Optical fiber laser coherent array optical communication system based on polarization control

Abstract

The invention provides an optical fiber laser coherent array optical communication system based on polarization control, and the system comprises an information input module which is used for determining a coding demand according to the to-be-transmitted text information; the optical fiber laser coherent array transmitting module is used for regulating and controlling the polarization direction of an array element corresponding to an optical fiber laser coherent array according to the coding requirement provided by the information input module, and generating a vector light field with a required polarization order in a far field; the polarization detection module is used for detecting the polarization order of the vector light field; and the information output module is used for decoding the detection data of the polarization detection module and outputting corresponding text information. According to the invention, the text information can be quickly and accurately transmitted.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber lasers, and in particular relates to an optical fiber laser coherent array optical communication system based on polarization control. Background Art

[0002] Coherent combining technology is considered to be the mainstream system solution for building high-brightness laser light sources at this stage. With the in-depth research on phase control methods, array transmission characteristics, array design, and synthetic beam evaluation systems, coherent arrays are gradually developing towards diversified light field control and practical application fields. At present, coherent combining technology has certain application potential in free-space optical communications due to its high-power laser output, large-scale array structure, atmospheric turbulence suppression technology, and non-mechanical pointing control, and can simultaneously meet the requirements of free-space optical communications such as long-distance, high performance, and high precision.

[0003] At present, the research on phase control schemes is mostly focused on the fiber laser coherent array optical communication system. However, the communication method based only on phase control has limited transmission capacity on the one hand, and on the other hand, considering that orbital angular momentum mode multiplexing is only through phase control, it is more complicated in demodulation. At present, there are relatively few reports on multi-dimensional control. Summary of the invention

[0004] In view of the defects and shortcomings in the prior art, the present invention discloses a fiber laser coherent array optical communication system based on polarization control.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0006] The fiber laser coherent array optical communication system based on polarization control includes:

[0007] An information input module, used to determine the encoding requirements according to the text information to be transmitted;

[0008] The fiber laser coherent array transmitting module is used to adjust the polarization direction of the corresponding array element of the fiber laser coherent array according to the coding requirements provided by the information input module, and generate a vector light field of the required polarization order in the far field;

[0009] A polarization detection module, used to detect the polarization order of the vector light field;

[0010] The information output module is used to decode the detection data of the polarization detection module and output corresponding text information.

[0011] In the present invention, vector light beams of different polarization orders present petal-shaped spot patterns with different numbers in the far field, and the information input module determines the encoding requirements according to the text information to be transmitted.

[0012] Preferably, the fiber laser coherent array transmitting module includes a fiber laser coherent synthesis optical path, which includes a seed source, a pre-amplifier, a fiber beam splitter, a phase modulator, a cascade fiber amplifier, and a collimator array. The fiber beam splitter has multiple output ends. The seed laser output by the seed source is amplified by the pre-amplifier and then divided into multiple unit light beams after passing through the fiber beam splitter. Each output end of the fiber beam splitter is respectively connected to a phase modulator, a cascade fiber amplifier, and a collimator. Multiple collimators are arranged in a circular array to form a collimator array. The collimator array includes multiple layers of annular collimator arrays from the inside to the outside, and each layer of the annular collimator array is composed of multiple collimators evenly distributed in a circular shape. The information input module also includes determining, based on the text information to be transmitted, that the annular laser array output from the emission surface of the fiber laser coherent synthesis optical path is specifically output from the layer of the annular adaptive fiber collimator array, and the waist radius of each unit light beam of the annular laser array output from the emission surface of the fiber laser coherent synthesis optical path is w0, the wavelength is λ, the beam aperture is d, and the output amplitude is A0.

