阅读说明：本技术 一种适用于短距离通信系统的椭圆度参量最优化选择方法 (Ovality parameter optimization selection method suitable for short-distance communication system ) 是由 王岩坤 白璐 郭雅� 高鹏慧 吕强 于 2020-11-26 设计创作，主要内容包括：本发明属于光通信技术领域,公开了一种适用于短距离通信系统的椭圆度参量最优化选择方法,推导得到椭圆高斯光束经过自由空间传输后在任意距离z平面处的光场分布；将任意距离z平面处的椭圆高斯光场按螺旋谐波展开,得到傅里叶系数模量的平方；根据傅里叶系数模量的平方,计算得到每一个OAM模态的能量含量；将每一个OAM模态的能量含量进行归一化,得到每一个OAM模态经过自由空间传输后的接收概率；运用软件编程实现每一个OAM模态接收概率的计算；将计算出的每一个OAM模态接收概率以Excel文件形式导出,构建与椭圆度参数的关系,达到对椭圆度参数选择的最优化。本发明给出不同距离下椭圆度参数的最优化选择。(The invention belongs to the technical field of optical communication, and discloses an ovality parameter optimization selection method suitable for a short-distance communication system, which is used for deducing and obtaining the optical field distribution of an oval Gaussian beam at an arbitrary distance z plane after the oval Gaussian beam is transmitted in a free space; expanding an elliptic Gaussian light field at any distance z plane according to spiral harmonic waves to obtain the square of the Fourier coefficient modulus; calculating the energy content of each OAM mode according to the square of the Fourier coefficient modulus; normalizing the energy content of each OAM mode to obtain the receiving probability of each OAM mode after free space transmission; calculating the receiving probability of each OAM mode by using software programming; and exporting the calculated receiving probability of each OAM mode in an Excel file form, and constructing a relation with the ellipticity parameter to achieve the optimization of ellipticity parameter selection. The invention provides the optimal selection of the ellipticity parameters at different distances.)

1. An ovality parameter optimization selection method, characterized in that the ovality parameter optimization selection method comprises:

based on the generalized Huygens-Fresnel principle, theoretically deducing to obtain the light field distribution of an elliptic Gaussian beam at a z plane at any distance after the elliptic Gaussian beam is transmitted in free space;

expanding an elliptic Gaussian light field at any distance z plane according to spiral harmonic waves to obtain the square of the Fourier coefficient modulus;

calculating the energy content of each OAM mode according to the square of the Fourier coefficient modulus;

normalizing the energy content of each OAM mode to obtain the receiving probability, namely the energy fraction, of each OAM mode after free space transmission;

calculating the receiving probability of each OAM mode by using software programming;

and exporting the calculated receiving probability of each OAM mode in an Excel file form, and constructing a relation with the ellipticity parameter to achieve the optimization of ellipticity parameter selection.

2. The ovality parameter optimization selection method according to claim 1, wherein the optical field distribution of the elliptical gaussian beam at the source plane z-0 is:

3. the ovality parameter optimization selection method according to claim 1, characterized in that, based on the generalized huygens-fresnel diffraction integral formula, the light field of the oval gaussian light beam at the z plane at any distance in free space transmission is obtained:

wherein:

H＝2p-n,

4. the ovality parameter optimization selection method according to claim 1, characterized in that the optical field of the elliptical gaussian beam transmitted in free space at any distance z plane is expanded in the form of a helix harmonic exp (im θ) to obtain the square of its fourier coefficient modulus as:

<|a_m(r,z)|²>＝SS^*exp[-2r²T]I_m-H(2r²T),

wherein:

5. an ovality parameter optimization selection method according to claim 1, characterized in that the energy content of each OAM mode is:

6. the ovality parameter optimization selection method according to claim 1, wherein the energy content of each OAM mode is normalized to obtain a reception probability of each OAM mode after free space transmission, that is, an energy fraction is:

7. a computer device, characterized in that the computer device comprises a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to carry out the steps of:

based on the generalized Huygens-Fresnel principle, theoretically deducing to obtain the light field distribution of an elliptic Gaussian beam at a z plane at any distance after the elliptic Gaussian beam is transmitted in free space;

expanding an elliptic Gaussian light field at any distance z plane according to spiral harmonic waves to obtain the square of the Fourier coefficient modulus;

calculating the energy content of each OAM mode according to the square of the Fourier coefficient modulus;

normalizing the energy content of each OAM mode to obtain the receiving probability, namely the energy fraction, of each OAM mode after free space transmission;

calculating the receiving probability of each OAM mode by using software programming;

and exporting the calculated receiving probability of each OAM mode in an Excel file form, and constructing a relation with the ellipticity parameter to achieve the optimization of ellipticity parameter selection.

