Fast calculation compensation method for influence of rainfall on visible-near infrared band optical communication

Abstract

The application provides a quick calculation compensation method for the influence of rainfall on visible light-near infrared band optical communication, and is used for solving the technical problems that the traditional Mie scattering calculation method is difficult to meet the fast and efficient requirements of related research because the programming implementation technology is complex, the calculation speed is slow, numerical instability is prone to occur and the like due to relying on the Bessel function, continued fraction recursion and the like. The quick calculation compensation method for the influence of rainfall on visible light-near infrared band optical communication can realize the quick and stable calculation of Mie scattering optical parameters of three rainfall types and any rainfall intensity in the visible light-near infrared band on the basis of guaranteeing the calculation accuracy, realizes the quick and real-time output of the calculation results, and can be widely applied to the optical communication compensation technology in the fields of laser communication, automatic driving and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a Mie scattering calculation method, and in particular to a fast calculation compensation method for the influence of rainfall on visible light-near infrared band optical communication. BACKGROUND

[0002] Rainfall has a serious attenuation effect on the propagation of light in the visible light-near infrared band, and in severe cases, it can even interrupt the optical communication link. Therefore, the study of the above problem has become one of the research focuses in the fields of laser communication, autonomous driving, etc. However, due to the wide range of particle size intervals of rainfall, the maximum can reach centimeter level, and compared with the wavelength of the visible light-near infrared band, the scale parameter range spans 10~10 5 Therefore, the Mie scattering optical parameters of rainfall are the basis for the above research.

[0003] The Mie scattering optical parameters generally include the extinction coefficient, scattering coefficient, asymmetry factor and absorption coefficient. The existing Mie scattering calculation method is the exact solution of the electromagnetic field equation of homogeneous spherical particles under monochromatic light irradiation, which is suitable for spherical particles of all sizes and different refractive indices. Therefore, this method is a general tool for calculating the Mie scattering optical parameters of rainfall. However, due to the reliance on Bessel functions, continued fraction recursion, etc., the traditional Mie scattering calculation method has the problems of complex programming implementation technology, slow calculation speed, and numerical instability, etc., which makes it difficult to meet the fast and efficient calculation requirements of the Mie scattering optical parameters of rainfall in the compensation of visible light-near infrared band optical communication. SUMMARY

[0004] The purpose of the present application is to solve the technical problem that the traditional Mie scattering calculation method, due to the reliance on Bessel functions, continued fraction recursion, etc., has the problems of complex programming implementation technology, slow calculation speed, and numerical instability, etc., which makes it difficult to meet the fast and efficient calculation requirements of the Mie scattering optical parameters of rainfall in the compensation of visible light-near infrared band optical communication, and to provide a fast calculation compensation method for the influence of rainfall on visible light-near infrared band optical communication.

[0005] In order to achieve the above purpose, the technical solution provided by the present application is as follows:

[0006] A fast calculation compensation method for the influence of rainfall on visible light-near infrared band optical communication, characterized in that it comprises the following steps:

[0007] Step 1: Based on the Mie scattering optical parameter algorithm, the extinction coefficient, scattering coefficient and asymmetry factor of different intensity and different type of rainfall under different incident light wavelengths are calculated respectively to obtain the basic data set of Mie scattering optical parameters of visible light-near infrared band rainfall;

[0008] Step 2, according to the visible-near infrared band rainfall Mie scattering optical parameter basic data set, respectively build the extinction coefficient fast calculation model, scattering coefficient fast calculation model and asymmetric factor fast calculation model;

[0009] The expression formula of the extinction coefficient fast calculation model is:

[0010] Q ext =(a lambda+b)R c

[0011] In the formula, Q ext is the extinction coefficient, R is the rainfall intensity, and lambda is the visible-near infrared band incident light wavelength;

[0012] The expression formula of the scattering coefficient fast calculation model is:

[0013] Q sca =f(lambda)R g *10 -3

[0014] In the formula, Q sca is the scattering coefficient,

[0015] The expression formula of the asymmetric factor fast calculation model is:

[0016] <g>= l(λ)R m

[0017] wherein <g>an asymmetry factor,

[0018] wherein a, b, c, f1, f2, f3, g, l1, l2, l3, m are all constants related to the rainfall type, and are obtained by least square fitting;

[0019] Step 3, input the corresponding rainfall intensity, rainfall type and incident light wavelength of the visible-near infrared band in the optical communication link to be compensated into the extinction coefficient fast calculation model, the scattering coefficient fast calculation model and the asymmetry factor fast calculation model respectively, and calculate the extinction coefficient, scattering coefficient and asymmetry factor of the rainfall; and then calculate the absorption coefficient of the rainfall according to the extinction coefficient and the scattering coefficient;

[0020] Step 4, input the extinction coefficient, scattering coefficient, asymmetry factor and absorption coefficient obtained in step 3 into the optical communication link to be compensated, and perform signal compensation.

