064] The data signal processing is used to perform nonlinear compensation on the bus-linearly compensated signal light information, and to compensate for the nonlinear distortion in the bus-linearly compensated signal light information, thereby restoring the signal light to a state close to the lossless signal light emitted by the laser, which is the lossless signal light information at the source position.

[0065] It is important to note that the lossless signal light information at the origin needs to be pre-processed to remove the phase information and retain the amplitude information.

[0066] In step 403, the bus-linearly compensated signal optical information is loaded with bus-linear distortion on the communication optical fiber 4 to obtain signal optical information with complete linear distortion.

[0067] The bus distortion on the communication optical fiber 4 is the total dispersion corresponding to the total link length on the communication optical fiber 4, which is: Where D is the link dispersion value and L is the length of the communication optical fiber 4; by loading the bus linear distortion onto the bus-linearly compensated signal light information, the signal light information now contains complete linear distortion over the total link length, so that the linear distortion of the signal light is restored to approximately the signal light state of the receiving end 7, which facilitates the subsequent positioning of the signal light information at each location on the communication optical fiber 4. In this embodiment, loading the bus-linearly compensated signal light information with bus linear distortion is to load the linear distortion corresponding to each location on the communication optical fiber 4 to obtain the information at each location on the communication optical fiber 4.

[0068] In step 404, according to each position on the communication optical fiber 4, the signal light information with complete linear distortion is compensated for partial linear distortion from the corresponding position to the receiving end 7, so as to obtain the signal light information with partial linear compensation at each position on the communication optical fiber 4.

[0069] After obtaining the complete linearly distorted signal light information, linear compensation is performed at various distances. This involves compensating for a portion of the linear distortion along the distance from the complete linearly distorted signal light information; this partial linear distortion compensation, also known as partial dispersion compensation, adjusts the linear distortion in the signal light information to the corresponding position within the communication fiber 4, resulting in the partially linearly compensated signal light information. This allows for the positioning of various locations on the communication fiber 4. For example, if the communication fiber 4 is 100 meters long, following the direction from the transmitting end (laser 1) to the receiving end (7), the complete linearly distorted signal light information is: 100 meters of linearly distorted signal light information accumulated from the transmitting end. To locate the signal light information at a position of 70 meters, 100 - 70 = 30 meters of linear distortion is compensated, resulting in 70 meters of linearly distorted signal light information, i.e., the partially linearly compensated signal light information. Following the above method and the reference example, the partially linearly compensated signal light information at various positions on the communication fiber 4 can be obtained.

[0070] The corresponding formula is: , where D is the link dispersion value and X is the distance between the corresponding location and the receiver 7.

[0071] In step 405, the partially linearly compensated signal light information at each position is subjected to nonlinear probe processing to subtract the nonlinear distortion at the corresponding position, and residual linear compensation is performed to obtain the signal light information with nonlinear information at each position.

[0072] It is important to note that the nonlinear distortion is consistent across all partially linearly compensated signal light information locations. This is because the nonlinear distortion was not compensated or adjusted in the preceding steps. Therefore, the nonlinear distortion in the partially linearly compensated signal light information at all locations is consistent with the partial linear distortion of the signal light at receiver 7. Based on this, nonlinear probe processing is performed on the partially linearly compensated signal light information at each location: only the nonlinear distortion corresponding to each location is compensated, while the nonlinear distortion at other locations on the communication fiber 4 is not compensated. The difference between each location after nonlinear probe processing is the difference in nonlinear distortion at the corresponding location. Based on the above, since the remaining linear distortion in the signal light information has already completed the positioning function, in order to compare it with the lossless transmitting signal light, the remaining linear distortion in the signal light information at each position can be compensated. This is called the remaining linear compensation, which is also called the remaining dispersion compensation process. That is, the linear distortion between laser 1 and the corresponding position in the signal light information at each position is compensated. At this point, the linear distortion in the signal light information at each position is basically completely compensated. The signal light information still has the nonlinear distortion after being processed by the nonlinear probe, which is the signal light information with nonlinear information at each position.

[0073] The formula for nonlinear probe processing is: ; signal optical information, for power.