[0013] Furthermore, the present invention also includes a polarization control module, which includes a polarization control unit and a polarization controller array, wherein the polarization controller array is arranged behind the collimator array, the number of polarization controllers in the polarization controller array is the same as the number of collimators in the collimator array, and the collimators in the collimator array correspond one-to-one to the polarization controllers in the polarization controller array;

[0014] The polarization control unit encodes the polarization mode information of the vector light field corresponding to the required polarization order according to the preset coding rules based on the coding requirements to apply corresponding polarization control to each polarization controller in the polarization controller array; the ring laser array output by the collimator array is input to the polarization controller array, and each polarization controller in the polarization controller array controls the polarization direction of the corresponding array element, thereby generating a vector light beam of the required polarization order as a code element for transmitting information.

[0015] The polarization detection module performs polarization detection on the vector light fields in the vector light field sequence in turn, and transmits the detection results to the information output module. The information output module analyzes the polarization order of the vector light fields in the vector light field sequence in turn, and performs decoding analysis according to preset coding rules, and finally identifies and outputs the corresponding text information.

[0016] Furthermore, the present invention also includes a phase control module, which includes a beam splitter, a focusing lens, a photodetector and a phase control unit; the annular laser array output from the emission surface of the fiber laser coherent synthesis optical path is divided into two parts by the beam splitter, a part of the high-power light beam is transmitted in free space, and the other part of the power light beam is received by the photodetector after passing through the focusing lens and converted into an electrical signal and transmitted to the phase control unit, and the phase control unit performs signal processing by running a pre-loaded phase optimization control algorithm to generate a phase control signal corresponding to each unit light beam, and transmits it to the phase modulator corresponding to each unit light beam in the fiber laser coherent synthesis optical path for phase modulation to compensate for the phase noise of the fiber laser coherent synthesis optical path.

[0017] Furthermore, the phase optimization control algorithm described in the present invention is not limited, including but not limited to a random parallel gradient descent algorithm, a simulated annealing algorithm or a particle swarm optimization algorithm.

[0018] Furthermore, the polarization detection module described in the present invention includes a spatial filtering system and a polarization detector; the spatial filtering system is composed of two focusing lenses and an aperture, the aperture is located between the two focusing lenses, and is used to filter out sidelobe interference; the polarization detector is used to detect the polarization direction of the vector light field and output the detection result to the information output module.

[0019] Furthermore, the information output module of the present invention includes a light spot analysis module and an information output module. The light spot analysis module analyzes the polarization order of the vector light field based on the detection information of the polarization detector, and the information output module realizes information output after solving the corresponding code elements.

[0020] Based on the above technical solution, the technical effects that can be produced by the present invention are:

[0021] The present invention introduces polarization parameters into the fiber laser coherent array to generate high-order vector light fields of different polarization orders, which can efficiently perform multi-mode switching, simplify the demodulation scheme, and help improve the communication efficiency of the system.

[0022] The present invention constructs a fiber laser coherent array system with integrated multi-parameter control (including amplitude, phase and polarization), which is beneficial to further improve the communication capacity and form a multi-dimensional keyed communication link.

[0023] In summary, the present invention provides a new dimension for the application of fiber laser coherent arrays in the communication field and explores a solution to effectively improve the performance of communication systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0025] Figure 1 It is a schematic structural diagram of a fiber laser coherent array optical communication system based on polarization control according to an embodiment;

[0026] Figure 2 It is a schematic diagram of a radial vector light field generated by a fiber laser coherent array in one embodiment;

[0027] Figure 3 It is a schematic diagram of information transmission of a fiber laser coherent array based on polarization control in one embodiment. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Vector light beams of different polarization orders present different numbers of petal-shaped spot patterns in the far field, and accordingly corresponding data information can be transmitted through vector light beams of different polarization orders to achieve communication.

[0030] One embodiment provides a fiber laser coherent array optical communication system based on polarization control, comprising:

[0031] The information input module is used to determine the encoding requirements according to the text information to be transmitted; similarly, vector light beams of different polarization orders present different numbers of petal-shaped spot patterns in the far field, and the information input module determines the encoding requirements according to the text information to be transmitted.

