Sensing demodulation system and method based on multimode fiber and mode comb

Abstract

The invention discloses a sensing demodulation system and method based on a multimode fiber and a mode comb. The sensing demodulation system comprises a laser light source; the multimode optical fiber sensing unit is coupled with the laser light source and generates a light field with different modes of interference distribution based on external disturbance; the mode comb chip comprises a three-dimensional multi-mode optical waveguide and a plurality of electrodes, the refractive index of the three-dimensional multi-mode optical waveguide is changed by heating the electrode array to comb the light fields in different modes, and a detection signal is generated; the control unit is used for controlling the heating amount of the electrode at each position according to the detection signal, so that the signal value of the detection signal is maximum, and a single-mode light spot or a Gaussian-like light spot is obtained at the output end of the mode comb chip; and the demodulation model unit is used for demodulating external disturbance according to the electrodes at different positions when the quasi-single-mode light spots are obtained and the configuration of the electrodes. The system is compact in structure and can demodulate external interference information suffered by the multimode optical fiber without using an imaging system to capture interference images of the output end of the multimode optical fiber.

Description

Technical Field

[0001] The present invention relates to the field of optical sensing technology, and in particular to a sensing demodulation system and method based on multimode optical fiber and mode comb. Background Art

[0002] Sensors, as core components for information perception, typically consist of sensitive and transducer elements. They convert the measured physical quantity into a recognizable signal output according to specific patterns. Fiber optic sensors, with their outstanding advantages such as small size, light weight, strong resistance to electromagnetic interference, corrosion resistance, and good environmental adaptability, have demonstrated significant competitiveness in fields such as industrial inspection, environmental monitoring, and biomedicine. Fiber optic sensors use light waves as information carriers and optical fiber as the transmission medium. They modulate the parameters of the light waves transmitted through the fiber (such as wavelength, polarization state, phase, and intensity) by changes in external physical quantities. The measured signal is then processed by a demodulation system. Fiber optic sensors, represented by fiber Bragg gratings (FBGs), primarily monitor changes in the central wavelength to sense external physical quantities. This requires complex and expensive spectral demodulation equipment such as optical spectrometers (OSAs). Furthermore, the fabrication cost of FBGs is relatively high, requiring sophisticated fabrication equipment. To overcome these technical bottlenecks, sensing technology based on multimode fiber (MMF) has garnered significant attention in recent years. This technology achieves sensing detection by analyzing the multimode interference (MMI) pattern formed at the output end of a multimode optical fiber. When external environmental parameters (such as stress, displacement, and deformation) act on a multimode optical fiber, the spatiotemporal distribution characteristics of this interference pattern are extremely sensitive to external disturbances along the optical fiber's light-guiding path. Compared to traditional FBG technology, this MMF-based sensing solution not only exhibits ultra-high sensitivity but also has advantages such as simple system structure and low cost, offering significant advantages in practical applications.

[0003] In recent years, machine learning (ML) has rapidly developed in image training and recognition, and is widely used to solve various engineering problems. A large number of research studies have used machine learning algorithms to analyze the interference patterns output by multimode fiber sensors and demodulate information about external disturbances affecting the multimode fiber. Machine learning-based demodulation methods first require building an imaging system, including components such as a free-space lens and a camera, at the output end of the multimode fiber to capture the interference image at the output end of the multimode fiber. Then, by repeatedly perturbing the multimode fiber, a large number of interference images corresponding to the fiber state are collected to establish an image dataset. Machine learning algorithms are then used to train and learn these images, thereby demodulating information about the external disturbances affecting the fiber.

[0004] Although these sensors feature simplified sensing structures and optimized manufacturing processes, their output MMI images must be captured by an imaging system, which involves constructing complex spatial optical paths, thus limiting their further practical applications. Furthermore, these solutions require the collection of large numbers of images, the creation of image datasets, and the training of complex two-dimensional light field images, placing certain demands on the performance of machine learning algorithm models and increasing training complexity and cost. Summary of the Invention

[0005] The purpose of the present invention is to provide a sensing and demodulation system and method based on multimode optical fiber and mode comb, which can solve at least one of the technical problems mentioned above. The specific solution is as follows:

[0006] According to the specific embodiments disclosed in the present invention, the first aspect of the present invention discloses a sensing and demodulation system based on a multimode optical fiber and a mode comb, comprising: a laser light source, wherein the laser light source is a single-mode optical fiber output or a free-space output;

[0007] A multimode optical fiber sensing unit is coupled to the laser light source and generates an interference light field with superposition of different modes based on external disturbances;

[0008] A mode combing chip includes a three-dimensional multimode optical waveguide and a plurality of electrodes arranged at different positions on the three-dimensional multimode optical waveguide. The light fields of different modes are combed by heating the electrode array to change the refractive index of the three-dimensional multimode optical waveguide and generate a detection signal.

