A method and apparatus for calculating nonlinear noise in a high-bandwidth optical fiber communication system.

Abstract

This invention discloses a method and apparatus for calculating nonlinear noise in a high-bandwidth optical fiber communication system. The method includes: calculating the SPM noise of a monitoring channel in the high-bandwidth optical fiber communication system; calculating the sum of first XPM noise caused by crosstalk channels with a frequency interval less than a preset frequency threshold on the monitoring channel; calculating the sum of second XPM noise caused by crosstalk channels with a frequency interval greater than or equal to a preset frequency threshold on the monitoring channel, based on relative nonlinear noise figures; and adding the SPM noise, the sum of the first XPM noise, and the sum of the second XPM noise to obtain the nonlinear noise corresponding to the monitoring channel. This method separately calculates the large-interval crosstalk noise component, which is computationally time-consuming but has a small impact on overall noise levels. This improves computational efficiency without significantly affecting computational accuracy, thus addressing the shortcomings of the integral-method GN model.

Description

Technical Field

[0001] This invention belongs to the field of communication technology, and more specifically, relates to a method and apparatus for calculating nonlinear noise in a high-bandwidth optical fiber communication system. Background Technology

[0002] With the continuous development of video services and cloud technologies, communication traffic is experiencing explosive growth, placing demands on optical transport networks for high-speed, high-capacity transmission at low construction costs. To further expand system capacity, dense wavelength division multiplexing (DWDM) is needed to increase the number of channels while simultaneously widening the wavelength range of channel operation as much as possible. The signal transmission band is expanding from the original C-band to C+L band, C+L+S band, and other bands.

[0003] Nonlinear impairments in optical communication transmission systems are increasingly becoming a major factor limiting signal transmission capabilities. In practical networks, considering factors such as cost, security, and feasibility, it is necessary to anticipate nonlinear impairment performance during planning, design, and system maintenance. When evaluating or calculating the nonlinear noise of a channel, the Gaussian Noise Model (GN) is a commonly used approach. However, the conventional GN model integration algorithm for solving large-bandwidth scenarios is complex, computationally intensive, time-consuming, and difficult to apply in engineering. When calculating system nonlinear noise, the GN model performs integration calculations based on information such as the input optical power, fiber type, and input optical signal spectrum. Furthermore, the integration is a triple integration of the signal spectrum over frequency; the wider the signal spectrum bandwidth, the longer the calculation time. The computation time of the GN model is also related to the number of fiber segments being calculated; the more segments, the longer the calculation time.

[0004] In summary, a major drawback of the conventional GN model is its low computational efficiency, which decreases further with wider bands. Compared to calculating C-band systems, calculating the same link scenario in the C+L band takes more than four times longer. Taking an 11-span G.652 long-fiber system as an example, current solutions for calculating the nonlinear noise of a monitoring channel in the C+L band takes several minutes, making it difficult to apply in engineering.

[0005] Therefore, it is necessary to establish a fast and accurate calculation method to calculate the nonlinear noise of a high-bandwidth optical transmission system, improve the computational efficiency of the algorithm without affecting the calculation accuracy, and enable the complex evaluation process to be quickly implemented in simulation to ensure the reliability of the transmission system. Summary of the Invention

[0006] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a method and apparatus for calculating nonlinear noise in a high-bandwidth optical fiber communication system. Its purpose is to simulate and calculate the nonlinear noise of each channel in a high-bandwidth optical fiber communication system with high accuracy and as fast as possible, so as to evaluate the performance of the system, thereby solving the technical problem of long time consumption in calculating and monitoring channel nonlinear noise.

[0007] To achieve the above objectives, according to one aspect of the present invention, a method for calculating nonlinear noise in a high-bandwidth optical fiber communication system is provided, comprising:

[0008] Calculate the SPM noise of the monitoring channel in a high-bandwidth fiber optic communication system;

[0009] Calculate the sum of the first XPM noise caused by crosstalk channels with a frequency interval less than a preset frequency threshold on the monitoring channel;

[0010] Combined with the relative nonlinear noise figure, the sum of the second XPM noise caused by crosstalk channels with a frequency interval greater than or equal to a preset frequency threshold on the monitoring channel is calculated.

[0011] The sum of the SPM noise, the first XPM noise, and the second XPM noise is added together to obtain the nonlinear noise corresponding to the monitoring channel.

[0012] Furthermore, the calculation of the sum of second XPM noise caused by crosstalk channels with a frequency interval greater than or equal to a preset frequency threshold on the monitoring channel, incorporating the relative nonlinear noise figure, includes:

[0013] Calculate the reference XPM noise caused by a crosstalk channel with a frequency interval equal to a preset frequency threshold on the monitoring channel;

[0014] Calculate and monitor the relative nonlinear noise figure of each crosstalk channel whose frequency interval is greater than or equal to a preset frequency threshold;

[0015] Based on the reference XPM noise and the relative nonlinear noise coefficients of each crosstalk channel, the sum of the second XPM noise caused by crosstalk channels with a frequency interval greater than or equal to a preset frequency threshold on the monitoring channel is obtained.

