An optical waveguide array structure based on multimode optical fiber and its design method

Abstract

The present invention relates to an optical waveguide array structure based on multimode optical fiber and its design method. The optical waveguide array structure comprises multiple optical waveguide composite structures arranged along the length direction, the optical waveguide composite structure comprising a first curved waveguide, a first straight waveguide, and multiple single-mode waveguide structures arranged along the length direction. The first curved waveguide and the first straight waveguide are sequentially connected to form a waveguide guidance region. The multiple single-mode waveguide structures form a waveguide selection region. The single-mode waveguide structure is composed of a second straight waveguide and a second curved waveguide connected together. The second straight waveguide forms a waveguide coupling with the first straight waveguide, and the terminal end of the second curved waveguide is perpendicular to the cladding interface of the multimode optical fiber. By inscribing a structure for guiding light waves at different positions on the multimode optical fiber and adjusting the parameters of the optical waveguide structure, an optical waveguide array with wavelength selectivity and energy consistency is formed, solving the problem of difficulty in controlling the wavelength and energy of propagating light in array structures for multimode optical fiber light field control.

Description

Technical Field

[0001] The present invention relates to the technical field of optical elements, and in particular to an optical waveguide array structure based on multimode optical fiber and a design method thereof. Background Art

[0002] With the rapid development of information and communication technology, optical communication, as an important component, has demonstrated tremendous potential in high-speed, large-capacity, and low-loss transmission. Optical fiber, as the fundamental transmission medium for optical communication, is typically manufactured through methods such as material doping, stretching, and heat treatment. The manufacturing process is complex and costly, and device performance is limited by the materials and processes. For example, traditional light field manipulation technologies, such as lenses, mirrors, and beam splitters, are difficult to quickly adjust or adapt to varying light field requirements. Manufacturing and integration involve complex processes and high costs, making them unsuitable for distributed applications. Common optical fiber devices with controllable wavelength selectivity and energy include tunable filters, tunable fiber Bragg gratings, and tunable fiber couplers. However, their stability and reliability are affected by the environment, and the manufacturing process is complex and costly, making them unsuitable for application in distributed systems.

[0003] Wide-area ultrasound coverage requires the ability to multiplex a large number of photoacoustic transducers on a single optical fiber, with each transducer generating an evenly balanced ultrasonic signal intensity. Currently, no effective solution exists for this problem. Therefore, a light-emitting waveguide structure is urgently needed that can flexibly control the intensity of the coupled output light, thereby achieving balanced light output along the fiber, while also utilizing wavelength division multiplexing to double the multiplexing capacity. Summary of the Invention

[0004] The present invention provides an optical waveguide array structure based on multimode optical fiber and a design method thereof. By inscribing the structure of the guided light waves in the multimode optical fiber, the refractive index, shape, size and position of the waveguide structure are changed. Without the need for complex preparation processes, the refractive index, shape, size and position of the waveguide can be precisely controlled, thereby achieving controllable adjustment of the energy coupling ratio and wavelength selectivity of the structure, greatly improving the flexibility and performance of the device.

[0005] The present invention solves the above-mentioned technical problems as follows: an optical waveguide array structure based on a multimode optical fiber, comprising a plurality of optical waveguide composite structures arranged along the length direction of the multimode optical fiber, wherein the optical waveguide composite structure comprises a first curved waveguide, a first straight waveguide, and a plurality of single-mode waveguide structures arranged equidistantly along the length direction of the multimode optical fiber;

[0006] The starting end of the first curved waveguide is arranged in the core region of the multimode optical fiber, and the terminal end is arranged in the cladding region of the multimode optical fiber. The first straight waveguide is arranged in the cladding region of the multimode optical fiber. The terminal end of the first curved waveguide is connected to the starting end of the first straight waveguide to form a waveguide guiding region. The terminal end of the first straight waveguide faces the next optical waveguide composite structure.