[0009] a control unit, configured to control the heating amount of the electrodes at each position according to the detection signal to maximize the signal value of the detection signal, thereby obtaining a single-mode light spot or a Gaussian-like light spot at the output end of the mode comb chip;

[0010] The demodulation model unit demodulates the external disturbance according to the electrodes at different positions and the configuration of the electrodes when the quasi-single-mode light spot is obtained.

[0011] Optionally, it further includes: a power detection unit, which is connected to the control unit and the mode comb chip respectively, and inputs the measured optical power value of the detection signal into the control unit.

[0012] Optionally, the mold comb chip further includes: a photodiode, which is arranged on the output end face of the mold comb chip to generate the detection signal.

[0013] Optionally, the multimode optical fiber sensing unit is a multimode optical fiber, and the core diameter of the multimode optical fiber is not greater than 105 μm.

[0014] Optionally, the core layer of the three-dimensional multimode optical waveguide covers the core diameter of the multimode optical fiber.

[0015] Optionally, a plurality of the electrodes are arranged in layers, evenly or unevenly within the structure of the three-dimensional multimode optical waveguide.

[0016] According to a specific embodiment disclosed in the present invention, a second aspect of the present invention discloses a sensing demodulation method based on a multimode optical fiber and a mode comb, comprising:

[0017] Building a sensor demodulation system as described in any one of claims 1 to 6;

[0018] Applying external disturbances of different physical quantities to the multimode optical fiber sensing unit to obtain a detection signal;

[0019] Adjusting the input signal of each electrode to change the heating amount of the electrodes at different positions of the mode comb chip so as to maximize the signal value of the detection signal, thereby obtaining a single-mode light spot or a Gaussian-like light spot at the output end of the mode comb chip;

[0020] According to the heating amount of the electrodes at each position when the quasi-single-mode light spot is obtained, the physical quantity of the corresponding external disturbance is obtained from the electrode configuration data set to achieve demodulation of the external disturbance.

[0021] Optionally, the input signal includes: an optical power signal, a voltage signal or a current signal.

[0022] Optionally, the physical quantity includes: direction, position, stress, etc.

[0023] Optionally, the step of acquiring the electrode configuration data set includes:

[0024] applying different physical quantities to the multimode optical fiber sensing unit multiple times, and recording electrode configuration data at various positions of the mode comb chip corresponding to each adjustment of the mode comb chip to obtain a single-mode light spot or a Gaussian-like light spot;

[0025] A machine learning algorithm is used to train the acquired data set to demodulate the physical quantity of external interference to the multimode optical fiber.

[0026] Compared with the prior art, the above solution of the embodiment disclosed in the present invention has at least the following beneficial effects:

[0027] The present invention's multimode fiber and mode comb-based sensing and demodulation system can demodulate the physical quantity of external disturbances affecting the multimode fiber sensing unit simply by determining the electrode configurations at different locations within the mode comb chip, corresponding to whether a single-mode light spot or a Gaussian-like light spot is obtained at the output end of the mode comb chip. This system is compact and can demodulate external interference information affecting the multimode fiber without requiring an imaging system to capture interference patterns at the output end of the multimode fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are incorporated into and constitute a part of the specification, illustrating embodiments consistent with the present disclosure and, together with the specification, explaining the principles of the present disclosure. Obviously, the drawings described below are only some embodiments of the present disclosure, and those skilled in the art can derive other drawings based on these drawings without inventive effort. In the drawings:

[0029] Figure 1 A schematic structural diagram of a sensing and demodulation system based on multimode optical fiber and mode comb provided by an embodiment of the present invention;

[0030] Figure 2 A schematic structural diagram of a sensing and demodulation system with integrated photodiodes provided in an embodiment of the present invention;

[0031] Figure 3 Schematic diagram of the reference coordinate system for the optical fiber bending direction in the multimode optical fiber bending sensing unit provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] To further clarify the objectives, technical solutions, and advantages of the present invention, a sensing and demodulation system and method based on a multimode optical fiber and a mode comb disclosed herein will be further described in detail below with reference to the accompanying drawings. It should be understood that the embodiments described herein are merely a portion of the embodiments disclosed herein, and not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments disclosed herein without inventive effort are intended to fall within the scope of protection disclosed herein.