[0016] Furthermore, the second XPM noise sum is calculated according to the following formula:

[0017]

[0018] Among them, PLAGARGE BdP represents the sum of noise from the second XPM; i represents the channel index difference between the crosstalk channel and the monitoring channel; k represents the channel index difference between the crosstalk channel with a frequency interval equal to a preset frequency threshold and the monitoring channel; M is the channel index difference between the crosstalk channel to the left of the monitoring channel and the monitoring channel; N is the channel index difference between the crosstalk channel to the right of the monitoring channel and the monitoring channel; P NL_ref For reference XPM noise, G_i represents the relative nonlinear noise figure of the i-th channel, and G_ref represents the relative nonlinear noise figure of the crosstalk channel whose frequency interval with the monitoring channel is equal to a preset frequency threshold.

[0019] Furthermore, the relative nonlinear noise figure of each crosstalk channel whose frequency interval with the monitoring channel is greater than or equal to a preset frequency threshold is calculated according to the following formula:

[0020]

[0021] Where G is the relative nonlinear noise figure caused by the crosstalk channel on the monitoring channel, γ is the nonlinear coefficient, and L w L is the walk-off length, α is the attenuation coefficient, and t is time; C Δ (t′1, t′2) are trigonometric functions.

[0022] Furthermore, the method for calculating the nonlinear noise of a high-bandwidth optical fiber communication system further includes:

[0023] Establish at least one table of relatively nonlinear noise figures based on the fiber type, fiber length, code pattern, and monitoring channel that may be involved in a high-bandwidth optical fiber communication system.

[0024] Select the appropriate relative nonlinear noise figure table based on the actual fiber type, fiber length, code pattern, and monitoring channel used in the large-bandwidth fiber optic communication system to be calculated;

[0025] Based on the selected relative nonlinear noise figure table, the relative nonlinear noise figure of each crosstalk channel is obtained by table lookup or interpolation calculation.

[0026] Furthermore, the sum of SPM noise and first XPM noise is calculated based on the simplified GN model. The simplified GN model is as follows:

[0027]

[0028] Among them, G NLI (f) represents the nonlinear noise power density spectrum, where γ is the nonlinear coefficient, and L eff G is the effective length of the optical fiber. WDMLet f be the signal optical power density spectrum, f1, f2 be the frequencies, ρ be the four-wave mixing transfer function, and χ be the four-wave mixing enhancement factor.

[0029] For G NLI (f) Integrate at the corresponding frequency to obtain the nonlinear noise of the corresponding channel.

[0030] Further, the step of adding the SPM noise, the sum of the first XPM noise, and the sum of the second XPM noise to obtain the nonlinear noise corresponding to the monitoring channel includes:

[0031] A simplified Raman correction factor is obtained, and the first XPM noise sum is optimized using the Raman correction factor to obtain the optimized first XPM noise sum.

[0032] The second XPM noise sum is optimized by using a Raman correction factor to obtain the optimized second XPM noise sum;

[0033] The nonlinear noise corresponding to the monitoring channel is obtained by summing the SPM noise, the optimized first XPM noise, and the optimized second XPM noise.

[0034] Furthermore, the preset frequency threshold is 500GHz + 10GHz.

[0035] Furthermore, the transmission band of the high-bandwidth optical fiber communication system is C-band, L-band, C+L-band, or C+L+S-band.

[0036] To achieve the above objectives, according to one aspect of the present invention, an apparatus for calculating nonlinear noise in a high-bandwidth optical fiber communication system is provided, comprising at least one processor and a memory, wherein the at least one processor and the memory are connected via a data bus, and the memory stores instructions executable by the at least one processor, wherein the instructions, after being executed by the processor, are used to perform the method for calculating nonlinear noise in a high-bandwidth optical fiber communication system.

[0037] In summary, compared with existing technologies, the technical solutions conceived in this invention have the following beneficial effects: Since the large-interval crosstalk channel is far from the monitoring channel, its impact on the nonlinear noise of the monitoring channel is smaller, and the correlation of nonlinear noise generated by each channel in the monitoring channel is weak. Therefore, a relative nonlinear coefficient can be introduced, and the XPM noise caused by the large-interval crosstalk channel can be calculated in combination with the relative nonlinear noise coefficient. This eliminates the need to calculate the XPM noise of the large-interval crosstalk channel using the GN model, thus allowing for the separate calculation of the large-interval crosstalk noise component, which is computationally time-consuming but has a small noise impact. This improves computational efficiency without significantly affecting computational accuracy, thus compensating for the shortcomings of the integral method GN model.

[0038] On the other hand, the calculation process of the integral method GN model has been simplified, which simplifies the calculation process of XPM noise caused by small-interval crosstalk channels. Attached Figure Description

[0039] Figure 1 This is a flowchart illustrating a method for calculating nonlinear noise in a high-bandwidth optical fiber communication system according to an embodiment of the present invention.

[0040] Figure 2 This is a flowchart of the method for calculating nonlinear noise in a high-bandwidth optical fiber communication system provided in an embodiment of the present invention.

[0041] Figure 3 This is a schematic diagram of the variation curves of single-wave calculation time and calculation error provided in an embodiment of the present invention;

[0042] Figure 4 This is a schematic diagram of the specific process of step 30 provided in an embodiment of the present invention;

[0043] Figure 5 This is a three-dimensional schematic diagram of relative nonlinear noise figure, channel spacing, and channel step provided in an embodiment of the present invention;

[0044] Figure 6 This is a two-dimensional schematic diagram illustrating the relationship between channel spacing and relative nonlinear noise figure, provided by an embodiment of the present invention.

