Long-distance single-span optical transmission method and system

Abstract

The present invention relates to a long-distance single-span optical transmission method and system. The method comprises: constructing a digital model based on optical transmission system parameters, the digital model being used to determine the corresponding relationship between the terminal output spectral signal-to-noise ratio and the required pump power; inputting the target output spectral signal-to-noise ratio into the digital model and obtaining a predicted pump power based on the corresponding relationship; and iteratively adjusting the actual terminal output spectral signal-to-noise ratio of the optical transmission system based on the difference between the predicted pump power and the actual pump power to optimize the digital model. This method can effectively improve the transmission distance and capacity of ultra-long-distance single-span optical communication systems and enhance the system's pump calculation and regulation efficiency.

Description

Technical Field

[0001] The present invention relates to the field of optical transmission technology, and in particular to a long-distance single-span optical transmission method and system. Background Art

[0002] In the context of 5G, big data, and cloud computing, with the continuous development of marine networks, the single-span transmission mode has increasingly higher requirements for transmission performance and is developing towards longer distances and larger capacities.

[0003] Currently, the physical implementation of single-span, long-distance optical transmission systems primarily relies on backward remote pumping, supplemented by Raman amplification. The optical cable utilizes traditional G.652D fiber, and the remote pump subsystem is networked using either a follow-on or bypass approach. However, due to inherent limitations in gain, noise figure, and insertion loss, traditional first-order remote pumping, first-order Raman, and G.652D fiber networking methods are increasingly unable to meet the transmission requirements of ultra-long single spans. Furthermore, due to issues such as fiber nonlinearity, device insertion loss, aging, and submarine cable maintenance, system designers often need to establish an offline test environment and perform calculations based on extensive laboratory test data to optimize the Raman and remote pump configurations before and after the project launch. This is a time-consuming and labor-intensive process. Summary of the Invention

[0004] The embodiments of the present invention provide a long-distance single-span optical transmission method and system, which improve the transmission distance and capacity of an ultra-long-distance single-span optical communication system and enhance the pump calculation and regulation efficiency of the system.

[0005] On the one hand, a long-distance single-span optical transmission method is provided, characterized in that it includes the steps of:

[0006] Building a digital model based on optical transmission system parameters, wherein the digital model is used to determine the corresponding relationship between the terminal output spectral signal-to-noise ratio and the required pump power;

[0007] Inputting the target output spectrum signal-to-noise ratio into the digital model and obtaining the predicted pump power based on the corresponding relationship;

[0008] The actual terminal output spectrum signal-to-noise ratio of the optical transmission system is iteratively adjusted based on the difference between the predicted pump power and the actual pump power to optimize the digital model.

[0009] In some embodiments, constructing a digital model based on optical transmission system parameters comprises the steps of:

[0010] Determining the corresponding relationship between the terminal output spectral signal-to-noise ratio and the required pump power based on the Raman power coupling equation, the remote pump transmission equation and the Gaussian noise model;

[0011] The digital model is trained based on the measured terminal output spectrum signal-to-noise ratio and the actual input pump power to optimize the corresponding relationship.

[0012] In some embodiments, determining the correspondence between the terminal output spectral signal-to-noise ratio and the required pump power based on the Raman power coupling equation, the remote pump transmission equation, and the Gaussian noise model comprises the following steps:

[0013] The gain and noise of each channel are calculated using the Raman power coupling equation;

[0014] The gain and noise of each channel are calculated using the tele-pump transmission equation;

[0015] The Gaussian noise model is used to calculate the noise of each channel and the signal-to-noise ratio of the terminal output spectrum is calculated by amplifying the spontaneous emission noise and nonlinear noise.

[0016] In some embodiments, the calculation of the gain and noise of each channel using the Raman power coupling equation includes:

[0017] The gain and noise of each channel are calculated based on a first formula, where the first formula is:

[0018]

[0019] Among them, α sigi represents the loss coefficient of the signal channel i in the optical fiber, P sigi (z) represents the power of the ith channel at position z, C R (f pj , f sigi ) represents the frequency f pj The pump frequency is f sigi The Raman coupling coefficient between the signals, P p1j (z) is the pump power of the Raman amplifier at the transmitting end, P 3j (z) is the Raman amplifier pump power at the receiving end.