8. A computer-readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the steps of:

based on the generalized Huygens-Fresnel principle, theoretically deducing to obtain the light field distribution of an elliptic Gaussian beam at a z plane at any distance after the elliptic Gaussian beam is transmitted in free space;

expanding an elliptic Gaussian light field at any distance z plane according to spiral harmonic waves to obtain the square of the Fourier coefficient modulus;

calculating the energy content of each OAM mode according to the square of the Fourier coefficient modulus;

normalizing the energy content of each OAM mode to obtain the receiving probability, namely the energy fraction, of each OAM mode after free space transmission;

calculating the receiving probability of each OAM mode by using software programming;

and exporting the calculated receiving probability of each OAM mode in an Excel file form, and constructing a relation with the ellipticity parameter to achieve the optimization of ellipticity parameter selection.

9. An information data processing terminal of a short-distance optical communication system, wherein the information data processing terminal of the short-distance optical communication system is used for implementing the ovality parameter optimization selection method according to any one of claims 1 to 6, and giving optimization selection of the ovality parameter.

10. An ovality parameter optimization selection system for implementing the ovality parameter optimization selection method according to any one of claims 1 to 6, the ovality parameter optimization selection system comprising:

the light field distribution acquisition module is used for theoretically deducing and obtaining the light field distribution of the elliptic Gaussian beam at an arbitrary distance z plane after the elliptic Gaussian beam is transmitted in free space based on the generalized Huygens-Fresnel principle;

the Fourier coefficient modulus square acquisition module is used for expanding the elliptic Gaussian light field at any distance z plane according to the spiral harmonic to obtain the square of the Fourier coefficient modulus;

the energy content calculation module is used for calculating the energy content of each OAM mode according to the square of the Fourier coefficient modulus;

the receiving probability calculation module is used for normalizing the energy content of each OAM mode to obtain the receiving probability of each OAM mode after free space transmission;

each receiving probability calculation module is used for realizing the calculation of the receiving probability of each OAM mode by using software programming;

and the ovality parameter selection optimization module is used for exporting the calculated receiving probability of each OAM mode in an Excel file form, and establishing a relation with the ovality parameter so as to achieve optimization of ovality parameter selection.

Technical Field

The invention belongs to the technical field of optical communication, and particularly relates to an ovality parameter optimization selection method suitable for a short-distance communication system.

Background

At present: in the design of optical communication systems based on Orbital Angular Momentum (OAM) multiplexing, a mode division multiplexing technique has been introduced, which means that OAM optical beams can greatly expand the capacity of the optical communication system. OAM has been widely used in various fields as a completely new degree of freedom of optical waves. However, in the design of free space optical communication systems, the effect of atmospheric turbulence is not negligible. Due to the random refractive index variation of the atmospheric turbulence, the OAM beam may be distorted and cross-talk during transmission, which may significantly reduce the transmission performance. The transmission performance and channel capacity of the Laguerre Gaussian beam, the Bessel Gaussian beam and the like serving as the alternative beams for free space transmission cannot meet the requirements yet. The elliptical Gaussian beam is used as the limited superposition of different topological loads of the Laguerre Gaussian beam, and the number of channels and the capacity of the channels can be greatly improved. However, due to the selection of the ellipticity parameter, the problem arises that the required channel capacity is not large enough. Therefore, a method for optimally selecting the ellipticity parameter is urgently needed, so that the required channel capacity is maximized, and the anti-turbulence effect is stronger in the design of a short-distance communication system.

Through the above analysis, the problems and defects of the prior art are as follows: due to the selection of the ellipticity parameter, the problem arises that the required channel capacity is not large enough.

The difficulty in solving the above problems and defects is: the selection of the ellipticity parameter directly relates to the capacity of a required channel, and if the ellipticity parameter is not properly selected, the detection probability of OAM is reduced, and the transmission performance is reduced.

The significance of solving the problems and the defects is as follows: after the selection of the ellipticity parameter is optimized, the capacity of the required channel can be maximized, and the anti-turbulence effect is stronger in a short-distance communication system.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides an ovality parameter optimization selection method suitable for a short-distance communication system.