[0045] Figure 7 This is a schematic diagram of the specific process of step 40 provided in an embodiment of the present invention;

[0046] Figure 8 This is a schematic diagram of a scenario for a 100G QPSK code pattern, C120+L120 waveband, 11-span 100km G.652 long fiber system provided in an embodiment of the present invention;

[0047] Figure 9 This is a comparison of simulation results (computational cost comparison) before and after algorithm optimization provided in the embodiments of the present invention;

[0048] Figure 10 This is a comparison of simulation results (comparison of computation time) before and after the algorithm optimization provided in the embodiments of the present invention;

[0049] Figure 11 This is a schematic diagram showing the integration range before and after algorithm optimization provided in this embodiment of the invention;

[0050] Figure 12 This is a schematic diagram of the structure of a device for calculating nonlinear noise in a high-bandwidth optical fiber communication system, provided in an embodiment of the present invention. Detailed Implementation

[0051] 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. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0052] Example 1:

[0053] This embodiment provides a method for calculating nonlinear noise in a high-bandwidth optical fiber communication system, wherein the transmission band of the high-bandwidth optical fiber communication system is C-band, L-band, C+L-band, or C+L+S-band. Specifically, the transmission band of the high-bandwidth optical fiber communication system is a C-band, such as C80 band, C96 band, C120 band; an L-band, such as L96 band, L120 band; a C+L-band, such as C96+L96 band, C120+L20 band; and a C+L+S-band, etc.

[0054] See Figure 1 and Figure 2 Methods for calculating nonlinear noise in high-bandwidth optical fiber communication systems include:

[0055] Step 10: Calculate the self-phase modulation (SPM) noise of the monitoring channel in a high-bandwidth optical fiber communication system.

[0056] In one embodiment, the SPM noise of the monitoring channel in a high-bandwidth optical fiber communication system is obtained based on the simplified GN model.

[0057] The simplified GN model is as follows:

[0058]

[0059] Among them, G NLI (f) represents the nonlinear noise power density spectrum, where γ is the nonlinear coefficient, and L eff G is the effective length of the optical fiber. WDM Let f be the signal optical power density spectrum, f1, f2 be the frequencies, ρ be the four-wave mixing transfer function, and X be the four-wave mixing enhancement factor.

[0060] The nonlinear noise power density spectrum G at each frequency is calculated based on the simplified GN model. NLI (f), for G NLI (f) Integrating at the corresponding frequency yields the nonlinear noise of the corresponding channel. Specifically, the nonlinear noise power density spectrum G at a given frequency f is calculated. NLIIn case (f), theoretically, the values ​​of f1 and f2 both traverse from negative infinity to positive infinity. For a specific scenario, this means covering the entire waveband of the scenario.

[0061] Before calculating the nonlinear noise, the parameters of the system to be simulated are first determined. These parameters include variable variables and constants in the simulation process. The variable variables include: the optical power P of the input signal. i The input optical power spectrum (SP) and monitoring channel number are included; constants include: fiber type, fiber length (L), and number of fiber spans.

[0062] Although nonlinear noise is also related to loss and dispersion parameters, determining the fiber type also clarifies its loss and dispersion characteristics for different frequencies of light. Therefore, the loss parameters corresponding to the loss characteristics and the dispersion parameters related to the dispersion characteristics are not used as input parameters. The GN model calls typical parameters internally based on the fiber type, replacing the actual loss and dispersion parameters with typical coefficients.

[0063] Step 20: Calculate the sum of the first cross-phase modulation (XPM) noise caused by crosstalk channels with a frequency interval less than a preset frequency threshold on the monitoring channel.

[0064] The monitoring channel refers to the channel on which nonlinear noise needs to be calculated. Any channel in the entire band can be a monitoring channel.

[0065] Crosstalk channels refer to all channels in the entire band except for the monitoring channel.

[0066] For example, there are 40 channels in a waveband, from channel 1 to channel 40. If we need to know the nonlinear noise of channel 3, then channel 3 is the monitoring channel, and channels 1 to 2 and channels 4 to 40 are all crosstalk channels. Similarly, if we need to calculate the nonlinear noise of channel 40, then channel 40 is the monitoring channel, and channels 1 to 39 are all crosstalk channels.

[0067] In one embodiment, based on the simplified GN model, the XPM noise of each crosstalk channel with a frequency interval less than a preset frequency threshold from the monitoring channel is obtained, and the calculated XPM noise is added together to obtain the first XPM noise sum.

[0068] The selection of the preset frequency threshold depends mainly on the calculation efficiency and calculation accuracy, and different values ​​can be taken according to different focuses.

[0069] In one embodiment, the preset frequency threshold can be 500GHz ± 10GHz, or more precisely, 500GHz, thus achieving a relative balance between computational efficiency and computational accuracy. Of course, if computational efficiency is a greater priority, other values ​​can be selected for higher efficiency; similarly, if computational accuracy is a greater priority, other values ​​can be selected for higher accuracy.

[0070] The design intent behind setting the preset frequency threshold to 500GHz is explained below:

[0071] This embodiment achieves speedup by simplifying the integration calculation of the large interval section. The smaller the preset frequency threshold GB_ref, the smaller the spectrum bandwidth that needs to be integrated, and therefore the less time is spent on calculation. However, it also means that the noise proportion of the simplified calculation part is larger, so the simplification error introduced will be larger.

