A few-mode optical control same-frequency multi-beam forming system and method based on power distribution

Abstract

The application discloses a few-mode light control same-frequency multi-beam forming system and method based on power distribution, and belongs to the technical field of communication, comprising a tunable laser module, a signal generation module, an electro-optical modulation module, an optical true delay network module, an optoelectronic detection module, a phased array antenna module, a receiving antenna module and a signal processing module; wherein the optical true delay network module is used to realize arithmetic progression delay on mode signals, and reasonable beam pointing angle design is carried out through power distribution, so that the suppression of same-frequency interference in the same-frequency multi-beam system is realized, so that the multi-beam realizes main lobe scanning without deterioration in a large range, and the utilization rate of the spectrum is improved; secondly, the system further reduces the system volume and cost through a multiplexing few-mode fiber Bragg grating group in the optical true delay network module.

Description

Technical Field

[0001] This invention belongs to the field of communication technology, specifically relating to a few-mode optically controlled co-frequency multi-beamforming system and method based on power allocation. Background Technology

[0002] With the development of communication technology, the increasing amount of information places higher demands on channel load capacity. Using a single beam to scan all areas in an antenna transceiver system is insufficient to meet communication efficiency requirements. To accommodate a large number of users accessing the system simultaneously, configuring the antenna with multiple beams for simultaneous scanning is a solution. However, configuring different frequencies for each beam in a multi-beam system puts excessive pressure on limited spectrum resources. Especially in satellite communication, one of the main bottlenecks in the development of space-based information systems is the scarcity of frequency and orbit resources. Therefore, simultaneous multi-beam scanning at the same frequency can be considered to alleviate frequency resource pressure. However, beams with the same frequency within a certain physical distance will cause co-channel interference, leading to a degraded beam quality. Therefore, in practical applications, it is necessary to analyze the causes of interference in co-channel multi-beam systems and find a suitable solution. An important future development direction for low-Earth orbit satellite communication systems is spaceborne multi-beam phased array antenna technology.

[0003] Currently, in optical beamforming technology, there are two main methods for achieving true signal delay through optical control: dispersion-based beamforming and group delay-based beamforming. Dispersion beamforming generates the required time delay by controlling the refractive index of the optical carrier, but due to its relatively small dispersion coefficient, it is difficult to achieve large delays for wide-area scanning under high integration in practical applications. Group delay beamforming generates the required time delay by controlling the physical length of the optical waveguide and achieves binary fiber delay through the use of optical switches. However, this type of technology often uses single-mode fiber to achieve true signal delay, which is not conducive to component integration when there are many signal paths.

[0004] Therefore, it is of great significance to explore multi-beamforming technology with few modes and the same frequency. Summary of the Invention

[0005] To address the issues of excessive spectrum resources, high system cost, and large size associated with traditional optically controlled phased arrays forming multiple beams at multiple frequencies, this invention proposes a few-mode optically controlled co-frequency multi-beamforming system and method based on power allocation. By analyzing the far-field radiation pattern of the beams, a smaller number of Bragg gratings are used in the optical true delay network to provide the required delay values ​​for multiple beams. This method offers advantages such as low cost, simple structure, and good beam directivity.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A power-allocation-based few-mode optically controlled co-frequency multi-beamforming system includes a tunable laser module 1, a signal generation module 2, an electro-optic modulation module 3, an optical true delay network module 4, a photodetector module 5, a phased array antenna module 6, a receiving antenna module 7, and a signal processing module 8. The output port of the tunable laser module 1 is connected to the optical signal input port of the electro-optic modulation module 3; the output port of the signal generation module 2 is connected to the electrical signal input port of the electro-optic modulation module 3; the output port of the electro-optic modulation module 3 is connected to the input port of the optical true delay network module 4; the output port of the optical true delay network module 4 is connected to the input port of the photodetector module 5; the output port of the photodetector module 5 is connected to the input port of the phased array antenna module 6; and the output port of the receiving antenna module 7 is connected to the input port of the signal processing module 8.

