Method and apparatus for calculating nonlinear noise of large-bandwidth optical fiber communication system

Abstract

Disclosed in the present invention are a method and apparatus for calculating nonlinear noise of a large-bandwidth optical fiber communication system. The method comprises: calculating SPM noise of a monitoring channel in the large-bandwidth optical fiber communication system; calculating first XPM noise sum caused on the monitoring channel by crosstalk channels of which frequency spacing from the monitoring channel is less than a preset frequency threshold; on the basis of relative nonlinear noise coefficients, calculating second XPM noise sum caused on the monitoring channel by crosstalk channels of which frequency spacing from the monitoring channel is greater than or equal to the preset frequency threshold; and adding the SPM noise, the first XPM noise sum, and the second XPM noise sum to obtain nonlinear noise corresponding to the monitoring channel. A large-spacing crosstalk noise part, which is greatly time-consuming in calculation but has a small noise impact proportion, is separately calculated. The calculation efficiency is improved, and the calculation accuracy is not greatly affected, thereby remedying the shortcomings of an integral method GN model.

Description

Method and device for calculating nonlinear noise of large-bandwidth optical fiber communication system TECHNICAL FIELD

[0001] The present application belongs to the technical field of communication, and more particularly relates to a method and device for calculating nonlinear noise of a large-bandwidth optical fiber communication system. BACKGROUND

[0002] With the continuous development of video services, cloud technology, and the like, communication traffic is growing in a sustained explosive manner, which puts forward requirements of high rate, large capacity transmission and low networking cost for optical transport networks. In order to further expand the system capacity, it is necessary to use Dense Wavelength-Division Multiplexing (DWDM) to expand the number of channels, and at the same time, to expand the wavelength range of channel operation as much as possible. The signal transmission band is expanded from the original C band to C+L band, C+L+S band, and the like.

[0003] Nonlinear impairment in an optical communication transmission system is becoming a major factor limiting the signal transmission capacity. In actual networks, considering factors such as cost, security, and feasibility, it is necessary to predict the nonlinear impairment performance in the planning and design, system maintenance, and the like. When evaluating or calculating the nonlinear noise of a channel, using a Gaussian Noise Model (GN) is a common solution. However, the conventional GN model integral algorithm is complex, has a large amount of calculation, and takes a long time, which makes it difficult to apply in engineering. When calculating the nonlinear noise of a system using the GN model, integral calculation is performed based on the input fiber optical power, fiber type, input fiber optical signal spectrum, and the like. Moreover, the integral is a triple integral with respect to the signal spectrum in frequency. The wider the signal spectrum bandwidth, the longer the time consumption. The time consumption of the GN model calculation is also related to the number of fiber spans. The more the number of spans, the longer the time consumption.

[0004] In summary, a major drawback of the conventional GN model is low calculation efficiency, and the wider the waveband, the lower the calculation efficiency. Compared with a system calculating a C band, the time consumption of a scenario calculating a C+L band of the same link is more than 4 times that of the original. Taking an 11-span G.652 long fiber system as an example, the time consumption of a current solution for calculating the nonlinear noise of a monitoring channel is in the order of several minutes, which makes it difficult to apply in engineering.

[0005] Therefore, it is necessary to establish a fast and accurate calculation method for calculating the nonlinear noise of a large-bandwidth optical transmission system. On the premise of not affecting the calculation accuracy, the calculation efficiency of the algorithm is improved, so that the complex evaluation process can be quickly realized in simulation, and the reliability of the transmission system is ensured. SUMMARY

[0006] In view of the above defects or improvement needs of the prior art, the present application provides a method and device for calculating nonlinear noise of a large-bandwidth optical fiber communication system, which aims to simulate and calculate the fiber nonlinear noise of each channel in the large-bandwidth optical fiber communication system as fast as possible with high accuracy, so as to evaluate the performance of the system, thereby solving the technical problem of long time consumption in calculating the nonlinear noise of a monitoring channel.

[0007] To achieve the above object, according to one aspect of the present application, there is provided a method for calculating nonlinear noise of a large-bandwidth optical fiber communication system, comprising:

[0008] calculating SPM noise of a monitoring channel in the large-bandwidth optical fiber communication system;

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

[0010] calculating a second XPM noise sum caused by crosstalk channels with a frequency interval greater than or equal to the preset frequency threshold to the monitoring channel on the monitoring channel in combination with a relative nonlinear noise coefficient;

[0011] adding the SPM noise, the first XPM noise sum and the second XPM noise sum to obtain nonlinear noise corresponding to the monitoring channel.

[0012] Further, the calculating the second XPM noise sum caused by the crosstalk channels with the frequency interval greater than or equal to the preset frequency threshold to the monitoring channel on the monitoring channel in combination with the relative nonlinear noise coefficient comprises:

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

[0014] calculating a relative nonlinear noise coefficient of each crosstalk channel with the frequency interval greater than or equal to the preset frequency threshold to the monitoring channel;

[0015] obtaining the second XPM noise sum caused by the crosstalk channels with the frequency interval greater than or equal to the preset frequency threshold to the monitoring channel on the monitoring channel according to the reference XPM noise and the relative nonlinear noise coefficient of each crosstalk channel.