[0074] To clearly illustrate the above steps, the following example is provided: The communication fiber optic cable 4 is 100 meters long, and the direction is from the transmitting end (i.e., the laser 1 position) to the receiving end 7. The object of processing is the partially linearly compensated signal light information at the 70-meter position. It should be noted that at this time, the signal light information contains complete nonlinear distortion as well as linear distortion from the transmitting end position to the 70-meter position.

[0075] Nonlinear probe processing is performed on the partially linearly compensated signal light information at the 70-meter position, that is, the nonlinear distortion at the 70-meter position in the signal light information is compensated; then the linear distortion from the originating position to the 70-meter position is compensated, that is, the residual linear compensation, to obtain the signal light information with nonlinear information at the 70-meter position. At this time, the linear distortion in the signal light information with nonlinear information is basically completely compensated, and the nonlinear distortion part includes all nonlinear distortions except for those at the 70-meter position.

[0076] It is important to note that the signal light information with nonlinear information at each location needs to be pre-processed to remove the phase information and retain the amplitude information.

[0077] In step 406, the signal light information with nonlinear information at each position is correlated with the lossless signal light information at the transmitting end position to obtain the longitudinal power distribution curve on the communication optical fiber 4.

[0078] Since the linear and nonlinear distortions in the lossless signal light information at the originating position have been basically compensated, the difference obtained by comparing the nonlinear signal light information at each position with the lossless signal light information at the originating position is the nonlinear distortion at each position. Since the nonlinear distortion is related to the power of the signal light, the power of the signal light at each position can be obtained based on the nonlinear distortion at each position, which is the longitudinal power distribution curve.

[0079] It is important to note that in existing technologies, the power at different locations in the optical fiber is typically determined by transmitting pulses from the transmitting end and receiving the scattered light reflected back from different positions within the fiber. This method requires an additional pulsed laser and corresponding receiving equipment at the transmitting end. However, the method used in this embodiment only requires normal processing of the signal light received at the receiving end 7, without the need for additional equipment. This accurately obtains the longitudinal power distribution curve while reducing device costs. Figure 8 The diagram shown is a schematic of the process for obtaining the longitudinal power distribution curve.

[0080] Furthermore, in this embodiment, after obtaining the longitudinal power distribution curve of the communication optical fiber 4, it is necessary to perform nonlinear compensation calculation on the receiving signal based on the longitudinal power distribution curve and the parameters of the communication optical fiber 4. The corresponding method is designed as follows.

[0081] The method involves performing a reverse calculation of the receiving signal from the receiving end 7 to the transmitting end based on the longitudinal power distribution curve and the parameters of the communication optical fiber 4, to perform nonlinear compensation calculation on the receiving signal, thereby obtaining the nonlinearly compensated signal light information at the corresponding position on the communication optical fiber 4, such as... Figure 2 As shown, the method flow is as follows.

[0082] The distributed gain coefficient on the communication optical fiber 4 is obtained based on the longitudinal power distribution curve. The dispersion coefficient, loss coefficient, and nonlinearity coefficient are obtained based on the parameters of the communication optical fiber 4. The nonlinear Schrödinger equation is then inversely calculated based on the received signal, distributed gain coefficient, dispersion coefficient, loss coefficient, and nonlinearity coefficient. Nonlinear compensation is then applied to the received signal along the direction from the receiver 7 to the transmitter to obtain the nonlinearly compensated signal light information at the corresponding position on the communication optical fiber 4.

[0083] In this embodiment, the power information corresponding to different positions on the communication optical fiber 4 can be obtained through the longitudinal power distribution curve of the communication optical fiber 4. By comparing the optical power information at different positions, the amplification factor of the optical power at the corresponding position can be obtained, and then the Raman gain coefficient of the optical signal at different positions on the communication optical fiber 4 can be obtained, that is, the distributed gain coefficient.

[0084] The specific steps are as follows: obtain the optical power information corresponding to each position of the communication optical fiber 4 according to the longitudinal power distribution curve; obtain the optical power gain corresponding to each position of the communication optical fiber 4 according to the optical power information corresponding to each position of the communication optical fiber 4; obtain the gain coefficient corresponding to each position of the communication optical fiber 4 according to the optical power gain corresponding to each position of the communication optical fiber 4, and then obtain the distributed gain coefficient on the communication optical fiber 4.

