Fiber laser coherent array optical communication system based on polarization control

Abstract

The application provides a polarization control-based optical fiber laser coherent array optical communication system, which comprises an information input module, an optical fiber laser coherent array transmitting module, a polarization detection module and an information output module. The information input module is used for determining coding requirements according to to-be-transmitted text information. The optical fiber laser coherent array transmitting module is used for regulating the polarization direction of corresponding array elements of the optical fiber laser coherent array according to the coding requirements provided by the information input module, so as to generate 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. The information output module is used for decoding the detection data of the polarization detection module and outputting corresponding text information. The application can quickly and accurately transmit text information.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fiber laser, and particularly relates to a fiber laser coherent array optical communication system based on polarization control. BACKGROUND

[0002] Coherent synthesis technology is considered to be a mainstream scheme for constructing high-brightness laser light sources at present. With in-depth research on phase control methods, array transmission characteristics, array design and evaluation system of synthesized light beams, coherent arrays gradually develop towards diversified light field regulation and practical application fields. At present, coherent synthesis technology has certain application potential in free space optical communication by virtue of high-power laser output, large-scale array structure, atmospheric turbulence suppression technology and non-mechanical pointing control, and can meet the requirements of long distance, high performance and high precision of free space optical communication.

[0003] At present, fiber laser coherent array optical communication systems are mostly focused on the research on phase control schemes. However, the communication mode based on only phase control has the problems of limited transmission capacity and complex demodulation of orbital angular momentum mode multiplexing by only phase control. At present, there are relatively few reports on multi-dimensional regulation. SUMMARY

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

[0005] To achieve the above technical purposes, the technical scheme adopted by the application is as follows:

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

[0007] An information input module is configured to determine coding requirements according to text information to be transmitted.

[0008] A fiber laser coherent array transmitting module is configured to regulate the polarization direction of corresponding array elements of the fiber laser coherent array according to the coding requirements provided by the information input module, so as to generate a vector light field with a required polarization order in a far field.

[0009] A polarization detection module is configured to detect the polarization order of the vector light field.

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

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

[0012] Preferably, the fiber laser coherent array emission module comprises a fiber laser coherent synthesis optical path, the fiber laser coherent synthesis optical path comprises a seed source, a preamplifier, a fiber beam splitter, a phase modulator, a cascaded fiber amplifier, a collimator array, the fiber beam splitter has a plurality of output ends, the seed laser output by the seed source is divided into a plurality of unit light beams after being amplified by the preamplifier and then passing through the fiber beam splitter, each output end of the fiber beam splitter is respectively connected with a phase modulator, a cascaded fiber amplifier and a collimator, the plurality of collimators are arranged in a circular array to form a collimator array, the collimator array comprises a plurality of annular collimator arrays from inside to outside, and each annular collimator array is composed of a plurality of collimators uniformly distributed in a circular ring.

[0013] Further, the application further comprises a polarization control module, the polarization control module comprises a polarization control unit and a polarization controller array, the polarization controller array is arranged after 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 by 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 encoding rule to exert corresponding polarization control on each polarization controller in the polarization controller array; the annular laser array output by the collimator array is input into the polarization controller array, the polarization direction of each array element is controlled by each polarization controller in the polarization controller array, so as to generate a vector light beam with a required polarization order as a code element of transmission information.

[0015] The polarization detection module sequentially performs polarization detection on the vector light fields in the vector light field sequence, and transmits the detection results to the information output module, the information output module sequentially analyzes the polarization orders of the vector light fields in the vector light field sequence, and decodes and analyzes according to the preset encoding rule, finally recognizes the corresponding text information and outputs.

[0016] Further, the application further comprises a phase control module, the phase control module comprising a beam splitter, a focusing lens, a photodetector and a phase control unit; the annular laser array output by 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 low-power light beam is received by the photodetector after passing through the focusing lens and is 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 the phase control signal to the phase modulator corresponding to each unit light beam in the fiber laser coherent synthesis optical path for phase modulation, so as to compensate for the phase noise of the fiber laser coherent synthesis optical path.

