High-precision plantar pressure monitoring system based on fiber grating ring laser structure

Abstract

The invention relates to an insole capable of monitoring plantar pressure in real time, in particular to a high-precision plantar pressure monitoring system based on a fiber grating ring laser structure. The system comprises an insole body integrated with a fiber bragg grating sensor and an annular laser structure composed of a wavelength division multiplexer, an erbium-doped fiber and the like, the central wavelength 3dB bandwidth of the fiber bragg grating sensor is narrowed from 0.23 nm to 0.0175 nm by introducing the laser structure, the pressure measurement precision can be optimized from 2.4% FS to 0.18% FS according to 0.00457 nm / N sensor pressure sensitivity and 2100 N measuring range calculation, and the pressure measurement precision can be optimized from 2.4% FS to 0.18% FS according to 0.00457 nm / N sensor pressure sensitivity and 2100 N measuring range calculation. Dynamic pressure data are acquired and recorded in real time through the sweep frequency demodulator terminal equipment, and precise measurement of tiny changes of plantar pressure is achieved. And the requirements on high precision of the pressure sensor in the fields of sports biomechanical analysis, diabetic foot monitoring, athlete injury rehabilitation detection, scientific research level foot mechanics research and the like can be met.

Description

Technical Field

[0001] This invention relates to an insole capable of real-time monitoring of plantar pressure, and more particularly to an insole based on fiber optic ring laser technology that accurately and objectively measures plantar pressure in a quantitative manner. It belongs to the field of fiber optic sensing technology, and specifically to a high-precision plantar pressure monitoring system based on a fiber optic ring laser structure. Background Technology

[0002] Human plantar pressure data plays a crucial role in many fields, including sports biomechanics analysis, monitoring of diabetic patients, athlete injury rehabilitation, and foot mechanics research. For example, in sports biomechanics analysis, plantar pressure data is a key basis for analyzing human movement patterns. During activities such as walking, running, and jumping, the dynamic changes in plantar pressure are closely related to biomechanical processes such as muscle exertion, joint movement, and energy transfer.

[0003] For example, excessive force on the forefoot during running can lead to plantar fasciitis, while uneven force on the heel can cause Achilles tendonitis. By accurately monitoring plantar pressure, it is possible to quantify the force distribution in different areas of the foot during exercise, develop personalized exercise technique improvement plans for athletes, help them optimize their posture, and reduce the risk of sports injuries. At the same time, it also provides scientific guidance for the daily exercise and health management of ordinary people.

[0004] Furthermore, approximately 500 million people worldwide currently suffer from diabetes, which is one of the leading causes of non-traumatic lower limb amputations. 85% of these cases are due to the worsening of diabetic foot ulcers. Multiple factors contribute to the development of diabetic foot ulcers, primarily including peripheral neuropathy, bone and joint deformities, and minor trauma. Abnormal plantar pressure is a significant pathological factor in the development of foot ulcers in diabetic patients; therefore, monitoring plantar pressure allows patients to understand their condition promptly.

[0005] By obtaining changes in plantar pressure during a person's movement, the movement can be analyzed to obtain important parameters such as gait cycle, plantar pressure distribution, and force range, providing reliable reference data for related research. In recent years, research on plantar pressure testing systems has gradually increased. Currently, common plantar pressure testing systems include treadmill-type, flat-plate-type, and insole-type systems, each with its own advantages and disadvantages.

[0006] Treadmill-style systems can measure the distribution of dynamic pressure under various postures, but their large size and lack of portability limit their application scenarios. While flat-panel systems are relatively portable, their accuracy and sensitivity are often difficult to guarantee, and subjects often need to be tested within a specific area, affecting the naturalness of the data. Insole-style systems offer better portability and comfort, but most insole-style systems currently on the market use resistive or capacitive sensors, which have relatively low accuracy and stability and are easily affected by environmental factors such as temperature and humidity.

[0007] Patent CN118975791A uses multiple components such as an ionized flexible pressure sensor array, a signal processing module, and an inertial sensing unit, making the system design and manufacturing complex and increasing the difficulty of production and maintenance. Furthermore, the use of a high-precision sensor array and complex signal processing circuits results in high manufacturing costs. Patent CN117556324A employs a complex algorithm analysis process, including multilayer perceptrons, one-dimensional convolutional layers, and multi-head attention mechanisms, which places high demands on data processing capabilities and computing resources, increasing the barrier to entry for the system. Patent CN105725982A describes a pressure testing insole and its demodulation system that are directly connected to a terminal device. While this allows for accurate measurement of plantar pressure, it restricts the user's range of motion and poses safety hazards such as cable dragging and tripping during exercise. Additionally, this system has low pressure sensitivity, making it difficult to achieve high-precision pressure monitoring.