[0033] The terms used in the examples of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms "a," "the," and "the" used in the examples of this application and the appended claims are also intended to include plural forms, and unless the context clearly indicates otherwise, "a plurality" generally includes at least two.

[0034] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0035] It should be understood that although the terms first, second, third, etc. may be used to describe in the embodiments of the present application, these should not be limited to these terms. These terms are only used to distinguish. For example, without departing from the scope of the embodiments of the present application, the first may also be referred to as the second, and similarly, the second may also be referred to as the first.

[0036] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or device. In the absence of further limitations, an element defined by the phrase "comprising a" does not exclude the presence of other identical elements in the product or device comprising the element.

[0037] The following is combined with Figure 1-3 Alternative embodiments of the present invention are described in detail.

[0038] Example 1

[0039] According to a specific embodiment of the present invention, the present invention provides a sensing and demodulation system based on multimode optical fiber and mode comb, comprising:

[0040] A laser light source, wherein the laser light source is output through a single-mode fiber or a free-space output;

[0041] A multimode optical fiber sensing unit is coupled to the laser light source and generates an interference light field with superposition of different modes based on external disturbances;

[0042] A mode combing chip includes a three-dimensional multimode optical waveguide and a plurality of electrodes arranged at different positions on the three-dimensional multimode optical waveguide. The light fields of different modes are combed by heating the electrode array to change the refractive index of the three-dimensional multimode optical waveguide and generate a detection signal.

[0043] a control unit, configured to control the heating amount of the electrodes at each position according to the detection signal to maximize the signal value of the detection signal, thereby obtaining a single-mode light spot or a Gaussian-like light spot at the output end of the mode comb chip;

[0044] The demodulation model unit demodulates the external disturbance according to the electrodes at different positions and the configuration of the electrodes when the quasi-single-mode light spot is obtained.

[0045] The sensing and demodulation system of the present invention has a compact structure and can demodulate external interference information on the multimode optical fiber without using an imaging system to capture the interference image at the output end of the multimode optical fiber.

[0046] Specifically, such as Figure 1 or Figure 2 As shown, the laser light source is output as a single-mode optical fiber, and the single-mode optical fiber is coupled to the multi-mode optical fiber sensing unit.

[0047] As an optional implementation, the laser light source may be a single-wavelength laser in the visible light band or near-infrared band, such as 635 nm, 1550 nm, etc., and the laser light source is free-space output.

[0048] As an optional embodiment, a multimode fiber sensing unit is coupled to a single-mode fiber. When fundamental mode light from a single-mode fiber enters a multimode fiber, due to the larger core and higher NA of the multimode fiber, the light field excites multiple modes within the multimode fiber. Initially, each mode has a fixed phase relationship (determined by the incident field). During forward transmission through the multimode fiber, these modes experience phase differences that accumulate over distance due to their different propagation velocities. These modes then couple and superimpose to form light field distributions with different modes, generating a multimode interference effect. This effect is extremely sensitive to perturbations and deformations within the multimode fiber. When subjected to varying degrees of interference, the interference pattern produced by a multimode fiber varies significantly. The variation in this pattern depends not only on the amplitude of the interference but also on its direction, creating a form of vectorial sensing. Therefore, when different external disturbances act on the multimode fiber, different multimode interference patterns are formed at the output end of the multimode fiber. Therefore, using a multimode fiber as a sensing unit can be used to detect physical quantities such as direction, force, and position.

[0049] As an optional implementation, the core diameter of the multimode optical fiber is no greater than 105 μm, and may be 50 μm, 62.5 μm, or 105 μm.

[0050] Furthermore, the light field at the output end of the multimode optical fiber is coupled into a mode comb chip, which is used to comb the complex light field into a quasi-single-mode light field.