[0017] Further, the phase optimization control algorithm of the application 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] Further, the polarization detection module of the application comprises a spatial filtering system and a polarization detector; the spatial filtering system is composed of two focusing lenses and an aperture, and the aperture is located between the two focusing lenses and is used for filtering out the side lobe interference; the polarization detector is used for detecting the polarization direction of the vector light field and outputting the detection result to the information output module.

[0019] Further, the information output module of the application comprises 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, solves the corresponding code elements, and then realizes information output by the information output module.

[0020] Based on the above technical solutions, the application can produce the following technical effects:

[0021] The application introduces the polarization parameter into the fiber laser coherent array to generate high-order vector light fields of different polarization orders, can efficiently perform multi-mode switching, simplifies the demodulation scheme, and is beneficial to improving the communication efficiency of the system.

[0022] The application constructs a fiber laser coherent array system integrated with multi-parameter regulation (including amplitude, phase and polarization), which is beneficial to further improving the communication capacity and forming a multi-dimensional keying communication link.

[0023] In summary, the application provides a new dimension of application of the fiber laser coherent array in the communication field, and explores a scheme for effectively improving the performance of the communication system. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only show some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from the structure shown in the drawings without creative labor.

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

[0026] Figure 2 FIG. 2 is a schematic diagram of generating a radial vector light field by a fiber laser coherent array in an embodiment;

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

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

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

[0030] In an embodiment, a fiber laser coherent array optical communication system based on polarization control is provided, comprising:

[0031] An information input module is configured to determine the encoding requirement according to the text information to be transmitted. Similarly, the vector light beams of different polarization orders present different numbers of petal-shaped light spot patterns in the far field, and accordingly the information input module determines the encoding requirement according to the text information to be transmitted.

[0032] A fiber laser coherent array transmitting module is configured to regulate the polarization direction of the corresponding array elements of the fiber laser coherent array according to the encoding requirement provided by the information input module, so as to generate the vector light field of the required polarization order in the far field.

[0033] A polarization detection module is configured to detect the polarization order of the vector light field.

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

[0035] Further, in addition to polarization control, the phase and amplitude of the fiber laser coherent array can also be controlled. According to the encoding requirements provided by the information input module, the amplitude, phase and polarization of the fiber laser coherent array are flexibly adjusted in multiple dimensions to generate a vector light field in the far field coherent superposition. After the polarization order of the vector light field is detected by the polarization detection module, the decoding is completed by the information output module. The present application 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 based on high-power fiber laser coherent synthesis technology under polarization control.

[0036] Reference Figure 1 An embodiment provides a polarization control-based fiber laser coherent array optical communication system, which comprises an information input module, a fiber laser coherent array emission module, a phase control module, a polarization control module, a polarization detection module and an information output module.

[0037] The information input module 1, the seed source 2, the preamplifier 3, the fiber beam splitter 4, the phase modulator array 5, the cascaded fiber amplifier 6, the adaptive fiber collimator array 7, the polarization controller array 8, the beam splitter 9, the focusing lens 10, the photodetector 11, the control module 12, the spatial filtering system (lens groups 13a and 13c, diaphragm 13b) 13, the polarization detection element 14, the spot analysis module 15 and the 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, the vector light beams with 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 emission module comprises a seed source 2, a preamplifier 3, a fiber beam splitter 4, a phase modulator array 5, a cascaded 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 connected to a phase modulator, a cascaded fiber amplifier 6 and an adaptive fiber collimator. Multiple phase modulators form a phase modulator array 5, and multiple adaptive fiber collimators are arranged in a circular array to form an adaptive fiber collimator array 7. The adaptive fiber collimator array 7 contains multiple layers of annular adaptive fiber collimator arrays from the inside to the outside, and each layer of 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 encoding requirement according to the text information to be transmitted, and further comprises determining the ring laser array output by the fiber laser coherent synthesis optical path according to the text information to be transmitted. The beam waist radius of each unit beam of the ring laser array output by the fiber laser coherent synthesis optical path is w0, the wavelength is λ, the beam aperture is d, and the exit amplitude is A0.