[0008] Existing technologies (such as patent CN105725982A) also use fiber Bragg grating sensors to create insoles for testing sole temperature and pressure. However, they directly use a signal acquisition device to collect plantar pressure signals from the fiber Bragg grating sensor. This installation method uses the fiber Bragg grating sensor to measure lateral load to obtain the magnitude of plantar pressure. However, domestic and international research has proven that the fiber Bragg grating sensor has extremely low sensitivity to lateral load, making it difficult to directly apply to the measurement of lateral load. Although the patent considers the low pressure sensitivity coefficient of the fiber Bragg grating and encapsulates it, the pressure sensitivity of the encapsulated fiber Bragg grating sensor, as shown in the patent, is only 0.0013 nm / g. This low sensitivity leads to adverse effects such as low measurement accuracy, small dynamic range, and low signal-to-noise ratio, thus affecting its ability to measure plantar pressure and failing to meet the detection requirements for minute pressure changes in clinical and sports science (such as the requirement of measurement accuracy <0.5%FS in many fields).

[0009] Measurement accuracy is a crucial indicator of a system's responsiveness to dynamic strain signals; higher accuracy translates to a stronger ability to detect minute strain signals. The Fujian Provincial Standard "Test Method for Plantar Pressure Distribution" stipulates that the data sampling frequency for plantar pressure distribution testing insole systems should be no less than 100Hz, with a data lag time of no less than 0.1s. In practical applications, sensor requirements typically include a sampling frequency ≥400Hz and a measurement range ≥200N / cm². 2 Furthermore, the force measurement accuracy is ≤ ±2% of the maximum range. Studies have shown that the time required for an athlete's plantar pressure to reach its maximum value from the moment the foot touches the ground is only about 120ms. If the sensor's measurement accuracy for plantar pressure is too low, it will lead to serious problems such as inaccurate data measurement and data loss. Therefore, the accuracy of the sensor's pressure measurement plays a crucial role in applications. However, the plantar pressure testing insole proposed in patent CN105725982A does not meet practical standards. Therefore, improving the measurement accuracy of fiber optic grating sensors for plantar pressure is of paramount importance.

[0010] Most existing plantar pressure testing systems use resistive or capacitive sensors, which have low sensitivity and are easily affected by environmental factors such as temperature and humidity, making it difficult to achieve high-precision pressure monitoring. Furthermore, existing fiber Bragg grating sensors are limited in their application in plantar pressure monitoring due to issues such as the fragility of bare fibers and low sensitivity. To address these problems, this invention significantly improves the measurement accuracy of plantar pressure sensors by introducing a fiber Bragg grating ring laser structure. This enables real-time and precise monitoring of minute changes in plantar pressure, solving the problem of insufficient measurement accuracy in existing technologies. Summary of the Invention

[0011] The present invention aims to solve the problems of low measurement accuracy in existing fiber Bragg grating plantar pressure monitoring systems, and to provide a portable, high-precision insole that can monitor plantar pressure in real time and accurately.

[0012] To achieve the above objectives, this invention provides a high-precision plantar pressure monitoring system based on a fiber Bragg grating ring laser structure, comprising: a fiber Bragg grating ring laser structure, which includes a light source, a circulator, a coupler, an erbium-doped fiber, and a wavelength division multiplexer; an insole body, in which a fiber Bragg grating sensor for monitoring plantar pressure is embedded, the fiber Bragg grating sensor being connected to the fiber Bragg grating ring laser structure; a sweep frequency demodulator connected to the fiber Bragg grating ring laser structure via a coupler; and a terminal device, which, through connection with the sweep frequency demodulator, acquires plantar pressure data measured by the fiber Bragg grating sensor in the insole body, thereby achieving real-time monitoring of plantar pressure; wherein, the fiber Bragg grating sensor is encapsulated at different locations within the insole body to obtain pressure data at different locations on the sole of the foot.