[0007] A plurality of the single-mode waveguide structures form a waveguide selection area. The single-mode waveguide structure includes a second straight waveguide and a second curved waveguide connected in sequence. The second straight waveguide is arranged in the cladding region of the multimode optical fiber between the first straight waveguide and the cladding interface of the multimode optical fiber. The terminal end of the second straight waveguide is connected to the starting end of the second curved waveguide. The terminal end of the second curved waveguide is perpendicular to the cladding interface of the multimode optical fiber (the terminal end of the second curved waveguide can be arranged in the cladding region or connected to the cladding interface); the starting end direction of the second straight waveguide corresponds to the starting end direction of the first straight waveguide.

[0008] The first straight waveguide in each optical waveguide composite structure forms a waveguide coupling with the corresponding second straight waveguide.

[0009] The first curved waveguide is used to guide part of the light wave energy of the fiber core, the first straight waveguide is used to transmit the light wave from the first curved waveguide, the second straight waveguide is waveguide-coupled with the first straight waveguide, and the second curved waveguide guides the light wave energy transmitted by the second straight waveguide to the designated cladding interface.

[0010] Preferably, the first curved waveguide is an S-shaped waveguide, and the second curved waveguide is an L-shaped waveguide.

[0011] Designing the first curved waveguide to be S-shaped can reduce bending loss and also help connect with the straight waveguide structure. Designing the second curved waveguide to be L-shaped can reduce loss and also help light waves transmit to the cladding interface.

[0012] Preferably, the first curved waveguide is formed by connecting two centrosymmetric arcs.

[0013] Preferably, the connecting section between the second curved waveguide and the second straight waveguide is an arc chamfer, and a straight waveguide is provided between the connecting section of the second curved waveguide and the terminal.

[0014] Preferably, the width of the first curved waveguide is 8-12 μm, the length of the curved arc is 1000-1500 μm, the bending radius of the arc is 3-40 μm, and the refractive index is 10 -3 ~10 -2 The center of the first curved waveguide (1) (i.e., the connection point of the two arc waveguides) is 0 to 5 μm away from the core center of the multimode optical fiber.

[0015] Preferably, the width of the first linear waveguide is 8 to 12 μm, the length is 10,000 to 20,000 μm, and the refractive index is 10 -3 ~10 -2 The first curved waveguide has the same width and refractive index as the first straight waveguide.

[0016] Preferably, the width of the second curved waveguide is 5 to 8 μm, the total length of the connecting section and the straight waveguide is 12 to 17 μm; the refractive index is 10 -3 ~10 -2 .

[0017] Preferably, the width of the second straight waveguide is 5-8 μm, and the length is 500-1500 μm; the coupling distance between the second straight waveguide and the first curved waveguide is 8-10 μm; the refractive index is 10 -3 ~10 -2 The width and refractive index of the second curved waveguide are consistent with those of the second straight waveguide.

[0018] By designing the structure and parameters of the first curved waveguide, the energy of the light wave entering it is controlled. After passing through the first curved waveguide, the light wave is input into the first straight waveguide. When the light signal reaches the perpendicular region of the second straight waveguide, the two straight waveguides form a typical directional coupler. Because directional couplers can achieve controllable energy coupling ratios and wavelength selectivity through structural parameter regulation, when the structure and parameters of the second straight waveguide are constant, the second straight waveguide only couples light waves with a specific energy and a specific central wavelength, which are ultimately guided by the second curved waveguide to the specified cladding interface location.