[0032] The fiber laser coherent array transmitting module is used to adjust the polarization direction of the corresponding array element of the fiber laser coherent array according to the coding requirements provided by the information input module, and generate a vector light field of the required polarization order in the far field;

[0033] A polarization detection module, used to detect the polarization order of the vector light field;

[0034] The information output module is used to decode the detection data of the polarization detection module and output corresponding text information.

[0035] Furthermore, in addition to the controllable polarization of the fiber laser coherent array, the phase and amplitude of the fiber laser coherent array can also be controlled. According to the coding requirements provided by the information input module, the amplitude, phase and polarization dimensions of the fiber laser coherent array are flexibly adjusted to generate a vector light field by coherent superposition in the far field. After the polarization detection module detects the polarization order of the vector light field, the information output module completes the decoding. The present invention solves the problems of few adjustable dimensions, small transmission capacity and low transmission efficiency in the prior art, and explores the possibility of constructing an optical communication system using high-power fiber laser coherent synthesis technology under polarization control.

[0036] refer to Figure 1 An embodiment provides a fiber laser coherent array optical communication system based on polarization control, including an information input module, a fiber laser coherent array transmitting module, a phase control module, a polarization control module, a polarization detection module and an information output module.

[0037] Information input module 1, seed source 2, pre-amplifier 3, fiber splitter 4, phase modulator array 5, cascade fiber amplifier 6, adaptive fiber collimator array 7, polarization controller array 8, spectroscope 9, focusing lens 10, photodetector 11, control module 12, spatial filtering system (lens group 13a and 13c, aperture 13b) 13, polarization detection element 14, spot analysis module 15 and information output module 16.

[0038] The information input module 1 is used to determine the encoding requirements according to the text information to be transmitted; similarly, vector light beams of different polarization orders present different numbers of petal-shaped spot patterns in the far field, and the information input module determines the encoding requirements according to the text information to be transmitted.

[0039] The fiber laser coherent synthesis optical path in the fiber laser coherent array transmitting module includes a seed source 2, a preamplifier 3, a fiber beam splitter 4, a phase modulator array 5, a cascade fiber amplifier 6, and an adaptive fiber collimator array 7. The seed laser output by the seed source 2 is amplified by the preamplifier 3 and then divided into multiple unit light beams by the fiber beam splitter 4. Each output end of the fiber beam splitter 4 is respectively connected to a phase modulator, a cascade fiber amplifier 6, and an adaptive fiber collimator. Multiple phase modulators constitute the phase modulator array 5, and multiple adaptive fiber collimators are arranged in a circular array to constitute the adaptive fiber collimator array 7. The adaptive fiber collimator array 7 includes multiple layers of annular adaptive fiber collimator arrays from the inside to the outside, and each layer of the annular adaptive fiber collimator array is composed of multiple adaptive fiber collimators uniformly distributed in a circular ring.

[0040] The information input module 1 determines the coding requirements according to the text information to be transmitted, and also includes determining the specific layer of the annular adaptive fiber collimator array output by the annular laser array output from the emission surface of the fiber laser coherent synthesis optical path according to the text information to be transmitted. The waist radius of each unit light beam of the annular laser array output from the emission surface of the fiber laser coherent synthesis optical path is w0, the wavelength is λ, the beam diameter is d, and the output amplitude is A0.

[0041] The polarization control module includes a polarization control unit and a polarization controller array 8, wherein the polarization controller array 8 is arranged behind the adaptive optical fiber collimator array 7, the number of polarization controllers in the polarization controller array 8 is the same as the number of collimators in the adaptive optical fiber collimator array 7, and the collimators in the adaptive optical fiber collimator array 7 correspond one to one to the polarization controllers in the polarization controller array 8;

[0042] The polarization control unit encodes the polarization mode information of the vector light field corresponding to the required polarization order according to the preset coding rules based on the coding requirements to apply corresponding polarization control to each polarization controller in the polarization controller array 8; the ring laser array output by the adaptive fiber collimator array 7 is input to the polarization controller array 8, and each polarization controller in the polarization controller array 8 controls the polarization direction of the corresponding array element, thereby generating a vector light beam of the required polarization order as a code element for transmitting information.