[0051] In this embodiment, the mode comb chip is established in a three-dimensional multimode optical waveguide system, and multiple electrodes are set at different positions of the three-dimensional multimode optical waveguide. By heating the multiple electrodes, the refractive index of the material is changed, so that it presents a distribution of superimposed quadratic curves in space, which is equivalent to a multi-parameter adjustable lens group. It can achieve a focusing effect on almost any light field and realize the function of combing any complex mode field into a single-mode, Gaussian-like light spot.

[0052] As an optional implementation, in order to ensure that all light in the multimode optical fiber can be coupled into the three-dimensional multimode optical waveguide, the core thickness of the three-dimensional multimode optical waveguide is greater than the core diameter of the multimode optical fiber.

[0053] As an optional implementation, based on the core thickness of the three-dimensional multimode optical waveguide, the purpose is to adjust the mode distribution of the multimode interference zone by loading electrical signals on the electrode array on the mode comb chip, and comb a complex light field at the input end of the mode comb into a quasi-single-mode Gaussian light spot output. The number, number of layers and arrangement of electrodes are designed through simulation software, and multiple electrodes are arranged in layers, evenly or unevenly in the structure of the three-dimensional multimode optical waveguide.

[0054] Furthermore, the sensing and demodulation system also includes a power detection unit, which is connected to the control unit and the mode comb chip respectively, and is used to detect the detection signal generated by the mode comb chip. The control unit adjusts the heating amount of the electrode according to the result of the power detection unit to achieve the output of a quasi-single-mode light spot.

[0055] As an optional implementation, the power detection unit is an optical power meter connected to the mode comb chip via a single-mode fiber. When the power reaches its maximum value, the mode comb chip is considered to have combed the light field into a single-mode spot. At this point, the electrode configuration applied to the mode comb corresponds to a state of multimode fiber.

[0056] As an optional embodiment, the control unit includes: a microcircuit control unit and a processor. The microcircuit control unit is used to control the electrode array of the mode comb chip and adjust the refractive index of the mode comb chip material to comb any complex mode field into a single-mode, Gaussian-like spot;

[0057] The processor is used to control the microcircuit control unit and the optical power meter, and is used to adjust the input signals of each electrode using the microcircuit control unit according to the feedback of the optical power meter value, so as to ultimately maximize the value of the optical power meter.

[0058] As an optional implementation, the input signal is not limited to current, but can also be represented by voltage, power, etc.

[0059] As an optional implementation, the optical power meter may also be a photodiode integrated on the output end face of the mode comb chip.

[0060] Every time the multimode optical fiber is subject to external interference, the light field at the output end of the multimode optical fiber, that is, coupled into the mode comb chip, will change. By using electrodes with different numbers on the mode comb chip and different configuration currents for each electrode, different input light fields can be combed into a quasi-single-mode light spot at the same position at the output end of the mode comb chip. These different electrode configurations include different state information of the multimode optical fiber, such as the degree and direction of interference. By repeatedly changing the state of the multimode optical fiber, adjusting the different electrode configurations of the mode comb chip, recording these electrode numbers and corresponding current configuration data, establishing a database, and using a simple neural network to train and learn the current configuration database, it is possible to demodulate the disturbance on the optical fiber.

[0061] Therefore, the model demodulation unit demodulates the external disturbance according to the electrodes at different positions and the configuration of the electrodes when the quasi-single-mode light spot is obtained.

[0062] The present invention's multimode fiber and mode comb-based sensing and demodulation system can demodulate the physical quantity of external disturbances affecting the multimode fiber sensing unit simply by determining the electrode configurations at different locations within the mode comb chip, corresponding to whether a single-mode light spot or a Gaussian-like light spot is obtained at the output end of the mode comb chip. This system is compact and can demodulate external interference information affecting the multimode fiber without requiring an imaging system to capture interference patterns at the output end of the multimode fiber.

[0063] Example 2

[0064] The present invention also provides method embodiments that are consistent with the above embodiments. The explanations based on the same name meanings are the same as those of the above embodiments, and have the same technical effects as the above embodiments, which will not be repeated here.

[0065] like Figure 2 As shown, the present invention discloses a sensing demodulation method based on multimode optical fiber and mode comb, comprising the following steps:

[0066] Step S101: Build a sensing and demodulation system based on multimode optical fiber and mode comb.

