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

Abstract

The invention provides a rapid calculation and compensation method for influences of rainfall on visible light-near infrared band optical communication, and aims to solve the problems that a traditional Mie scattering calculation method depends on Bessel function, continued fraction recursion and other methods, the programming implementation technology is complex, the calculation speed is low, and numerical instability is prone to occurring. And rapid and efficient requirements of related research are difficult to meet. According to the rapid calculation and compensation method for the influence of rainfall on visible light-near infrared band optical communication, an extinction coefficient rapid calculation model, a scattering coefficient rapid calculation model and an asymmetry factor rapid calculation model are established; according to the method, the Mie scattering optical parameters of rainfall of three rainfall types and any rainfall intensity in the visible light-near infrared band can be rapidly and stably calculated, the calculation result is rapidly output in real time on the basis of ensuring the calculation accuracy, and the method 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 invention 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 Art

[0002] Rainfall has a serious attenuation effect on the light propagation in the visible-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 key research contents in the fields of laser communication and autonomous driving. And because the particle size range of rainfall particles is wide, the maximum can reach the centimeter level. Compared with the wavelength of the visible-near infrared band, its scale parameter range spans 10~10 5 Therefore, the optical parameters of rainfall Mie scattering are the basis of the above research.

[0003] Mie scattering optical parameters usually include extinction coefficient, scattering coefficient, asymmetry factor and absorption coefficient. The existing Mie scattering calculation method is an accurate solution to the electromagnetic field equation of homogeneous spherical particles under monochromatic light irradiation. It is applicable to spherical particles of all sizes and different refractive indices. Therefore, this method is a general tool for calculating the optical parameters of rainfall Mie scattering. However, the traditional Mie scattering calculation method relies on Bessel functions, continued fraction recursion and other methods, which have problems such as complex programming implementation technology, slow calculation speed, and easy numerical instability. It is difficult to meet the requirements of fast and efficient calculation of rainfall Mie scattering optical parameters in optical communication compensation in the visible light-near infrared band. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problem that the traditional Mie scattering calculation method relies on Bessel functions, continued fraction recursion and other methods, and has the problems of complex programming implementation technology, slow calculation speed, and easy numerical instability. It is difficult to meet the technical problem of fast and efficient calculation of rainfall Mie scattering optical parameters when compensating for optical communications in the visible light-near infrared band. A method for fast calculation compensation of the impact of rainfall on optical communications in the visible light-near infrared band is provided.

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

[0006] A method for quickly calculating and compensating the effect of rainfall on visible-near infrared band optical communication is special in that it includes the following steps:

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

[0008] Step 2: Based on the basic data set of rainfall Mie scattering optical parameters in the visible-near infrared band, a fast calculation model for extinction coefficient, a fast calculation model for scattering coefficient, and a fast calculation model for asymmetry factor are respectively constructed;

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

[0010] Q ext =(aλ+b)R c

[0011] 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;

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

[0013] Q sca =f(λ)R g *10 -3

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

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

[0016] <g>=l(λ)R m

[0017] In the formula, <g>is the asymmetry factor,

[0018] Among them, a, b, c, f 1 、f 2 、f 3 ,g,l 1 , l 2 , l 3 , m are constants related to rainfall types and are obtained by least squares fitting;

[0019] Step 3, inputting the corresponding rainfall intensity, rainfall type and incident light wavelength in 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 calculating the extinction coefficient, scattering coefficient and asymmetry factor of the rainfall; and then calculating the absorption coefficient of the rainfall based on the extinction coefficient and the scattering coefficient;

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

[0021] Furthermore, in step 2, a, b, c, f 1 、f 3 ,g,l 1 , l 3 , m is obtained by direct fitting through the least squares method;

[0022] f 2 , l 2 Obtained indirectly through least squares fitting, the specific expression is:

[0023] f 2 =p1*sin(p2*λ*+p3)+p4*sin(p5*λ+p6)+p7*sin(p8*λ+

[0024] p9)+p10*sin(p11*λ+p12);

[0025] l 2 =n1*sin(n2*λ*+n3)+n4*sin(n5*λ+n6)+n7*sin(n8*λ+

[0026] n9)+n10*sin(n11*λ+n12);

[0027] Among them, p1~p12 and n1~n12 are all obtained by least squares fitting.