[0020] In some embodiments, the calculation of the gain and noise of each channel using the remote pump transmission equation includes the steps of:

[0021] The gain and noise of each channel are calculated based on a second formula, where the second formula is:

[0022]

[0023] Among them, μ k Indicates the direction of light transmission, μ k =1 means forward, μ k =-1 means backward, σ ek Indicates the emission cross-sectional coefficient, mhv k Δvk The spontaneous radiation of P caused by the number of particles in the upper energy level n2 k contribution, m represents the number of modes, v k To amplify the bandwidth of spontaneous emission, σ ak represents the absorption cross-section coefficient, represents the normalized intensity distribution function of the beam, r and represents the cross-sectional coordinates of the erbium fiber, P k (z) represents the optical power at point z along the fiber length in the fiber amplifier.

[0024] In some embodiments, the method of calculating the noise of each channel using a Gaussian noise model and calculating the terminal output spectrum signal-to-noise ratio by amplifying spontaneous emission noise and nonlinear noise includes the steps of:

[0025] The terminal output spectrum signal-to-noise ratio is calculated based on a third formula, wherein the third formula includes:

[0026]

[0027]

[0028]

[0029]

[0030] Among them, SNR i represents the signal-to-noise ratio of the i-th channel, P ASE To amplify the spontaneous emission noise power, η n is the nonlinear crosstalk coefficient, P si is the signal power, G(f) is the power spectral density of nonlinear crosstalk, f i is the center frequency of the ith channel, Φ is the intermediate variable, γ is the nonlinear coefficient, β2 is the group velocity dispersion parameter, β3 is the slope of the group velocity dispersion parameter, is the normalized signal power distribution, B ch is the signal bandwidth, G(v+f i ) is V, the frequency integral symbol, G Tx is the input signal power spectral density, is the intermediate variable, is the transmission distance.

[0031] In some embodiments, the iterative adjustment of the actual terminal output spectral signal-to-noise ratio of the optical transmission system based on the difference between the predicted pump power and the actual pump power to optimize the digital model comprises the steps of:

[0032] Calculating a root mean square error between the predicted pump power and the actual pump power;

[0033] If the root mean square error does not meet the target accuracy, calculating the signal gain required by the optical transmission system based on the root mean square error and adjusting the actual terminal output spectrum signal-to-noise ratio of the optical transmission system based on the signal gain;

[0034] The adjusted actual terminal output spectrum signal-to-noise ratio is used as the input of the digital model, and a new predicted pump power and a corresponding new root mean square error are calculated until the new root mean square error meets the target accuracy.

[0035] In some embodiments, the root mean square error is calculated based on a fourth formula, which is:

[0036]

[0037] Wherein, RMSE is the root mean square error, P pi，GPR is the predicted pump power, P pi is the actual pump power, and m is the number of pumps.

[0038] On the other hand, a long-distance single-span optical transmission system is provided, characterized in that it includes:

[0039] An automatic adjustment system interacting with an optical transmission system, the automatic adjustment system comprising:

[0040] A digital model building module, which is used to build a digital model based on the optical transmission system parameters, wherein the digital model is used to determine the corresponding relationship between the terminal output spectrum and the required pump power;

[0041] A prediction output module, configured to input a target output spectrum into the digital model and obtain a predicted pump power based on the corresponding relationship;

[0042] An automatic adjustment module is used to iteratively adjust the actual terminal output spectral signal-to-noise ratio of the optical transmission system based on the difference between the predicted pump power and the actual pump power to optimize the digital model.

[0043] In some embodiments, the optical transmission system is further included, and from the transmitting end to the receiving end of the optical signal, the optical transmission system includes:

[0044] Signal transmitting unit, transmitting optical amplifier, forward second-order Raman amplifier, forward remote pumping gain unit, backward remote pumping gain unit, backward Raman amplifier, receiving optical amplifier, wave splitter and signal receiving unit;

[0045] The forward remote pump gain unit is connected to the forward second-order pump emission unit, and the forward second-order pump emission unit is used to provide pump light to the forward remote pump gain unit through a pump optical fiber;

[0046] The backward remote pumping gain unit is connected to the backward second-order pumping emission unit, and the backward second-order pumping emission unit provides pumping light for the backward remote pumping gain unit through a pumping optical fiber.