[0041] The polarization control module comprises a polarization control unit and a polarization controller array 8, which is arranged after the adaptive 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 fiber collimator array 7, and the collimators in the adaptive 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 encoding rule to apply corresponding polarization control to each polarization controller in the polarization controller array 8 according to the encoding requirement. The ring laser array output by the adaptive fiber collimator array 7 is input to the polarization controller array 8, and the polarization direction of the corresponding array element is controlled by each polarization controller in the polarization controller array 8, thereby generating a vector light beam of the required polarization order as a code element of the transmission information.

[0043] The phase control module comprises a beam splitter 9, a focusing lens 10, a photodetector 11 and a phase control unit. The ring laser array output by the fiber laser coherent synthesis optical path is divided into two parts by the beam splitter 9, and one part of the beam divided by the beam splitter 9 is transmitted in free space to the polarization detection module. The other small part of the power beam divided by the beam splitter 9 is received by the photodetector 11 after passing through the focusing lens 9, and is converted into an electrical signal which is transmitted to the phase control unit. The phase control unit generates a phase control signal corresponding to each unit beam by running a pre-loaded phase optimization control algorithm for signal processing, and transmits the phase control signal to the phase modulator corresponding to each unit beam in the fiber laser coherent synthesis optical path for phase modulation, thereby compensating 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 comprises 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 located between the two focusing lenses 13a and 13c for filtering out the sidelobe interference; the polarization detector 14 is used for detecting the polarization direction of the vector light field and outputting the detection result to the information output module. The information output module comprises a light spot analysis module 15 and an information output module 16; the light spot analysis module 15 analyzes the polarization order of the vector light field based on the detection information of the polarization detector, solves the corresponding code element and realizes information output by the information output module 16.

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

[0046] Through the polarization control module, the polarization direction of each array element controlled by each polarization controller in the polarization controller array 8 can be controlled, specific polarization control can be applied to each array element, and a vector light beam with a required polarization order, including a high-order vector light beam, can be generated.

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

[0048]

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

[0050] Further, by independently integrating the components in the x and y directions of the light field distribution, the following can be obtained:

[0051]

[0052] Where p0 is the order of the vector light beam, φ represents the integral of φ j The summation with respect to j can be approximated as the integral of φ j .

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

[0054]

[0055] wherein is the approximate result.

[0056] That is:

[0057]

[0058] wherein, when p0=1, φ0=0, it is a radial polarization light; when p0=1, φ0=π / 2, it is an angular polarization light; when p0>1, it is a high-order vector light field.

[0059] When the polarization direction changes by 2π around the ring laser array beam, p0=1; when the polarization direction changes by 2π*p0 around the ring laser array beam, 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 ring laser array at the confocal plane column coordinate (r2,θ2) in the spatial filtering system 13 is:

[0061]

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

[0063] The ring laser array output from the emission surface of the optical fiber laser coherent synthesis optical path in an embodiment is composed of a second layer ring laser array (12 unit light beams), the beam waist radius w0=8.9×10 -5 m of each unit light beam on the second layer ring laser array; the wavelength is λ=1064nm, the beam aperture is d=9.8×10 -5 m, the exit amplitude is A0, the transmission distance z=0.6m, the lens focal length in the spatial filtering system is f=0.6m, and the diaphragm aperture d f =3.8×10 -3 m. According to the setting parameters, reference Figure 2The polarization state of a single array element in a second layer annular laser array is controlled to generate a radial vector beam, and the far-field light intensity distribution before and after filtering is given, and the far-field light intensity distribution in different polarization directions is also given.

[0064] Reference Figure 3 The figure shows the information transmission of fiber laser coherent array based on polarization control. Since different order vector beams present different number of petal-shaped spot patterns in the far field, after encoding the text information, different order (p=1, 2, 3, 4) vector light field polarization mode information can be encoded as ('00', '01', '10', '11') according to the encoding requirements. For example, to transmit the letter N ('4E'), the 16-bit encoding method can be converted into a more simple binary encoding method, and the polarization mode of the laser array is controlled accordingly to generate the corresponding '00', '10', '11' and '10' vector beam sequence, which is transmitted to the spot analysis module and decoded and analyzed according to the above encoding method. Finally, the corresponding text information is identified. The results show that the system can quickly and accurately transmit text information.

[0065] The present application uses polarization control to generate a vector light field with non-uniform polarization distribution in space and polarization singularities, which not only can switch between multiple modes, but also is more simple in demodulation method.