[0019] The present invention provides a method for structuring an optical waveguide array based on a multimode optical fiber as described above, comprising the following steps:

[0020] 1) Setting the operating wavelength and output energy of the optical waveguide array structure, thereby determining the wavelength and energy output by each single-mode waveguide structure;

[0021] 2) Modeling the optical waveguide array structure through simulation, with the performance parameters determined in step 1) as a target, to determine the structural parameters of the first curved waveguide and the first straight waveguide, and the structural parameters of the second straight waveguide and the second curved waveguide corresponding to each single-mode waveguide structure;

[0022] 3) Based on the structural parameters determined in step 2, a first curved waveguide, a first straight waveguide, and a second straight waveguide and a second curved waveguide corresponding to each single-mode waveguide structure are sequentially inscribed in the optical fiber using a femtosecond laser, thereby completing a single optical waveguide composite structure. After a set number of optical waveguide composite structures are inscribed in accordance with this step, the optical waveguide array structure is obtained.

[0023] The first bending waveguide in the guiding region is connected to all the working wavelengths (λ1…λ n …λ m ) is non-selectively guided to the first straight waveguide. The structural parameters of the second straight waveguide are set according to the working wavelength λ1 required by the single single-mode waveguide structure. Similarly, the working wavelength band λ required by the nth single-mode waveguide structure is set according to the working wavelength λ n Set the structural parameters corresponding to the second linear waveguide. Similarly, according to the working band λ required by the mth single-mode waveguide structure m Set the structural parameters of the corresponding second linear waveguide. Then the single-mode waveguide structure of the selected area is realized...n...m, which guides λ1...λ n …λ m The light waves in the working band can be matched, and the coupling energy can be made consistent by setting the structural parameters, that is, a single optical waveguide composite structure can be completed.

[0024] The optical waveguide composite structure with similar structure is written at different length positions of the optical fiber to form the optical waveguide array structure in the multimode optical fiber. All the working wavelengths (λ1…λ n …λ m ) is non-selectively guided into the optical waveguide composite structure at the front end, and the light wave energy of the unguided working wavelength continues to transmit along the fiber core. When it reaches the optical waveguide composite structure at the rear end, all working wavelength bands are still non-selectively guided into the optical waveguide composite structure. By precisely controlling the structural parameters and position of the selective area structure of the optical waveguide composite structure at the rear end, the light wave energy guided to the optical waveguide composite structure at the rear end is controlled to be consistent, and the corresponding working wavelength (λ1…λ n …λ m )'s structure 5…n…m has the same structure and parameters as the previous optical waveguide composite structure.

[0025] The present invention also provides a light wave transmission method based on the optical waveguide array structure of the multimode optical fiber, comprising the following steps: a first curved waveguide of the first optical waveguide composite structure inputs all the working wavelengths λ1 ...λ n …λ m The light waves are non-selectively guided to the first straight waveguide, the second straight waveguide forms a waveguide coupling with the first straight waveguide, and the light waves of the corresponding wavelength are selected to be transmitted to the corresponding second curved waveguide. The corresponding second curved waveguide transmits the received light wave energy to the designated cladding interface, and the unselected light waves are transmitted along the multimode optical fiber to the next optical waveguide composite structure.

[0026] The present invention also provides an application of the above-mentioned optical waveguide array structure based on multimode optical fiber in the preparation of a photoacoustic transducer. Based on a waveguide structure array with high multiplexing capacity and high energy consistency, it is compounded with a light-heat-acoustic high-efficiency conversion material to prepare a high multiplexing capacity and high-efficiency photoacoustic transducer array. The high-multiplexing capacity photoacoustic transducer can be used to construct a photoacoustic imaging system. In the industrial field, it can be used for non-destructive testing, such as detecting defects inside materials and monitoring chemical changes in the production process; in the medical field, it can be used for tumor detection, vascular imaging, skin disease diagnosis, etc. In addition, combined with optical microscopy technology, the photoacoustic transducer array can construct an optical microscope for high-resolution biological tissue imaging and analysis.