[0047] The embodiment of the present invention provides a long-distance single-span optical transmission method and system. The long-distance single-span optical transmission method provided by the embodiment of the present invention calculates and constructs a digital model acting on the optical transmission system based on the parameters of the optical transmission system, and predicts and adjusts the pump light power through the digital model to change the output signal OSNR spectrum. The combination of digital modeling and automatic pump adjustment technology can quickly and accurately perform Raman pumping and remote pumping adjustments, and intelligently achieve automatic balancing of OSNR (Optical Signal Noise Ratio). On the other hand, in the system provided by the embodiment of the present invention, a second-order Raman and second-order remote pump optical transmission system structure is adopted, which has a lower equivalent noise coefficient and a higher system Q factor while achieving higher gain, can reduce transmission noise, improve signal-to-noise ratio, and at the same time provide a higher-power pump signal for the remote pump unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] 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.

[0049] Figure 1 A schematic diagram of a flow chart of a long-distance single-span optical transmission method provided by an embodiment of the present invention;

[0050] Figure 2 A schematic diagram of the optical transmission system structure provided by an embodiment of the present invention;

[0051] Figure 3 A schematic diagram of the interaction between the digital model and the optical transmission system provided by an embodiment of the present invention;

[0052] Figure 4 A schematic diagram of the structure of a long-distance single-span optical transmission system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0054] like Figure 1 As shown, an embodiment of the present invention provides a long-distance single-span optical transmission method, characterized in that it includes the steps of:

[0055] S100: Constructing a digital model based on optical transmission system parameters, wherein the digital model is used to determine a corresponding relationship between a terminal output spectral signal-to-noise ratio and a required pump power;

[0056] S200: Inputting the target output spectrum signal-to-noise ratio into the digital model and obtaining a predicted pump power based on the corresponding relationship;

[0057] S300: Iteratively adjusting the actual terminal output spectral signal-to-noise ratio of the optical transmission system based on the difference between the predicted pump power and the actual pump power to optimize the digital model.

[0058] It should be noted that the optical transmission system parameters in S100 may include: Raman amplifier parameters, remote pump parameters, device insertion loss, and fiber parameters. Among them, Raman amplifier parameters include wavelength-dependent insertion loss spectrum, pump center wavelength, and maximum pump power of each pump; remote pump parameters include wavelength-dependent insertion loss spectrum, pump center wavelength, and maximum pump power of each pump; fiber parameters include wavelength-dependent insertion loss spectrum of transmission fiber, Raman gain coefficient, and pump light wavelength-dependent insertion loss spectrum of pump fiber;

[0059] This embodiment of the present invention calculates and constructs a digital model of the optical transmission system based on its parameters. This digital model is then used to predict and adjust the pump optical power, thereby altering the output signal's OSNR spectrum. This combination of digital modeling and automatic pump adjustment allows for rapid and precise Raman and remote pumping adjustments, intelligently achieving automatic OSNR (Optical Signal Noise Ratio) balancing.

[0060] In a specific embodiment, for example Figure 2 The optical transmission system shown can obtain the OSNR of each channel in the input spectrum of the optical transmission system, the wavelength-dependent insertion loss spectrum of Raman amplifier 1 and Raman amplifier 2, the pump center wavelength, and the maximum pump power of each pump; the wavelength-dependent insertion loss spectrum of pump transmitting unit 1 and pump transmitting unit 2, the pump center wavelength, and the maximum pump power of each pump; the wavelength-dependent insertion loss spectrum and Raman gain coefficient of transmission fiber 1 and transmission fiber 2; and the wavelength-dependent insertion loss spectrum of pump fiber 1 and pump fiber 2.

[0061] The required parameters include but are not limited to the input signal power P of the Raman amplifier 1 sig , pump power [P p1 , P p2 , Pp3 , P p4 ], system insertion loss Att1, VOA attenuation value Att2 of optical amplifier 2, fiber parameters (length L eff , loss coefficient α s and the Raman coupling coefficient C R ).

[0062] In some embodiments, constructing a digital model based on optical transmission system parameters in S100 includes the following steps:

[0063] S110: Determine a corresponding relationship between the terminal output spectrum signal-to-noise ratio and the required pump power based on a Raman power coupling equation, a remote pump transmission equation, and a Gaussian noise model;

[0064] S120: Training the digital model based on the measured terminal output spectrum signal-to-noise ratio and the actual input pump power to optimize the corresponding relationship.