[0013] The aforementioned high-precision plantar pressure monitoring system based on a fiber Bragg grating ring laser structure comprises a light source, a circulator, a coupler, an erbium-doped fiber, and a wavelength division multiplexer (WDM). The WDM, erbium-doped fiber, circulator, and coupler are sequentially connected to form a ring cavity, with the light source connected to the WDM. The working principle of the fiber Bragg grating ring laser structure is as follows: First, the pump light generated by the light source enters the ring cavity through the WDM, exciting the erbium-doped fiber to generate laser light. Then, the laser light passes through the circulator and enters the fiber Bragg grating sensor, with a portion of the laser light reflected back into the ring cavity. After multiple cyclic amplifications, the laser light finally enters a sweep frequency demodulator through the coupler. Finally, the wavelength data is acquired by the sweep frequency demodulator and transmitted wirelessly to a terminal device for pressure calculation, achieving real-time plantar pressure monitoring. This ring laser structure significantly improves the sensitivity of the fiber Bragg grating sensor through multiple cyclic amplifications of the laser signal, enabling the system to monitor minute changes in plantar pressure in real time and with precision. The terminal device collects and displays plantar pressure data in real time by connecting to a sweep frequency demodulator.

[0014] The aforementioned high-precision plantar pressure monitoring system based on a fiber optic ring laser structure has a fiber optic sensor embedded within the structure of the insole body, ensuring effective contact with the sole of the foot and accurate pressure sensing.

[0015] The aforementioned high-precision plantar pressure monitoring system based on a fiber optic ring laser structure includes the following steps in manufacturing the insole body: Step 1: Make the two parts of the insole body; The second step is to carve a groove in one of the sections to place the fiber optic grating sensor and its fiber optic connector. The third step is to place the fiber optic grating sensor and its fiber optic connection into the groove and encapsulate it with epoxy resin. After it solidifies, the two parts of the insole body are glued together.

[0016] Epoxy resin has high mechanical strength, wear resistance and corrosion resistance, which can effectively protect fiber Bragg grating sensors from external pressure and environmental influences, while ensuring the sensitivity and stability of the sensors.

[0017] The aforementioned high-precision plantar pressure monitoring system based on a fiber Bragg grating ring laser structure comprises five fiber Bragg grating sensors embedded in five key biomechanical stress points of the insole body. The five fiber Bragg grating sensors are distributed according to the plantar biomechanical model, corresponding to the toe (big toe) area, the first and fifth metatarsal bone areas, the lateral arch of the foot, and the calcaneus (heel) area, respectively. Furthermore, these fiber Bragg grating sensors are arranged in series to simplify the circuit layout and improve the pressure sensitivity and accuracy of the system.

[0018] The aforementioned high-precision plantar pressure monitoring system based on a fiber optic ring laser structure features a double-layer wooden insole. The fiber optic sensor and its encapsulation structure are placed on the upper surface of the lower insole. The upper and lower insoles are bonded together with adhesive to provide sufficient support and stability while protecting the fiber optic sensor from external pressure. The main advantage of using a double-layer wooden structure for the insole is its excellent thermal insulation, which can effectively prevent changes in external temperature from affecting the test data.

[0019] The aforementioned high-precision plantar pressure monitoring system based on a fiber grating ring laser structure enables real-time data transmission and remote monitoring by wirelessly connecting the frequency sweep demodulator to the terminal device.

[0020] The aforementioned high-precision plantar pressure monitoring system based on a fiber grating ring laser structure includes a terminal device comprising a data receiving module, a data processing module, and a data display module, used to receive wavelength data transmitted by a sweep frequency demodulator, convert it into pressure data, and display it on the user interface in real time.

[0021] This invention, based on the fiber Bragg grating (FBG) sensing principle and combined with the high sensitivity of the FBG ring laser structure, develops a foot pressure testing insole. After actual testing, the 3dB bandwidth of the center wavelength of the FBG sensor, enhanced by the FBG ring laser structure, was narrowed from 0.23nm to 0.0175nm. Based on a sensor pressure sensitivity of 0.00457nm / N and a range of 2100N, the pressure measurement accuracy can be optimized from 2.4%FS to 0.18%FS. Furthermore, a linear relationship between the wavelength change and the applied load was obtained, with a sensitivity coefficient ranging from 0.00148nm / N (FBG2) to 0.00457nm / N (FBG5), both higher than the 0.0013nm / g in the prior art (patent CN105725982A). The differences in pressure sensitivity among the individual FBG sensors are due to packaging; however, since all sensors are independently calibrated, this does not affect the final test results.