[0021] Further, in step 2, a, b, c, f1, f3, g, l1, l3, m are obtained by direct least square fitting;

[0022] f2 and l2 are obtained by indirect least square fitting, and the specific expression is:

[0023] f2=p1*sin(p2*λ*+p3)+p4*sin(p5*λ+p6)+p7*sin(p8*λ+

[0024] p9)+p10*sin(p11*λ+p12);

[0025] l2=n1*sin(n2*λ*+n3)+n4*sin(n5*λ+n6)+n7*sin(n8*λ+

[0026] n9)+n10*sin(n11*λ+n12);

[0027] wherein p1-p12 and n1-n12 are obtained by least square fitting.

[0028] Further, in step 3, the absorption coefficient Q of the rainfall is calculated according to the following formula: abs :

[0029] Q abs =Q ext -Q sca .

[0030] Further, in step 1, the rainfall type includes convective rainfall, stratiform rainfall and mixed rainfall.

[0031] The beneficial effects of the present application compared with the prior art are as follows:

[0032] The present application provides a quick calculation compensation method for the influence of rainfall on visible light-near infrared band optical communication, which avoids the problems of complex programming implementation technology, slow calculation speed and numerical instability of the traditional Mie scattering calculation method. Through the extinction coefficient quick calculation model, the scattering coefficient quick calculation model and the asymmetry factor quick calculation model built, the Mie scattering optical parameters of rainfall in visible light-near infrared band under three types of rainfall and any rainfall intensity can be quickly and stably calculated. On the basis of ensuring the calculation accuracy, the quick real-time output of the calculation result is realized, which can be widely applied in optical communication compensation technology in the fields of laser communication, automatic driving and the like. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The flowchart of the quick calculation compensation method for the influence of rainfall on visible light-near infrared band optical communication of the present application is shown in the figure.

[0034] Figure 2 The determination coefficient diagram of the Mie scattering optical parameters of rainfall under three types of rainfall by using the present application is shown in the figure.

[0035] Figure 3 (a)-(f) are respectively the extinction coefficient comparison diagrams of 27 rainfall categories at 0.25 μm, 0.5 μm, 0.75 μm, 1.5 μm, 3.2 μm and 4.0 μm incident light wavelengths calculated by using the present application and the traditional Mie scattering calculation method.

[0036] Figure 4 (a)-(f) are respectively the scattering coefficient comparison diagrams of 27 rainfall categories at 0.25 μm, 0.5 μm, 0.75 μm, 1.5 μm, 3.2 μm and 4.0 μm incident light wavelengths calculated by using the present application and the traditional Mie scattering calculation method.

[0037] Figure 5 (a)-(f) are respectively the absorption coefficient comparison diagrams of 27 rainfall categories at 0.25 μm, 0.5 μm, 0.75 μm, 1.5 μm, 3.2 μm and 4.0 μm incident light wavelengths calculated by using the present application and the traditional Mie scattering calculation method.

[0038] Figure 6 (a)-(f) are respectively the asymmetry factor comparison diagrams of 27 rainfall categories at 0.25 μm, 0.5 μm, 0.75 μm, 1.5 μm, 3.2 μm and 4.0 μm incident light wavelengths calculated by using the present application and the traditional Mie scattering calculation method. DETAILED DESCRIPTION

[0039] In order to make the advantages and characteristics of the present application more clear, the present application is further described in detail below in combination with the drawings and specific embodiments.

[0040] A quick calculation compensation method for the influence of rainfall on visible-near infrared band optical communication, as shown in Figure 1 The specific steps include:

[0041] Step 1, constructing a visible-near infrared band rainfall Mie scattering optical parameter basic data set.