[0008] Furthermore, the tunable laser module 1 generates a continuous 1550nm wavelength light wave with an output power of 10dBm.

[0009] Furthermore, the signal generation module 2 generates a microwave signal with a frequency of 4-6 GHz and an output power of 10 mW.

[0010] Furthermore, the electro-optic modulation module 3 employs a Mach-Zehnder modulator to modulate the microwave signal from the signal generation module 2 onto the optical carrier generated by the tunable laser module 1.

[0011] Furthermore, the optical true delay network module 4 includes a beam splitter 41, a mode converter 42, a few-mode beam splitter 43, a delay multiplexing module 44, a mode demultiplexer 45, and a compensated single-mode fiber 46; the output port of the electro-optic modulation module 3 is connected to the input port of the beam splitter 41, the output port of the beam splitter 41 is connected to the input port of the mode converter 42, the output port of the mode converter 42 is connected to the input port of the few-mode beam splitter 43, the output port of the few-mode beam splitter 43 is connected to the input port of the delay multiplexing module 44, the output port of the delay multiplexing module 44 is connected to the input port of the mode demultiplexer 45, the output port of the mode demultiplexer 45 is connected to the input port of the compensated single-mode fiber 46, and the output port of the compensated single-mode fiber 46 is connected to the input port of the photoelectric detection module 5.

[0012] Furthermore, the beam splitter 41 is a 1:N equal-division beam splitter; the few-mode beam splitter 43 is a 1:M equal-division beam splitter.

[0013] Furthermore, the delay multiplexing module 44 includes an N*N optical switch 441, a circulator 442, and a few-mode fiber Bragg grating group 443; the output port of the few-mode beam splitter 43 is connected to the input port 1 of the N*N optical switch 441, the output port 1 of the N*N optical switch 441 is connected to port 1 of the circulator 442, the port 2 of the circulator 442 is connected to the few-mode fiber Bragg grating group 443, the port 3 of the circulator 442 is connected to the input port 2 of the N*N optical switch 441, and the output port 2 of the N*N optical switch 441 is connected to the input port of the mode demultiplexer 45.

[0014] Furthermore, the few-mode fiber Bragg grating group 443 is composed of N cascaded few-mode Bragg gratings, reflecting N modes.

[0015] Furthermore, the photoelectric detection module 5 is used to convert the detected optical signal into an electrical signal, amplify it, and then output it. The photoelectric detection module 5 can detect optical signals of -30dBm.

[0016] Another objective of this invention is to provide a few-mode optically controlled co-frequency multi-beamforming method based on power allocation, specifically including the following steps:

[0017] The tunable laser module generates continuous light. The microwave signal is modulated onto the optical carrier in the form of amplitude and phase information by the electro-optic modulation module. The modulated signal light is split into N in-phase and in-amplitude signal lights after passing through the beam splitter. The N signal lights are then connected to the single-mode end of the mode converter. The few-mode end outputs signal light containing N higher-order modes. The signal light is then output from the N*N optical switch to the few-mode fiber Bragg grating group connected to the circulator. The position of each few-mode fiber Bragg grating is designed according to the power allocation. Each mode is reflected and then output from the N*N optical switch to the mode demultiplexer and compensated by the compensated single-mode fiber, finally achieving the equal time delay required for different beams.

[0018] Furthermore, the compensation of the single-mode fiber specifically includes the following:

[0019] To ensure that the delay difference is zero when the signal does not pass through the Bragg grating, the compensation lengths L1, L2, ..., L for each mode are... m-1 The expression is as follows:

[0020]

[0021] The signal light, after passing through the photoelectric detection module, forms M beams that are emitted into free space. These M beams can share a few-mode fiber Bragg grating array. Each beam contains m array elements. L is the length of the few-mode fiber in the mode converter and mode demultiplexer. The delay difference between each mode and the fundamental mode is Δτ. 2，1 ,Δτ 3，1, …, Δτ m-1，1 c is the speed of light in a vacuum, n eff1 The effective refractive index of the fundamental mode;

[0022] The pointing angles of the M beams formed are θ1, θ2, ..., θ M The expression for the far-field radiation pattern E SA (θ) is:

[0023]

[0024] Where θ is the angle in the far field, each beam is formed by m array elements, there are n subarrays, k is the wave number, d is the element spacing of the phased array antenna module, exp is the exponential function with the natural constant e as the base, and j is the imaginary unit.