[0027] The working principle of the present invention is:

[0028] In order to achieve distributed light field control, it is necessary to consider the wavelength selectivity and energy coupling ratio of the structure to be accurately controlled. According to the waveguide coupling theory, if light is input from one port, energy transfer occurs through the coupling region, and the coupling efficiency of the two output ports satisfies the following formula:

[0029]

[0030] Where δ represents the detuned oscillation value, and the energy coupling efficiency of the output port is mainly related to the coupling coefficient k, length L and initial phase. At the same time, the coupling coefficient k is related to the size and distribution of the refractive index of the two waveguides, and also to the degree of mode overlap; the coupling energy ratio of the waveguide can be controlled by parameters such as coupling length L, coupling spacing d, width w, and refractive index n.

[0031] The operating wavelength of a waveguide is related to its effective refractive index and structure, and its resonant center wavelength is correlated with the effective refractive index. The width of the waveguide affects the effective refractive index, which in turn affects its resonant center wavelength. The operating wavelength can be precisely controlled by adjusting the waveguide's refractive index and width.

[0032] The beneficial effects of the present invention are:

[0033] 1. The optical waveguide array structure provided by the present invention has a controllable output energy coupling ratio, and each optical waveguide composite structure has a different operating wavelength. When a lightwave of a specific wavelength is input, the first curved waveguide in the guiding region couples a portion of the optical signal at that wavelength to the first linear waveguide. However, only the second linear waveguides in the selective region that meet the coupling conditions will couple a portion of the optical signal from the first linear waveguide, which is then guided to the designated cladding interface by the second curved waveguide. Second linear waveguides that do not meet the operating wavelength do not guide the lightwave, resulting in excellent selectivity for the input wavelength.

[0034] 2. The optical waveguide array structure provided by this invention can double the multiplexing capacity by utilizing wavelength-division multiplexing and space-division multiplexing. The single-mode waveguide structures within the array guide lightwaves of different operating wavelengths. The array allows for distributed transmission and coupling of optical signals within the waveguides, achieving space-division multiplexing on a single optical fiber. Furthermore, within the array structure, optical signals of different wavelengths can be controlled to transmit within different waveguide layers, enabling multiplexing of different wavelengths.

[0035] 3. The optical waveguide array structure provided by this invention precisely controls the propagation path and mode of optical signals, enabling array-based light field control within optical fibers, improving transmission flexibility and functionality. By inscribing distributed waveguide structures within optical fibers, this approach achieves enhanced light field control, increased transmission capacity, reduced signal loss and interference, and the realization of complex optical functions.

[0036] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and to implement it according to the contents of the description, the following preferred embodiments of the present invention are described in detail with reference to the accompanying drawings. The specific implementation methods of the present invention are given in detail by the following embodiments and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0038] Figure 1 Schematic cross-sectional view of a multimode optical fiber-based optical waveguide array structure according to Example 1;

[0039] Figure 2 is a schematic cross-sectional view of the optical waveguide composite structure of Example 1;

[0040] Figure 3 This is a flow chart of the design of the optical waveguide array structure of the multimode optical fiber of Example 2;

[0041] Figure 4 This is a flowchart for writing the optical waveguide array structure of the multimode optical fiber of Example 2.

[0042] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0043] 1. First curved waveguide; 2. First straight waveguide; 3. Second straight waveguide; 4. Second curved waveguide; 5. Single-mode waveguide structure; 10. Optical waveguide composite structure. DETAILED DESCRIPTION

[0044] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0045] Example 1

[0046] like Figure 1 As shown, this embodiment provides an optical waveguide array structure based on a multimode optical fiber, which is composed of a plurality of optical waveguide composite structures 10 arranged equidistantly along the length direction of the multimode optical fiber. Figure 2 As shown, the optical waveguide composite structure 10 is composed of a waveguide guiding region and a waveguide selection region;

[0047] The first curved waveguide 1 and the first straight waveguide 2 are connected in sequence to form a waveguide guiding area; the starting end of the first curved waveguide 1 is arranged in the core area of ​​the multimode optical fiber, and the terminal end is arranged in the cladding area of ​​the multimode optical fiber, and the first straight waveguide 2 is arranged in the cladding area of ​​the multimode optical fiber;

[0048] Three single-mode waveguide structures 5 equidistantly arranged along the length of the multimode optical fiber form a waveguide selection area; the single-mode waveguide structure 5 includes a second straight waveguide 3 and a second curved waveguide 4. The second straight waveguide 3 is arranged in the cladding area between the first straight waveguide 2 and the cladding interface of the multimode optical fiber. The terminal end of the second straight waveguide 3 is connected to the starting end of the second curved waveguide 4, and the terminal end of the second curved waveguide 4 is perpendicular to the cladding interface of the multimode optical fiber.