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

[0017] wherein, P LargeBdis the second XPM noise sum; i represents the channel number difference between the crosstalk channel and the monitoring channel; k represents the channel number difference between the crosstalk channel and the monitoring channel whose frequency interval is equal to the preset frequency threshold; M is the channel number difference between the crosstalk channel farthest to the left of the monitoring channel and the monitoring channel; N is the channel number difference between the crosstalk channel farthest to the right of the monitoring channel and the monitoring channel; P NL_ref is the reference XPM noise, G_i represents the relative nonlinear noise coefficient of the i-th channel, and G_ref represents the relative nonlinear noise coefficient of the crosstalk channel whose frequency interval is equal to the preset frequency threshold.

[0018] Further, the relative nonlinear noise coefficient of each crosstalk channel whose frequency interval is greater than or equal to the preset frequency threshold is calculated according to the following formula:

[0019] wherein G is the relative nonlinear noise coefficient caused by the crosstalk channel on the monitoring channel, γ is the nonlinear coefficient, L w is the walk-off length, L is the fiber length, α is the attenuation coefficient, and t is the time; C Δ (t'1, t'2) is a trigonometric function.

[0020] Further, the method for calculating the nonlinear noise of the large-bandwidth optical fiber communication system further comprises:

[0021] establishing at least one relative nonlinear noise coefficient table based on the types of optical fibers, the lengths of optical fibers, the code types, and the monitoring channels that the large-bandwidth optical fiber communication system can involve;

[0022] selecting a corresponding relative nonlinear noise coefficient table according to the types of optical fibers, the lengths of optical fibers, the code types, and the monitoring channels actually used by the large-bandwidth optical fiber communication system to be calculated;

[0023] obtaining the relative nonlinear noise coefficients of the crosstalk channels by using the look-up table or the interpolation calculation method based on the selected relative nonlinear noise coefficient table.

[0024] Further, the SPM noise and the first XPM noise sum are calculated according to the simplified GN model, and the simplified GN model is:

[0025] wherein G NLI (f) represents the nonlinear noise power density spectrum, γ is the nonlinear coefficient, L eff is the effective length of the optical fiber, G WDM is the signal light power density spectrum, f, f1, and f2 are frequencies, ρ is the four-wave mixing transmission function, and χ is the four-wave mixing enhancement factor.

[0026] GNLI (f) integrating over the corresponding frequencies to obtain the nonlinear noise of the corresponding channel.

[0027] Further, the adding the SPM noise, the first XPM noise sum and the second XPM noise sum to obtain the nonlinear noise corresponding to the monitoring channel comprises:

[0028] The first XPM noise sum is optimized by a Raman correction factor to obtain an optimized first XPM noise sum;

[0029] The second XPM noise sum is optimized by the Raman correction factor to obtain an optimized second XPM noise sum;

[0030] The SPM noise, the optimized first XPM noise sum and the optimized second XPM noise sum are added to obtain the nonlinear noise corresponding to the monitoring channel.

[0031] Further, the preset frequency threshold is 500GHz±10GHz.

[0032] Further, the transmission waveband of the large-bandwidth fiber communication system is C waveband, L waveband, C+L waveband or C+L+S waveband.

[0033] To achieve the above object, according to one aspect of the present application, there is provided a device for calculating nonlinear noise of a large-bandwidth fiber communication system, comprising at least one processor and a memory, the at least one processor and the memory are connected through a data bus, the memory stores instructions executable by the at least one processor, and the instructions are used to complete the method for calculating nonlinear noise of a large-bandwidth fiber communication system after being executed by the processor.

[0034] Overall, compared with the prior art, the above technical scheme conceived by the present application has the following beneficial effects: since the large-interval crosstalk channel is far away from the monitoring channel, the influence on the nonlinear noise of the monitoring channel is smaller, and the nonlinear noise correlation of each channel generated in the monitoring channel is weak, so the relative nonlinear coefficient can be introduced, and the XPM noise caused by the large-interval crosstalk channel is calculated by combining the relative nonlinear noise coefficient, without calculating the XPM noise of the large-interval crosstalk channel through the GN model, so that the part of the large-interval crosstalk noise which is time-consuming to calculate but has a small noise impact ratio is calculated separately. This improves the calculation efficiency and does not greatly affect the calculation accuracy, and makes up for the defects of the integral GN model.

