CN115378500A - Method for calculating output power of dense wavelength division multiplexing coherent optical channel - Google Patents
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Abstract
The invention relates to a method for calculating the output power of a dense wavelength division multiplexing coherent optical channel. The calculation method comprises the following steps: step 1, determining initial performance indexes of an ith channel and a jth channel, wherein the initial performance indexes comprise the incident power of the ith channel and the length L of an optical fiber, and calculating the required channel physical parameters according to the initial performance indexes; step 2, establishing a stimulated Raman scattering effect model of the coherent optical channel by using the physical parameters to form an optical signal transmission distance z and an output power P at an ith channel z i (z) an equation; and 3, determining a step length h according to the required calculation precision and the calculation time, and solving the equation in the step 2 by using a Longge Kutta method to obtain the output power of the optical fiber at any optical signal transmission distance z. The present invention provides a method for DWDM communication systemA fast and accurate channel output power distribution calculation method.
Description
Technical Field
The invention relates to the technical field of optical fiber communication, in particular to a method for calculating the output power of a dense wavelength division multiplexing coherent optical channel.
Background
The wavelength Division Multiplexing technology is one of the pillars of modern communication systems, and divides the wavelength range in which the optical fiber can be applied into a plurality of bands, and each band is used as an independent signal transmission channel to transmit an optical signal with a specific optical wavelength, which is the same as the principle of Frequency Division Multiplexing (FDM) in an electrical signal, but is generally described by using a wavelength for light, and is therefore named as the wavelength Division Multiplexing technology. Dense wavelength division multiplexing is a wavelength division multiplexing technique in which the channel distribution is denser, and there is no essential difference in principle.
At present, the communication band of Dense Wavelength Division Multiplexing (DWDM) system mainly uses C window, that is, the Wavelength range of 1529.16nm to 1560.61nm, and the total spectral width is 4THz. The next generation optical communication simultaneously comprises an L wave band (the wavelength range is 1570 nm-1611 nm), namely C + L double-wave-band common transmission, the total spectral width can reach 9.6Thz at the lowest, and can reach about 13Thz at the highest, thereby greatly improving the transmission capacity.
The Stimulated Raman Scattering effect SRS (Stimulated Raman Scattering) becomes more serious due to the larger spectral width of the C + L two-band communication. The stimulated raman scattering effect is a very important nonlinear phenomenon in an optical fiber, and is specifically represented by that energy of a signal channel at a short wavelength can be gradually transferred to a signal at a long wavelength along with transmission of an optical fiber link, so that a power of an optical signal at the short wavelength is greatly different after the optical signal is transmitted through the optical fiber. For backbone optical networks, coherent optical communication is mainly used, i.e. in the case of continuous waves, stimulated raman scattering is more severe in the case of continuous waves than in the case of pulsed waves. Under the condition of pulse wave, due to optical fiber dispersion, a walk-off effect can occur among different channel optical pulses, so that the influence of an SRS (sounding reference signal) effect is relatively small; in the continuous wave case, the optical field does not walk away, and the optical field is interacted with the incident and emergent optical fibers, wherein the SRS effect is continuously and stably generated. The influence of SRS is therefore quite high in the continuous wave case, affecting in particular the power flatness at the output of the fiber, impairing the optical signal reception quality. In short, SRS is one of the important factors that restrict the C + L spread spectrum communication quality of the backbone optical network.
The existing calculation method of the fiber link SRS model for the coherent light (continuous wave) communication system is the same as the solution method of the pulse signal transmission equation, and is a step-by-step Fourier method, which needs a smaller calculation step length to ensure the accuracy of the calculation result. For C + L dual-band transmission, the number of channels may reach as many as 200, and the transmission link may include a plurality of spans, the total transmission distance reaches hundreds or even thousands of kilometers, and it is necessary to spend a lot of computation power and time if the computation is performed by using the step fourier method, so that it is imperative to improve the computation efficiency of the SRS model of the optical fiber link.