[0072] Similarly, the larger the preset frequency threshold GB_ref is, the larger the spectral bandwidth that needs to be integrated, and therefore the longer the calculation time; it also means that the noise proportion of the simplified calculation part is smaller, so the simplification error introduced will be smaller.

[0073] Figure 3 The curves show the changes in single-wavelength computation time and computational error when the preset frequency threshold GB_ref takes different values. From these curves, we can see that: when GB_ref is greater than 10 times the bandwidth of 50GHz, the computational error is less than 4%, and it begins to decrease slowly as GB_ref increases; the computation time changes approximately linearly with GB_ref, with larger GB_ref resulting in longer computation times. Therefore, based on the balance between computational efficiency and accuracy, GB_ref is set to 500GHz. Specifically, in... Figure 3 In the diagram, the horizontal axis represents the boundary between the selected large-interval and small-interval scenes. Each scale represents 50 GHz, so 10 on the horizontal axis represents 500 GHz.

[0074] Step 30: Combine the relative nonlinear noise figure to calculate the sum of the second XPM noise caused by crosstalk channels with a frequency interval greater than or equal to a preset frequency threshold on the monitoring channel.

[0075] That is, calculate the total noise caused by the channel outside the ±GB_ref (preset frequency threshold) interval range.

[0076] Based on the assumption that the nonlinear crosstalk noise of each crosstalk channel is independent, the nonlinear noise caused by a large-interval crosstalk channel (i.e., a crosstalk channel with a frequency interval greater than or equal to a preset frequency threshold from the monitoring channel) can be simplified to the superposition of the corresponding crosstalk channel XPM noise. In a dispersion-free compensation system, the nonlinear noise of the large-interval crosstalk channel to the monitoring channel mainly consists of XPM, and other complex terms can be ignored. Furthermore, since the information transmitted by each crosstalk channel is independent, the nonlinear noise caused by each crosstalk channel to the monitoring channel is also independent and can be calculated independently and linearly added.

[0077] In this embodiment, the relative nonlinear noise coefficients between each crosstalk channel are introduced, eliminating the need to calculate the XPM noise of large-interval crosstalk channels using the GN model. This simplifies the calculation of XPM noise generated by crosstalk channels with an interval greater than a preset frequency threshold from the monitoring channel.

[0078] In this embodiment, the nonlinear noise of the large-bandwidth optical fiber communication system to be calculated is divided into two parts: the first sum of XPM noise obtained in step 20 and the second sum of XPM noise obtained in step 30.

[0079] Step 40: Add the sum of the SPM noise, the first XPM noise, and the second XPM noise to obtain the nonlinear noise corresponding to the monitoring channel.

[0080] In this embodiment, based on the assumption that the nonlinear noise of each channel is linearly independent, the SPM noise of the monitoring channel calculated by the GN model, the XPM noise caused by the small-interval crosstalk channel calculated by the GN model (i.e., the sum of the first XPM noise), and the XPM noise caused by the large-interval crosstalk channel obtained by combining the relative nonlinear noise coefficient (i.e., the sum of the second XPM noise) are linearly superimposed to obtain the total nonlinear noise.

[0081] Unlike existing technologies, this embodiment simplifies the calculation process of the integral GN model, simplifying the calculation of XPM noise caused by small-interval crosstalk channels. Furthermore, since large-interval crosstalk channels are farther from the monitoring channel, their impact on the nonlinear noise of the monitoring channel is smaller, and the correlation of nonlinear noise generated by each channel in the monitoring channel is weak. Therefore, a relative nonlinear coefficient can be introduced, and the XPM noise caused by large-interval crosstalk channels can be calculated in conjunction with the relative nonlinear noise coefficient. This allows for the separate calculation of the large-interval crosstalk noise component, which is computationally time-consuming but has a small noise impact. This improves computational efficiency without significantly affecting calculation accuracy, thus addressing the shortcomings of the integral GN model.

[0082] See Figure 4In step 30, the calculation of the sum of the second XPM noise caused by crosstalk channels with a frequency interval greater than or equal to a preset frequency threshold on the monitoring channel includes:

[0083] Step 301: Calculate the reference XPM noise caused by the crosstalk channel on the monitoring channel when the frequency interval between the monitoring channel and the monitoring channel is equal to the preset frequency threshold.

[0084] In one embodiment, the reference XPM noise caused by a crosstalk channel with a frequency interval equal to a preset frequency threshold on the monitoring channel is calculated based on a simplified GN model.

[0085] Step 302: Calculate the relative nonlinear noise figure of crosstalk channels with frequency intervals greater than or equal to a preset frequency threshold.

[0086] For a single fiber segment, the XPM effect caused by a crosstalk channel can be calculated by calculating the nonlinear phase induced by the crosstalk channel. This nonlinear phase can then be obtained through time-domain power integration.

[0087]

[0088] Where B is the XPM parameter, which is 3 / 2 in a typical scenario; γ is the nonlinear coefficient; L is the fiber length; α is the attenuation coefficient; P2 is the power of the crosstalk light; d12 is the walk-off parameter characterizing the GVD mismatch between channels; t is time; and z is the integral variable over length.