[0043] The phase control module includes a beam splitter 9, a focusing lens 10, a photodetector 11 and a phase control unit; the annular laser array output from the emission surface of the fiber laser coherent synthesis optical path is divided into two parts by the beam splitter 9, and a part of the light beam separated by the beam splitter 9 is transmitted to the polarization detection module in free space. The other small part of the power light beam separated by the beam splitter 9 is received by the photodetector 11 after passing through the focusing lens 9 and converted into an electrical signal and transmitted to the phase control unit. The phase control unit generates a phase control signal corresponding to each unit light beam by running a pre-loaded phase optimization control algorithm for signal processing, and transmits it to the phase modulator corresponding to each unit light beam in the fiber laser coherent synthesis optical path for phase modulation to compensate for the phase noise of the fiber laser coherent synthesis optical path. The phase optimization control algorithm is not limited, including but not limited to a random parallel gradient descent algorithm, a simulated annealing algorithm or a particle swarm optimization algorithm.

[0044] The polarization detection module includes a spatial filtering system 13 and a polarization detector 14; the spatial filtering system 13 is composed of a first focusing lens 13a, a second focusing lens 13c, an aperture 13b and an aperture 13b, and the aperture 13b is located between the two focusing lenses 13a and 13c, and is used to filter out sidelobe interference; the polarization detector 14 is used to detect the polarization direction of the vector light field and output the detection result to the information output module. The information output module includes a spot analysis module 15 and an information output module 16. The spot analysis module 15 analyzes the polarization order of the vector light field based on the detection information of the polarization detector, and the information output module 16 realizes information output after solving the corresponding code element.

[0045] In the present invention, the polarization control unit, phase control unit and control unit of the adaptive fiber collimator array can be separately provided or integrated in the control module 12, that is, the control module 12 includes the polarization control unit, phase control unit and control unit of the adaptive fiber collimator array.

[0046] The polarization control module can control the polarization direction of the corresponding array element of each polarization controller in the polarization controller array 8, and can apply specific polarization control to each array element to generate a vector beam of a desired polarization order, including a high-order vector beam. Specifically:

[0047] The light field distribution of the ring laser array output from the emission surface of the fiber laser coherent synthesis optical path is expressed in the polar coordinate system as follows:

[0048]

[0049] Where p0 is the polarization order, that is, the order of the vector beam, φ0 is the polarization direction and radial angle on the light field cross section, r1 and θ1 represent the cylindrical coordinate system, e x and e y Represents the components of the light field distribution in the x and y directions, and the relationship is φ j represents the polarization direction and radial angle of the cross section of the jth unit beam in the annular laser array, R0 is the distance between the center of each unit beam in the annular laser array and the center of the annular laser array, w0 is the waist radius of the unit beam, and N represents the number of unit beams in the annular laser array.

[0050] Furthermore, by independently integrating the components of the light field distribution in the x-direction and the y-direction, we can obtain:

[0051]

[0052] Where p0 is the order of the vector beam, φ represents φ j The sum about j can be approximated as φ j 's points.

[0053] Furthermore, using the modified first-kind Bessel function relationship and Euler's formula, E x (r1,θ1),E y (r1,θ1) is simplified as:

[0054]

[0055] in for Approximate results.

[0056] That is:

[0057]

[0058] Among them, when p0=1, φ0=0, it is radially polarized light; when p0=1, φ0=π / 2, it is angularly polarized light; when p0>1, it is a high-order vector light field.