Disclosure of Invention
Therefore, the technical problem to be solved by the present invention is to overcome the deficiencies in the prior art, and provide a method for calculating the output power of a dense wavelength division multiplexing coherent optical channel, which calculates the output power of the channel at different optical signal transmission distances by using the longge library tower method, and provides a fast and accurate method for calculating the output power distribution of the channel for a DWDM communication system.
The calculation method comprises the following steps:
step 1, determining initial performance indexes of an ith channel and a jth channel, wherein the initial performance indexes comprise the incident power of the ith channel and the length L of an optical fiber, and calculating the required channel physical parameters according to the initial performance indexes;
wherein, i and j are positive integers, one of the ith channel and the jth channel is a pumping channel, and the other channel is a Stokes channel;
step 2, establishing a stimulated Raman scattering effect model of the coherent optical channel by using the physical parameters to form an optical signal transmission distance z and an output power P at an ith channel z i (z) an equation;
step 3, determining a step length h according to the required calculation precision and the calculation time, solving the equation in the step 2 by using a Runge Kutta method, obtaining the ith channel output power at the position where the optical signal transmission distance z = h according to the incident power by taking the incident power as an initial value, and performing iterative operation to obtain the ith channel output power P at the next step of the length h i (z + h) until the optical signal transmission distance z reaches the optical fiber length L, and obtaining the output power of the optical fiber terminal.
In step 1, the initial performance index further comprises an ith channel center frequency, a jth channel center frequency and a jth channel incident power; the articleThe physical parameters include attenuation coefficient a of ith channel i The Raman gain coefficient g between the ith channel and the jth channel ij Polarization coefficient K ij And the mode field overlapping area A between the ith channel and the jth channel ij Optical wavelength lambda of ith channel i And the jth channel optical wavelength λ j 。
In step 2, the transmission distance x of the optical signal and the output power P at the ith channel z i The equation for (z) is:
in step 3, solving the equation in step 2 by using a Runge Kutta method to obtain a Runge Kutta solving formula, wherein the Runge Kutta solving formula is as follows:
wherein, the first and the second end of the pipe are connected with each other,
K 1 is the slope at the beginning of step h, K 2 Is the first slope at the midpoint of step h, K 3 Is the second slope at the midpoint of step h, K 4 Is the slope at the end of step h; when i is less than j, the ith channel is a pumping channel, and the jth channel is a Stokes channel; when i > j, the ith channel is the Stokes channel and the jth channel is the pump channel.
Transmitting the optical signal by a distance z and an output power P at an ith channel z i The equation of (z) is written in matrix form:
wherein, P = (P) 1 (z)，P 2 (z)，...，P N (z)) T ，C＝(a 1 ,a 2 ,...,a N ) T ，B＝diag(P 1 (z)，P 2 (z)，...，P N (z)), N is the number of channels, G S Is a Raman pump gain matrix, G P For Raman pumping depletion matrix, raman pumping matrix G = G S -G P 。
The Raman pump gain matrix G S Comprises the following steps:
raman gain G in which the ith channel is pumped by the jth channel si，j ＝g ij /(A ij *K ij )；
The Raman pump consumption matrix G P Comprises the following steps:
wherein the ith channel pumps the Raman gain C of the jth channel p i，j ＝(g ij *λ j )/(A ij *K ij *λ i )。
Compared with the prior art, the technical scheme of the invention has the following advantages:
the output power of the channel at different optical signal transmission distances is calculated by adopting a Runge-Kutta method, the slope of each step is calculated for four times, and then the average value is obtained, so that the calculation precision is improved, the value of the step can be increased, the calculation time is shortened, and the calculation efficiency is improved; transmitting an optical signal a distance z from an output power P at an i-th channel i The equation of (z) is written in a matrix form, so that the output power of any number of channels can be calculated simultaneously, a computer program is convenient to write, the hardware requirement on the computer is reduced, and the method is suitable for practical application.
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In order that the present invention may be more readily and clearly understood, reference will now be made in detail to the present invention, examples of which are illustrated in the accompanying drawings.