[0049] The first linear waveguide 2 in each optical waveguide composite structure 10 forms a waveguide coupling with the corresponding plurality of second linear waveguides 3 .

[0050] This embodiment takes the optical waveguide composite structure 10 as an example, where the output energy ratio is 10%, the multimode optical fiber cladding diameter is 125 μm, the core diameter is 50 μm, and the three single-mode waveguide structures 5 have operating wavelengths of 0.85 μm, 1.3 μm, and 1.55 μm. The structural parameters of the first curved waveguide 1, the first straight waveguide 2, the second straight waveguide 3, and the second curved waveguide 4 are as follows:

[0051] The first curved waveguide 1 is S-shaped and is composed of two circular arcs with a central symmetry and a bending radius of 35 μm. It has a width of 10 μm and a length of 1000 μm. Its center is set at the core center of the multimode optical fiber. The first straight waveguide 2 has a width of 10 μm and a length of 10000 μm. The refractive index of the first curved waveguide is the same as that of the first straight waveguide and is increased by two orders of magnitude (1×10 -2 ).

[0052] When the operating wavelength of the first single-mode waveguide structure 5 is within the 0.85μm band, the coupling spacing between the second straight waveguide 3 and the first straight waveguide 2 is 8μm, the length of the second straight waveguide 3 is 1000μm, and the width is 5μm; the second curved waveguide 4 is L-shaped, consisting of a 1 / 4 arc connected by a straight line, with a length of 17μm and a width of 8μm.

[0053] When the operating wavelength of the second single-mode waveguide structure 5 is within the 1.3μm band, the coupling spacing between the second straight waveguide 3 and the first straight waveguide 2 is 9μm, the length of the second straight waveguide 3 is 1000μm, and the width is 7μm; the second curved waveguide 4 is L-shaped, consisting of a 1 / 4 circular arc connected by a straight line, with a length of 14μm and a width of 8μm.

[0054] When the operating wavelength of the third single-mode waveguide structure 5 is within the 1.55 μm band, the coupling spacing between the second straight waveguide 3 and the first straight waveguide 2 is 10 μm, the length of the second straight waveguide 3 is 1000 μm, and the width is 8 μm; the second curved waveguide 4 is L-shaped, consisting of a 1 / 4 arc connected by a straight line, with a length of 12 μm and a width of 8 μm.

[0055] Example 2

[0056] like Figure 3-4 As shown, this embodiment provides a method for designing an optical waveguide array structure based on a multimode optical fiber as described in Example 1, which specifically includes the following steps:

[0057] 1) The operating wavelength and output energy of the optical waveguide array structure are set to determine the wavelength and energy output by each single-mode waveguide structure 5. In this embodiment, the output energy ratio of the optical waveguide composite structure 10 is 10%, and the operating wavelengths of the three single-mode waveguide structures 5 are 0.85 μm, 1.3 μm, and 1.55 μm.

[0058] 2) Using the performance parameters determined in step 1) as a target, the optical waveguide array structure is modeled through simulation to determine the structural parameters of the first curved waveguide 1 and the first straight waveguide 2, and the structural parameters of the second straight waveguide 3 and the second curved waveguide 4 corresponding to each single-mode waveguide structure 5, as follows;

[0059] The first curved waveguide 1 is S-shaped and is composed of two circular arcs with a central symmetry and a bending radius of 35 μm. The width is 10 μm and the length is 1000 μm. The first straight waveguide 2 is 10 μm wide and 10000 μm long. The refractive index of the waveguides is the same and increases by 1×10 relative to the refractive index of the core. -2 about.