[0025] The far-field radiation pattern is received by the receiving antenna module at each angle and the amplitude is measured by the signal processing module; in the power-division-based few-mode optically controlled co-frequency multi-beamforming system, scanning of different beams is achieved by switching the optical switching state.

[0026] Compared with the prior art, the advantages of the present invention are as follows:

[0027] The present invention relates to a power-allocation-based few-mode optically controlled co-frequency multi-beamforming system and method. By using devices such as few-mode optical fibers and Bragg gratings, the system achieves equal time delay of signals and enables multiple signals to share a single delay system, thereby reducing system size and cost. The system employs a power allocation method to allow multiple beams to operate at the same frequency. Compared with traditional single-mode optically controlled co-frequency multi-beamforming systems based on wavelength division multiplexing (WDM) technology, this system improves spectrum utilization and enables simultaneous large-area scanning of multiple beams. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0029] Figure 1 This is a schematic diagram of the structure of the power-division-based few-mode optically controlled co-frequency multi-beamforming system described in this invention;

[0030] Figure 2 This is a schematic diagram of the optical true delay network module structure described in this invention;

[0031] Figure 3 This is a schematic diagram of the delay multiplexing module structure described in this invention;

[0032] Figure 4 This is a schematic diagram of the structure of the power allocation-based few-mode optically controlled co-frequency multi-beamforming system described in the example.

[0033] Figure 5 The diagram shows the theoretical, experimental, and fitting results of the amplitude of the dual beams formed by the power-division-based few-mode optically controlled co-frequency multi-beamforming system at various angles when the antenna array has 3 elements and the frequency is 6 GHz.

[0034] Among them, (a) shows the theoretical, experimental and fitting results of the amplitude of the two beams with pointing angles of 12° and -48° at various angles;

[0035] (b) Theoretical, experimental, and fitting results for the amplitude of two beams with pointing angles of 28° and -29° at various angles;

[0036] Figure 6 The antenna pattern of a power-allocation-based few-mode optically controlled co-frequency multi-beamforming system with 3 antenna array elements and a frequency of 6 GHz.

[0037] Among them, (a) shows the theoretical, experimental, and fitted antenna patterns with pointing angles of 12° and -48°, 28° and -29°;

[0038] (b) To generate experimental fitting results with two pointing angles of 12° and -48°, 28° and -29°, 16° and -43°, and 20° and -36°;

[0039] In the diagram: 1. Tunable laser module; 2. Signal generation module; 3. Electro-optic modulation module; 4. Optical true delay network module; 5. Photodetector module; 6. Phased array antenna module; 7. Receiving antenna module; 8. Signal processing module; 9. Beam splitter; 10. Mode converter; 11. Few-mode beam splitter; 12. Delay multiplexing module; 13. Mode demultiplexer; 14. Compensated single-mode fiber; 15. N*N optical switch; 16. Circulator; 17. Few-mode fiber Bragg grating group; 18. Detailed Implementation

[0040] The embodiments of the technical solution of the present invention will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and are therefore only examples and should not be used to limit the scope of protection of the present invention.

[0041] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0042] Example 1

[0043] This example establishes a few-mode optically controlled co-frequency multi-beamforming system based on power allocation, and its block diagram is as follows: Figure 1 As shown, it consists of a tunable laser module 1, a signal generation module 2, an electro-optic modulation module 3, an optical true delay network module 4, a photoelectric detection module 5, a phased array antenna module 6, a receiving antenna module 7, and a signal processing module 8. The output port of the tunable laser module 1 is connected to the optical signal input port of the electro-optic modulation module 3; the output port of the signal generation module 2 is connected to the electrical signal input port of the electro-optic modulation module 3; the output port of the electro-optic modulation module 3 is connected to the input port of the optical true delay network module 4; the output port of the optical true delay network module 4 is connected to the input port of the photoelectric detection module 5; the output port of the photoelectric detection module 5 is connected to the input port of the phased array antenna module 6; and the output port of the receiving antenna module 7 is connected to the input port of the signal processing module 8.