[0065] It is understood that in S120, the initial values ​​of the corresponding hyperparameters are set according to the kernel function of step S110, thereby determining the prior model of the digital model. By training the prior model, the optimal hyperparameters are obtained, and then the posterior model, i.e., the final digital model, is determined. The digital model is used to predict the input of the test set (the input is the actual output spectrum OSNR, and the prediction result is the required pump power), and the distribution of the predicted output points can be obtained, i.e., the mean and covariance with the ability to express uncertainty. The predicted output of the test set is compared with the actual output, and the corresponding root mean square error and mean absolute error are calculated to analyze and evaluate the prediction performance of the digital model.

[0066] Furthermore, S110 includes the steps of:

[0067] S111: Calculate the gain and noise of each channel using the Raman power coupling equation;

[0068] S112: Calculate the gain and noise of each channel using the remote pump transmission equation;

[0069] S113: The noise of each channel is calculated using a Gaussian noise model and the signal-to-noise ratio of the terminal output spectrum is calculated by amplifying the spontaneous emission noise and nonlinear noise.

[0070] Preferably, in S111, the gain and noise of each channel are calculated based on a first formula, and the first formula is:

[0071]

[0072] Among them, α sigi represents the loss coefficient of the signal channel i in the optical fiber, P sigi (z) represents the power of the ith channel at position z, CR (f pj , f sigi ) represents the frequency f pj The pump frequency is f sigi The Raman coupling coefficient between the signals, P p1j (z) is the pump power of the Raman amplifier at the transmitting end, P 3j (z) is the Raman amplifier pump power at the receiving end.

[0073] Preferably, in S112, the gain and noise of each channel are calculated based on a second formula, and the second formula is:

[0074]

[0075] Among them, μ k Indicates the direction of light transmission, μ k =1 means forward, μ k =-1 means backward, σ ek Indicates the emission cross-sectional coefficient, mhv k Δv k The spontaneous radiation of P caused by the number of particles in the upper energy level n2 k contribution, m represents the number of modes, v k To amplify the bandwidth of spontaneous emission, σ ak represents the absorption cross-section coefficient, represents the normalized intensity distribution function of the beam, r and represents the cross-sectional coordinates of the erbium fiber, P k (z) represents the optical power at point z along the fiber length in the fiber amplifier.

[0076] Preferably, in S113, the terminal output spectrum signal-to-noise ratio is calculated based on a third formula, and the third formula includes:

[0077]

[0078]

[0079]

[0080]

[0081] Among them, SNR i represents the signal-to-noise ratio of the i-th channel, P ASE To amplify the spontaneous emission noise power, η n is the nonlinear crosstalk coefficient, P si is the signal power, G(f) is the power spectral density of nonlinear crosstalk, f iis the center frequency of the ith channel, Φ is the intermediate variable, γ is the nonlinear coefficient, β2 is the group velocity dispersion parameter, β3 is the slope of the group velocity dispersion parameter, is the normalized signal power distribution, B ch is the signal bandwidth, G(v+f i ) is v is the frequency integral symbol, G Tx is the input signal power spectral density, is the intermediate variable, is the transmission distance.

[0082] In some embodiments, S300 further includes the steps of:

[0083] S310: Calculating a root mean square error between the predicted pump power and the actual pump power;

[0084] S320: If the root mean square error does not meet the target accuracy, calculating the signal gain required by the optical transmission system based on the root mean square error and adjusting the actual terminal output spectrum signal-to-noise ratio of the optical transmission system based on the signal gain;

[0085] S330: Using the adjusted actual terminal output spectrum signal-to-noise ratio as the input of the digital model and calculating a new predicted pump power and a corresponding new root mean square error until the new root mean square error meets the target accuracy.

[0086] Preferably, in S310, the root mean square error may be calculated based on a fourth formula, and the fourth formula is:

[0087]

[0088] Wherein, RMSE is the root mean square error, P pi，GPR is the predicted pump power, P pi is the actual pump power, and m is the number of pumps.