[0085] In this embodiment, the dispersion coefficient, loss coefficient, and nonlinear coefficient are related to the optical path configuration. Once the optical path configuration is determined, the dispersion coefficient, loss coefficient, and nonlinear coefficient will hardly change.

[0086] The expression for the nonlinear Schrödinger equation is as follows.

[0087] ; Where A(z,t) is the signal light information at position z from the transmitting end on the communication optical fiber 4, z is the length from the transmitting end to the specified position on the communication optical fiber 4, α is the loss coefficient, g(z) is the gain coefficient at position z from the transmitting end on the communication optical fiber 4, i is the imaginary unit, β is the dispersion coefficient, and γ is the nonlinear coefficient.

[0088] In this embodiment, based on the known distributed gain coefficient, dispersion coefficient, loss coefficient, and nonlinear coefficient, the receiving signal is substituted into the nonlinear Schrödinger equation for inverse solution. The signal light information at each position of the communication optical fiber 4 is gradually calculated along the direction from the receiving end 7 to the transmitting end until the signal light information A(0,t) at the transmitting end position is obtained, which is the signal light information after nonlinear compensation.

[0089] Furthermore, since the aforementioned nonlinear Schrödinger equation contains both linear and nonlinear terms, it cannot be solved directly with an exact solution. Therefore, in this embodiment, the corresponding equation can be solved by finding an approximate solution. The corresponding method is designed as follows.

[0090] The method involves performing inverse calculation of the nonlinear Schrödinger equation based on the received signal, distributed gain coefficient, dispersion coefficient, loss coefficient, and nonlinear coefficient, and then performing nonlinear compensation on the received signal along the direction from the receiver 7 to the transmitter. The procedure is as follows.

[0091] The communication optical fiber 4 is divided into multiple segments of equal length. Starting from the segment closest to the receiving end 7, the received signal is substituted into the nonlinear Schrödinger equation for backward recursive calculation. In step 302, following the order from the receiving end 7 to the transmitting end, for all adjacent segments of the communication optical fiber 4, the linear and nonlinear terms in the nonlinear Schrödinger equation are calculated alternately to sequentially obtain the signal light information corresponding to each segment of the optical fiber. The obtained signal light information corresponding to the corresponding optical fiber position is used as the nonlinearly compensated signal light information corresponding to the corresponding optical fiber position.

[0092] In this embodiment, the linear term in the nonlinear Schrödinger equation is: and The nonlinear term is In this embodiment, to improve the accuracy of the obtained approximate solution, it is necessary to ensure that the length of each segment of optical fiber is as short as possible. Furthermore, when solving for the signal light information corresponding to each segment of optical fiber, for two adjacent segments, one communication optical fiber 4 is solved using the linear term of the nonlinear Schrödinger equation, while the other communication optical fiber 4 is solved using the nonlinear term of the nonlinear Schrödinger equation. When using the linear term of the nonlinear Schrödinger equation, the nonlinear term is treated as 0, and the corresponding parameters are substituted into the linear term to obtain the signal light information corresponding to the corresponding position.

[0093] To illustrate the above solution method more intuitively, the following example is used: For instance, the communication fiber 4 is divided into 10 segments of equal length. From the transmitter to the receiver 7, all segments are numbered sequentially from 1 to 10. Starting with the 10th segment, which is closest to the receiver 7, the 10th segment is solved using nonlinear terms. The 9th segment is solved using linear terms, and the 8th segment of the communication fiber 4 is solved using nonlinear terms. The solutions for adjacent segments of the communication fiber 4 are performed alternately using nonlinear and linear terms until the solution is reached for the 1st segment of the communication fiber 4, thus obtaining the signal light information at the transmitter position.

[0094] 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, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A nonlinear compensation method for an ultra-long single-span optical communication system, characterized in that, include: Obtain the receiving signal from the receiving end (7), and obtain the longitudinal power distribution curve on the communication optical fiber (4) based on the receiving signal; The calculated coefficients are obtained based on the longitudinal power distribution curve and the parameters of the communication optical fiber (4); Based on the calculated coefficient, the receiving signal is reversed from the receiving end (7) to the transmitting end in the direction of the receiving end, so as to perform nonlinear compensation calculation on the receiving signal and obtain the nonlinear compensated signal light information at the corresponding position on the communication optical fiber (4).