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

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

[0030] Furthermore, in step 1, the rainfall types include convective rainfall, stratiform cloud rainfall and mixed rainfall.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention provides a fast calculation compensation method for the impact of rainfall on optical communication in the visible light-near infrared band, which avoids the problems of complex programming implementation technology, slow calculation speed and easy numerical instability in traditional Mie scattering calculation methods. By constructing a fast calculation model of extinction coefficient, a fast calculation model of scattering coefficient and asymmetry factor, the Mie scattering optical parameters of three rainfall types and rainfall of any rainfall intensity in the visible light-near infrared band can be calculated quickly and stably. On the basis of ensuring the calculation accuracy, the fast real-time output of the calculation results is achieved. The method can be widely used in optical communication compensation technology in the fields of laser communication, autonomous driving, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A flowchart of a method for rapidly calculating and compensating for the effect of rainfall on optical communications in the visible-near infrared band according to the present invention;

[0034] Figure 2 A schematic diagram of the coefficient of determination of optical parameters of Mie scattering of rainfall under three types of rainfall using the present invention;

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

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

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

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

[0039] In order to make the advantages and features of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

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

[0041] Step 1: Construct a basic dataset of rainfall Mie scattering optical parameters in the visible-near infrared band.

[0042] Based on the existing Mie scattering optical parameter algorithm, the extinction coefficient, scattering coefficient and asymmetry factor of rainfall of different intensities and types at different wavelengths of incident light are calculated respectively, and the basic data set of Mie scattering optical parameters of rainfall in the visible-near infrared band is obtained. In the present invention, since the absorption coefficient is obtained based on the extinction coefficient and the scattering coefficient, in order to reduce the amount of data, the basic data set of Mie scattering optical parameters of rainfall in the visible-near infrared band may not calculate a large number of absorption coefficients, but the absorption coefficient can also be calculated for subsequent verification. The rainfall intensity refers to the depth of liquid water that falls from the sky to the ground within 1 hour, without evaporation, infiltration, or loss, and accumulates on the horizontal surface, in units of mm / h; rainfall types include convective rainfall, stratiform cloud rainfall and mixed rainfall; the wavelength range of incident light in the visible-near infrared band is 0.2μm to 4.0μm. When constructing the basic data set of Mie scattering optical parameters of rainfall in the visible-near infrared band, the values ​​of rainfall of different intensities and types at different wavelengths of incident light are calculated respectively.

[0043] Step 2: Build a fast calculation model based on the basic data set of rainfall Mie scattering optical parameters in the visible-near infrared band. The fast calculation model includes the fast calculation model of extinction coefficient, the fast calculation model of scattering coefficient and the fast calculation model of asymmetry factor.

[0044] Step 2.1, the specific expression formula of the rapid calculation model of the extinction coefficient in the present invention 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 directly fitted by the least squares method. The specific values ​​are shown in Table 1:

[0047] Table 1 Values ​​of a, b, and c corresponding to different rainfall types

[0048] Rainfall Type a b c Convective rainfall 0.095 2.578 0.318 Stratiform rain 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 rapid calculation model in the present invention 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 wavelength of incident light in the visible-near infrared band is in the 0.25μm to 1.0μm band, then f(λ) is f 1 , if the wavelength of incident light in the visible-near infrared band is in the 1.0μm to 2.0μm band, then f(λ) is f 2 , if the wavelength of incident light in the visible-near infrared band is in the 2.0μm to 4.0μm band, then f(λ) is f 3 .

[0052] Among them, f 1 、f 3 , g are constants related to rainfall types, which are directly obtained by least squares fitting. The specific values ​​are shown in Table 2:

[0053] Table 2. f corresponding to different rainfall types 1 、f 3 , the value of g

[0054] Rainfall Type <![CDATA[f 1 ]]> <![CDATA[f 3 ]]> g Convective rainfall 2.644 1.561 0.308 Stratiform rain 1.625 0.894 0.714 Mixed rainfall 1.702 0.948 0.514

[0055] f 2 Calculated according to the following formula:

[0056] f 2 =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 rainfall types, which are obtained by least squares fitting. The specific values ​​are shown in Table 3:

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

[0059]

[0060]

[0061] Step 2.3, the specific expression formula for building a fast calculation model of asymmetry factor in the present invention is as follows:

[0062] <g>=l(λ)R m

[0063] In the above formula, <g>is the asymmetry factor, If the wavelength of incident light in the visible-near infrared band is in the 0.25 μm to 1.0 μm band, then l(λ) is l 1 , if the wavelength of incident light in the visible-near infrared band is in the 1.0μm to 2.0μm band, then l(λ) is l 2 , if the wavelength of incident light in the visible-near infrared band is in the 2.0μm to 4.0μm band, then l(λ) is l 3 .