[0089] In some embodiments, a gradient descent method is used to adjust the gain, seeking to minimize the root mean square error or lowering it below a given value along a decreasing root mean square error path. During each iterative adjustment, the output spectrum OSNR is corrected to minimize the root mean square error between the predicted pump power and the actual pump power. The iterative adjustment process can be expressed as:

[0090]

[0091] Where k is the number of iterations, λ k For the iteration step, select a suitable initial value OSNR k , (k=0), let the target accuracy be ε, when RMSEk-RMSE k+1When it is less than ε, the iterative adjustment is stopped and it is considered that the root mean square error at this time meets the preset conditions.

[0092] like Figure 4 As shown, an embodiment of the present invention further provides a long-distance single-span optical transmission system, which includes: an automatic adjustment system interacting with the optical transmission system, the automatic adjustment system including:

[0093] A digital model building module, which is used to build a digital model based on the optical transmission system parameters, wherein the digital model is used to determine the corresponding relationship between the terminal output spectrum and the required pump power;

[0094] A prediction output module, configured to input a target output spectrum into the digital model and obtain a predicted pump power based on the corresponding relationship;

[0095] An automatic adjustment module is used to iteratively adjust the actual terminal output spectral signal-to-noise ratio of the optical transmission system based on the difference between the predicted pump power and the actual pump power to optimize the digital model.

[0096] In some embodiments, the digital model construction module is further used to: determine the correspondence between the terminal output spectral signal-to-noise ratio and the required pump power based on the Raman power coupling equation, the remote pump transmission equation and the Gaussian noise model; and train the digital model based on the measured terminal output spectral signal-to-noise ratio and the actual input pump power to optimize the correspondence.

[0097] In some embodiments, the digital model construction module is further used to: calculate the gain and noise of each channel using the Raman power coupling equation; calculate the gain and noise of each channel using the remote pump transmission equation; calculate the noise of each channel using the Gaussian noise model and calculate the terminal output spectral signal-to-noise ratio by amplifying the spontaneous radiation noise and nonlinear noise.

[0098] In some embodiments, the digital model building module is further configured to calculate the gain and noise of each channel based on a first formula, where the first formula is:

[0099]

[0100] Among them, α sigi represents the loss coefficient of the signal channel i in the optical fiber, P sigi (z) represents the power of the ith channel at position z, C R (f pj , f sigi ) represents the frequency f pj The pump frequency is f sigi The Raman coupling coefficient between the signals, P p1j (z) is the pump power of the Raman amplifier at the transmitting end, P 3j(z) is the Raman amplifier pump power at the receiving end.

[0101] In some embodiments, the digital model building module is further configured to calculate the gain and noise of each channel based on a second formula, where the second formula is:

[0102]

[0103] Among them, μ k Indicates the direction of light transmission, μ k =1 means forward, μ k =-1 means backward, σ ek Indicates the emission cross-sectional coefficient, mhv k Δv k The spontaneous radiation of P caused by the number of particles in the upper energy level n2 k contribution, m represents the number of modes, v k To amplify the bandwidth of spontaneous emission, σ ak represents the absorption cross-section coefficient, represents the normalized intensity distribution function of the beam, r and represents the cross-sectional coordinates of the erbium fiber, P k (z) represents the optical power at point z along the fiber length in the fiber amplifier.

[0104] In some embodiments, the digital model building module is further configured to calculate the terminal output spectrum signal-to-noise ratio based on a third formula, and the third formula includes:

[0105]

[0106]

[0107]

[0108]

[0109] Among them, SNR i represents the signal-to-noise ratio of the i-th channel, P ASE To amplify the spontaneous emission noise power, η n is the nonlinear crosstalk coefficient, P si is the signal power, G(f) is the power spectral density of nonlinear crosstalk, f i is the center frequency of the ith channel, Φ is the intermediate variable, γ is the nonlinear coefficient, β2 is the group velocity dispersion parameter, β3 is the slope of the group velocity dispersion parameter, is the normalized signal power distribution, B ch is the signal bandwidth, G(v+f i ) is v is the frequency integral symbol, G Tx is the input signal power spectral density, is the intermediate variable, is the transmission distance.

[0110] In some embodiments, the automatic adjustment module is further used to: calculate the root mean square error between the predicted pump power and the actual pump power; if the root mean square error does not meet the target accuracy, calculate the signal gain required by the optical transmission system based on the root mean square error and adjust the actual end output spectrum signal-to-noise ratio of the optical transmission system based on the signal gain; use the adjusted actual end output spectrum signal-to-noise ratio as the input of the digital model and calculate the new predicted pump power and the corresponding new root mean square error until the new root mean square error meets the target accuracy.