[0044] The workflow for this example is as follows:

[0045] The output power and wavelength of a tunable laser are set, and the generated continuous light is used as the optical carrier of the system. A vector network analyzer generates a microwave signal, which is modulated onto the optical carrier by an electro-optic modulator in the form of amplitude and phase information. The modulated signal light passes through a beam splitter and is then connected to a mode converter to excite different modes. Each mode is output through an optical switch to a few-mode fiber Bragg grating connected to a circulator, reflected, and then output by another optical switch to a mode demultiplexer. After separation, each mode passes through a compensated single-mode fiber to achieve the required equal time delay for different beams. Each optical signal simultaneously enters a corresponding photodetector for photoelectric conversion. The converted electrical signals are then input to the ports of the phased array antenna. In the far field, the receiving antenna receives the signal amplitude of the beam at each angle and inputs the signal to the vector network analyzer for measurement. Based on the measurement results, the radiation pattern of the power-allocation-based few-mode optically controlled co-frequency multi-beamforming system can be plotted.

[0046] The connection method is as follows:

[0047] The output port 11 of the tunable laser module 1 is connected to the optical signal input port 31 of the electro-optic modulation module 3. The output port of the signal generation module 2 is connected to the electrical signal input port 32 of the electro-optic modulation module 3. The output port 33 of the electro-optic modulation module 3 is connected to the input port 411 of the beam splitter 41. The output port 412 of the beam splitter 41 is connected to the single-mode fiber input port of the mode converter 42. The output port of the mode converter 42 is connected to the input port of the few-mode beam splitter 43. The output port of the few-mode beam splitter 43 is connected to the input port 4411 of the 2*2 optical switch 441. The output port 4412 of the 2*2 optical switch 441 is connected to the circulator 442. Port 4421 and port 4422 of circulator 442 are connected to few-mode fiber Bragg grating group 443. Port 4423 of circulator 442 is connected to input port 4413 of 2*2 optical switch 441. Output port 4414 of 2*2 optical switch 441 is connected to input port of mode demultiplexer 45. Output port of mode demultiplexer 45 is connected to input port of compensated single-mode fiber 46. Output port of compensated single-mode fiber 46 is connected to input port of photoelectric detection module 5. Output port of photoelectric detection module 5 is connected to input port of phased array antenna module 6. Output port of receiving antenna module 7 is connected to input port of signal processing module 8.

[0048] In this embodiment, the tunable laser module 1 uses a semiconductor narrow linewidth laser from Feiboyuan Optoelectronics Technology Co., Ltd., which generates continuous 1550nm wavelength light waves with an output power of 10dBm. The narrow linewidth laser has low phase noise and has little impact on the system performance of this embodiment.

[0049] In this embodiment, the signal generation module 2 is an R&S ZNB40 vector network analyzer, set to output a microwave signal with a frequency of 4-6 GHz and an output power of 10 mW. The microwave signal generated by the vector network analyzer is connected to the electrical signal input port of the electro-optic modulator module 3 via a phase-stabilized cable and modulated onto the optical carrier. The optical carrier signal is then used by the optical true delay network module 4 to achieve delay control of multiple beams.

[0050] The schematic diagram of optical true delay network module 4 in this example is as follows: Figure 2As shown, photonic lantern A is selected as the mode converter, and photonic lanterns B and C are selected as mode demultiplexers, with an average insertion loss of 2.5 dB. The selected photonic lanterns are all-fiber 6-mode selective multiplexers from OLKIN OPTICS. In this example, three modes are selected: LP01, LP11a, and LP21a. The differential group delays between modes are 2.8 ps / m between LP01 and LP11a, and 5.9 ps / m between LP01 and LP21a. The mode signals of every two branches can share a set of gratings to achieve delay. The schematic diagram of delay multiplexing module 4 is shown below. Figure 3 As shown.