[0035] On the other hand, the calculation process of the integral GN model is simplified, and the calculation process of the XPM noise caused by the small-interval crosstalk channel is simplified. BRIEF DESCRIPTION OF DRAWINGS

[0036] Fig. 1 is a flow chart of a method for calculating nonlinear noise of a large-bandwidth optical fiber communication system according to an embodiment of the present application;

[0037] Fig. 2 is a flow chart of a method for calculating nonlinear noise of a large-bandwidth optical fiber communication system according to an embodiment of the present application;

[0038] Fig. 3 is a curve diagram showing the variation of calculation time and calculation error of a single wave according to an embodiment of the present application;

[0039] Fig. 4 is a detailed flow chart of step 30 according to an embodiment of the present application;

[0040] Fig. 5 is a three-dimensional diagram showing the relative nonlinear noise coefficient, channel spacing and channel step according to an embodiment of the present application;

[0041] Fig. 6 is a two-dimensional diagram showing the relationship between channel spacing and relative nonlinear noise coefficient according to an embodiment of the present application;

[0042] Fig. 7 is a detailed flow chart of step 40 according to an embodiment of the present application;

[0043] Fig. 8 is a diagram showing a scenario of a 100G QPSK code type, C120+L120 waveband and 11-span 100km G.652 long fiber system according to an embodiment of the present application;

[0044] Fig. 9 is a comparison of simulation results before and after optimization of the algorithm (comparison of calculation cost) according to an embodiment of the present application;

[0045] Fig. 10 is a comparison of simulation results before and after optimization of the algorithm (comparison of calculation time) according to an embodiment of the present application;

[0046] Fig. 11 is a diagram showing the integration range before and after optimization of the algorithm according to an embodiment of the present application;

[0047] Fig. 12 is a diagram showing the structure of a device for calculating nonlinear noise of a large-bandwidth optical fiber communication system according to an embodiment of the present application. DETAILED DESCRIPTION

[0048] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application 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 only used to explain the present application and should not be used to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0049] Embodiment 1:

[0050] The embodiment provides a method for calculating nonlinear noise of a large-bandwidth optical fiber communication system, wherein the transmission wave band of the large-bandwidth optical fiber communication system is a C wave band, an L wave band, a C+L wave band or a C+L+S wave band. Specifically, the transmission wave band of the large-bandwidth optical fiber communication system is a C wave band, such as a C80 wave band, a C96 wave band or a C120 wave band; an L wave band, such as an L96 wave band or an L120 wave band; a C+L wave band, such as a C96+L96 wave band or a C120+L20 wave band; and a C+L+S wave band.

[0051] Referring to FIG. 1 and FIG. 2, the method for calculating nonlinear noise of a large-bandwidth optical fiber communication system comprises the following steps.

[0052] Step 10: calculating self-phase modulation (SPM) noise of a monitoring channel in the large-bandwidth optical fiber communication system.

[0053] In one embodiment, the SPM noise of the monitoring channel in the large-bandwidth optical fiber communication system is obtained according to a simplified GN model.

[0054] The simplified GN model is as follows:

[0055] Wherein, G NLI (f) represents nonlinear noise power density spectrum, γ is a nonlinear coefficient, L eff is an effective length of the optical fiber, G WDM is a signal light power density spectrum, f, f1 and f2 are frequencies, ρ is a four-wave mixing transmission function, and χ is a four-wave mixing enhancement factor.

[0056] The nonlinear noise power density spectrum G NLI (f) at each frequency is calculated according to the simplified GN model, and the nonlinear noise of the corresponding channel is obtained by integrating G NLI (f) at the corresponding frequency. When calculating the nonlinear noise power density spectrum G NLI (f) at a certain frequency f, f1 and f2 theoretically traverse from negative infinity to positive infinity. For a specific scenario, it is enough to cover the entire wave band of the scenario.

[0057] Wherein, before calculating the nonlinear noise, parameters of the system to be simulated are determined, the parameters including variable quantities and constant quantities in the simulation process. The variable quantities include: in-fiber signal light power P i , in-fiber light power spectrum SP and monitoring channel serial number; and the constant quantities include: optical fiber type, optical fiber length L and optical fiber span number.

[0058] Although the nonlinear noise is also related to the loss parameter and the dispersion parameter, the type of the optical fiber is determined, and the loss characteristics and the dispersion characteristics of the light of different frequencies are also determined. Therefore, the loss parameter corresponding to the loss characteristics and the dispersion parameter related to the dispersion characteristics are not input quantities, and the GN model internally calls typical parameters according to the type of the optical fiber, and replaces the actual loss parameter and the dispersion parameter with the typical coefficients.

[0059] Step 20: Calculate the first Cross Phase Modulation (XPM) noise sum caused by the crosstalk channels with a frequency interval less than a preset frequency threshold from the monitoring channel.

[0060] The monitoring channel refers to a channel that needs to calculate the nonlinear noise at present, and any channel in the entire waveband can be the monitoring channel.

[0061] The crosstalk channel refers to all channels in the entire waveband except the monitoring channel.

[0062] For example, there are channels 1 to channels 40 in the waveband, a total of 40 channels. Assuming that the nonlinear noise of channel 3 needs to be known, channel 3 is the monitoring channel, and channels 1 to 2 and channels 4 to 40 are crosstalk channels; similarly, if the nonlinear noise of channel 40 needs to be calculated, channel 40 is the monitoring channel, and channels 1 to 39 are crosstalk channels.

[0063] In an embodiment, according to 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 to obtain the first XPM noise sum.

[0064] The preset frequency threshold is mainly determined by the calculation efficiency and the calculation accuracy, and different values can be taken according to different emphases.