[0059] When the polarization direction of the light beam around the annular laser array changes by 2π, p0=1; when the polarization direction of the light beam around the annular laser array changes by 2π*p0, it is a p0-order high-order vector light field, and at this time, p0>1.

[0060] In the polarization detection module, the complex amplitude distribution E(r2,θ2) of the annular laser array at the cylindrical coordinate (r2,θ2) of the confocal plane of the spatial filtering system 13 is:

[0061]

[0062] Where F{E(r1,θ1)} is the Fourier transform of the complex amplitude distribution E(r1,θ1) of the ring laser array on the emission surface, f1 is the focal length of the focusing lens in the spatial filtering system, d f is the aperture of the aperture in the spatial filtering system, λ is the wavelength, and i is the imaginary unit.

[0063] The ring laser array outputted from the emission surface of the fiber laser coherent synthesis optical path in one embodiment is composed of a second layer of ring laser arrays (12 unit beams), and the beam waist radius of each unit beam on the second layer of ring laser array is w0=8.9×10 -5 m; wavelength λ = 1064nm, beam diameter d = 9.8 × 10 -5 m, the emission amplitude is A0, the transmission distance is z = 0.6m, the focal length of the lens in the spatial filtering system is f = 0.6m, and the aperture diameter is d f =3.8×10 -3 m. According to the setting parameters, refer to Figure 2By controlling the polarization state of a single element in the second-layer ring laser array, a radial vector beam can be generated. The far-field light intensity distribution before and after filtering, as well as the corresponding far-field light intensity distribution in different polarization directions, are given.

[0064] refer to Figure 3 , is a schematic diagram of information transmission of fiber laser coherent array based on polarization control. Since vector beams of different orders present different numbers of petal-shaped spot patterns in the far field, after encoding the text information, the polarization mode information of vector light fields of different orders (p = 1, 2, 3, 4) can be encoded as ("00", "01", "10", "11") according to the encoding requirements. For example, to transmit the letter N ("4E"), the hexadecimal encoding method can be converted into a simpler binary encoding method, and the polarization mode of the laser array can be controlled accordingly to generate vector beam sequences corresponding to "00", "10", "11" and "10", and transmit them to the spot analysis module, and decode and analyze them according to the above-mentioned agreed encoding method, and finally identify the corresponding text information. The results show that the system can transmit text information quickly and accurately.

[0065] The present invention utilizes polarization control to generate a vector light field with non-uniform polarization distribution in space and polarization singularity, which can not only perform multi-mode switching but also is simpler in demodulation method.

[0066] Introducing polarization control into the field of fiber laser coherent synthesis technology can further solve the problems of difficulty in extracting composite mode information and small transmission capacity in the existing technology, which is conducive to building multi-dimensional keying communication links and expanding its application potential in the field of free-space structured optical communications.

[0067] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0068] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A fiber laser coherent array optical communication system based on polarization control, characterized in that: include: An information input module, used to determine the encoding requirements according to the text information to be transmitted; The fiber laser coherent array transmitting module is used to adjust the polarization direction of the corresponding array element of the fiber laser coherent array according to the coding requirements provided by the information input module, and generate a vector light field of the required polarization order in the far field; A polarization detection module, used to detect the polarization order of the vector light field; The information output module is used to decode the detection data of the polarization detection module and output corresponding text information.

2. The fiber laser coherent array optical communication system based on polarization control according to claim 1, characterized in that: Vector light beams of different polarization orders present different numbers of petal-shaped spot patterns in the far field, and the information input module determines the encoding requirements based on the text information to be transmitted.