[0089] By calculating the mean square error of the nonlinear phase, the corresponding equivalent XPM noise power can be obtained:

[0090]

[0091] Where σ is the nonlinear noise; B is the XPM parameter, typically taken as 3 / 2 in standard scenarios; γ is the nonlinear coefficient; L is the fiber length; α is the attenuation coefficient; P p For the power of the crosstalk light, L w C represents the distance traveled, t represents time; Δ (t′1, t′2) are trigonometric functions.

[0092] For different crosstalk channels, only their relative values ​​are needed. Therefore, the above formula can be simplified to a relative nonlinear noise calculation. The specific formula for calculating the relative nonlinear noise coefficient of a crosstalk channel whose frequency interval with the monitoring channel is greater than or equal to a preset frequency threshold is as follows:

[0093]

[0094] Where G is the relative nonlinear noise figure caused by the crosstalk channel on the monitoring channel, γ is the nonlinear coefficient, and L w L is the walk-off length, α is the attenuation coefficient, and t is time; C Δ (t′1, t′2) are trigonometric functions.

[0095] The relative nonlinear noise figure varies depending on the code pattern, fiber type, and fiber length. The relative nonlinear noise figure also varies depending on the monitoring channel and channel spacing.

[0096] In summary, in this embodiment, the relative nonlinear noise figure of a crosstalk channel whose frequency interval with the monitoring channel is greater than or equal to a preset frequency threshold can be calculated according to the aforementioned formula. Using this equivalent nonlinear noise G, once the XPM noise of a certain crosstalk channel is known, it can be quickly converted into the XPM noise of other crosstalk channels.

[0097] Step 303: Based on the reference XPM noise and the relative nonlinear noise coefficients of each channel, obtain the sum of the second XPM noise caused by crosstalk channels with a frequency interval greater than or equal to a preset frequency threshold on the monitoring channel.

[0098] Calculate the sum of the second XPM noise using the following formula:

[0099]

[0100] Among them, PLAGARGE Bd P represents the sum of noise from the second XPM; i represents the channel index difference between the crosstalk channel and the monitoring channel; k represents the channel index difference between the crosstalk channel with a frequency interval equal to a preset frequency threshold and the monitoring channel; M is the channel index difference between the crosstalk channel to the left of the monitoring channel and the monitoring channel; N is the channel index difference between the crosstalk channel to the right of the monitoring channel and the monitoring channel; P NL_ref For reference XPM noise, G_i represents the relative nonlinear noise figure of the i-th channel, and G_ref represents the relative nonlinear noise figure of the crosstalk channel whose frequency interval with the monitoring channel is equal to a preset frequency threshold.

[0101] Right now, This represents the sum of noise from all large-interval crosstalk channels located to the left of the monitoring channel. This represents the sum of noise from all large-interval crosstalk channels located to the right of the monitoring channel. Adding these two noise sums together gives the second XPM noise sum.

[0102] Among them, the crosstalk channel located to the left of the monitoring channel refers to the crosstalk channel with a frequency lower than that of the monitoring channel; the crosstalk channel located to the right of the monitoring channel refers to the crosstalk channel with a frequency higher than that of the monitoring channel.

[0103] The XPM noise caused by large-interval crosstalk channels in the current scenario can be quickly calculated using the aforementioned method.

[0104] In practical applications, the relative nonlinearity coefficient is related to parameters such as fiber type, fiber length, code pattern, and monitoring channel. Therefore, once these parameters are determined, the relative nonlinearity coefficient of the crosstalk channel can also be determined. In actual use, the relative nonlinearity coefficient of each crosstalk channel under the current condition can be obtained by looking up a table.

[0105] Therefore, in order to improve the efficiency of obtaining the relative nonlinear coefficients of crosstalk channels, the method for calculating the nonlinear noise of a large-bandwidth optical fiber communication system further includes:

[0106] At least one relative nonlinear noise figure table should be established based on the fiber type, fiber length, code pattern, and monitoring channel that may be involved in a high-bandwidth optical fiber communication system. Specifically, the fiber type, fiber length, code pattern, and monitoring channel that may be involved in the actual scenario can be pre-summarized, and at least one relative nonlinear noise figure table should be proposed based on these parameters.

[0107] Select the appropriate relative nonlinear noise figure table based on the actual fiber type, fiber length, code pattern, and monitoring channel used in the large-bandwidth fiber optic communication system to be calculated. Before performing the calculation, obtain the fiber type, fiber length, code pattern, and monitoring channel used in the large-bandwidth fiber optic communication system to be calculated, and obtain the relative nonlinear noise figure table corresponding to the large-bandwidth fiber optic communication system to be calculated from at least one pre-established relative nonlinear noise figure table.

[0108] Based on the selected relative nonlinear noise figure table, the relative nonlinear noise figure of each crosstalk channel is obtained by table lookup or interpolation calculation.