[0042] Based on the existing Mie scattering optical parameter algorithm, the extinction coefficient, scattering coefficient and asymmetry factor of different intensity and different type of rainfall under different incident light wavelengths are calculated respectively to obtain the visible-near infrared band rainfall Mie scattering optical parameter basic data set. In the present application, since the absorption coefficient is obtained according to the extinction coefficient and the scattering coefficient, in order to reduce the data amount, the visible-near infrared band rainfall Mie scattering optical parameter basic data set can not calculate a large number of absorption coefficients, but also can calculate the absorption coefficient for subsequent verification. The rainfall intensity refers to the depth of liquid water accumulated on the horizontal plane within 1 hour from the sky to the ground without evaporation, penetration, loss, and the unit is mm / h; the rainfall type includes convective rainfall, stratiform cloud rainfall and mixed rainfall; the wavelength range of the incident light in the visible-near infrared band is 0.2 μm-4.0 μm. When constructing the visible-near infrared band rainfall Mie scattering optical parameter basic data set, the values of different intensity and different type of rainfall under different incident light wavelengths are calculated respectively.

[0043] Step 2, according to the visible-near infrared band rainfall Mie scattering optical parameter basic data set, a quick calculation model is built. The quick calculation model includes an extinction coefficient quick calculation model, a scattering coefficient quick calculation model and an asymmetry factor quick calculation model.

[0044] Step 2.1, the specific expression formula of the extinction coefficient quick calculation model in the present application is as follows:

[0045] Q ext =(aλ+b)R c

[0046] In the above formula, Q ext is the extinction coefficient, R is the rainfall intensity (unit: mm / h), λ is the incident light wavelength in the visible-near infrared band (unit: μm), a, b, c are constants related to the rainfall type, which are obtained by direct fitting by the least square method, and the specific values are shown in Table 1:

[0047] Table 1 values of a, b, c corresponding to different rainfall types

[0048] Rainfall type a b c Convective rainfall 0.095 2.578 0.318 Stratiform cloud rainfall 0.0057 1.626 0.717 Mixed rainfall 0.02 1.696 0.517

[0049] Step 2.2, the specific expression formula of the scattering coefficient fast calculation model in the application is as follows:

[0050] Q sca = f (λ) R g *10 -3

[0051] In the above formula, Q sca is the scattering coefficient, If the incident light wavelength in the visible light-near infrared band is in the 0.25 μm-1.0 μm band, f (λ) takes the value f1, if the incident light wavelength in the visible light-near infrared band is in the 1.0 μm-2.0 μm band, f (λ) takes the value f2, and if the incident light wavelength in the visible light-near infrared band is in the 2.0 μm-4.0 μm band, f (λ) takes the value f3.

[0052] Where f1, f3, and g are constants related to the type of rainfall, which are obtained by direct fitting by the least square method, and the specific values are shown in Table 2:

[0053] Table 2 Values of f1, f3, and g corresponding to different types of rainfall

[0054] Rainfall type f1 f3 g Convective rainfall 2.644 1.561 0.308 Stratiform cloud rainfall 1.625 0.894 0.714 Mixed rainfall 1.702 0.948 0.514

[0055] f2 is calculated according to the following formula:

[0056] f2 = p1*sin(p2*λ*+p3)+p4*sin(p5*λ+p6)+p7*sin(p8*λ+p9)+p10*sin(p11*λ+p12)

[0057] In the above formula, p1-p12 are constants related to the type of rainfall, which are obtained by fitting by the least square method, and the specific values are shown in Table 3:

[0058] Table 3 Values of p1-p12 corresponding to different types of rainfall

[0059]

[0060]

[0061] Step 2.3, the specific expression formula of the asymmetric factor fast calculation model built in the application is as follows:

[0062] <g>= l(λ)R m

[0063] In the above formulae, <g>for the asymmetry factor, If the incident light wavelength in the visible-near infrared band is in the 0.25-1.0 μm band, l(λ) takes the value of l1, if the incident light wavelength in the visible-near infrared band is in the 1.0-2.0 μm band, l(λ) takes the value of l2, and if the incident light wavelength in the visible-near infrared band is in the 2.0-4.0 μm band, l(λ) takes the value of l3.