[0065] In an embodiment, the preset frequency threshold can be 500 GHz ± 10 GHz, and more accurately, the preset frequency threshold can be 500 GHz, so that the calculation efficiency and the calculation accuracy can reach a relative balance. Of course, if more emphasis is placed on the calculation efficiency, other values can be selected to make the calculation efficiency higher, and if more emphasis is placed on the calculation accuracy, other values can be selected to make the calculation accuracy higher.

[0066] The design intention of setting the preset frequency threshold to 500 GHz is introduced as follows:

[0067] The embodiment is to speed up by simplifying the integral calculation of the large interval part. The smaller the preset frequency threshold GB_ref is, the smaller the spectrum bandwidth that needs to be integrated is, and the less time the calculation takes. However, the noise ratio of the simplified calculation part is larger, and the introduced simplification error is larger.

[0068] Similarly, the larger the preset frequency threshold GB_ref is, the larger the spectrum bandwidth that needs to be integrated is, and the more time the calculation takes. Also, the noise ratio of the simplified calculation part is smaller, and the introduced simplification error is smaller.

[0069] FIG. 3 is a curve of the calculation time and the calculation error of a single wave when the preset frequency threshold GB_ref takes different values. From the curve, it can be seen that when GB_ref is greater than 10 50GHz bandwidths, the calculation error is less than 4%, and starts to decrease slowly with the increase of GB_ref. The calculation time changes approximately linearly with GB_ref, and the larger GB_ref is, the longer the calculation time is. Therefore, according to the balance between the calculation efficiency and the calculation accuracy, GB_ref is 500GHz. In FIG. 3, the abscissa represents the boundary of the selected large interval scenario and the small interval scenario. Each scale represents 50GHz, so the abscissa 10 represents 500GHz.

[0070] Step 30: Calculate the total second XPM noise caused by the crosstalk channels with a frequency interval greater than or equal to the preset frequency threshold in the monitoring channel in combination with the relative nonlinear noise coefficients.

[0071] That is, calculate the total noise caused by the channels outside the interval range of ±GB_ref (preset frequency threshold).

[0072] Based on the assumption that the nonlinear crosstalk noises of the crosstalk channels are independent of each other, the nonlinear noise caused by the large interval crosstalk channels (i.e., the crosstalk channels with a frequency interval greater than or equal to the preset frequency threshold from the monitoring channel) can be simplified as the superposition of the corresponding crosstalk channel XPM noise. In a dispersion uncompensated system, the nonlinear noise of the large interval crosstalk channels to the monitoring channel is mainly composed of XPM, and other complex terms can be ignored. At the same time, since the information transmitted by each crosstalk channel is independent of each other, the nonlinear noise caused by each crosstalk channel to the monitoring channel is also independent of each other, and can be calculated and linearly added independently.

[0073] In the embodiment, the relative nonlinear noise coefficients between the crosstalk channels are introduced, and the XPM noise of the large interval crosstalk channels is calculated without the GN model, which simplifies the calculation of the XPM noise of the crosstalk channels with an interval greater than the preset frequency threshold from the monitoring channel.

[0074] In the embodiment, the nonlinear noise of the large bandwidth optical fiber communication system to be calculated is divided into two parts: the first XPM noise sum obtained in step 20 and the second XPM noise sum obtained in step 30.

[0075] Step 40: adding the SPM noise, the first XPM noise sum and the second XPM noise sum to obtain the nonlinear noise corresponding to the monitoring channel.

[0076] In the embodiment, based on the assumption that the nonlinear noises of the channels are linearly independent, the SPM noise of the monitoring channel calculated by the GN model, the XPM noise caused by the small interval crosstalk channels calculated by the GN model (i.e. the first XPM noise sum) and the XPM noise caused by the large interval crosstalk channels combined with the relative nonlinear noise coefficients (i.e. the second XPM noise sum) are linearly superimposed to obtain the total nonlinear noise.

[0077] Compared with the prior art, the calculation process of the integral GN model is simplified in the embodiment, and the calculation process of the XPM noise caused by the small interval crosstalk channels is simplified. In addition, since the large interval crosstalk channels are far away from the monitoring channel, the influence on the nonlinear noise of the monitoring channel is smaller, and the nonlinear noise correlation of each channel in the monitoring channel is weak. Therefore, the relative nonlinear noise coefficient can be introduced to calculate the XPM noise caused by the large interval crosstalk channels, so that the part of the large interval crosstalk noise which is time-consuming to calculate but has a small proportion of noise influence is calculated separately. The calculation efficiency is improved, and the calculation accuracy is not greatly affected, which makes up for the defects of the integral GN model.

[0078] Referring to FIG. 4, in step 30, the second XPM noise sum caused by the crosstalk channels with a frequency interval greater than or equal to a preset frequency threshold in the monitoring channel includes:

[0079] Step 301: calculating the reference XPM noise caused by the crosstalk channel with a frequency interval equal to the preset frequency threshold in the monitoring channel.

[0080] In one embodiment, the reference XPM noise caused by the crosstalk channel with a frequency interval equal to the preset frequency threshold in the monitoring channel is calculated according to the simplified GN model.