3. The fiber laser coherent array optical communication system based on polarization control according to claim 2, characterized in that: The fiber laser coherent array transmitting module includes a fiber laser coherent synthesis optical path, which includes a seed source, a pre-amplifier, a fiber beam splitter, a phase modulator, a cascade fiber amplifier, and a collimator array. The fiber beam splitter has multiple output ends. The seed laser output by the seed source is amplified by the pre-amplifier and then divided into multiple unit light beams after passing through the fiber beam splitter. Each output end of the fiber beam splitter is respectively connected to a phase modulator, a cascade fiber amplifier, and a collimator. Multiple collimators are arranged in a circular array to form a collimator array. The collimator array includes multiple layers of annular collimator arrays from the inside to the outside, and each layer of the annular collimator array is composed of multiple collimators evenly distributed in a circular ring shape.

4. The fiber laser coherent array optical communication system based on polarization control according to claim 3, characterized in that: The information input module also includes determining, based on the text information to be transmitted, that the annular laser array output from the emission surface of the fiber laser coherent synthesis optical path is specifically output from which layer of the annular collimator array, and the waist radius of each unit light beam of the annular laser array output from the emission surface of the fiber laser coherent synthesis optical path is w0, the wavelength is λ, the beam aperture is d, and the output amplitude is A0.

5. The fiber laser coherent array optical communication system based on polarization control according to claim 3 or 4, characterized in that: It also includes a polarization control module, which includes a polarization control unit and a polarization controller array. The polarization controller array is arranged behind the collimator array. The number of polarization controllers in the polarization controller array is the same as the number of collimators in the collimator array. The collimators in the collimator array correspond to the polarization controllers in the polarization controller array one by one. The polarization control unit encodes the polarization mode information of the vector light field corresponding to the required polarization order according to the preset coding rules based on the coding requirements to apply corresponding polarization control to each polarization controller in the polarization controller array; the ring laser array output by the collimator array is input to the polarization controller array, and each polarization controller in the polarization controller array controls the polarization direction of the corresponding array element, thereby generating a vector light beam of the required polarization order as a code element for transmitting information.

6. The fiber laser coherent array optical communication system based on polarization control according to claim 5, characterized in that: The polarization detection module performs polarization detection on the vector light fields in the vector light field sequence in turn, and transmits the detection results to the information output module. The information output module analyzes the polarization order of the vector light fields in the vector light field sequence in turn, and performs decoding analysis according to preset coding rules, and finally identifies and outputs the corresponding text information.

7. The fiber laser coherent array optical communication system based on polarization control according to claim 3, 4 or 6, characterized in that: It also includes a phase control module, which includes a beam splitter, a focusing lens, a photodetector and a phase control unit. The annular laser array output from the emission surface of the fiber laser coherent synthesis optical path is divided into two parts by the beam splitter. One part of the high-power light beam is transmitted in free space, and the other part of the power light beam is received by the photodetector after passing through the focusing lens and converted into an electrical signal and transmitted to the phase control unit. The phase control unit performs signal processing by running a pre-loaded phase optimization control algorithm to generate a phase control signal corresponding to each unit light beam, and transmits it to the phase modulator corresponding to each unit light beam in the fiber laser coherent synthesis optical path for phase modulation to compensate for the phase noise of the fiber laser coherent synthesis optical path.

8. The fiber laser coherent array optical communication system based on polarization control according to claim 7, characterized in that: The phase optimization control algorithm is a random parallel gradient descent algorithm, a simulated annealing algorithm or a particle swarm optimization algorithm.

9. The fiber laser coherent array optical communication system based on polarization control according to claim 3 or 4 or 6 or 8, characterized in that: The polarization detection module includes a spatial filtering system and a polarization detector; the spatial filtering system is composed of two focusing lenses and an aperture, the aperture is located between the two focusing lenses, and is used to filter out sidelobe interference; the polarization detector is used to detect the polarization direction of the vector light field and output the detection result to the information output module.

10. The fiber laser coherent array optical communication system based on polarization control according to claim 9, characterized in that: The information output module includes a light spot analysis module and an information output module. The light spot analysis module analyzes the polarization order of the vector light field based on the detection information of the polarization detector, and the information output module realizes information output after solving the corresponding code element.

Images