[0064] wherein l1, l3, and m are constants related to the rainfall type, which are obtained by direct fitting by the least square method, and the specific values are shown in Table 4:

[0065] Table 4 Values of l1, l3, and m corresponding to different rainfall types

[0066] Rainfall type ​ [l3] m Convective rainfall 2.296E-04 1.490E-04 0.3146 Stratiform cloud rainfall 1.432E-04 8.653E-05 0.7146 Mixed rainfall 1.499E-04 9.198E-05 0.5145

[0067] l2 is calculated according to the following formula:

[0068] l2 = n1*sin(n2*λ*+n3)+n4*sin(n5*λ+n6)+n7*sin(n8*λ+n9)+n10*sin(n11*λ+n12)

[0069] In the above formula, n1-n12 are constants related to the rainfall type, which are obtained by fitting by the least square method, and the specific values are shown in Table 5:

[0070] Table 5 Values of n1-n12 corresponding to different rainfall types

[0071]

[0072]

[0073] Step 3, calculating the rainfall Mie scattering optical parameters in the optical communication link to be compensated.

[0074] According to the values of a, b, and c corresponding to the rainfall type of the optical communication link to be compensated in Table 1, the selected values of a, b, and c are substituted into the extinction coefficient fast calculation model together with the rainfall intensity and the incident light wavelength in the visible-near infrared band corresponding to the optical communication link to be compensated, to calculate the extinction coefficient Q of the rainfall ext .

[0075] According to the values of f1, f3, and g corresponding to the rainfall type of the optical communication link to be compensated in Table 2, and the values of p1-p12 in Table 3, f2 is calculated according to the values of p1-p12, and then the values of f1, f2, f3, and g are substituted into the scattering coefficient fast calculation model together with the rainfall intensity and the incident light wavelength in the visible-near infrared band corresponding to the optical communication link to be compensated, to calculate the scattering coefficient Q of the rainfall sca .

[0076] According to the values of l1, l3, m selected in Table 4 and the values of n1-n12 selected in Table 3, the value of l2 is calculated, and the values of l1, l2, l3, m and the corresponding rainfall intensity and the incident light wavelength of the visible-near infrared band of the optical communication link to be compensated are substituted into the fast calculation model of the asymmetry factor to obtain the asymmetry factor of the rainfall <g>.

[0077] Finally, the absorption coefficient Q of the rainfall is calculated according to the following formula abs :

[0078] Q abs = Q ext -Q sca .

[0079] Step 4, the extinction coefficient, scattering coefficient, asymmetry factor and absorption coefficient obtained in step 3 are input into a to-be-compensated optical communication link in the field of laser communication or automatic driving, etc., to perform signal compensation.

[0080] In order to illustrate the effect of the present application, the following selects 9 levels of rainfall intensity, i.e. 2.0 mm / h, 5.0 mm / h, 7.5 mm / h, 10.0 mm / h, 12.5 mm / h, 15.0 mm / h, 17.5 mm / h, 20.0 mm / h and 25.0 mm / h, 3 types of rainfall, i.e. convective rainfall, stratiform cloud rainfall and mixed rainfall, a total of 27 rainfall categories, and the extinction coefficient, scattering coefficient, asymmetry factor and absorption coefficient of the above 27 rainfall categories at different incident light wavelengths are calculated respectively. Among them, the incident light wavelength of the visible-near infrared band is between 0.2 μm and 4.0 μm, and the value is taken once every 0.1 μm interval. The calculation results are compared with the results obtained by the traditional Mie scattering calculation method, as shown in Figure 2 , the determination coefficients R 2 of the Mie scattering optical parameter calculation results of the three types of rainfall are all above 0.96, which indicates that the algorithm results based on the fast calculation model of the present application and the algorithm results of the traditional Mie scattering calculation method are in good agreement, and the fast and stable calculation of the Mie scattering optical parameters of the rainfall of the three types of rainfall and any rainfall intensity in the visible-near infrared band can be realized.

[0081] In addition, in order to further illustrate the effect of the present application, the extinction coefficient, scattering coefficient, asymmetry factor and absorption coefficient of the above 27 rainfall categories at the incident light wavelengths of 0.25 μm, 0.5 μm, 0.75 μm, 1.5 μm, 3.2 μm and 4.0 μm are calculated based on the fast calculation model of the present application, and the results are compared with the results obtained by the traditional Mie scattering calculation method. The comparison results of the extinction coefficient are as shown in Figure 3 , the comparison results of the scattering coefficient are as shown in Figure 4 , the comparison results of the absorption coefficient are as shown in Figure 5 , and the comparison results of the asymmetry factor are as shown in Figure 6 It can be seen that the algorithm result based on the fast calculation model of the application is basically consistent with the algorithm result of the traditional Mie scattering calculation method, although Figure 5 The absorption coefficients of different rainfall categories at 0.25 μm, 0.5 μm and 0.75 μm of incident light wavelength deviate from the traditional algorithm result, but since the absorption coefficients of the above three wavelengths are 10 -5 orders of magnitude, which is one order of magnitude smaller than the 10 -4 orders of magnitude of the absorption coefficients of other wavelengths, which belongs to a weak absorption band, and the average absolute percentage error of the overall calculation result of the application is less than 3%, so the deviation can be ignored for the application of optical communication.