The invention is realized in such a way that an ovality parameter optimization selection method comprises the following steps:

based on the generalized Huygens-Fresnel principle, theoretically deducing to obtain the light field distribution of an elliptic Gaussian beam at a z plane at any distance after the elliptic Gaussian beam is transmitted in free space;

expanding an elliptic Gaussian light field at any distance z plane according to spiral harmonic waves to obtain the square of the Fourier coefficient modulus;

calculating the energy content of each OAM mode according to the square of the Fourier coefficient modulus;

normalizing the energy content of each OAM mode to obtain the receiving probability, namely the energy fraction, of each OAM mode after free space transmission;

calculating the receiving probability of each OAM mode by using software programming;

and exporting the calculated receiving probability of each OAM mode in an Excel file form, and constructing a relation with the ellipticity parameter to achieve the optimization of ellipticity parameter selection.

Further, the optical field distribution of the elliptical gaussian beam at the source plane z-0 is:

further, based on a generalized Huygens-Fresnel diffraction integral formula, a light field of an elliptic Gaussian beam at a z plane at any distance in free space transmission is obtained:

wherein:

further, the optical field of the elliptic Gaussian beam transmitted at any distance z plane in free space is expanded in the form of spiral harmonic exp (im theta), and the square of the Fourier coefficient modulus is obtained as follows:

〈|a_m(r,z)|²〉＝SS^*exp[-2r²T]I_m-H(2r²T),

wherein:

further, the energy content of each OAM mode is:

further, normalizing the energy content of each OAM mode to obtain the reception probability of each OAM mode after free space transmission, that is, the energy fraction is:

it is a further object of the invention to provide a computer device comprising a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to perform the steps of:

based on the generalized Huygens-Fresnel principle, theoretically deducing to obtain the light field distribution of an elliptic Gaussian beam at a z plane at any distance after the elliptic Gaussian beam is transmitted in free space;

expanding an elliptic Gaussian light field at any distance z plane according to spiral harmonic waves to obtain the square of the Fourier coefficient modulus;

calculating the energy content of each OAM mode according to the square of the Fourier coefficient modulus;

normalizing the energy content of each OAM mode to obtain the receiving probability, namely the energy fraction, of each OAM mode after free space transmission;

calculating the receiving probability of each OAM mode by using software programming;

and exporting the calculated receiving probability of each OAM mode in an Excel file form, and constructing a relation with the ellipticity parameter to achieve the optimization of ellipticity parameter selection.

It is another object of the present invention to provide a computer-readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the steps of:

based on the generalized Huygens-Fresnel principle, theoretically deducing to obtain the light field distribution of an elliptic Gaussian beam at a z plane at any distance after the elliptic Gaussian beam is transmitted in free space;

expanding an elliptic Gaussian light field at any distance z plane according to spiral harmonic waves to obtain the square of the Fourier coefficient modulus;

calculating the energy content of each OAM mode according to the square of the Fourier coefficient modulus;

normalizing the energy content of each OAM mode to obtain the receiving probability, namely the energy fraction, of each OAM mode after free space transmission;

calculating the receiving probability of each OAM mode by using software programming;

and exporting the calculated receiving probability of each OAM mode in an Excel file form, and constructing a relation with the ellipticity parameter to achieve the optimization of ellipticity parameter selection.

Another object of the present invention is to provide an information data processing terminal of a short-distance optical communication system, which is used for implementing the method for optimally selecting an ellipticity parameter, and giving an optimal selection of the ellipticity parameter.

Another object of the present invention is to provide an ovality parameter optimization selection system for implementing the ovality parameter optimization selection method, the ovality parameter optimization selection system including:

the light field distribution acquisition module is used for theoretically deducing and obtaining the light field distribution of the elliptic Gaussian beam at an arbitrary distance z plane after the elliptic Gaussian beam is transmitted in free space based on the generalized Huygens-Fresnel principle;

the Fourier coefficient modulus square acquisition module is used for expanding the elliptic Gaussian light field at any distance z plane according to the spiral harmonic to obtain the square of the Fourier coefficient modulus;

the energy content calculation module is used for calculating the energy content of each OAM mode according to the square of the Fourier coefficient modulus;

the receiving probability calculation module is used for normalizing the energy content of each OAM mode to obtain the receiving probability of each OAM mode after free space transmission;

each receiving probability calculation module is used for realizing the calculation of the receiving probability of each OAM mode by using software programming;

and the ovality parameter selection optimization module is used for exporting the calculated receiving probability of each OAM mode in an Excel file form, and establishing a relation with the ovality parameter so as to achieve optimization of ovality parameter selection.