[0022] The insole provided by this invention can monitor the dynamic changes of foot pressure in real time and accurately. It has the advantages of simple manufacturing, low cost, high precision, high sensitivity and good portability. It can meet the needs of high-precision pressure sensors (measurement accuracy <0.5%FS) in fields such as sports biomechanical analysis, diabetic foot monitoring, athlete injury rehabilitation detection and scientific research foot mechanics research. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a high-precision plantar pressure monitoring system based on a fiber Bragg grating ring laser structure.

[0024] Figure 2 This is a graph showing the relationship between the wavelength change of the fiber Bragg grating sensor and the magnitude of the pressure, obtained through experiments in this example.

[0025] Figure 3 This is a schematic diagram showing the center wavelength and 3dB bandwidth of a fiber grating that does not include a ring laser structure.

[0026] Figure 4 This is a schematic diagram showing the center wavelength and 3dB bandwidth of a fiber grating containing a ring laser structure, for comparison. Figure 3 and Figure 4 Without ring laser structure ( Figure 3 ), with a wide 3dB bandwidth and a relatively flat "broad peak" spectrum; after introducing a ring laser structure ( Figure 4 The 3dB bandwidth is significantly narrowed, and the spectrum is characterized by "narrow spikes".

[0027] In the figure: 1-Fiber Bragg grating ring laser structure, 2-Insole body, 3-Fiber Bragg grating sensor, 4-Terminal equipment, 5-Sweep frequency demodulator, 6-Circulator, 7-Erbium-doped fiber, 8-Wavelength division multiplexer, 9-Fiber optic connection line, 10-Light source, 11-Coupler. Detailed Implementation

[0028] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the description of this invention, those skilled in the art can make various modifications and alterations to the invention, and these equivalent forms also fall within the scope defined by the appended claims. It should be noted that the embodiments described in this invention are merely illustrative examples, and those skilled in the art, within the scope defined by the claims, can achieve equivalent solutions by adjusting the fiber type, coupler splitting ratio, or encapsulation material.

[0029] In this embodiment, to improve the sensitivity of the sensor to plantar pressure testing, a fiber grating ring laser structure 1 is adopted, consisting of a light source 10, a circulator 6, a 90:10 coupler 11, an erbium-doped fiber 7 (EDF), and a wavelength division multiplexer 8 (WDM). Its working principle is as follows: 1. Pump light emission and laser excitation. The pump light emitted from the light source 10 passes through the wavelength division multiplexer 8 and is then excited by the erbium-doped fiber 7 to form a laser. The laser light is then transmitted to the fiber optic grating sensor 3 via the circulator 6. The function of the circulator 6 is to ensure the transmission direction of the laser light and to prevent interference from reflected light.

[0030] 2. Laser Reflection and Amplification. When the laser passes through the fiber optic grating sensor 3, part of the light is reflected back. The reflected light passes through the circulator 6 and re-enters the ring cavity. After multiple cycles of amplification, a stable laser output is finally formed.

[0031] 3. Signal Transmission. The amplified laser signal is transmitted to the sweep frequency demodulator 5 via a 90:10 coupler 11. The sweep frequency demodulator 5 is wirelessly connected to the terminal device 4 to collect and display pressure data in real time.

[0032] Actual measurements showed that by adding a ring laser structure, the 3dB bandwidth of the center wavelength of the fiber Bragg grating sensor 3 was significantly reduced from 0.23nm to 0.0175nm. The ring laser, with its unique optical resonance characteristics, significantly improves measurement accuracy, allowing the fiber Bragg grating sensor 3 to more precisely define its wavelength response range and make the wavelength change-pressure mapping relationship more accurate. This effectively improves the sensor's pressure measurement accuracy and enhances its ability to resolve subtle changes in physical quantities. Furthermore, it significantly enhances the sensor's measurement stability by suppressing environmental interference with narrowband filtering characteristics, reducing signal fluctuations, and improving measurement repeatability.