[0066] The introduction of polarization control into the field of fiber laser coherent synthesis can further solve the problems of difficulty in extracting complex mode information and small transmission capacity in the prior art, and is conducive to building a multi-dimensional keying communication link and expanding its application potential in the field of free space structured light communication.

[0067] The technical features of the above embodiments can be combined in any way. To make the description concise, not all possible combinations of the technical features in the above embodiments are described, but as long as the combinations of the technical features do not contradict, they should be considered as within the scope of the present application.

[0068] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the application. It should be noted that for those skilled in the art, without departing from the concept of the present application, some modifications and improvements can be made, which are all within the scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A polarization control based fiber laser coherent array optical communication system, characterized in that, The application relates to a vector light field information transmission device and method. The information input module is used for determining the coding requirement according to the text information to be transmitted, different polarization orders of the vector light beams present different numbers of petal-shaped light spot patterns in a far field, and the information input module determines the coding requirement according to the text information to be transmitted. The fiber laser coherent array emission module is used for regulating the polarization directions of the corresponding array elements of the fiber laser coherent array according to the coding requirement provided by the information input module, and generating a vector light field of a required polarization order in a far field. The polarization detection module is used for detecting the polarization order of the vector light field. The information output module is used for decoding and outputting the corresponding text information according to the detection data of the polarization detection module.

2. The polarization control based coherent fiber laser array optical communication system according to claim 1, wherein, The fiber beam splitter has a plurality of output ends, the seed laser output by the seed source is divided into a plurality of unit light beams after being amplified by the preamplifier and passing through the fiber beam splitter, each output end of the fiber beam splitter is respectively connected with a phase modulator, a cascaded fiber amplifier and a collimator, the plurality of collimators are arranged in a circular array to form a collimator array, and the collimator array contains a plurality of ring-shaped collimator arrays from inside to outside.

3. The polarization control based coherent fiber laser array optical communication system according to claim 1, wherein, The information input module further comprises determining the fiber laser coherent synthesis light path according to the text information to be transmitted, and the annular laser array output by the emission surface of the fiber laser coherent synthesis light path is output by the array of the first layer of annular collimators, the beam waist radius of each unit beam of the annular laser array output by the emission surface of the fiber laser coherent synthesis light path is , the wavelength is , the beam aperture is , and the exit amplitude is .

4. The polarization control based coherent fiber laser array optical communication system according to claim 1 or 2 or 3, characterized in that, The polarization detection module sequentially detects the polarization of the vector light field in the vector light field sequence, transmits the detection result to the information output module, the information output module sequentially analyzes the polarization order of the vector light field in the vector light field sequence, and finally recognizes and outputs the corresponding text information according to the preset coding rule.

5. The polarization control based coherent fiber laser array optical communication system of claim 4, wherein, The phase control module comprises a beam splitter, a focusing lens, a photoelectric detector and a phase control unit; the annular laser array output by the emission surface of the fiber laser coherent synthesis light 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 light beam with small power is received by the photoelectric detector after passing through the focusing lens, and is 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 the phase control signal to the phase modulator corresponding to each unit light beam in the fiber laser coherent synthesis light path for phase modulation, so as to compensate for the phase noise of the fiber laser coherent synthesis light path.

6. The polarization control based coherent fiber laser array optical communication system of claim 5, wherein, The phase optimization control algorithm is a random parallel gradient descent algorithm, a simulated annealing algorithm or a particle swarm optimization algorithm.

7. The polarization control based coherent fiber laser array optical communication system according to claim 1 or 2 or 3 or 5 or 6, wherein, The polarization detection module comprises a spatial filtering system and a polarization detector; the spatial filtering system is composed of two focusing lenses and an optical stop, and the optical stop is located between the two focusing lenses and is used for filtering out sidelobe interference; the polarization detector is used for detecting the polarization direction of the vector light field and outputting the detection result to the information output module.

8. The polarization control based coherent fiber laser array optical communication system of claim 7, wherein, The information output module comprises a spot analysis module and an information output module; the spot analysis module analyzes the polarization order of the vector light field based on the detection information of the polarization detector, solves the corresponding code elements, and realizes information output by the information output module.

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