[0067] Step S102: applying external disturbances of different physical quantities to the multimode optical fiber sensing unit to obtain a detection signal.

[0068] Step S103 , adjusting the input signal of each electrode to change the heating amount of the electrodes at different positions of the mode comb chip to maximize the signal value of the detection signal, thereby obtaining a single-mode light spot or a Gaussian-like light spot at the output end of the mode comb chip.

[0069] Step S104 : acquiring the corresponding physical quantity of the external disturbance from the electrode configuration data set according to the heating amount of the electrodes at each position when the quasi-single-mode light spot is obtained, and realizing demodulation of the external disturbance.

[0070] The sensing demodulation method of this embodiment does not need to collect complex two-dimensional light field images. It only needs to record the electrode configuration, establish an electrode configuration database, and combine it with a simple machine learning algorithm to achieve demodulation of the disturbance suffered by the optical fiber.

[0071] Specifically, the laser light source is output from a single-mode fiber, and an optical power meter is used to detect the detection signal from the mode comb chip. The core diameter of the multimode fiber is 50μm, which is used to sense the fiber's bend direction and bend radius. The core layer of the three-dimensional multimode optical waveguide of the mode comb chip is 64.5μm thick. Within the three-dimensional multimode optical waveguide structure, a total of 32 electrodes are arranged in three layers. The physical quantities of the external disturbance include direction, position, and stress.

[0072] Light from a laser light source is injected from a single-mode fiber into a multimode fiber, exciting multiple modes. A complex interference light field is generated at the output end of the multimode fiber and coupled into the input end of the mode comb chip, exciting a complex mode distribution in the mode comb chip. The microcircuit control unit controls the various electrodes on the mode comb chip, and the electrical signals applied to the electrodes adjust the mode distribution in the multimode interference zone, combing the complex light field at the input end of the mode comb chip into a single-mode Gaussian light spot output, which is coupled into the single-mode fiber. The output end of the single-mode fiber is connected to an optical power meter for monitoring the optical power. When the power value reaches the maximum value, it is considered that the mode comb chip has combed the light field into a single-mode light spot. At this time, the electrode configuration applied to the mode comb corresponds to a state of the multimode fiber. When an optical fiber is disturbed, it affects the mode distribution in the multimode fiber, the effective refractive index of each mode, the light field distribution at the output end of the multimode fiber, and the mode distribution in the mode comb. At this point, the electrode configuration needs to be changed to regain a single-mode spot at the output end of the mode comb. The power value at the output end of the single-mode fiber is then detected by a power meter. When the power value reaches the maximum, the mode combing is considered complete, and the new electrode configuration corresponds to the new state of the fiber. By initially collecting a large amount of electrode configuration data corresponding to different multimode fiber states, establishing an electrode configuration dataset, and using simple machine algorithms to train and learn this data, it is possible to demodulate multimode fibers subjected to external interference.

[0073] Furthermore, the step of obtaining the electrode configuration data set includes:

[0074] applying different physical quantities to the multimode optical fiber sensing unit multiple times, and recording configuration data of electrodes at various positions corresponding to the mode comb chip when the mode comb chip is adjusted each time to obtain a single-mode light spot or a Gaussian-like light spot;

[0075] A machine learning algorithm is used to train the acquired data set to demodulate external interference information on the optical fiber.

[0076] The following describes an embodiment of the sensing and demodulation method based on a multimode fiber and a mode comb according to the present invention. Table 1 shows the optical field distribution at the output end of the multimode fiber, the electrodes used, and the optical field distribution at the output end of the mode comb chip before and after combing, at different bending directions and radii.

[0077] Table 1 Light field distribution and selected electrodes under different fiber disturbance states

[0078]

[0079] Table 2 Current configuration (mA) applied to electrodes when different input light fields of multimode fibers are combed into single-mode light spots under different fiber disturbance states

[0080]

[0081] As shown in Table 2, the electrode numbers and current values ​​used by the electrodes for combing different input light fields of the multimode optical fiber into single-mode light spots using the mode comb chip are listed in detail under five conditions of the multimode optical fiber in Table 1.