[0081] Step 302: calculating the relative nonlinear noise coefficient of the crosstalk channel with a frequency interval greater than or equal to the preset frequency threshold in the monitoring channel.

[0082] For a single fiber, the XPM effect caused by a certain crosstalk channel can be calculated by calculating the nonlinear phase caused by the crosstalk channel. The nonlinear phase caused by the crosstalk channel can be obtained by time domain power integration:

[0083] 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.

[0084] By calculating the mean square error of the nonlinear phase, the corresponding equivalent XPM noise power can be obtained:

[0085] 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.

[0086] 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:

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] Calculate the sum of the second XPM noise using the following formula:

[0092] wherein P LargeBd is the second XPM noise summation; i represents the channel number difference between the crosstalk channel and the monitoring channel; k represents the channel number difference between the crosstalk channel and the monitoring channel whose frequency interval is equal to the preset frequency threshold; M is the channel number difference between the crosstalk channel farthest to the left of the monitoring channel and the monitoring channel; N is the channel number difference between the crosstalk channel farthest to the right of the monitoring channel and the monitoring channel, P NL_ref is the reference XPM noise, and G_i represents the relative nonlinear noise coefficient of the ith channel, and G_ref represents the relative nonlinear noise coefficient of the crosstalk channel whose frequency interval is equal to the preset frequency threshold.

[0093] that is, represents the noise summation of all large-interval crosstalk channels to the left of the monitoring channel, represents the noise summation of all large-interval crosstalk channels to the right of the monitoring channel, and the sum of the two noise summations is the second XPM noise summation.

[0094] wherein the crosstalk channel to the left of the monitoring channel refers to the crosstalk channel whose frequency is less than that of the monitoring channel, and the crosstalk channel to the right of the monitoring channel refers to the crosstalk channel whose frequency is greater than that of the monitoring channel.

[0095] The XPM noise caused by the large-interval crosstalk channel in the current scenario can be quickly calculated in the foregoing manner.

[0096] In actual application scenarios, the relative nonlinear coefficient is related to the fiber type, fiber length, code type, and monitoring channel. Therefore, when the above parameters are determined, the relative nonlinear coefficient of the crosstalk channel can also be determined, and in actual use, the relative nonlinear coefficient of each crosstalk channel in the current situation can be obtained by using a lookup table.

[0097] Therefore, in order to improve the efficiency of obtaining the relative nonlinear coefficient of the crosstalk channel, the method for calculating the nonlinear noise of the large-bandwidth optical fiber communication system further comprises:

[0098] At least one relative nonlinear noise coefficient table is established based on the fiber type, fiber length, code type, and monitoring channel that can be involved in the large-bandwidth optical fiber communication system. Wherein, the fiber type, fiber length, code type, and monitoring channel that can be involved in the actual scenario can be pre-collected, and at least one relative nonlinear noise coefficient table is suggested based on the above parameters.

[0099] According to the type of optical fiber, the length of optical fiber, the code type and the monitoring channel used in the large-bandwidth optical fiber communication system to be calculated, a corresponding relative nonlinear noise coefficient table is selected. Before the calculation, the type of optical fiber, the length of optical fiber, the code type and the monitoring channel used in the large-bandwidth optical fiber communication system to be calculated are obtained, and a relative nonlinear noise coefficient table corresponding to the large-bandwidth optical fiber communication system to be calculated is obtained from at least one pre-established relative nonlinear noise coefficient table.

[0100] According to the selected relative nonlinear noise coefficient table, the relative nonlinear noise coefficients of each crosstalk channel are obtained by table lookup or interpolation calculation.

[0101] If the selected relative nonlinear noise coefficient table is completely matched with the large-bandwidth optical fiber communication system to be calculated (that is, the type of optical fiber, the length of optical fiber, the code type and the monitoring channel are consistent), the relative nonlinear noise coefficients of each crosstalk channel are directly obtained by table lookup; if the selected relative nonlinear noise coefficient table is not completely matched with the large-bandwidth optical fiber communication system to be calculated (that is, the type of optical fiber, the code type and the monitoring channel are consistent, but the length of optical fiber is not consistent), the relative nonlinear noise coefficients of each crosstalk channel are obtained by interpolation calculation, and the interpolation calculation is explained as follows:

[0102] Generally, in actual scenarios, the type of optical fiber and the code type of the large-bandwidth optical fiber communication system can be pre-set and will not change with the actual scenario. However, the length of optical fiber will change with the actual scenario and is not controllable. Therefore, in a more preferred embodiment, a relative nonlinear noise coefficient table of a classical optical fiber length relative to different optical fiber lengths and different code types can be pre-established. If there is no relative nonlinear noise coefficient table consistent with the length of optical fiber used in the large-bandwidth optical fiber communication system to be calculated, two relative nonlinear noise coefficient tables with the least difference in the length of optical fiber used in the large-bandwidth optical fiber communication system to be calculated are selected, which are denoted as relative nonlinear noise coefficient table A and relative nonlinear noise coefficient table B, wherein the type of optical fiber, the code type and the monitoring channel corresponding to the relative nonlinear noise coefficient table A and the relative nonlinear noise coefficient table B are consistent with those of the large-bandwidth optical fiber communication system to be calculated.