[0109] If the selected relative nonlinear noise figure table perfectly matches the large-bandwidth fiber optic communication system to be calculated (meaning the fiber type, fiber length, code pattern, and monitoring channel are all consistent), then the relative nonlinear noise figure of each crosstalk channel is obtained directly by looking up the table. If the selected relative nonlinear noise figure table does not perfectly match the large-bandwidth fiber optic communication system to be calculated (meaning the fiber type, code pattern, and monitoring channel are consistent, but the fiber length is inconsistent), then the relative nonlinear noise figure of each crosstalk channel is obtained by interpolation. The explanation of the interpolation method is as follows:

[0110] Generally, in real-world scenarios, parameters such as fiber type and code pattern in high-bandwidth fiber optic communication systems can be preset and do not change with the actual scenario. However, fiber length varies with the actual scenario and is less controllable. Therefore, in a more preferred embodiment, a table of relative nonlinear noise figures for classic fiber lengths relative to different fiber lengths and code patterns can be pre-established. If no table of relative nonlinear noise figures with the same fiber length as the high-bandwidth fiber optic communication system to be calculated exists, then the two table of relative nonlinear noise figures with the smallest difference in fiber length from the high-bandwidth fiber optic communication system to be calculated are selected and denoted as Table A and Table B, respectively. The fiber type, code pattern, and monitoring channel corresponding to Table A and Table B are consistent with the fiber type, code pattern, and monitoring channel of the high-bandwidth fiber optic communication system to be calculated.

[0111] Using the relative nonlinear noise figure table A and the relative nonlinear noise figure table B as a reference, interpolation calculations are performed to obtain the relative nonlinear noise figure table corresponding to the large bandwidth optical fiber communication system to be calculated. Then, the relative nonlinear noise figure of each crosstalk channel is obtained by looking up the table.

[0112] That is, if the table of relative nonlinear noise figures corresponding to the large-bandwidth optical fiber communication system to be calculated has been established in advance, the relative nonlinear noise figures of each crosstalk channel are obtained by looking up the table; if the nonlinear noise figures corresponding to the actual optical fiber length of the large-bandwidth optical fiber communication system to be calculated have not been established in advance, the corresponding relative nonlinear noise figures are obtained by interpolation.

[0113] For example, when modeling a fiber optic cable, to accommodate any fiber length, nine typical fiber lengths—10km, 20km, 30km, 40km, 60km, 100km, 200km, 300km, and 400km—are set as benchmarks, and the relative nonlinear noise figure tables for these nine lengths are pre-calculated. For example... Figure 5 As shown, in each table, the first dimension is the monitoring signal channel number (SigCH#); the second dimension is the relative non-noise figure (G) generated by the crosstalk channel in the corresponding monitoring channel at frequency intervals from 50 GHz to 12300 GHz, with a 50 GHz increment. Figure 6 As shown, a 10km G.652 optical fiber was provided. After normalization, the first monitoring channel was used in each channel interval (i.e. Figure 6 The relative nonlinear coefficients under the channel spacing.

[0114] In this embodiment, the XPM noise is corrected using a simplified Raman correction factor to improve calculation accuracy. For large bandwidth scenarios, the inter-band Raman effect cannot be ignored. To account for the impact of the Raman effect on nonlinearity, the Raman correction factor for each channel can be calculated in advance. The expression for the Raman correction factor is as follows:

[0115]

[0116] Where LAMAN is the calculated Raman effect correction coefficient; Crk is the polarization-related factor, which is 2 in conventional scenarios; toopPower is the total power of the entire waveband; Cr is the Raman gain coefficient; α is the fiber attenuation coefficient; L is the fiber length; and Freq is the signal frequency.

[0117] See Figure 7 In step 40, the sum of the SPM noise, the first XPM noise, and the second XPM noise to obtain the nonlinear noise corresponding to the monitoring channel includes:

[0118] Step 401: Obtain a simplified Raman correction factor, and optimize the first XPM noise sum using the Raman correction factor to obtain the optimized first XPM noise sum.

[0119] In this embodiment, the nonlinear noise P caused by small-interval crosstalk channels is calculated using a simplified GN model. NL_i(GB<GB_ref) This allows us to calculate the sum of the first XPM noise in the monitoring channel for the small-interval crosstalk channel, and then combine it with the Raman correction factor LAMAN. i The optimized first XPM noise sum P is obtained. NL_SmallBd That is, P NL_SmallBd =∑P NL_i(GB<GB_ref) *LAMAN i , where i represents the channel number.

[0120] Step 402: Obtain a simplified Raman correction factor, and optimize the second XPM noise sum using the Raman correction factor to obtain the optimized second XPM noise sum.

[0121] In this embodiment, when calculating the nonlinear noise caused by the large-interval crosstalk channel, the nonlinear noise P of the crosstalk channel with a frequency interval of GB_ref from the monitoring channel is calculated based on the GN model. NL_ref Combined with the relative nonlinear noise figure G of other crosstalk channels i The relative nonlinear noise figure G of the crosstalk channel at GB_ref k This allows us to calculate the second XPM noise sum of a large-interval crosstalk channel, taking into account the Raman correction factor LAMAN. iThe optimized second XPM noise sum P is obtained. NL_LargeBd ;

[0122] P NL_LargeBd =P LargeBd *LAMAN i ;

[0123] Where i represents the channel number, k represents the channel number of the crosstalk channel at GB_ref, and N is the total number of channels.

[0124] Step 403: Add the SPM noise, the optimized first XPM noise, and the optimized second XPM noise together to obtain the nonlinear noise corresponding to the monitoring channel.

[0125] Finally, the nonlinear noise of each segment of the system is accumulated, and the total nonlinear noise of the system is calculated, which specifically includes:

[0126] P NL =∑ Span (P NL_SmallBd +P NL_LargeBd +SPM noise)

[0127] Among them, P NL This represents the total nonlinear noise power caused by the system on the monitoring channel; Span represents the number of segments, ranging from 1 to NSpan.