FIG. 1 is a flow chart of a calculation using the fourth order Runge Kutta method of the present invention;
FIG. 2 is a flow chart of a conventional step-by-step Fourier method;
FIG. 3 is a schematic diagram of VPIphoronics simulation according to the present invention;
FIG. 4 is a diagram showing the simulation results of VPIphoronics according to the present invention;
FIG. 5 is a schematic diagram showing the comparison between the formula calculation result of the conventional step-by-step Fourier method and the simulation result of VPIphostronics of the present invention;
FIG. 6 is an enlarged view of FIG. 5 a;
FIG. 7 is a schematic diagram showing comparison of calculation results of different step lengths by using a fourth-order Runge Kutta method according to the present invention;
FIG. 8 is an enlarged view of FIG. 7 b;
FIG. 9 is a schematic diagram illustrating comparison of calculation results of different step sizes in the conventional step-by-step Fourier method;
FIG. 10 is an enlarged view of FIG. 9 c;
FIG. 11 is a schematic diagram showing comparison between the four-step Runge Kutta method and the conventional step-by-step Fourier method under the same calculation times;
fig. 12 is an enlarged view of fig. 11 d.
Detailed Description
The present invention is further described below in conjunction with the drawings and the embodiments so that those skilled in the art can better understand the present invention and can carry out the present invention, but the embodiments are not to be construed as limiting the present invention.
As shown in fig. 1, in order to provide a fast and accurate channel output power distribution calculation method for DWDM communication systems, the calculation method of the present invention comprises the steps of:
step 1, determining initial performance indexes of an ith channel and a jth channel, wherein the initial performance indexes comprise the incident power of the ith channel and the length L of an optical fiber, and calculating the physical parameters of the needed channels according to the initial performance indexes;
wherein, i and j are positive integers, one of the ith channel and the jth channel is a pumping channel, and the other channel is a Stokes channel;
specifically, according to the stimulated raman scattering effect, the energy of the short wavelength channel is gradually transferred to the long wavelength channel along with the transmission of the optical signal through the optical fiber link, that is, the short wavelength channel pumps the long wavelength channel, and at this time, the short wavelength channel is a pumping channel and the long wavelength channel is a stokes channel. When calculating the power distribution of the optical signal transmission channel, a pump channel and a stokes channel corresponding to the pump channel need to be determined, which is well known to those skilled in the art and will not be described herein.
As shown in fig. 1, calculating the output power of a channel, i.e. an optical signal transmission channel, first needs to determine initial performance indicators of the channel, i.e. an ith channel center frequency, a jth channel center frequency, an ith channel incident power, a jth channel incident power, and an optical fiber length L. Determining physical parameters according to the initial performance index, wherein the physical parameters comprise attenuation coefficient a of ith channel i And a Raman gain coefficient g between the ith channel and the jth channel ij Polarization coefficient K ij The overlap area A of the mode field between the ith channel and the jth channel ij Optical wavelength lambda of ith channel i And j channel optical wavelength λ j 。
The attenuation coefficient a of the ith channel can be determined according to the center frequency of the ith channel i And ith channel optical wavelength λ i Determining j channel optical wavelength lambda according to j channel central frequency j Determining the Raman gain coefficient g between the ith channel and the jth channel according to the center frequency of the ith channel and the center frequency of the jth channel ij As is well known to those skilled in the art, further description is omitted here.
Generally, if a polarization maintaining fiber is not used in practical long-distance optical fiber communication, the mode of the optical fiber cannot maintain a constant polarization state, and the polarization state changes randomly during transmission, which results in a reduced raman effect, so that the polarization coefficient K is reduced ij A value of 2 may be taken to approximate the actual situation. Area of mode field overlap A between ith and jth channels ij Related to the channel wavelength, but with a small rate of change with the wavelength of the light, and therefore preferably the effective core area of the fiber, which may be 80 μm 2 The details are the same as those of the prior art, and are not described herein again.