[0103] Based on the relative nonlinear noise coefficient table A and the relative nonlinear noise coefficient table B, interpolation calculation is performed to obtain a relative nonlinear noise coefficient table corresponding to the large-bandwidth optical fiber communication system to be calculated, and the relative nonlinear noise coefficients of each crosstalk channel are obtained by table lookup.

[0104] If a relative nonlinear noise coefficient table corresponding to the large-bandwidth optical fiber communication system to be calculated has been established in advance, the relative nonlinear noise coefficients of the crosstalk channels are obtained by looking up the table; if the nonlinear noise coefficient corresponding to the actual optical fiber length of the large-bandwidth optical fiber communication system to be calculated has not been established in advance, the corresponding relative nonlinear noise coefficient is obtained by interpolation calculation.

[0105] For example, when modeling a certain optical fiber, in order to be applicable to any optical fiber length, 9 typical optical fiber lengths of 10 km, 20 km, 30 km, 40 km, 60 km, 100 km, 200 km, 300 km, 400 km, etc. are set as references, and the relative nonlinear noise coefficient tables under the 9 lengths are calculated in advance. As shown in FIG. 5, each table, the first dimension is the monitoring signal channel number (SigCH#); the second dimension is the relative non-noise coefficient (G) of the crosstalk channel under the frequency interval of 50 GHz to 12300 GHz generated in the corresponding monitoring channel with a step of 50 GHz. As shown in FIG. 6, a 10 km G.652 optical fiber is provided, and after normalization, the relative nonlinear coefficient of the first monitoring channel under each channel interval (i.e., channel spacing in FIG. 6) is provided.

[0106] In this embodiment, the XPM noise is corrected by the simplified Raman correction factor, and the calculation accuracy is improved. For a large-bandwidth scenario, the inter-band Raman effect cannot be ignored, and in order to consider the influence of the Raman effect on the nonlinearity, the Raman correction factor of each channel can be calculated in advance. The expression of the Raman correction factor is as follows:

[0107] Wherein, LAMAN is the calculated Raman effect correction coefficient; Crk is a polarization-related factor, which is 2 in a conventional scenario; toopPower is the total power of the entire waveband; Cr is a Raman gain coefficient; a is an optical fiber attenuation coefficient; L is an optical fiber length; and Freq is a signal frequency.

[0108] Referring to FIG. 7, in step 40, the adding of the SPM noise, the first XPM noise sum and the second XPM noise sum to obtain the nonlinear noise corresponding to the monitoring channel comprises:

[0109] Step 401: obtaining a simplified Raman correction factor, and optimizing the first XPM noise sum by the Raman correction factor to obtain an optimized first XPM noise sum.

[0110] In this embodiment, the nonlinear noise P caused by the small-interval crosstalk channel is calculated by the simplified GN model. NL_i(GB＜GB_ref) The first XPM noise sum of the small-interval crosstalk channel on the monitoring channel can be calculated, and the Raman correction factor LAMAN i, to obtain the optimized first XPM noise sum P NL_SmallBd , that is, P NL_SmallBd =∑P NL_i(GB＜GB_ref) *LAMAN i , wherein i represents the channel number.

[0111] Step 402: obtaining a simplified Raman correction factor, and optimizing the second XPM noise sum by the Raman correction factor to obtain an optimized second XPM noise sum.

[0112] In the embodiment, when calculating the nonlinear noise caused by the large-interval crosstalk channel, the nonlinear noise P NL_ref of the crosstalk channel with a frequency interval of GB_ref from the monitoring channel is calculated according to the GN model, and the relative nonlinear noise coefficient G i of other crosstalk channels and the relative nonlinear noise coefficient G k of the crosstalk channel at GB_ref are combined, so that the second XPM noise sum of the large-interval crosstalk channel is calculated, and the Raman correction factor LAMAN i is considered to obtain the optimized second XPM noise sum P NL_LargeBd ; P NL_LargeBd =P LargeBd *LAMAN i .

[0113] , wherein i represents the channel number, k represents the channel number of the crosstalk channel at GB_ref, and N represents the total number of channels.

[0114] Step 403: adding the SPM noise, the optimized first XPM noise sum and the optimized second XPM noise sum to obtain the nonlinear noise corresponding to the monitoring channel.

[0115] Finally, the nonlinear noise of each span of the system is accumulated to calculate the total nonlinear noise of the system, specifically including: P NL =∑ Span (P NL_SmallBd +P NL_LargeBd +SPM noise)

[0116] , wherein P NL represents the total nonlinear noise power caused by the system on the monitoring channel; and Span represents the number of spans, ranging from 1 to NSpan.