[0051] In this embodiment, the photoelectric detection module 5 adopts a high-speed APD detection module from Beijing Kangguan Company, with a noise voltage of less than 20mV, a working bandwidth of 6.8GHz, a minimum optical power of -33dBm, and a gain of 4KV / W. It meets the minimum detection optical power after system loss, receives the signal light from the output end of the compensated single-mode fiber 47, and converts the signal light into an electrical signal for low-noise amplification and output.

[0052] In this embodiment, the phased array antenna module 6 is a customized 4*4 phased array antenna, operating at a frequency of 4-6 GHz, with an element spacing d. x =d x =26mm, when the maximum radiation angle θ max =60° satisfies

[0053] In this embodiment, the receiving antenna module 7 is a pyramidal horn antenna, which adopts vertical polarization.

[0054] In this embodiment, the signal processing module 8 is a ZNB40 vector network analyzer from R&S Corporation. In the far field range, the electrical signal received by the receiving antenna module 7 is used to obtain the amplitude of the beam at each angle through the S21 parameter in the vector network analyzer.

[0055] Example 2

[0056] This embodiment provides a few-mode optically controlled co-frequency multi-beamforming method based on power allocation. A detailed system block diagram is shown below. Figure 4 As shown, the specific steps include the following:

[0057] The tunable laser is set to an output power of 10 dBm and a wavelength of 1550 nm to provide an optical carrier for the system. A vector network analyzer generates a 6 GHz microwave signal with an output power of 10 mW, which is modulated onto the optical carrier by a Mach-Zehnder modulator. The modulated signal light passes through a beam splitter to generate three in-phase and in-amplitude signal lights, which are then excited into three modes: LP01, LP11a, and LP21a by a mode-selective photonic lantern. The excited mode signals are split into two paths by a few-mode beam splitter and then enter their corresponding optical switches. When the optical switches are in a parallel state, due to mode dispersion, the propagation speeds of each mode in the few-mode fiber differ. After transmission through a certain length of few-mode fiber, a time delay occurs between the modes. Since a certain length of few-mode fiber exists within the mode converter and mode demultiplexer, to ensure that the time delay difference between the modes is only generated by the few-mode fiber Bragg grating, the LP01 and LP11a modes require compensation of the single-mode fiber after the mode demultiplexer. The compensation length is:

[0058]

[0059] Where c is the speed of light in a vacuum, and Δτ is the unit length delay difference between the three selected modes. 11a,01 =5.9ps / m, Δτ 21a,01 = 2.8 ps / m, the effective refractive index n of the LP01 mode in this example few-mode fiber eff01 The effective refractive index n of the LP11a mode is 1.4488. eff11a The effective refractive index n of the LP21a mode is 1.4474. eff21a It is 1.4456.

[0060] When the optical switch is in the crossover state, the mode signal enters the circulator and the few-mode fiber Bragg grating group. Different modes are reflected at their corresponding few-mode fiber Bragg gratings, resulting in equal time delays. Mode coupling can only occur when the few-mode fiber Bragg grating meets the phase-matching condition. In a grating with a period of Λ, the effective refractive index is n. eff1 n eff2 When the modes are coupled together, the Bragg wavelength is:

[0061] λ'=(n eff1 +n eff2 )Λ (2)

[0062] Let λ' = 1550.00 nm. When writing a third-order fiber Bragg grating, we can obtain from formula (2) that the period of FBG1 is 1604.78 nm, at which time the LP01 mode undergoes total internal reflection; the period of FBG2 is 1606.33 nm, at which time the LP11a mode undergoes total internal reflection; the period of FBG3 is 1608.33 nm, at which time the LP21a mode undergoes total internal reflection.