[0082] In summary, the application based on the fast calculation model calculation method can quickly and effectively calculate the rainfall Mie scattering optical parameters of the to-be-compensated optical communication link while ensuring the calculation accuracy, and effectively avoids the problems of the traditional Mie scattering calculation method, such as complex programming implementation technology, slow calculation speed and numerical instability.

[0083] The above description is only used to illustrate the technical solutions of the application, and not to limit them. For ordinary skilled in the art, the specific technical solutions recorded in the above embodiments can be modified, or some technical features can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions protected by the application.< / g> < / g> < / g> < / g> < / g>

Claims

1. A method for fast calculation and compensation of the influence of rainfall on optical communication in the visible-near infrared band, characterized in that, The method comprises the following steps: Step 1: Based on the Mie scattering optical parameter algorithm, the extinction coefficient, scattering coefficient and asymmetry factor of different intensity and different type of rainfall at different incident light wavelengths are calculated respectively to obtain a visible-near infrared band rainfall Mie scattering optical parameter basic data set; Step 2: According to the visible-near infrared band rainfall Mie scattering optical parameter basic data set, an extinction coefficient fast calculation model, a scattering coefficient fast calculation model and an asymmetry factor fast calculation model are respectively built; The expression formula of the extinction coefficient fast calculation model is: Q ext = (aA + b)R c In the formula, Q ext is the extinction coefficient, R is the rainfall intensity, and λ is the wavelength of incident light in the visible-near infrared band. The expression formula of the scattering coefficient fast calculation model is: Q sca = f(λ)R g *10 -3 In the formula, Q sca is a scattering coefficient, The expression formula of the asymmetry factor fast calculation model is: <g>= l(λ)R m < / g> In the formulae, <g>for the asymmetry factor, < / g> Wherein, a, b, c, f1, f2, f3, g, l1, l2, l3, m are all constants related to the type of rainfall, which are obtained by least square fitting; Step 3: The corresponding rainfall intensity, rainfall type and visible-near infrared band incident light wavelength in the to-be-compensated optical communication link are input into the extinction coefficient fast calculation model, the scattering coefficient fast calculation model and the asymmetry factor fast calculation model respectively, and the extinction coefficient, scattering coefficient and asymmetry factor of the rainfall are calculated and obtained; and then the absorption coefficient of the rainfall is calculated according to the extinction coefficient and the scattering coefficient; Step 4: The extinction coefficient, scattering coefficient, asymmetry factor and absorption coefficient obtained in step 3 are input into the to-be-compensated optical communication link for signal compensation.

2. The fast calculation compensation method for the influence of rainfall on visible-near infrared band optical communication according to claim 1, characterized in that: In step 2, a, b, c, f1, f3, g, l1, l3, m are directly fitted by least square method; f2, l2 are indirectly fitted by least square method, and the specific expression is: f2=p1*sin(p2*λ*+p3)+p4*sin(p5*λ+p6)+p7*sin(p8*λ+p9)+p10*sin(p11*λ+p12); l2=n1*sin(n2*λ*+n3)+n4*sin(n5*λ+n6)+n7*sin(n8*λ+n9)+n10*sin(n11*λ+n12); Wherein, p1~p12, n1~n12 are fitted by least square method.

3. The fast calculation compensation method for the influence of visible-near infrared band rainfall on optical communication according to claim 1 or 2, characterized in that:

4. The fast calculation compensation method for the influence of rainfall on visible-near infrared band optical communication according to claim 1, characterized in that: In step 3, the absorption coefficient Q of the rainfall is calculated according to the following formula abs : Q abs = Q ext - Q sca . In step 1, the types of rainfall include convective rainfall, stratiform cloud rainfall and mixed rainfall. ​

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