Step 2, establishing a stimulated Raman scattering effect model of the coherent optical channel by using the physical parameters to form an optical signal transmission distance z and an output power P at an ith channel z i (z) an equation;
the optical signal transmission distance z and the output power P at the ith channel z i The equation for (z) is:
specifically, the process of establishing the stimulated Raman scattering effect model of the coherent optical channel, the obtained optical signal transmission distance z and the output power P at the ith channel z i The equations of (z) are consistent with the prior art and are not described in detail here.
Step 3, determining a step length h according to the required calculation precision and the calculation time, solving the equation in the step 2 by using a Runge Kutta method, obtaining the ith channel output power at the position where the optical signal transmission distance z = h according to the incident power by taking the incident power as an initial value, and performing iterative operation to obtain the ith channel output power P at the next step of the length h i (z + h) until the optical signal transmission distance z reaches the optical fiber length L, and obtaining the output power of the optical fiber terminal.
Specifically, in order to prove the accuracy and high efficiency of the calculation method of the present invention, in the embodiment of the present invention, the conventional step-by-step fourier method is compared with the longguta method employed in the present invention, and in order to fully explain the step-by-step fourier method, the present invention explains that the step-by-step fourier method solves the output power of the incoherent light channel as an example, and the process of solving the stimulated raman scattering effect model of the incoherent light (pulse wave) channel by the conventional step-by-step fourier method is as follows:
establishing a stimulated Raman scattering effect model (pulse transmission equation) of an incoherent optical channel:
wherein, A P Indicating pumpsAmplitude of the wave; v. of gP Representing the group velocity of the pump wave; beta is a beta 2P A GVD (group velocity dispersion) parameter representing the pump wave; a is a P Represents an attenuation coefficient of the pump wave; gamma ray P A nonlinear coefficient representing a pump wave; g P Represents the pump raman gain coefficient; a. The s Represents the amplitude of the stokes wave; v. of gs Represents the group velocity of the stokes wave; beta is a 2s A GVD (group velocity dispersion) parameter representing a stokes wave; a is s An attenuation coefficient representing a stokes wave; gamma ray s A nonlinear coefficient representing a stokes wave; g S Expressing a stokes wave raman gain coefficient; f. of R Representing the contribution of the delayed raman effect to the non-linear polarizability, is typically 0.18. The meaning of the pulse transmission equation is shown in table 1.
TABLE 1
Equation (2) is written as follows:
wherein a represents amplitude;
is a linear operator, which expresses the dispersion and loss in the optical fiber;
is a nonlinear operator and represents the nonlinear effect in the optical fiber.
And
can be expressed as:
the basic principle of the split-step Fourier transform method is that when the optical signal transmission distance z is small enough, the influence of dispersion and nonlinear effect on the pulse can be calculated respectively, and finally an approximate result is obtained. Specifically, the reaction is carried out in two steps from z to z + h. First, only non-linear effects are present, in which case
A second step, in which only the scattering effect is present, in which case
And finally, multiplying the two results to obtain an approximate solution when the optical pulse signal is transmitted in the optical fiber by the distance z = h. By the thought, a mathematical model of the following step-by-step Fourier numerical algorithm is established (h is the step size and can be adjusted according to the precision requirement):
therein
In the Fourier domain (F) T Which is indicative of the fourier transform,
representing the inverse fourier transform, T represents the time of the pulse):
in the formula
By mixing
Differential operator in (1)
Substituted by i ω, which is the frequency in the fourier domain. This solution principle is illustrated by equation (2): in the first step
The equation is written as:
wherein, A PN Representing the amplitude when there is only non-linearity, which is an ordinary differential equation, solved by:
in the second step
The equation can now be written as:
wherein A is PD The amplitude is expressed only with dispersion, and an ordinary differential equation is obtained by Fourier transform:
solving the equation:
at this time, according to the mathematical model of SSFT, the
By Fourier transformation of the result of the first operation, i.e.