[0060] When the operating wavelength of the first single-mode waveguide structure 5 is within the 0.85μm band, the coupling spacing between the second straight waveguide 3 and the first straight waveguide 2 is 8μm, the length of the second straight waveguide 3 is 1000μm, and the width is 5μm; the second curved waveguide 4 is L-shaped, consisting of a 1 / 4 arc connected by a straight line, with a length of 17μm and a width of 8μm.

[0061] When the operating wavelength of the second single-mode waveguide structure 5 is within the 1.3μm band, the coupling spacing between the second straight waveguide 3 and the first straight waveguide 2 is 9μm, the length of the second straight waveguide 3 is 1000μm, and the width is 7μm; the second curved waveguide 4 is L-shaped, consisting of a 1 / 4 circular arc connected by a straight line, with a length of 14μm and a width of 8μm.

[0062] When the operating wavelength of the third single-mode waveguide structure 5 is within the 1.55 μm band, the coupling spacing between the second straight waveguide 3 and the first straight waveguide 2 is 10 μm, the length of the second straight waveguide 3 is 1000 μm, and the width is 8 μm; the second curved waveguide 4 is L-shaped, consisting of a 1 / 4 arc connected by a straight line, with a length of 12 μm and a width of 8 μm.

[0063] 3) Based on the structural parameters determined in step 2, a first curved waveguide 1, a first straight waveguide 2, and a second straight waveguide 3 and a second curved waveguide 4 corresponding to each single-mode waveguide structure 5 are sequentially inscribed in the optical fiber using a femtosecond laser, thereby completing a single optical waveguide composite structure 10.

[0064] 4) After the writing is completed, the written area is inspected using an optical microscope. The waveguide structure is observed to be smoothly connected, with no obvious defects or cracks. The waveguide's refractive index change and waveguide width are consistent, indicating good writing quality. Testing is performed using pulse energies of specific wavelengths (0.85μm, 1.3μm, and 1.55μm). An energy meter is used to measure the energy of the fiber core before and after processing, as well as the energy of the second curved waveguide 4. Each time the second curved waveguide 4 is processed, a pulse energy of a different specific wavelength is used to test the second curved waveguide 4 to ensure that each second curved waveguide 4 has wavelength selectivity and a controllable energy coupling ratio.

[0065] 5) After a set number of optical waveguide composite structures 10 are written according to the above steps, the optical waveguide array structure is obtained.

[0066] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in this industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of protection of the technical solution of the present invention.

Claims

1. An optical waveguide array structure based on multimode optical fiber, characterized in that: The optical waveguide composite structure (10) comprises a plurality of optical waveguide composite structures (10) arranged along the length direction of a multimode optical fiber, wherein the optical waveguide composite structure (10) comprises a first curved waveguide (1), a first straight waveguide (2), and a plurality of single-mode waveguide structures (5) arranged at equal distances along the length direction of the multimode optical fiber; The starting end of the first curved waveguide (1) is arranged in the core region of the multimode optical fiber, and the terminal end is arranged in the cladding region of the multimode optical fiber. The first straight waveguide (2) is arranged in the cladding region of the multimode optical fiber. The terminal end of the first curved waveguide (1) is connected to the starting end of the first straight waveguide (2) to form a waveguide guiding region. A plurality of the single-mode waveguide structures (5) form a waveguide selection region, wherein the single-mode waveguide structure (5) comprises a second straight waveguide (3) and a second curved waveguide (4) connected in sequence, wherein the second straight waveguide (3) is arranged in the cladding region of the multimode optical fiber between the first straight waveguide (2) and the cladding interface of the multimode optical fiber, wherein the terminal end of the second straight waveguide (3) is connected to the starting end of the second curved waveguide (4), and the terminal end of the second curved waveguide (4) is perpendicular to the cladding interface of the multimode optical fiber; The first straight waveguide (2) in each optical waveguide composite structure (10) forms a waveguide coupling with the corresponding plurality of second straight waveguides (3); The first curved waveguide (1) of the first optical waveguide composite structure (10) non-selectively guides light waves of all working wavelengths of the input multimode optical fiber to the first straight waveguide (2); the second straight waveguide (3) forms a waveguide coupling with the first straight waveguide (2) and selects light waves of corresponding wavelengths to be transmitted to the corresponding second curved waveguide (4); the corresponding second curved waveguide (4) transmits the received light wave energy to the designated cladding interface, and the unselected light waves are transmitted along the multimode optical fiber to the next optical waveguide composite structure (10).