[0111] Preferably, the automatic adjustment module further calculates the root mean square error based on a fourth formula, and the fourth formula is:

[0112]

[0113] Wherein, RMSE is the root mean square error, P pi，GPR is the predicted pump power, P pi is the actual pump power, and m is the number of pumps.

[0114] like Figure 2 As shown, the long-distance single-span optical transmission system provided by the present invention also includes an optical transmission system, and from the transmitting end to the receiving end of the optical signal, the optical transmission system includes:

[0115] Signal transmitting unit, transmitting optical amplifier, forward second-order Raman amplifier, forward remote pumping gain unit, backward remote pumping gain unit, backward Raman amplifier, receiving optical amplifier, wave splitter and signal receiving unit;

[0116] The forward remote pump gain unit is connected to the forward second-order pump emission unit, and the forward second-order pump emission unit is used to provide pump light to the forward remote pump gain unit through a pump optical fiber;

[0117] The backward remote pumping gain unit is connected to the backward second-order pumping emission unit, and the backward second-order pumping emission unit provides pumping light for the backward remote pumping gain unit through a pumping optical fiber.

[0118] It can be understood that the optical transmission system provided by the embodiment of the present invention is an ultra-low loss and high-power transmission system that can be applied to a single span of an ultra-long-distance submarine cable. The signal transmitting unit and the signal receiving unit complete the signal transmission and reception functions; the transmitting optical amplifier and the forward second-order Raman amplifier complete the signal amplification function and signal pre-emphasis; the forward second-order pump transmitting unit provides pump light to the forward remote pump gain unit via the pump fiber; the backward second-order pump transmitting unit provides pump light to the backward remote pump gain unit via the pump fiber; the transmission signal is amplified twice by the forward remote pump gain unit and the backward remote pump gain unit, then reaches the backward second-order Raman amplifier and the receiving optical amplifier, and then reaches the signal receiving unit after passing through the wavelength splitter, completing the signal transmission and reception. The transmission optical fiber and pump optical fiber used in the system network can be selected from low-loss and large-effective-area optical fibers to reduce transmission loss and extend transmission distance; the second-order Raman is used to increase signal gain and reduce noise figure; the second-order remote pump is used to provide a high-power pump signal to the remote pump gain unit.

[0119] Preferably, the optical signal transmission system, from the transmitting end to the receiving end, may include, in order: a signal transmitting unit, a combiner, a dispersion compensation unit, a transmitting optical amplifier, a forward second-order Raman amplifier, a forward remote pump gain unit, a backward remote pump gain unit, a backward Raman amplifier, a receiving optical amplifier, a wavelength splitter, and a signal receiving unit. The optical transmission system also includes two front and rear pumping systems, comprising a forward second-order pump transmitting unit and a backward second-order pump transmitting unit, respectively. The dispersion compensation unit is used to compensate for signal dispersion.

[0120] In a specific embodiment, the schematic unidirectional structure of the optical transmission system is as follows: Figure 2 As shown, the optical signal transmission and reception process includes: a signal transmission unit, a combiner, a dispersion compensation unit, optical amplifier 1, Raman amplifier 1, transmission fiber 1, remote pump gain unit 1, transmission fiber 2, remote pump gain unit 2, transmission fiber 3, Raman amplifier 2, optical amplifier 2, a wavelength splitter, and a signal reception unit. The ultra-long-haul submarine cable single-span transmission system also includes two front and rear pump systems, consisting of pump transmission unit 1, pump fiber 1, pump transmission unit 2, and pump fiber 2, respectively.

[0121] Among them, the signal transmitting unit and the signal receiving unit complete the signal transmission and reception functions, and the transceiver module rates can be selected as 10Gbit / s, 40Gbit / s, 100Gbit / s, 200Gbit / s, and 400Gbit / s; the combiner is arranged after the transmitting unit to combine optical signals of multiple channels; the dispersion compensation unit is arranged after the combiner to compensate for the dispersion of the combined transmission signal; the optical amplifier 1 uses an erbium-doped fiber amplifier (EDFA) and is arranged after the dispersion compensation unit to perform the first stage amplification of the combined signal.

[0122] The Raman amplifier 1 uses second-order Raman and is arranged after the optical amplifier 1 to re-amplify the multiplexed signal.