By combining all the technical schemes, the invention has the advantages and positive effects that: through the optimization selection of the ellipticity parameter in the elliptical Gaussian beam, the channel receiving probability of the short-distance communication system based on the elliptical Gaussian beam is maximized, and the transmission performance is improved. The invention adopts a numerical simulation method to embody the OAM distribution of the elliptic Gaussian beam after transmission in the atmospheric turbulence and give the optimal selection of the ellipticity parameters at different distances.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained from the drawings without creative efforts.

Fig. 1 is a flowchart of an ovality parameter optimization selection method according to an embodiment of the present invention.

FIG. 2 is a schematic structural diagram of an ovality parameter optimization selection system provided by an embodiment of the present invention;

in fig. 2: 1. a light field distribution acquisition module; 2. a Fourier coefficient modulus square acquisition module; 3. an energy content calculation module; 4. a reception probability calculation module; 5. each reception probability calculation module; 6. and an ovality parameter selection optimization module.

FIG. 3 is a schematic diagram of a value of an optimized ellipse parameter a, where a is greater than or equal to 0 and less than or equal to 1, according to an embodiment of the present invention.

Fig. 4 is a value diagram of an optimized ellipse parameter a with a >1 according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating partial data results provided by an embodiment of the present invention.

FIG. 6 is an exemplary embodiment of an optimal selection of ellipticity parameters for odd-order higher-order elliptical Gaussian beams: (a, b)3 th order; (c, d)5 th order; (e, f)7 th order diagram.

FIG. 7 is an exemplary embodiment of an optimization selection of ellipticity parameters for a higher order elliptical Gaussian beam of even order according to the present invention: (a, b) order 4; (c, d)6 th order diagram.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In view of the problems in the prior art, the present invention provides an ovality parameter optimization selection method suitable for a short-distance communication system, and the present invention is described in detail below with reference to the accompanying drawings.

As shown in fig. 1, the ovality parameter optimization selection method provided by the present invention includes the following steps:

s101: based on the generalized Huygens-Fresnel principle, theoretically deducing to obtain the light field distribution of an elliptic Gaussian beam at a z plane at any distance after the elliptic Gaussian beam is transmitted in free space;

s102: expanding an elliptic Gaussian light field at any distance z plane according to spiral harmonic waves to obtain the square of the Fourier coefficient modulus;

s103: calculating the energy content of each OAM mode according to the square of the Fourier coefficient modulus;

s104: normalizing the energy content of each OAM mode to obtain the receiving probability, namely the energy fraction, of each OAM mode after free space transmission;

s105: calculating the receiving probability of each OAM mode by using software programming;

s106: and exporting the calculated receiving probability of each OAM mode in an Excel file form, and constructing a relation with the ellipticity parameter to achieve the optimization of ellipticity parameter selection.

The ovality parameter optimization selection method provided by the present invention may also be implemented by other steps by those skilled in the art, and the ovality parameter optimization selection method provided by the present invention in fig. 1 is only one specific embodiment.

As shown in fig. 2, the ovality parameter optimization selection system provided by the present invention includes:

the light field distribution acquisition module 1 is used for theoretically deducing and obtaining the light field distribution of the elliptic Gaussian beam at an arbitrary distance z plane after the elliptic Gaussian beam is transmitted in a free space based on the generalized Huygens-Fresnel principle;

the Fourier coefficient modulus square acquisition module 2 is used for expanding the elliptic Gaussian light field at any distance z plane according to the spiral harmonic to obtain the square of the Fourier coefficient modulus;

the energy content calculation module 3 is configured to calculate an energy content of each OAM mode according to a square of a fourier coefficient modulus;

the receiving probability calculation module 4 is configured to normalize the energy content of each OAM mode to obtain a receiving probability of each OAM mode after free space transmission;

each receiving probability calculating module 5 is used for realizing the calculation of the receiving probability of each OAM mode by using software programming;

and the ovality parameter selection optimization module 6 is used for exporting the calculated receiving probability of each OAM mode in an Excel file form, and establishing a relation with the ovality parameters to achieve optimization of ovality parameter selection.

The technical solution of the present invention is further described below with reference to the accompanying drawings.