[0063] The antenna pointing angle is designed using a power allocation method. The required delay difference is calculated and applied to the design of the position of the few-mode fiber Bragg grating, so that the pointing angle of the main lobe of each beam coincides with that of the nth sidelobe with the larger peak sidelobe level. The pointing angle of the nth sidelobe is:

[0064]

[0065] In this example, the number of antenna array elements N for each beam is 3. The peak sidelobe level of the first sidelobe is relatively large. When the pointing angles of the two beams are 12° and -48°, according to formula (3), the peak sidelobe levels of the corresponding first sidelobe are -48° and 12°, respectively. The delay difference required for each beam is 18ps and 64ps, respectively.

[0066] By changing the optical switching state so that the pointing angles of the two beams are 28° and -29°, according to formula (3), the peak sidelobe levels of the corresponding first sidelobe are -29° and 28°, respectively, and the required delay differences for each beam are 41ps and 42ps, respectively. The Bragg grating group is LP. 01 LP 11a LP 21a The three modes provide a delay difference of 23 ps. The distance between the few-mode fiber Bragg grating FBG3 and port 2 of the few-mode circulator is: l 11a =(l 01 +20.8)cm、l 21a =(l 11a +10.2)cm.

[0067] Finally, the two signal beams with three equal delays are converted into electrical signals by the high-speed APD detection module and output. The resulting beam is received in the far field by the pyramidal horn antenna, and the amplitude of the beam at each angle is obtained by the S21 parameter in the vector network analyzer.

[0068] Figure 5 (a) Theoretical, experimental and fitting results are given for the amplitude of two beams with pointing angles of 12° and -48° at various angles when the antenna array has 3 elements and a frequency of 6 GHz. Figure 5 (b) Theoretical, experimental and fitting results of the amplitude of two beams with pointing angles of 28° and -29° at various angles are given after changing the light switching state. Power allocation and reasonable design of beam pointing angle enable the dual beams to achieve a pointing angle without main lobe degradation.

[0069] Figure 6Experimental fitting results are presented for an antenna array with 3 elements and a frequency of 6 GHz, forming two pointing angles of 12° and -48°, 28° and -29°, 16° and -43°, and 20° and -36°. In this system, co-channel interference is suppressed, and dual-beam scanning with no main lobe degradation can be achieved at multiple angles. This shows that power distribution has a suppressive effect on co-channel interference in co-channel multi-beam systems.

[0070] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0071] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0072] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A few-mode optical frequency reusing multi-beam forming system based on power allocation, characterized in that, The system includes a tunable laser module (1), a signal generation module (2), an electro-optic modulation module (3), an optical true delay network module (4), a photoelectric detection module (5), a phased array antenna module (6), a receiving antenna module (7), and a signal processing module (8). The output port of the tunable laser module (1) is connected to the optical signal input port of the electro-optic modulation module (3), the output port of the signal generation module (2) is connected to the electrical signal input port of the electro-optic modulation module (3), the output port of the electro-optic modulation module (3) is connected to the input port of the optical true delay network module (4), the output port of the optical true delay network module (4) is connected to the input port of the photoelectric detection module (5), the output port of the photoelectric detection module (5) is connected to the input port of the phased array antenna module (6), and the output port of the receiving antenna module (7) is connected to the input port of the signal processing module (8). The system operates as follows: a tunable laser module generates continuous light; a microwave signal is modulated onto an optical carrier by an electro-optic modulation module in the form of amplitude and phase information; the modulated signal light is then split by a beam splitter to generate… The same amplitude and phase signal light of the road, and will The single-mode end of the optical signal access mode converter outputs a signal from the few-mode end that includes... A higher-order mode of signal light, from the signal light * The optical switch output is connected to a few-mode fiber Bragg grating array via a circulator. The position of each few-mode fiber Bragg grating is designed according to the power distribution. Each mode is reflected and then... * The optical switch output is sent to the mode demultiplexer and compensated through a compensated single-mode fiber to ultimately achieve the equal time delay required for different beams.