And then Fourier inversion is carried out to obtain a complete time domain solution:
in specific implementation, only a nonlinear operator needs to be calculated when a step Fourier method is used for solving the channel output power distribution of coherent light (continuous wave)
Without the need to compute linear operators
And the formula (1) does not contain a time derivative term, so the calculation steps of the formula (8) to the formula (13) do not need to be carried out. The specific solving formula is as follows:
as shown in fig. 2, solving by using the step-by-step fourier method also determines physical parameters according to initial performance indexes, and calculates the channel output power of each step after determining the physical parameters until the sum of the step reaches the length of the optical fiber, the step-by-step fourier method for solving formula (1) needs very small step, sometimes as small as several meters, while the optical signal transmission channel may reach dozens of kilometers, hundreds of kilometers, or even thousands of kilometers, the step-by-step fourier method cannot improve the calculation step and efficiency under the condition of ensuring that the calculation has a certain accuracy, and the requirements on computer hardware are relatively high, which is specifically consistent with the prior art and is not described herein.
Further, the invention utilizes the Runge Kutta method to solve the formula (2) to obtain a Runge Kutta solution formula, wherein the Runge Kutta solution formula is as follows:
wherein the content of the first and second substances,
K 1 is the slope at the beginning of step h, K 2 Is the first slope at the midpoint of step h, K 3 Is the second slope at the midpoint of step h, K 4 The slope at the end of step h.
Specifically, the lunger-Kutta method (Runge-Kutta methods) is a high-precision single-step algorithm widely applied to engineering, can be applied to physics, engineering, control and dynamics, such as fuzzy control, ballistic analysis, analysis of optical fiber characteristics and the like, is widely applied to system simulation, and is an important implicit or explicit iteration method commonly used for simulating solutions of ordinary differential equations. The invention adopts a four-order explicit Runge Kutta method, and the specific algorithm principle is as follows.
Consider the initial value problem of the first order ordinary differential equation:
the existing four-step Rungestota formula is as follows, wherein h represents the step length:
specifically, when x = x 0 When the temperature of the water is higher than the set temperature,y＝y 0 at this time y 0 After the initial value is obtained, the function y (x) can be solved by repeatedly iterating the formula (17) when any x is more than or equal to x 0 The value of (c). As can be seen from the above description, each step of the fourth-order Runge Kutta method requires the calculation of a fourth-order function value f with a truncation error of O (h) 5 ) The error is rather small.
It is easy to see that the structures of equation (1) and equation (16) are the same, and equation (1) is now rewritten as follows:
wherein, P i (0) Expression (15) is obtained by substituting expression (18) into expression (17), which represents the output power at the time when the second optical signal transmission distance z =0, that is, the input power of the i-th channel.
As shown in FIG. 1, the process of solving the output power distribution of the channel by using the Runge Kutta method comprises determining the incident power of the ith channel, substituting the incident power of the ith channel into a formula (15) as an initial value for solving, and sequentially obtaining K 1 、K 2 、K 3 、K 4 A value of (A) K 1 、K 2 、K 3 、K 4 Taking an average value to obtain the ith channel output power at the position where the optical signal transmission distance z = h, and then carrying out iterative operation to obtain the ith channel output power P at the position of the next step h i (z + h) until the optical signal transmission distance reaches the optical fiber length L, and obtaining the output power of the optical fiber terminal.
Further, in order to adapt to practical application and facilitate computer programming, the optical signal is transmitted by a distance z and the output power P at the ith channel z i The equation of (z) is written in matrix form:
wherein, P = (P) 1 (z)，P 2 (z)，...，P N (z)) T ，C＝(a 1 ,a 2 ,...,a N ) T ，B＝diag(P 1 (z)，P 2 (z)，...，P N (z)), N is the number of channels, G S Is a Raman pump gain matrix, G P For Raman pump consumption matrix, raman pump matrix G = G S -G P (ii) a When i is less than j, the ith channel is a pumping channel, and the jth channel is a Stokes channel; when i > j, the ith channel is the Stokes channel and the jth channel is the pump channel.