[0064] Among them, l 1 , l 3 , m are constants related to rainfall types, which are directly obtained by least squares fitting. The specific values ​​are shown in Table 4:

[0065] Table 4 l corresponding to different rainfall types 1 , l 3 , the value of m

[0066] Rainfall Type <![CDATA[l 1 ]]> <![CDATA[l 3 ]]> m Convective rainfall 2.296E-04 1.490E-04 0.3146 Stratiform rain 1.432E-04 8.653E-05 0.7146 Mixed rainfall 1.499E-04 9.198E-05 0.5145

[0067] l 2 Calculated according to the following formula:

[0068] l 2 =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 rainfall types, which are obtained by least squares fitting. 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: Calculate the rainfall Mie scattering optical parameters in the optical communication link to be compensated.

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

[0075] Select f in Table 2 according to the rainfall type corresponding to the optical communication link to be compensated 1 、f 3 , g, select the values ​​of p1 to p12 in Table 3, and calculate f according to the values ​​of p1 to p12 2 , and then f 1 、f 2 、f 3 The values ​​of g, the rainfall intensity corresponding to the optical communication link to be compensated, and the wavelength of incident light in the visible-near infrared band are substituted into the scattering coefficient fast calculation model to calculate the rainfall scattering coefficient Q sca .

[0076] Select l in Table 4 according to the rainfall type corresponding to the optical communication link to be compensated 1 , l 3 , m, select n1 to n12 in Table 3, and calculate l according to the values ​​of n1 to n12 2 , and then l 1 , l 2 , l 3 The values ​​of m, the rainfall intensity corresponding to the optical communication link to be compensated, and the wavelength of incident light in the visible-near infrared band are substituted into the asymmetry factor fast calculation model to calculate the rainfall asymmetry factor. <g>.

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

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

[0079] Step 4, sending the extinction coefficient, scattering coefficient, asymmetry factor and absorption coefficient obtained in step 3 to the optical communication link to be compensated in the fields of laser communication or autonomous driving for signal compensation.

[0080] In order to illustrate the effect of the present invention, 9 levels of rainfall intensity are selected below, including 2.0mm / h, 5.0mm / h, 7.5mm / h, 10.0mm / h, 12.5mm / h, 15.0mm / h, 17.5mm / h, 20.0mm / h, and 25.0mm / h. There are 3 types of rainfall, namely convective rainfall, stratiform cloud rainfall, and mixed rainfall, for a total of 27 rainfall categories. The extinction coefficient, scattering coefficient, asymmetry factor, and absorption coefficient of the above 27 rainfall categories at different incident light wavelengths are calculated. Among them, the wavelength of incident light in the visible-near infrared band is between 0.2μm and 4.0μm, and the value is taken every 0.1μm. The calculation results are compared with those obtained by the traditional Mie scattering calculation method, as shown in FIG. Figure 2 As shown in the figure, the determination coefficient R of the calculated results of the optical parameters of the Mie scattering of rainfall for the three types of rainfall 2 All of them are above 0.96, indicating that the algorithm results based on the fast calculation model of the present invention are in good agreement with the algorithm results of the traditional Mie scattering calculation method, and can realize fast and stable calculation of Mie scattering optical parameters in the visible light-near infrared band for three rainfall types and rainfall of any rainfall intensity.

