Optical waveguide array structure based on multimode fiber and design method thereof

Abstract

The invention relates to an optical waveguide array structure based on multimode optical fibers and a design method thereof, the optical waveguide array structure comprises a plurality of optical waveguide composite structures arranged along the length direction, and each optical waveguide composite structure comprises a first bent waveguide, a first linear waveguide and a plurality of single-mode waveguide structures arranged along the length direction; the first bent waveguide and the first linear waveguide are sequentially communicated to form a waveguide guide area; the multiple single-mode waveguide structures form a waveguide selection area, each single-mode waveguide structure is formed by connecting a second linear waveguide and a second bent waveguide, the second linear waveguide and the first linear waveguide form waveguide coupling, and the terminal of the second bent waveguide vertically faces the cladding interface of the multimode fiber. The optical waveguide array with wavelength selectivity and energy consistency is formed by performing parameter adjustment on an optical waveguide structure by inscribing a structure of conducting light waves at different positions of the multimode optical fiber, so that the problem that the wavelength and energy of propagation light are difficult to control in an array structure controlled by a multimode optical fiber light field is solved.

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 shown great potential in high-speed, large-capacity, and low-loss transmission. Optical fiber is the basic transmission medium for optical communication. Traditional optical fiber devices are usually prepared by methods such as material doping, stretching, and heat treatment. The preparation process is complex and costly, and the device performance is limited by materials and processes. For example, traditional light field control technologies, such as lenses, reflectors, and beam splitters, are difficult to quickly adjust or adapt to different light field requirements. Manufacturing and integration involve complex processes and high costs, which are not convenient for distributed applications. Common optical fiber devices with controllable wavelength selectivity and energy include: tunable filters, tunable fiber gratings, tunable fiber couplers, etc. However, their stability and reliability are affected by the environment, and the preparation process is complex and costly, which is not conducive to application in distributed systems.

[0003] Large-scale ultrasonic coverage requires that a large number of photoacoustic transducers can be multiplexed on a single optical fiber, and the ultrasonic signal intensity generated by each transducer must be balanced. At present, there is no good solution to this problem. Therefore, there is an urgent need for an optical radiation waveguide structure that can flexibly adjust the intensity of the coupled output light to achieve balanced optical radiation output along the optical fiber, and on the other hand, it is necessary to use wavelength division methods 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 writing a structure for conducting light waves in the multimode optical fiber, the refractive index, shape, size and position of the waveguide structure are changed. Without the need for a complicated preparation process, precise control of the refractive index, shape, size and position of the waveguide can be achieved, 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 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, 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, and 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, wherein the single-mode waveguide structure comprises a second straight waveguide and a second curved waveguide connected in sequence, wherein 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, wherein the terminal of the second straight waveguide is connected to the starting end of the second curved waveguide, and the terminal of the second curved waveguide is perpendicular to the cladding interface of the multimode optical fiber (the terminal of the second curved waveguide may be arranged in the cladding region or may be connected to the cladding interface); and 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 optical 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 optical 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 to be transmitted 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 10000 to 20000 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, and 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 spacing 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 the first curved waveguide 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 vertical region of the second straight waveguide, the two straight waveguides form a typical directional coupler. Since the directional coupler can achieve controllable energy coupling ratio and wavelength selectivity through structural parameter regulation, when the structure and structural parameters of the second straight waveguide are constant, the second straight waveguide only couples light waves of a certain energy and a specific central wavelength, and is finally guided to the specified cladding interface position by the second curved waveguide.

[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) Taking the performance parameters confirmed in step 1) as the target, modeling the optical waveguide array structure through simulation, determining 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, a second straight waveguide and a second curved waveguide corresponding to each single-mode waveguide structure are sequentially engraved in the optical fiber by a femtosecond laser, thereby completing a single optical waveguide composite structure; after a set number of optical waveguide composite structures are engraved according to this step, the optical waveguide array structure is obtained.

[0023] The first curved waveguide in the guiding region is effective for all working wavelengths (λ 1 …λ n …λ m ) is non-selectively guided to the first straight waveguide. According to the working wavelength λ required by the single single-mode waveguide structure 1 Set the structural parameters of the second straight waveguide, and similarly, according to the working band λ required by the nth single-mode waveguide structure n Set the structural parameters corresponding to the second straight waveguide. Similarly, according to the working band λ required by the mth single-mode waveguide structure m Set the structural parameters corresponding to the second straight waveguide. Then the single-mode waveguide structure in the selection area is realized...n...m guides λ 1 …λ n …λ m The light waves in the working band can achieve the consistency of coupling energy through the setting of structural parameters, that is, complete a single optical waveguide composite structure.

[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 input working wavelengths (λ 1 …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 be transmitted 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 (λ 1 …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 as described above, comprising the following steps: a first curved waveguide of the first optical waveguide composite structure transmits all the working wavelengths λ of the input multimode optical fiber to the first curved waveguide of the first optical waveguide composite structure; 1 …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 corresponding wavelengths 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 optical waveguide array structure based on multimode optical fiber as described above 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-sound high-efficiency conversion material to prepare a high multiplexing capacity and high-efficiency photoacoustic transducer array. Photoacoustic transducers with high multiplexing capacity can be used to construct photoacoustic imaging systems. In the industrial field, they can be used for non-destructive testing, such as detecting defects inside materials, monitoring chemical changes in the production process, etc.; in the medical field, they can be used for tumor detection, vascular imaging, skin disease diagnosis, etc.; in addition, combined with optical microscopy technology, photoacoustic transducer arrays can construct optical microscopes for high-resolution biological tissue imaging and analysis, etc.