[0128] Unlike existing technologies, this embodiment has at least the following beneficial effects:

[0129] (1) The calculation process of the integral method GN model has been simplified, such as... Figure 11 As shown, the integration range is significantly reduced, and a relatively nonlinear coefficient is introduced to separately calculate the large-interval crosstalk noise component, which is computationally time-consuming but has a small impact on overall noise. This improves computational efficiency without significantly affecting computational accuracy, thus addressing the shortcomings of the integral method GN model.

[0130] (2) The practical nonlinear noise calculation method established according to the method of the present invention has a simple structure and is easy to implement.

[0131] (3) This invention can solve the problems of traditional theoretical models being too complex, difficult to solve, and time-consuming, making it more practical.

[0132] (4) The parameters required for the model established by the method of the present invention are easy to determine, and many parameters can be obtained directly from the product manual.

[0133] (5) Compared with other simplified calculation methods, the present invention has a significant advantage in terms of accuracy, but does not significantly improve complexity.

[0134] Example 2:

[0135] Based on the aforementioned Embodiment 1, this embodiment provides a comparison of the simulation results of the noise calculation scheme of Embodiment 1 with existing noise schemes in a specific scenario.

[0136] like Figure 8 As shown, in this embodiment, the high-bandwidth optical fiber communication system has 11 spans of G.652 optical fibers, with each span having a fiber length of 100km; the transmission band is C++ plus L++ band, with a total of 240 50GHz signals; the monitoring signal code is 100GQPSK, the signal is output from the transmitting OTU, coupled into the transmitting optical amplifier through the transmitting MUX, and then transmitted through 5 spans in sequence, after passing through a WSS equalization, it is transmitted through the next 6 optical fiber spans in sequence, and finally down-waved through the receiving DEMUX and enters the receiving end.

[0137] For example Figure 8 The simulation of the 11-span high-bandwidth optical fiber communication system shown yielded the following results: Figure 9 and Figure 10 The simulation results before and after algorithm optimization are shown below. Figure 9 This is a comparison of the computational costs of each monitoring channel before and after the implementation of the present invention. Figure 9 Each point in the "after speed-up" section represents the calculation result of a monitoring channel. Specifically, each point requires a nonlinear noise calculation. Taking the point at 185THz (the first point on the curve) as an example, during the calculation, the 185THz channel is the monitoring channel, while all other channels from 185.05THz to 196.6THz are crosstalk channels. The noise generated by the 185THz channel itself is SPM noise, the noise generated by the channels from 185.05 to 185.5THz on the 185THz channel is XPM noise of small-interval channels, and the noise generated by the channels from 185.55THz to 196.6THz on the 185THz channel is large-interval XPM noise. Figure 10 This is a comparison of the calculation time for each monitoring channel before and after the implementation of the present invention. From... Figure 9 As can be seen, the solution of this invention has minimal impact on the accuracy of the calculation, remaining to two decimal places; simultaneously, from Figure 10 As can be seen, the solution of this invention significantly improves computational efficiency, by nearly four times. It effectively solves the problem of long computation time in the nonlinear noise calculation process of high-bandwidth optical fiber transmission systems.

[0138] Example 3:

[0139] Based on the method for calculating nonlinear noise in a high-bandwidth optical fiber communication system provided in Embodiment 1 above, this invention also provides an apparatus for calculating nonlinear noise in a high-bandwidth optical fiber communication system, such as... Figure 12The diagram shown is a schematic representation of the device architecture according to an embodiment of the present invention. The device in this embodiment includes one or more processors 21 and a memory 22. Figure 12 Take a processor 21 as an example.

[0140] The processor 21 and the memory 22 can be connected via a bus or other means. Figure 12 Taking the example of a connection between China and Israel via a bus.

[0141] The memory 22 is a non-volatile computer-readable storage medium serving as a method for calculating nonlinear noise in a high-bandwidth optical fiber communication system. It can be used to store non-volatile software programs, non-volatile computer-executable programs, and modules, such as the method for calculating nonlinear noise in a high-bandwidth optical fiber communication system in Embodiment 1. The processor 21 executes various functional applications and data processing of the device by running the non-volatile software programs, instructions, and modules stored in the memory 22, thereby implementing the method for calculating nonlinear noise in a high-bandwidth optical fiber communication system as described in the embodiment.

[0142] The memory 22 may include high-speed random access memory and non-volatile memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device. In some embodiments, the memory 22 may optionally include memory remotely located relative to the processor 21, and these remote memories may be connected to the processor 21 via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0143] The program instructions / modules are stored in the memory 22 and, when executed by one or more processors 21, perform the method for calculating nonlinear noise in a high-bandwidth optical fiber communication system as described in the above embodiments.

[0144] Those skilled in the art will understand that all or part of the steps in the various methods of the embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, which may include: read-only memory (ROM), random access memory (RAM), magnetic disk or optical disk, etc.

[0145] Those skilled in the art will readily understand that the above description is merely 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 scope of protection of the present invention.

Claims

1. A method for calculating nonlinear noise in a high-bandwidth optical fiber communication system, characterized in that, include: Calculate the SPM noise of the monitoring channel in a high-bandwidth fiber optic communication system; Calculate the sum of the first XPM noise caused by crosstalk channels with a frequency interval less than a preset frequency threshold on the monitoring channel; Based on the relative nonlinear noise figure, the sum of the second XPM noise caused by crosstalk channels with a frequency interval greater than or equal to a preset frequency threshold on the monitoring channel is calculated. The sum of the SPM noise, the first XPM noise, and the second XPM noise is added together to obtain the nonlinear noise corresponding to the monitoring channel.