2. The nonlinear compensation method for an ultra-long single-span optical communication system according to claim 1, characterized in that, The calculation coefficients are obtained based on the longitudinal power distribution curve and the parameters of the communication optical fiber (4); the reverse calculation of the receiving signal from the receiving end (7) to the transmitting end is performed based on the calculation coefficients to perform nonlinear compensation calculation on the receiving signal, and the nonlinear compensated signal light information at the corresponding position on the communication optical fiber (4) is obtained, specifically including: The distributed gain coefficient on the communication optical fiber (4) is obtained based on the longitudinal power distribution curve. The dispersion coefficient, loss coefficient, and nonlinear coefficient are obtained based on the parameters of the communication optical fiber (4); The distributed gain coefficient, dispersion coefficient, loss coefficient and nonlinear coefficient are used together as the estimation coefficients. Based on the received signal and the estimation coefficients, the nonlinear Schrödinger equation is calculated in reverse. The received signal is nonlinearly compensated along the direction from the receiver (7) to the transmitter to obtain the nonlinearly compensated signal light information at the corresponding position on the communication optical fiber (4).

3. The nonlinear compensation method for ultra-long single-span optical communication systems according to claim 2, characterized in that, The process of obtaining the distributed gain coefficient on the communication optical fiber (4) based on the longitudinal power distribution curve specifically includes: The optical power information corresponding to each position on the communication optical fiber (4) is obtained according to the longitudinal power distribution curve; The optical power gain corresponding to each position on the communication optical fiber (4) is obtained based on the optical power information corresponding to each position on the communication optical fiber (4); The gain coefficients corresponding to each position on the communication optical fiber (4) are obtained based on the optical power gain corresponding to each position on the communication optical fiber (4), and then the distributed gain coefficients on the communication optical fiber (4) are obtained. The expression for obtaining the distributed gain coefficient is: ； in, for Location-based optical power information for Location-based optical power information The loss coefficient is... for Location and Distance between locations for Distributed gain coefficient at location.

4. The nonlinear compensation method for an ultra-long single-span optical communication system according to claim 2, characterized in that, The expression for the nonlinear Schrödinger equation is: ； Where z is the length of the communication optical fiber (4) from the transmitting end to the specified position, A(z,t) is the signal light information at length z of the communication optical fiber (4), α is the loss coefficient, g(z) is the gain coefficient at length z of the communication optical fiber (4), i is the imaginary unit, β is the dispersion coefficient, and γ is the nonlinear coefficient.

5. The nonlinear compensation method for an ultra-long single-span optical communication system according to claim 2, characterized in that, The step of performing a reverse calculation of the receiving signal from the receiving end (7) to the transmitting end based on the calculated coefficients, in order to perform nonlinear compensation calculation on the receiving signal, specifically includes: The communication optical fiber (4) is divided into multiple segments of the same length. Starting from the segment of the optical fiber closest to the receiving end (7), the receiving end signal is substituted into the nonlinear Schrödinger equation for reverse recursive calculation. Following the order from the receiver (7) to the transmitter, for all adjacent fiber segments in the communication fiber (4), the linear and nonlinear terms in the nonlinear Schrödinger equation are calculated alternately to obtain the nonlinear compensation signal light information of each fiber segment.

6. A nonlinear compensation device for an ultra-long single-span optical communication system, used to apply the nonlinear compensation method for an ultra-long single-span optical communication system as described in any one of claims 1-5, characterized in that, include: The system comprises a laser (1), a first wavelength division multiplexer (2), a forward Raman amplifier (3), a communication optical fiber (4), a second wavelength division multiplexer (5), a backward Raman amplifier (6), and a receiver (7), wherein: The first wavelength division multiplexer (2) receives the signal light from the laser (1) and the forward pump light from the forward Raman amplification unit (3), respectively. The forward pump light amplifies the signal light in the forward direction. The forward amplified signal light is transmitted to the second wavelength division multiplexer (5) through the communication optical fiber (4). The second wavelength division multiplexer (5) receives the signal light and the back pump light from the back Raman amplification unit (6), respectively. The back pump light amplifies the signal light in the back direction. The receiving end (7) receives the back amplified signal light as the receiving end signal. The receiving end (7) is used to obtain the longitudinal power distribution curve on the communication optical fiber (4) based on the receiving end signal; Based on the longitudinal power distribution curve and the parameters of the communication optical fiber (4), the receiving signal is reverse-calculated to perform nonlinear compensation calculation on the receiving signal, so as to obtain the nonlinearly compensated signal light information at the corresponding position on the communication optical fiber (4).