[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 of the structure and the energy coupling ratio 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 working 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 further affects its resonant center wavelength. The working wavelength can be precisely controlled by adjusting the refractive index and width of the waveguide.

[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 the working wavelength of each optical waveguide composite structure is different. When a light wave of a certain wavelength is input, the first curved waveguide in the guiding area will couple part of the light signal of the wavelength to the first straight waveguide, but only the second straight waveguide in the selection area that meets the coupling condition will couple part of the light signal in the first straight waveguide, and then the second curved waveguide will guide it to the designated cladding interface. The second straight waveguide that does not meet the working wavelength does not guide the light wave, and the structure has good selectivity for the input wavelength.

[0034] 2. The optical waveguide array structure provided by the present invention can realize the doubling of multiplexing capacity by using wavelength division multiplexing and space division multiplexing methods. The single-mode waveguide structure in the array guides light waves of different working wavelengths. The array allows optical signals to be distributedly transmitted and coupled in the waveguide, realizing space division multiplexing on a single optical fiber. At the same time, in the array structure, optical signals of different wavelengths can be controlled to be transmitted in different waveguide layers, realizing the multiplexing of different wavelengths.

[0035] 3. The optical waveguide array structure provided by the present invention can accurately control the propagation path and mode of the optical signal, and can realize array-type light field control in the optical fiber, thereby improving the flexibility and functionality of its transmission. By writing a distributed waveguide structure in the optical fiber, the effects of enhanced light field control capability, increased transmission capacity, reduced signal loss and interference, and realization of complex optical functions are achieved.

[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 implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. The specific implementation of the present invention is given in detail by the following embodiments and their 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 is a cross-sectional schematic diagram of an optical waveguide array structure based on a multimode optical fiber according to Example 1;

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

[0040] Figure 3 The optical waveguide array structure design flow chart 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 listed 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 in conjunction with 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, such as 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, 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 10 equidistantly arranged along the length direction of the multimode optical fiber form a waveguide selection area; the single-mode waveguide structure 10 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 of the second straight waveguide 3 is connected to the starting end of the second curved waveguide 4, and the terminal of the second curved waveguide 4 is perpendicular to the cladding interface of the multimode optical fiber.

[0049] 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 .

[0050] In this embodiment, the output energy ratio of the optical waveguide composite structure 10 is 10%, the cladding diameter of the multimode optical fiber is 125 μm, the core diameter is 50 μm, and the working wavelengths of the three single-mode waveguide structures 10 are 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. The width is 10 μm and the length is 1000 μm. The center of the first straight waveguide 2 is 10 μm wide and 10000 μm long. 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 10 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 10 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 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 10 is within the 1.55μm band, the coupling spacing between the second straight waveguide 3 and the first straight waveguide 2 is 10μm, the length of the second straight waveguide 3 is 1000μm, and the width is 8μm; the second curved waveguide 4 is L-shaped, consisting of a 1 / 4 arc connected by a straight line, with a length of 12μm and a width of 8μm.

[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 Embodiment 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 10. 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 10 are 0.85 μm, 1.3 μm, and 1.55 μm.

[0058] 2) Taking the performance parameters confirmed in step 1) as the target, the optical waveguide array structure is modeled by 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 10, 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 10 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 10 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 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 10 is within the 1.55μm band, the coupling spacing between the second straight waveguide 3 and the first straight waveguide 2 is 10μm, the length of the second straight waveguide 3 is 1000μm, and the width is 8μm; the second curved waveguide 4 is L-shaped, consisting of a 1 / 4 arc connected by a straight line, with a length of 12μm and a width of 8μm.

[0063] 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 10 are sequentially written in the optical fiber by a femtosecond laser, thereby completing a single optical waveguide composite structure 10.

[0064] 4) After the writing is completed, an optical microscope is used to check the writing area, and it is observed that the waveguide structure is smoothly connected, without obvious defects or cracks, and the refractive index change and waveguide width of the waveguide are consistent, showing good writing quality. The pulse energy of a specific wavelength (0.85μm, 1.3μm, 1.55μm) is used for testing, and the energy of the fiber core before and after processing and the energy of the second curved waveguide 4 are tested using an energy meter. Each time the second curved waveguide 4 is processed, a pulse energy of a different specific wavelength is used for testing 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 the 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 the 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 protection scope 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 the 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 equidistantly 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 area, 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 area of ​​the multimode optical fiber 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; The first straight waveguide (2) in each optical waveguide composite structure (10) forms waveguide coupling with a corresponding plurality of second straight waveguides (3).

2. According to claim 1, the optical waveguide array structure based on multimode optical fiber is 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. According to claim 2, an optical waveguide array structure based on multimode optical fiber is characterized in that: The first curved waveguide (1) is formed by connecting two centrosymmetric arc waveguides.

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 first linear waveguide (2) has a width of 8 to 12 μm and a length of 10,000 to 20,000 μm; a refractive index of 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 an optical waveguide array structure based on a multimode optical fiber 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 the target, modeling the optical waveguide array structure through simulation, determining 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 written 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 written according to this step, the optical waveguide array structure is obtained.

10. A light wave transmission method based on a multimode optical fiber optical waveguide array structure according to any one of claims 1 to 8, characterized in that: The invention comprises the following steps: a first curved waveguide (1) of a first optical waveguide composite structure (10) non-selectively guides light waves of all working wavelengths of an input multimode optical fiber to a first straight waveguide (2); a second straight waveguide (3) forms a waveguide coupling with the first straight waveguide (2) to select light waves of corresponding wavelengths for transmission to a corresponding second curved waveguide (4); the corresponding second curved waveguide (4) conducts the received light wave energy to a designated cladding interface; and unselected light waves are conducted along the multimode optical fiber to the next optical waveguide composite structure (10).

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