[0081] In addition, to further illustrate the effect of the present invention, the extinction coefficient, scattering coefficient, asymmetry factor and absorption coefficient of the above 27 rainfall categories at 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 invention, and compared with the results obtained by the traditional Mie scattering calculation method. The comparison results of the extinction coefficient are shown in Figure 2. Figure 3 The comparison results of scattering coefficients are shown in Figure 4 The comparison results of absorption coefficient are shown in Figure 5 As shown in Figure 2, the comparison results of the asymmetry factor are as follows: Figure 6 As shown, con. represents the traditional Mie scattering calculation result under convective rainfall, str. represents the traditional Mie scattering calculation result under layered cloud rainfall, mix. represents the traditional Mie scattering calculation result under mixed rainfall, con.-fit represents the calculation result fitting curve of the present invention under convective rainfall, str. represents the calculation result fitting curve of the present invention under layered cloud rainfall, mix. represents the calculation result fitting curve of the present invention under mixed rainfall. It can be seen that the algorithm result based on the fast calculation model of the present invention is basically consistent with the algorithm result of the traditional Mie scattering calculation method. Figure 5 The absorption coefficients of different rainfall categories at incident light wavelengths of 0.25 μm, 0.5 μm, and 0.75 μm deviate from the results of the traditional algorithm. However, since the absorption coefficients of the above three wavelengths are 10 -5 The absorption coefficient of other wavelengths is 10 -4 The magnitude is one order of magnitude smaller than that of the wavelength band, which belongs to the band with weak absorption effect, and the average absolute percentage error of the overall calculation result of the present invention is less than 3%, so the deviation can be ignored in terms of the impact on optical communication applications.

[0082] In summary, the present invention is based on a fast calculation model calculation method, which can quickly and effectively calculate the rainfall Mie scattering optical parameters of the optical communication link to be compensated while ensuring the calculation accuracy, effectively avoiding the problems of complex programming implementation technology, slow calculation speed and easy numerical instability in traditional Mie scattering calculation methods.

[0083] The above description is only used to illustrate the technical solution of the present invention rather than to limit it. For ordinary professional and technical personnel in the field, the specific technical solution recorded in the above embodiment can be modified, or some of the technical features therein can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution protected by the present invention.< / g> < / g> < / g> < / g> < / g>

Claims

1. A method for rapid calculation and compensation of the effect of rainfall on visible light-near infrared band optical communication, characterized in that: The following steps are involved: Step 1: Based on the Mie scattering optical parameter algorithm, the extinction coefficient, scattering coefficient and asymmetry factor of rainfall of different intensities and types at different incident light wavelengths are calculated to obtain a basic data set of Mie scattering optical parameters of rainfall in the visible-near infrared band; Step 2: According to the basic data set of rainfall Mie scattering optical parameters in the visible-near infrared band, a fast calculation model for extinction coefficient, a fast calculation model for scattering coefficient, and a fast calculation model for asymmetry factor are respectively constructed; The expression formula of the extinction coefficient rapid calculation model is: Q ext =(aλ+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 the scattering coefficient, The expression formula of the asymmetry factor fast calculation model is: <g>=l(λ)R m < / g> In the formula, <g>is the asymmetry factor, < / g> Among them, a, b, c, f1, f2, f3, g, l1, l2, l3, and m are all constants related to rainfall types and are obtained by least squares fitting; Step 3, inputting the corresponding rainfall intensity, rainfall type and incident light wavelength in 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 calculating the extinction coefficient, scattering coefficient and asymmetry factor of the rainfall; and then calculating the absorption coefficient of the rainfall based on the extinction coefficient and the scattering coefficient; Step 4: Send the extinction coefficient, scattering coefficient, asymmetry factor and absorption coefficient obtained in step 3 to the optical communication link to be compensated for signal compensation.

2. The method for rapid calculation and compensation of the effect of rainfall on visible light-near infrared band optical communication according to claim 1 is characterized by: In step 2, a, b, c, f1, f3, g, l1, l3, and m are directly fitted by the least squares method; f2 and l2 are obtained indirectly through least squares fitting, and the specific expressions are: 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); Among them, p1~p12 and n1~n12 are all obtained by least squares fitting.

3. The method for rapid calculation and compensation of the effect of rainfall in the visible light-near infrared band on optical communication according to claim 1 or 2, characterized in that: In step 3, the absorption coefficient Q of rainfall is calculated according to the following formula: abs : Q abs =Q ext -Q sca 。 4. The method for rapid calculation and compensation of the effect of rainfall on visible light-near infrared band optical communication according to claim 1, characterized in that: In step 1, the rainfall types include convective rainfall, stratiform cloud rainfall and mixed rainfall.

Images