[0117] Compared with the prior art, the embodiment has at least the following beneficial effects:

[0118] (1) The calculation process of the integral method GN model is simplified, as shown in Figure 11, the integral range is greatly reduced, and a relative nonlinear coefficient is introduced, so that the part of large interval crosstalk noise which is time-consuming to calculate but has a small noise impact is calculated separately. This improves the calculation efficiency and does not have too much impact on the calculation accuracy, making up for the defects of the integral method GN model.

[0119] (2) The practical nonlinear noise calculation method established according to the method of the application has a simple structure and is easy to implement.

[0120] (3) The application can solve the problems of traditional theoretical models, such as being too complex, difficult to solve, and time-consuming, and is more practical.

[0121] (4) The parameters required by the model established according to the method of the application are easy to determine, and many parameters can be directly obtained from product manuals.

[0122] (5) Compared with other simplified calculation methods, the application has a significant advantage in accuracy, but the complexity is not particularly improved.

[0123] Example 2

[0124] Based on the foregoing example 1, this example provides a simulation result comparison of the noise calculation scheme of example 1 relative to the existing noise scheme in a specific scenario.

[0125] As shown in Figure 8, in this example, the large bandwidth optical fiber communication system has a total of 11 spans of G.652 optical fiber, and the length of the optical fiber in each span is 100 km; the transmission waveband is C++ plus L++ waveband, a total of 240 50GHz signals; the monitoring signal code type is 100G QPSK, the signal is output by the sending end OTU, coupled into the sending end optical amplifier through the sending end MUX, then transmitted through 5 span sections in turn, after passing through a WSS equalizer, then transmitted through the next 6 optical fiber spans in turn, and finally passed through the receiving end DEMUX to enter the receiving end.

[0126] The simulation is performed for the scenario of 11-span large bandwidth optical fiber communication system as shown in FIG. 8, and the simulation results before and after optimization of the algorithm are compared as shown in FIG. 9 and FIG. 10. FIG. 9 is a comparison of the calculation cost of each monitoring channel before and after the implementation of the scheme of the application. Each point in FIG. 9 represents the calculation result of a monitoring channel. Specifically, each point needs to perform a nonlinear noise calculation. Taking the point (the first point on the curve) with a frequency of 185 THz as an example, the channel with a frequency of 185 THz is the monitoring channel, and all the channels with frequencies from 185.05 THz to 196.6 THz are the crosstalk channels. The noise generated by the channel with a frequency of 185 THz is the SPM noise, the noise generated by the channels with frequencies from 185.05 THz to 185.5 THz on the channel with a frequency of 185 THz is the XPM noise of the small interval channel, and the noise generated by the channels with frequencies from 185.55 THz to 196.6 THz on the channel with a frequency of 185 THz is the XPM noise of the large interval channel. FIG. 10 is a comparison of the calculation time of each monitoring channel before and after the implementation of the scheme of the application. As can be seen from FIG. 9, the scheme of the application has little effect on the calculation accuracy, with two decimal places. At the same time, as can be seen from FIG. 10, the scheme of the application has a significant improvement in the calculation efficiency, with an efficiency improvement of nearly 4 times. The problem of long calculation time in the process of nonlinear noise calculation of large bandwidth optical fiber transmission system is better solved.

[0127] Embodiment 3

[0128] Based on the method for calculating the nonlinear noise of the large bandwidth optical fiber communication system provided in the above embodiment 1, the application further provides a device for calculating the nonlinear noise of the large bandwidth optical fiber communication system, as shown in FIG. 12, which is a device architecture schematic diagram of the embodiment of the application. The device of the embodiment comprises one or more processors 21 and a memory 22. In FIG. 12, one processor 21 is taken as an example.

[0129] The processor 21 and the memory 22 can be connected through a bus or other means, and in FIG. 12, the connection through the bus is taken as an example.

[0130] The memory 22 serves as a non-volatile computer readable storage medium for a method for calculating the nonlinear noise of the large bandwidth optical fiber communication system, and can be used to store non-volatile software programs, non-volatile computer executable programs and modules, such as the method for calculating the nonlinear noise of the large bandwidth optical fiber communication system in embodiment 1. The processor 21 performs various functional applications and data processing of the device by running the non-volatile software programs, instructions and modules stored in the memory 22, that is, implements the method for calculating the nonlinear noise of the large bandwidth optical fiber communication system of the embodiment.

[0131] The memory 22 can include a high-speed random access memory, and can also include a non-volatile memory, such as at least one magnetic disk storage device, a flash memory device, or other non-volatile solid-state memory device. In some embodiments, the memory 22 can optionally include a memory that is remotely located with respect to the processor 21, and these remotely located memories can be connected to the processor 21 through a network. Examples of the network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0132] The program instructions / modules are stored in the memory 22, and when executed by the one or more processors 21, perform the method of calculating the nonlinear noise of a large-bandwidth fiber-optic communication system in the above-described embodiments.

[0133] Those of ordinary skill in the art can understand that all or part of the steps in the various methods of the embodiments can be instructed by programs to relevant hardware, and the programs can be stored in a computer-readable storage medium, which can include a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and the like.

[0134] Those of ordinary skill in the art will readily understand that the above description is only preferred embodiments of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present application shall fall within the protection scope of the present application.