The Raman pump gain matrix G S Comprises the following steps:
raman gain G in which the ith channel is pumped by the jth channel s，i，j ＝g ij /(A ij *K ij )；
The Raman pump consumption matrix G P Comprises the following steps:
wherein the ith channel pumps the Raman gain G of the jth channel pi，j ＝(g ij *λ j )/(A ij *K ij *λ i )。
In particular, in an actual optical signal transmission process, a DWDM system may have hundreds of channels, and the stimulated raman scattering effect of pumping and pumped may be generated between channels with different wavelengths. In the embodiment of the invention, the smaller the channel index i is, the shorter the wavelength of the optical carrier representing the channel is taken as an example for explanation, when the output power of the channel is calculated, when i is less than j, the ith channel is a pumping channel, and the jth channel is a stokes channel; when i > j, the ith channel is the Stokes channel and the jth channel is the pump channel.
During specific implementation, required physical parameters are calculated according to initial performance indexes of channels, the physical parameters of all the channels are substituted into a formula (19), at the moment, energy transfer generated by pumping of all the channels and pumped channels, namely energy consumption generated by the pumping channels and energy gain generated by the pumped channels are written into the same formula, and then unified calculation is performed by using a Longge Kutta method to obtain:
as can be seen from the above description, the solution method of equation (22) is not substantially different from that of equation (15), and each parameter is changed into an N-dimensional column vector, which can cover any band and any number of channels.
Furthermore, the method compares the solution result of solving the output power of the coherent optical channel by the Runge-Kutta method with the existing step Fourier method. In specific implementation, as shown in fig. 3, a VPIphotonics simulation schematic diagram of the present invention is shown, wherein the simulation schematic diagram includes a comb light source, a general optical fiber (including raman nonlinear effect), and an oscilloscope. In the parameters selected by simulation, the C-band channel frequency is 190.73 THz-196.65THz, the L-band channel frequency is 183.30 THz-190.30 THz, the channel intervals are 75GHz, the C + L band has 178 channels, the spectrum width is about 13THz, the input power of each channel is all 0dBm, and the total length of the optical fiber is 80KM. The simulation results are shown in fig. 4. The computer hardware parameters used in the present invention are shown in table 2.
TABLE 2
The results of the simulation of VPI were derived into Matlab and compared with the results calculated using the existing step fourier method (step size 0.5 m), as shown in fig. 5. From the comparison result of fig. 5, the output power distribution obtained by solving the formula (1) with the step size of 0.5 m based on the traditional fractional fourier method is almost consistent with the result obtained by VPI simulation, and it can be seen that the calculation result of the lunger stota method used in the invention is quite accurate.
FIG. 9 is a comparison of the results of the step Fourier transform calculation using different step sizes, where the specific calculation parameters are the same as those described above, and the calculation is repeated 20 times for each step size, so as to obtain the average calculation time consumed for each step size. It is clear from the figure that the calculation results at each larger step deviate significantly from the reference base. Although the calculation time is shortened by increasing the step size, the calculation result is seriously inaccurate, and if a more accurate result is needed, the calculation step size is necessarily reduced, so that the requirement on computer hardware is high, and the use condition is particularly limited.
Fig. 7 is a comparison of the calculation results of the lungasta method using the same step size as fig. 9, and the other calculation parameters are the same as those described above, and each step size is repeatedly calculated 20 times, so as to obtain the average calculation time consumed by each step size. It can be seen that there was no significant difference in the results for the non-magnified images, except for the larger error in the results for the step size of 16 KM. As shown in fig. 8, it can be seen from the magnified portion of the image that the results are quite accurate at steps below 8KM, the difference is below 0.005dBm, and the average time consumption for steps from 8KM to 2.667KM is around 0.015 seconds, which is about 0.2% of the time consumed by the 0.5 meter step fourier transform method.
In specific implementation, the longge stota method needs to perform 4 calculations in each step, and fig. 11 shows that the calculation results of the two methods are compared when the actual calculation times are the same. It can be seen from fig. 11 that the results of RK method still coincide with the reference standard for the same number of calculations, while the distributed fourier method already has a larger deviation. In conclusion, compared with the traditional step Fourier method, the method used by the invention has higher calculation efficiency and more accurate calculation result.