[0082] Figure 3 The bending direction coordinate system of a multimode fiber is shown. Table 1 shows different light field distributions at the output end of a multimode fiber for five conditions: no bending, bending 12 cm in the -Z direction, bending 4 cm in the -Y direction, bending 5 cm in the -Y direction, and bending 8 cm in the +Z direction. These light fields are coupled into a mode comb chip. By selecting different electrode configurations on the mode comb chip, the complex light field can be combed into a single-mode spot and coupled into the single-mode fiber, where the power is measured using a power meter. Table 2 details the electrode numbers of the mode comb chip corresponding to each multimode fiber state, as well as the current values ​​applied to each electrode. It can be seen that the electrode configurations and current values ​​used to comb the output light field into a single-mode spot vary across different multimode fiber states. This allows the creation of a database of mode comb electrode configurations and fiber states. Because the electrode configuration corresponding to each fiber state is equivalent to a 1×32 row vector, analysis of complex two-dimensional images is greatly simplified. Consequently, simple machine learning algorithms can be used to train and learn from the database.

[0083] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. References to the common and similar parts between the various embodiments will be sufficient. For the systems or devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, their descriptions are relatively simple; for relevant details, refer to the descriptions of the methods.

[0084] The above embodiments are only used to illustrate the technical solutions disclosed in the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments disclosed in the present invention.

Claims

1. A sensing and demodulation system based on multimode optical fiber and mode comb, characterized in that: include: A laser light source, wherein the laser light source is output through a single-mode fiber or a free-space output; A multimode optical fiber sensing unit is coupled to the laser light source and generates an interference light field with superposition of different modes based on external disturbances; A mode combing chip includes a three-dimensional multimode optical waveguide and a plurality of electrodes arranged at different positions on the three-dimensional multimode optical waveguide. The light fields of different modes are combed by heating the electrode array to change the refractive index of the three-dimensional multimode optical waveguide and generate a detection signal. a control unit, configured to control the heating amount of the electrodes at each position according to the detection signal to maximize the signal value of the detection signal, thereby obtaining a single-mode light spot or a Gaussian-like light spot at the output end of the mode comb chip; The demodulation model unit demodulates the external disturbance according to the electrodes at different positions and the configuration of the electrodes when the quasi-single-mode light spot is obtained.

2. The sensor demodulation system according to claim 1, characterized in that: Also includes: The power detection unit is connected to the control unit and the mode comb chip respectively, and inputs the measured optical power value of the detection signal into the control unit.

3. The sensor demodulation system according to claim 1, characterized in that: The mold comb chip further includes: a photodiode, which is arranged on the output end face of the mold comb chip to generate the detection signal.

4. The sensor demodulation system according to claim 1, characterized in that: The multimode optical fiber sensing unit is a multimode optical fiber, and the core diameter of the multimode optical fiber is no more than 105 μm.

5. The sensor demodulation system according to claim 4, characterized in that: The core layer of the three-dimensional multimode optical waveguide covers the core diameter of the multimode optical fiber.

6. The sensor demodulation system according to claim 1, characterized in that: The plurality of electrodes are arranged in layers, evenly or unevenly within the structure of the three-dimensional multimode optical waveguide.

7. A sensing demodulation method based on multimode optical fiber and mode comb, characterized in that: include: Building a sensor demodulation system as described in any one of claims 1 to 6; Applying external disturbances of different physical quantities to the multimode optical fiber sensing unit to obtain a detection signal; Adjusting the input signal of each electrode to change the heating amount of the electrodes at different positions of the mode comb chip so as to maximize the signal value of the detection signal, thereby obtaining a single-mode light spot or a Gaussian-like light spot at the output end of the mode comb chip; According to the electrode configurations at the various positions when the quasi-single-mode light spot is obtained, the physical quantity of the corresponding external disturbance is acquired from the electrode configuration data set to achieve demodulation of the external disturbance.

8. The sensing demodulation method according to claim 7, characterized in that: The input signal includes: an optical power signal, a voltage signal or a current signal.

9. The sensing demodulation method according to claim 7, characterized in that: The physical quantities include: direction, position and stress.

10. The sensing demodulation method according to claim 7, characterized in that: The step of acquiring the electrode configuration data set includes: applying different physical quantities to the multimode optical fiber sensing unit multiple times, and recording a data set of electrode configurations at various positions of the mode comb chip corresponding to each adjustment of the mode comb chip to obtain a single-mode light spot or a Gaussian-like light spot; A machine learning algorithm is used to train the acquired data set to demodulate external disturbance information on the multimode optical fiber.

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