Claims

1. A method of computing nonlinear noise in a large bandwidth fiber-optic communication system, comprising: The method comprises the following steps: calculating SPM noise of a monitoring channel in a large-bandwidth optical fiber communication system; calculating a first XPM noise sum caused by a crosstalk channel with a frequency interval less than a preset frequency threshold from the monitoring channel; calculating a second XPM noise sum caused by a crosstalk channel with a frequency interval greater than or equal to the preset frequency threshold from the monitoring channel in combination with a relative nonlinear noise coefficient; adding the SPM noise, the first XPM noise sum and the second XPM noise sum to obtain nonlinear noise corresponding to the monitoring channel.

2. The method of claim 1, wherein, The method for calculating the second XPM noise sum caused by the crosstalk channel with the frequency interval greater than or equal to the preset frequency threshold from the monitoring channel in combination with the relative nonlinear noise coefficient comprises the following steps: calculating a reference XPM noise caused by a crosstalk channel with a frequency interval equal to the preset frequency threshold from the monitoring channel; calculating a relative nonlinear noise coefficient of each crosstalk channel with a frequency interval greater than or equal to the preset frequency threshold from the monitoring channel; obtaining the second XPM noise sum caused by the crosstalk channel with the frequency interval greater than or equal to the preset frequency threshold from the monitoring channel according to the reference XPM noise and the relative nonlinear noise coefficient of each crosstalk channel.

3. The method of claim 2, wherein, The second XPM noise sum is calculated according to the following equation: wherein P LargeBd is the second XPM noise sum; i represents the channel number difference between the crosstalk channel and the monitoring channel; k represents the channel number difference between the crosstalk channel and the monitoring channel whose frequency interval is equal to the preset frequency threshold; M is the channel number difference between the crosstalk channel farthest to the left of the monitoring channel and the monitoring channel; N is the channel number difference between the crosstalk channel farthest to the right of the monitoring channel and the monitoring channel, P NL_ref is the reference XPM noise, and G_i represents the relative nonlinear noise coefficient of the i-th channel, and G_ref represents the relative nonlinear noise coefficient of the crosstalk channel whose frequency interval is equal to the preset frequency threshold.

4. The method of claim 2, wherein, The relative nonlinear noise figure of each crosstalk channel whose frequency interval from the monitoring channel is greater than or equal to the preset frequency threshold is calculated according to the following formula: where G is the relative nonlinear noise figure induced by the crosstalk channel on the monitored channel, γ is the nonlinear coefficient, L w is the walk-off length, L is the fiber length, a is the attenuation coefficient, t is time; C Δ (t'1, t'2) is a trigonometric function.

5. The method of claim 1, wherein, The method for calculating nonlinear noise of a large-bandwidth optical fiber communication system further comprises the following steps: establishing at least one relative nonlinear noise coefficient table based on fiber types, fiber lengths, code types and monitoring channels possibly involved in the large-bandwidth optical fiber communication system; selecting a corresponding relative nonlinear noise coefficient table according to fiber types, fiber lengths, code types and monitoring channels actually used in the large-bandwidth optical fiber communication system to be calculated; obtaining the relative nonlinear noise coefficient of each crosstalk channel by using a table lookup or interpolation calculation method based on the selected relative nonlinear noise coefficient table.

6. The method of claim 1-5, wherein, The sum of SPM noise and first XPM noise is calculated according to the simplified GN model, which is: wherein G NLI (f) represents a nonlinear noise power density spectrum, γ is a nonlinear coefficient, L eff is an effective length of the optical fiber, G WDM is a signal light power density spectrum, f, f1, f2 are frequencies, ρ is a four-wave mixing transfer function, and χ is a four-wave mixing enhancement factor; G NLI (f) integrating over the corresponding frequencies to obtain the non-linear noise of the corresponding channel.

7. The method of claim 1-5, wherein, The step of adding the SPM noise, the first XPM noise sum and the second XPM noise sum to obtain nonlinear noise corresponding to the monitoring channel comprises the following steps: obtaining a simplified Raman correction factor, optimizing the first XPM noise sum by using the Raman correction factor to obtain an optimized first XPM noise sum; optimizing the second XPM noise sum by using the Raman correction factor to obtain an optimized second XPM noise sum; adding the SPM noise, the optimized first XPM noise sum and the optimized second XPM noise sum to obtain nonlinear noise corresponding to the monitoring channel.

8. The method of claim 1-5, wherein, The preset frequency threshold is 500 GHz ± 10 GHz.

9. The method of claim 1-5, wherein, The transmission waveband of the large-bandwidth optical fiber communication system is C waveband, L waveband, C+L waveband or C+L+S waveband.

10. An apparatus for calculating nonlinear noise in a high-bandwidth optical fiber communication system, characterized in that, The device comprises at least one processor and a memory, the at least one processor and the memory are connected through a data bus, the memory stores instructions executable by the at least one processor, and the instructions are used to complete the method for calculating nonlinear noise of a large-bandwidth optical fiber communication system according to any one of claims 1-9 after being executed by the processor.

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