It can be known from the above description that the invention cooperates with the program structure of the high-efficient operation of the particular programming language, under the same hardware condition, only need about 50 calculations can achieve about 1000 accuracies of calculation of Fourier method step by step, the number of times of calculation is shortened to original 5%, the efficiency is promoted greatly, has reduced the requirement for computer hardware, the application range becomes more extensive consequently.
Claims (6)
1. A method for calculating output power of a dense wavelength division multiplexing coherent optical channel is characterized by comprising the following steps:
step 1, determining initial performance indexes of an ith channel and a jth channel, wherein the initial performance indexes comprise the incident power of the ith channel and the length L of an optical fiber, and calculating the physical parameters of the needed channels according to the initial performance indexes;
wherein, i and j are positive integers, one of the ith channel and the jth channel is a pumping channel, and the other channel is a Stokes channel;
step 2, establishing a stimulated Raman scattering effect model of the coherent optical channel by using the physical parameters to form an optical signal transmission distance z and an output power P at an ith channel z i (z) equation;
step 3, determining a step length h according to the required calculation precision and the calculation time, solving the equation in the step 2 by using the Runge Kutta method, obtaining the ith channel output power at the position where the optical signal transmission distance z = h by taking the incident power as an initial value according to the incident power, and performing iterative operation to obtain the ith channel output power P at the next step of the step length h i (z + h) until the optical signal transmission distance z reaches the optical fiber length L, and obtaining the output power of the optical fiber terminal.
2. The method of claim 1, wherein the calculating of the dwdm coherent optical channel output power comprises: in step 1, the initial performance index further includes an ith channel center frequency, a jth channel center frequency and a jth channel incident power; the physical parameters comprise attenuation coefficient a of ith channel i The Raman gain coefficient g between the ith channel and the jth channel ij Polarization coefficient K ij And the mode field overlapping area A between the ith channel and the jth channel ij I channel optical wavelength lambda i And the jth channel optical wavelength λ j 。
3. The method of calculating the output power of the dwdm coherent optical channel according to claim 2, wherein: in step 2, the transmission distance z of the optical signal and the output power at the ith channel zP i The equation for (z) is:
4. the method of claim 3, wherein the step of calculating the output power of the DWDM coherent optical channel comprises: in step 3, solving the equation in step 2 by using a Longgusta method to obtain a Longgusta solving formula, wherein the Longgusta solving formula is as follows:
wherein the content of the first and second substances,
K 1 is the slope at the beginning of step h, K 2 Is the first slope at the midpoint of step h, K 3 Is the second slope at the midpoint of step h, K 4 The slope at the end of step h.
5. The method of claim 3, wherein the calculating of the output power of the DWDM coherent optical channel comprises: transmitting the optical signal by a distance z and an output power P at an ith channel z i The equation of (z) is written in matrix form:
wherein, P = (P) 1 (z)，P 2 (z)，...，P N (z)) T ，C＝(a 1 ，a 2 ，...，a N ) T ，B＝diag(P 1 (z)，P 2 (z)，...，P N (z)), N is the number of channels, G s Is a Raman pump gain matrix, G P Is a matrix of consumption of the raman pump,raman pump matrix G = G s -G P (ii) a When i is less than j, the ith channel is a pumping channel, and the jth channel is a Stokes channel; when i > j, the ith channel is the Stokes channel and the jth channel is the pump channel.
6. The method of claim 5, wherein the step of calculating the output power of the DWDM coherent optical channel comprises: the Raman pump gain matrix G s Comprises the following steps:
raman gain G in which the ith channel is pumped by the jth channel si，j ＝g ij /(A ij *K ij )；
The Raman pump consumption matrix G P Comprises the following steps:
wherein the ith channel pumps the Raman gain G of the jth channel pi，j ＝(g ij *λ j )/(A ij *K ij *λ i )。
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