[0123] A remote pump gain unit 1 is provided at the end of a transmission optical fiber 1, wherein a signal receiving end thereof is connected to a signal output end of a Raman amplifier 1 via the transmission optical fiber 1, a pump receiving end thereof is connected to a pump transmitting unit 1 via the pump optical fiber 1, and a signal output end thereof is connected to a remote pump gain unit 2 via the transmission optical fiber 2;

[0124] The remote pump gain unit 2 is provided at the end of the transmission optical fiber 2, wherein the signal receiving end thereof is connected to the signal output end of the remote pump gain unit 1 via the transmission optical fiber 2, the pump receiving end thereof is connected to the pump transmitting unit 2 via the pump optical fiber 2, and the signal output end thereof is connected to the signal input end of the Raman amplifier 2 via the transmission optical fiber 3;

[0125] Raman amplifier 2 uses second-order Raman and is set at the end of transmission optical fiber 3; optical amplifier 2 uses EDFA and is set at the signal output end of Raman amplifier 2;

[0126] The demultiplexer is provided at the signal output end of the optical amplifier 2 and is used to demultiplex the combined signal and send the demultiplexed signal to the corresponding signal receiving unit for processing.

[0127] Pump-transmitting unit 1 uses a second-order remote pump, is located at the transmitting site, and its output end is connected to pump fiber 1; pump-transmitting unit 2 uses a second-order remote pump, is located at the receiving site, and its output end is connected to pump fiber 2;

[0128] Transmission optical fiber 1, transmission optical fiber 2, and transmission optical fiber 3 use G.654 type optical fibers for transmitting signal light; pump optical fiber 1 and pump optical fiber 2 use G.654 type optical fibers for transmitting pump light.

[0129] The ultra-low-loss, large-effective-area optical fiber used in this embodiment reduces fiber attenuation while allowing for increased input optical power, effectively extending signal transmission distance. The second-order Raman optics employed achieve higher gain while also possessing a lower equivalent noise figure and a higher system Q factor, reducing transmission noise and improving the signal-to-noise ratio. The second-order remote pump provides a higher-power pump signal to the remote pump unit.

[0130] It will be understood by those skilled in the art that all or some of the steps, systems, and functional modules / units in the methods disclosed above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In a hardware implementation, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed by several physical components in cooperation. Some or all physical components may be implemented as software executed by a processor, such as a central processing unit, a digital signal processor, or a microprocessor, or may be implemented as hardware, or may be implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable storage medium, which may include a computer-readable storage medium (or a non-transitory medium) and a communication medium (or a temporary medium).

[0131] It should be noted that, in the present invention, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0132] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown herein, but is intended to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A long-distance single-span optical transmission method, characterized in that: Including steps: Building a digital model based on optical transmission system parameters, wherein the digital model is used to determine the corresponding relationship between the terminal output spectral signal-to-noise ratio and the required pump power; Inputting the target output spectrum signal-to-noise ratio into the digital model and obtaining the predicted pump power based on the corresponding relationship; Iteratively adjusting the actual terminal output spectral signal-to-noise ratio of the optical transmission system based on the difference between the predicted pump power and the actual pump power to optimize the digital model; The method of constructing a digital model based on optical transmission system parameters comprises the following steps: Determining the corresponding relationship between the terminal output spectral signal-to-noise ratio and the required pump power based on the Raman power coupling equation, the remote pump transmission equation and the Gaussian noise model; Training the digital model based on the measured terminal output spectral signal-to-noise ratio and the actual input pump power to optimize the corresponding relationship; The iterative adjustment of the actual terminal output spectral signal-to-noise ratio of the optical transmission system based on the difference between the predicted pump power and the actual pump power to optimize the digital model comprises the steps of: Calculating a root mean square error between the predicted pump power and the actual pump power; If the root mean square error does not meet the target accuracy, calculating the signal gain required by the optical transmission system based on the root mean square error and adjusting the actual terminal output spectrum signal-to-noise ratio of the optical transmission system based on the signal gain; The adjusted actual terminal output spectrum signal-to-noise ratio is used as the input of the digital model, and a new predicted pump power and a corresponding new root mean square error are calculated until the new root mean square error meets the target accuracy.