The ovality parameter optimization selection method provided by the invention specifically comprises the following steps:

(1) the optical field distribution of the elliptical gaussian beam at the source plane z-0 is:

(2) based on a generalized Huygens-Fresnel diffraction integral formula, obtaining a light field of an elliptic Gaussian beam at a z plane at any distance in free space transmission:

wherein:

(3) expanding the light field of the elliptic Gaussian beam transmitted at any distance z plane in free space in the form of spiral harmonic exp (im theta), and obtaining the square of the Fourier coefficient modulus as follows:

〈|a_m(r,z)|²〉＝SS^*exp[-2r²T]I_m-H(2r²T),

wherein:

(4) the energy content of each OAM mode is:

(5) normalizing the energy content of each OAM mode to obtain the receiving probability of each OAM mode after free space transmission, namely the energy fraction is as follows:

(6) and programming by using Mathemica software, calculating to obtain each OAM mode receiving probability, exporting the calculated each OAM mode receiving probability in an Excel file form, and constructing a relation with the ellipticity parameter to achieve the optimization of the selection of the ellipticity parameter.

The invention theoretically deduces a light field expression of the elliptic Gaussian beam after free space transmission, expands the light field expression according to spiral harmonic waves and normalizes the light field expression to obtain the receiving probability of each OAM mode. Through distinguishing the ellipticity parameter a into two different intervals, the corresponding OAM mode receiving probability is maximized, and the optimal ellipticity parameter value is given in the two intervals corresponding to the design of a short-distance communication system with the transmission distance less than 2 km.

The technical effects of the present invention will be described in detail with reference to experiments.

(1) Theoretical calculation software and basic parameters used in calculation

The theoretical calculation software used was Mathematica software under Wolfram.

The basic parameters of the elliptical Gaussian beam and the receiving instrument are as follows:

topological charge number: n is 3, wavelength of light wave: λ 1550nm, beam width: w is 0.05m, atmospheric turbulence power spectrum index: 11/3, turbulence intensity:aperture of receiving instrument: and R is 0.05 m.

(2) Data results

Since the OAM distribution of the elliptical gaussian beam at the source plane appears to be multimode and its main energy is concentrated on the mode with m-1, its distribution with respect to the ellipticity parameter is as shown in fig. 3. The ellipticity parameter a is divided into two intervals, i.e. a is more than or equal to 0 and less than or equal to 1, and a is more than 1, and the ellipticity parameter a has different optimal values under the conditions corresponding to different transmission distances, as shown in fig. 4.

The invention is in the short distance communication system with the distance less than 2km, the optimization of the ellipticity parameter of the high-order elliptical Gaussian beam directly influences the communication performance, and the scheme of how to select the ellipticity parameter and the corresponding relation between the ellipticity parameter and the order under different transmission distances is given.

As shown in fig. 6 and 7, the present invention can optimally select the parameter a according to different transmission distance scenarios. The value of a is also related to the order. For a communication system with a transmission distance less than 2km, when the EGB order is odd, the relationship between the optimum value and the order is-0.05 n +0.5(0 ≦ a ≦ 1) and a ≦ 0.5n +2(a > 1). When the order is even, the relationship is that a is-0.05 n +0.7 (0. ltoreq. a.ltoreq.1) and a is 0.25n +1(a > 1).

In summary, the present invention provides an ovality parameter optimization selection for a short-distance communication system based on an elliptical gaussian beam. The optical field expression of the elliptic Gaussian beam after free space transmission is theoretically deduced, the elliptic Gaussian beam is expanded according to spiral harmonic waves and normalized, and the receiving probability of each OAM mode is obtained. Through distinguishing the ellipticity parameter a into two different intervals, the corresponding OAM mode receiving probability is maximized, and the optimal ellipticity parameter value is given in the two intervals corresponding to the design of a short-distance communication system with the transmission distance less than 2 km. The above is an advantage of the present invention in this field, but the present invention is not limited to the field of use, and any simple modification, variation and modification or simple field replacement made according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

It should be noted that the embodiments of the present invention can be realized by hardware, software, or a combination of software and hardware. The hardware portion may be implemented using dedicated logic; the software portions may be stored in a memory and executed by a suitable instruction execution system, such as a microprocessor or specially designed hardware. Those skilled in the art will appreciate that the apparatus and methods described above may be implemented using computer executable instructions and/or embodied in processor control code, such code being provided on a carrier medium such as a disk, CD-or DVD-ROM, programmable memory such as read only memory (firmware), or a data carrier such as an optical or electronic signal carrier, for example. The apparatus and its modules of the present invention may be implemented by hardware circuits such as very large scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of hardware circuits and software, e.g., firmware.

The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.