7. The nonlinear compensation device for an ultra-long single-span optical communication system according to claim 6, characterized in that, The receiving end (7) is used to obtain the longitudinal power distribution curve on the communication optical fiber (4) based on the receiving end signal, specifically including: The received signal is subjected to bus distortion compensation to obtain the bus-compensated signal optical information; The bus-compensated signal light information is processed to obtain lossless signal light information at the transmitting end position. The bus-linearly compensated signal optical information is loaded with bus-linear distortion on the communication optical fiber (4) to obtain signal optical information with complete linear distortion; According to each position on the communication optical fiber (4), the signal light information with complete linear distortion is compensated for the partial linear distortion from the corresponding position to the receiving end (7) to obtain the signal light information with partial linear compensation at each position of the communication optical fiber (4). Nonlinear probe processing is performed on the partially linearly compensated signal light information at each position to subtract the nonlinear distortion at the corresponding position, and residual linear compensation is performed to obtain the signal light information with nonlinear information at each position. The signal light information with nonlinear information at each location is correlated with the lossless signal light information at the originating location to obtain the longitudinal power distribution curve on the communication optical fiber (4).

8. The nonlinear compensation device for an ultra-long single-span optical communication system according to claim 6, characterized in that, The nonlinear compensation device for the ultra-long single-span optical communication system further includes a modulator (8), a first amplifier (9), a second amplifier (10), and a coherent receiver (11), wherein: The modulator (8) and the first amplifier (9) are sequentially disposed on the optical path between the laser (1) and the first wavelength division multiplexer (2); the modulator (8) is used to modulate the optical signal emitted by the laser (1), and the first amplifier (9) is used to amplify the modulated optical signal. The second amplifier (10) and the coherent receiver (11) are sequentially arranged in the optical path between the second wavelength division multiplexer (5) and the receiver (7); the second amplifier (10) is used to amplify the signal light from the second wavelength division multiplexer (5), and the coherent receiver (11) is used to acquire the phase information in the signal light.

9. The nonlinear compensation device for an ultra-long single-span optical communication system according to claim 6, characterized in that, The step of performing a reverse calculation of the receiving signal from the receiving end (7) to the transmitting end based on the calculated coefficient, in order to perform nonlinear compensation calculation on the receiving signal and obtain the nonlinearly compensated signal light information at the corresponding position on the communication optical fiber (4), specifically includes: The receiving end (7) obtains the distributed gain coefficient on the communication optical fiber (4) according to the longitudinal power distribution curve; The receiving end (7) obtains the dispersion coefficient, loss coefficient and nonlinear coefficient according to the parameters of the communication optical fiber (4); The receiving end (7) performs inverse calculation of the nonlinear Schrödinger equation based on the receiving end signal, distributed gain coefficient, dispersion coefficient, loss coefficient and nonlinear coefficient, and performs nonlinear compensation on the receiving end signal along the direction from the receiving end (7) to the transmitting end to obtain the nonlinear compensated signal light information at the corresponding position on the communication optical fiber (4).

10. The nonlinear compensation device for an ultra-long single-span optical communication system according to claim 9, characterized in that, The inverse calculation of the nonlinear Schrödinger equation based on the received signal, distributed gain coefficient, dispersion coefficient, loss coefficient, and nonlinear coefficient, and the nonlinear compensation of the received signal along the direction from the receiver (7) to the transmitter, specifically includes: The communication optical fiber (4) is divided into multiple segments of the same length. Starting from the segment of the optical fiber closest to the receiving end (7), the receiving end signal is substituted into the nonlinear Schrödinger equation for reverse recursive calculation. Following the order from the receiver (7) to the transmitter, for all adjacent fiber segments in the communication fiber (4), the linear and nonlinear terms in the nonlinear Schrödinger equation are calculated alternately to obtain the nonlinear compensation signal light information of each fiber segment.

11. A non-volatile computer storage medium, characterized in that, The computer storage medium stores computer-executable instructions, which are executed by one or more processors to perform the nonlinear compensation method for an ultra-long single-span optical communication system as described in any one of claims 1-5.

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