2. A few-mode optical co-frequency multi-beam forming system based on power allocation according to claim 1, wherein, The tunable laser module (1) generates a continuous 1550nm wavelength light wave with an output power of 10dBm; The signal generation module (2) generates a microwave signal with a frequency of 4-6 GHz and an output power of 10 mW.

3. A few-mode optical co-frequency multi-beam forming system based on power allocation according to claim 1, wherein, The electro-optic modulation module (3) uses a Mach-Zehnder modulator to modulate the microwave signal from the signal generation module (2) onto the optical carrier generated by the tunable laser module (1).

4. A few-mode optical co-frequency multi-beam forming system based on power allocation according to claim 1, wherein, The optical true delay network module (4) includes a beam splitter (41), a mode converter (42), a few-mode beam splitter (43), a delay multiplexing module (44), a mode demultiplexer (45), and a compensated single-mode fiber (46). The output port of the electro-optic modulation module (3) is connected to the input port of the beam splitter (41), the output port of the beam splitter (41) is connected to the input port of the mode converter (42), the output port of the mode converter (42) is connected to the input port of the few-mode beam splitter (43), the output port of the few-mode beam splitter (43) is connected to the input port of the delay multiplexing module (44), the output port of the delay multiplexing module (44) is connected to the input port of the mode demultiplexer (45), the output port of the mode demultiplexer (45) is connected to the input port of the compensated single-mode fiber (46), and the output port of the compensated single-mode fiber (46) is connected to the input port of the photoelectric detection module (5).

5. A few-mode optical co-frequency multi-beam forming system based on power allocation according to claim 4, wherein, The beam splitter (41) is a 1: out of 2 equal beam splitters; the few-mode beam splitter (43) is a 1: out of 2 equal beam splitters.

6. A few-mode optical co-frequency multi-beam forming system based on power allocation according to claim 4, wherein, The delay multiplexing module (44) includes Optical switch (441), circulator (442), and few-mode fiber Bragg grating assembly (443); the output port of the few-mode beam splitter (43) is connected to Input port 1 of the optical switch (441), The output port 1 of the optical switch (441) is connected to port 1 of the circulator (442), port 2 of the circulator (442) is connected to the few-mode fiber Bragg grating group (443), and port 3 of the circulator (442) is connected to... Input port 2 of the optical switch (441), The output port 2 of the optical switch (441) is connected to the input port of the mode demultiplexer (45).

7. A few-mode optical co-frequency multi-beam forming system based on power allocation according to claim 6, wherein, The few-mode fiber Bragg grating group (443) is formed by one few-mode Bragg grating cascade, and reflects one mode.

8. A few-mode optical co-frequency multi-beam forming system based on power allocation according to claim 1, wherein, The photoelectric detection module (5) is used to convert the detected optical signal into an electrical signal, amplify it, and then output it. The photoelectric detection module (5) can detect optical signals of -30dBm.

9. A few-mode optical co-frequency multi-beam forming system based on power allocation according to claim 1, wherein, The compensation for the single-mode fiber specifically includes the following: To ensure that the delay difference is zero when the signal does not pass through the Bragg grating, the compensation length for each mode is... The expression is as follows: （1） The signal light is formed after passing through the photoelectric detection module. One beam is emitted into free space. Each beam shares a few-mode fiber Bragg grating array, and each beam contains Each array element, The length of the few-mode fiber in the mode converter and mode demultiplexer is given, and the delay difference between each mode and the fundamental mode is given. , The speed of light in a vacuum The effective refractive index of the fundamental mode; Formed The pointing angles corresponding to each beam are respectively The expression for the far-field radiation pattern for: （2） wherein is an angle in the far field range, each beam is formed by array elements, there are sub-arrays, is the wave number, is the element spacing of the phased array antenna module, is the exponential function with the natural constant as base, is the imaginary unit; The far-field radiation pattern is received by the receiving antenna module at each angle and the amplitude is measured by the signal processing module; in the power-division-based few-mode optically controlled co-frequency multi-beamforming system, scanning of different beams is achieved by switching the optical switching state.

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