2. The method for calculating nonlinear noise in a high-bandwidth optical fiber communication system according to claim 1, characterized in that, The calculation of the sum of the second XPM noise caused by crosstalk channels with a frequency interval greater than or equal to a preset frequency threshold on the monitoring channel, combined with the relative nonlinear noise figure, includes: Calculate the reference XPM noise caused by a crosstalk channel with a frequency interval equal to a preset frequency threshold on the monitoring channel; Calculate and monitor the relative nonlinear noise figure of each crosstalk channel whose frequency interval is greater than or equal to a preset frequency threshold; Based on the reference XPM noise and the relative nonlinear noise coefficients of each crosstalk channel, the sum of the second XPM noise caused by crosstalk channels with a frequency interval greater than or equal to a preset frequency threshold on the monitoring channel is obtained.

3. The method for calculating nonlinear noise in a high-bandwidth optical fiber communication system according to claim 2, characterized in that, Calculate the sum of the second XPM noise using the following formula: Among them, P LargeBd P represents the sum of noise from the second XPM; i represents the channel index difference between the crosstalk channel and the monitoring channel; k represents the channel index difference between the crosstalk channel with a frequency interval equal to a preset frequency threshold and the monitoring channel; M is the channel index difference between the crosstalk channel to the left of the monitoring channel and the monitoring channel; N is the channel index difference between the crosstalk channel to the right of the monitoring channel and the monitoring channel; P NL_ref For reference XPM noise, G_i represents the relative nonlinear noise figure of the i-th channel, and G_ref represents the relative nonlinear noise figure of the crosstalk channel whose frequency interval with the monitoring channel is equal to a preset frequency threshold.

4. The method for calculating nonlinear noise in a high-bandwidth optical fiber communication system according to claim 2, characterized in that, The relative nonlinear noise figure of each crosstalk channel whose frequency interval with the monitoring channel is greater than or equal to a preset frequency threshold is calculated according to the following formula: Where G is the relative nonlinear noise figure caused by the crosstalk channel on the monitoring channel, γ is the nonlinear coefficient, and L w L is the walk-off length, α is the fiber length, and C is the attenuation coefficient. Δ (t ′ 1,t ′ 2) These are trigonometric functions.

5. The method for calculating nonlinear noise in a high-bandwidth optical fiber communication system according to claim 1, characterized in that, The method for calculating nonlinear noise in a high-bandwidth optical fiber communication system further includes: Establish at least one table of relatively nonlinear noise figures based on the fiber type, fiber length, code pattern, and monitoring channel that may be involved in a high-bandwidth optical fiber communication system. Select the appropriate relative nonlinear noise figure table based on the actual fiber type, fiber length, code pattern, and monitoring channel used in the large-bandwidth fiber optic communication system to be calculated; Based on the selected relative nonlinear noise figure table, the relative nonlinear noise figure of each crosstalk channel is obtained by table lookup or interpolation calculation.

6. The method for calculating nonlinear noise in a high-bandwidth optical fiber communication system according to any one of claims 1-5, characterized in that, The sum of SPM noise and first XPM noise is calculated based on the simplified GN model. The simplified GN model is as follows: Among them, G NLI (f) represents the nonlinear noise power density spectrum, where γ is the nonlinear coefficient, and L eff G is the effective length of the optical fiber. WDM Let f be the signal optical power density spectrum, f1, f2 be the frequencies, ρ be the four-wave mixing transfer function, and χ be the four-wave mixing enhancement factor. For G NLI (f) Integrate at the corresponding frequency to obtain the nonlinear noise of the corresponding channel.

7. The method for calculating nonlinear noise in a high-bandwidth optical fiber communication system according to any one of claims 1-5, characterized in that, The step of adding the SPM noise, the sum of the first XPM noise, and the sum of the second XPM noise to obtain the nonlinear noise corresponding to the monitoring channel includes: A simplified Raman correction factor is obtained, and the first XPM noise sum is optimized using the Raman correction factor to obtain the optimized first XPM noise sum. The second XPM noise sum is optimized by using a Raman correction factor to obtain the optimized second XPM noise sum; The nonlinear noise corresponding to the monitoring channel is obtained by summing the SPM noise, the optimized first XPM noise, and the optimized second XPM noise.

8. The method for calculating nonlinear noise in a high-bandwidth optical fiber communication system according to any one of claims 1-5, characterized in that, The preset frequency threshold is 500GHz±10GHz.

9. The method for calculating nonlinear noise in a high-bandwidth optical fiber communication system according to any one of claims 1-5, characterized in that, The transmission band of the high-bandwidth optical fiber communication system is C-band, L-band, C+L-band, or C+L+S-band.

10. An apparatus for calculating nonlinear noise in a high-bandwidth optical fiber communication system, characterized in that, The method includes at least one processor and a memory, which are connected via a data bus. The memory stores instructions that can be executed by the at least one processor. When executed by the processor, the instructions are used to perform the method for calculating nonlinear noise in a high-bandwidth optical fiber communication system as described in any one of claims 1-9.

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