2. The optical waveguide array structure based on multimode optical fiber according to claim 1, characterized in that: The first curved waveguide (1) is an S-shaped waveguide, and the second curved waveguide (4) is an L-shaped waveguide.

3. The optical waveguide array structure based on multimode optical fiber according to claim 2, characterized in that: The first curved waveguide (1) is formed by connecting two centrosymmetrical arc waveguide sections.

4. The optical waveguide array structure based on multimode optical fiber according to claim 2, characterized in that: The connecting section between the second curved waveguide (4) and the second straight waveguide (3) is an arc chamfer, and the section between the connecting section of the second curved waveguide (4) and the terminal is a straight waveguide.

5. The optical waveguide array structure based on multimode optical fiber according to claim 3, characterized in that: The width of the first curved waveguide (1) is 8 to 12 μm, the length of the curved arc is 1000 to 1500 μm, the bending radius of the arc in the first curved waveguide (1) is 3 to 40 μm; the refractive index is 10 -3 ~10 -2 The center of the first curved waveguide (1) is 0 to 5 μm away from the core center of the multimode optical fiber.

6. The optical waveguide array structure based on multimode optical fiber according to claim 3, characterized in that: The width of the first linear waveguide (2) is 8 to 12 μm, the length is 10,000 to 20,000 μm, and the refractive index is 10 -3 ~10 -2 .

7. The optical waveguide array structure based on multimode optical fiber according to claim 4, characterized in that: The width of the second curved waveguide (4) is 5 to 8 μm, the total length of the connecting section of the second curved waveguide (4) and the straight waveguide is 12 to 17 μm, and the refractive index is 10 -3 ~10 -2 .

8. The optical waveguide array structure based on multimode optical fiber according to claim 4, characterized in that: The width of the second straight waveguide (3) is 5 to 8 μm, and the length is 500 to 1500 μm; the coupling distance between the second straight waveguide (3) and the first curved waveguide (1) is 8 to 10 μm; the refractive index is 10 -3 ~10 -2 .

9. A method for designing a multimode optical fiber-based optical waveguide array structure according to any one of claims 1 to 8, characterized in that: The following steps are involved: 1) setting the operating wavelength and output energy of the optical waveguide array structure, thereby determining the wavelength and energy output by each single-mode waveguide structure (5) in the optical waveguide composite structure (10); 2) Taking the performance parameters confirmed in step 1) as a target, modeling the optical waveguide array structure through simulation to determine the structural parameters of the first curved waveguide (1) and the first straight waveguide (2), and the structural parameters of the second straight waveguide (3) and the second curved waveguide (4) corresponding to each single-mode waveguide structure (5); 3) Based on the structural parameters determined in step 2, a first curved waveguide (1), a first straight waveguide (2), a second straight waveguide (3), and a second curved waveguide (4) corresponding to each single-mode waveguide structure (5) are sequentially inscribed in the optical fiber by a femtosecond laser, thereby completing a single optical waveguide composite structure (10); after a set number of optical waveguide composite structures (10) are inscribed according to this step, the optical waveguide array structure is obtained.

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