2. A long-distance single-span optical transmission method according to claim 1, characterized in that: The method of determining the corresponding relationship between the terminal output spectrum signal-to-noise ratio and the required pump power based on the Raman power coupling equation, the remote pump transmission equation, and the Gaussian noise model comprises the following steps: The gain and noise of each channel are calculated using the Raman power coupling equation; The gain and noise of each channel are calculated using the tele-pump transmission equation; The Gaussian noise model is used to calculate the noise of each channel and the signal-to-noise ratio of the terminal output spectrum is calculated by amplifying the spontaneous emission noise and nonlinear noise.

3. A long-distance single-span optical transmission method according to claim 2, characterized in that: The Raman power coupling equation is used to calculate the gain and noise of each channel, including: The gain and noise of each channel are calculated based on a first formula, where the first formula is: ， in, Indicates signal The loss coefficient of each channel in the optical fiber is Indicates the Channels at location The power at Indicates the frequency The pump frequency is The Raman coupling coefficient between the signals is, is the pump power of the originating Raman amplifier, is the pump power of the Raman amplifier at the receiving end.

4. A long-distance single-span optical transmission method according to claim 2, characterized in that: The method of calculating the gain and noise of each channel using the remote pump transmission equation includes the following steps: The gain and noise of each channel are calculated based on a second formula, where the second formula is: ， in, Indicates the direction of light transmission, =1 means forward, =-1 means backward, represents the emission cross-section coefficient, The number of particles in the upper energy level is The spontaneous emission caused by Contribution, represents the number of modes, To amplify the bandwidth of spontaneous emission, represents the absorption cross-section coefficient, represents the normalized intensity distribution function of the beam, r and represents the cross-sectional coordinates of the erbium fiber, It represents the optical power at point z along the fiber length in the fiber amplifier.

5. The long-distance single-span optical transmission method according to claim 2, wherein: The method of calculating the noise of each channel by using a Gaussian noise model and calculating the terminal output spectrum signal-to-noise ratio by amplifying spontaneous emission noise and nonlinear noise includes the following steps: The terminal output spectrum signal-to-noise ratio is calculated based on a third formula, wherein the third formula includes: ， ， ， in, Indicates the The signal-to-noise ratio of the channel, To amplify the spontaneous emission noise power, is the nonlinear crosstalk coefficient, is the signal power, is the power spectral density of the nonlinear crosstalk, For the The center frequency of the channel, is the intermediate variable, is the nonlinear coefficient, is the group velocity dispersion parameter, is the slope of the group velocity dispersion parameter, is the normalized signal power distribution, is the signal bandwidth, is the frequency integral, is the input signal power spectral density, is the transmission distance.

6. The long-distance single-span optical transmission method according to claim 1, wherein: The root mean square error is calculated based on the fourth formula, which is: ， in, is the root mean square error, is the predicted pump power, is the actual pump power, is the number of pumps.

7. A long-distance single-span optical transmission system, used to implement the long-distance single-span optical transmission method according to any one of claims 1 to 6, characterized in that: It includes: An automatic adjustment system interacting with an optical transmission system, the automatic adjustment system comprising: A digital model building module, which is used to build a digital model based on the optical transmission system parameters, wherein the digital model is used to determine the corresponding relationship between the terminal output spectrum and the required pump power; A prediction output module, configured to input a target output spectrum into the digital model and obtain a predicted pump power based on the corresponding relationship; An automatic adjustment module is used to iteratively adjust the actual terminal output spectral signal-to-noise ratio of the optical transmission system based on the difference between the predicted pump power and the actual pump power to optimize the digital model.

8. The long-distance single-span optical transmission system according to claim 7, wherein: It also includes an optical transmission system, from the optical signal transmitting end to the receiving end, the optical transmission system includes: Signal transmitting unit, transmitting optical amplifier, forward second-order Raman amplifier, forward remote pumping gain unit, backward remote pumping gain unit, backward Raman amplifier, receiving optical amplifier, wave splitter and signal receiving unit; The forward remote pump gain unit is connected to the forward second-order pump emission unit, and the forward second-order pump emission unit is used to provide pump light to the forward remote pump gain unit through a pump optical fiber; The backward remote pumping gain unit is connected to the backward second-order pumping emission unit, and the backward second-order pumping emission unit provides pumping light for the backward remote pumping gain unit through a pumping optical fiber.

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