[0033] The significant reduction in bandwidth greatly enhances the plantar pressure measurement performance of the fiber Bragg grating sensor 3, significantly improving measurement accuracy. The narrow bandwidth allows the sensor to be more sensitive and precise in sensing wavelength changes; minute wavelength drifts caused by plantar pressure can be accurately captured, effectively avoiding measurement errors caused by wavelength fluctuations within the bandwidth, and achieving high-resolution measurement of subtle changes in plantar pressure.

[0034] Fiber Bragg gratings (FBGs) offer advantages such as light weight, small size, corrosion resistance, and immunity to electromagnetic interference. However, exposed FBGs are fragile, easily broken, have weak shear resistance, and relatively low sensitivity, limiting their application range and making them unsuitable for direct foot pressure monitoring. Therefore, encapsulating FBGs is an important method to improve their sensitivity and provide adequate protection for the sensor.

[0035] In this embodiment, the fiber Bragg grating sensor 3 needs to be packaged. The specific steps are as follows: Step 1: Grooving. First, circular grooves are dug out at five pre-defined locations on the selected insole body 2 to accommodate the fiber optic grating sensor 3. These locations typically correspond to the main stress areas of the sole of the foot, as shown in Figure (1).

[0036] The second step is to place the fiber Bragg grating sensors. Place the bare fiber Bragg grating sensors one by one into the prepared grooves. Ensure the sensors are accurately positioned to accurately monitor the pressure distribution on the sole of the foot.

[0037] The third step is to determine the fiber optic route. Based on the distribution of the fiber optic grating sensors 3, the route of the fiber optic route is determined, and grooves are cut into the insole body to accommodate the fiber optics. These grooves ensure that the fiber optics are minimally affected by external pressure inside the insole.

[0038] Step 4: Encapsulating the fiber Bragg grating sensor. After placing the fiber Bragg grating sensor 3, pour the prepared epoxy resin (epoxy resin and curing agent are mixed in a 3:1 ratio, stirred well, and left to stand for half an hour) into the circular groove. After the epoxy resin solidifies, the fiber Bragg grating sensor is securely encapsulated in the insole.

[0039] Step 5: Glue the insole together. Glue the lower insole containing the encapsulated fiber Bragg grating sensor to the upper insole together, ensuring the overall structure of the insole is sturdy and comfortable.

[0040] In this embodiment, there are five fiber Bragg grating sensors 3, which are embedded in five different positions on the insole body, and the sensors are arranged in series. The advantages of the series arrangement are: 1. Simplified wiring: By arranging them in series, the amount of optical fiber used is reduced, simplifying the wiring layout inside the insole and reducing manufacturing difficulty; 2. Improved accuracy: The series arrangement allows the signals from multiple sensors to be processed centrally, improving the overall sensitivity of the system and enabling the system to more accurately reflect changes in plantar pressure; 3. Reduced cost: The series arrangement reduces the amount of optical fiber and connectors used, reducing the system manufacturing cost.

[0041] To avoid interference from multiple series signals, the center wavelengths of each fiber Bragg grating sensor 3 were sequentially set to 1520nm, 1530nm, 1540nm, 1550nm, and 1560nm. This prevents the center wavelengths of the various fiber Bragg grating sensors 3 from crossing during testing, thus ensuring accuracy. Actual testing showed that a 10nm center wavelength interval ensures a sensor measurement range greater than 2100N.

[0042] The plantar pressure monitoring system of this invention achieves remote real-time data acquisition and monitoring through wireless transmission technology. The specific data acquisition steps are as follows: 1. Data acquisition: Fiber optic grating sensor 3 monitors changes in plantar pressure in real time and transmits the grating wavelength data to the sweep frequency demodulator 5 via optical fiber.

[0043] 2. Transmission: The sweep frequency demodulator 5 transmits the obtained wavelength data to the terminal device 4 via wireless connection.

[0044] 3. Real-time analysis and display: After receiving the signal transmitted by the sweep frequency demodulator 5, the terminal device 4 performs real-time conversion of wavelength data to pressure data through dedicated software and displays the plantar pressure data in real time.

[0045] In this embodiment, the insole body 2 adopts a double-layer wooden structure. The specific design is as follows: The lower insole is used to house the fiber Bragg grating sensor 3 and its encapsulation structure. The wooden material provides good support and stability, effectively protecting the fiber Bragg grating sensor 3 from external pressure. The upper and lower insoles are bonded together with adhesive, ensuring the overall structure of the insole is robust and resistant to deformation. The main function of the upper insole is to ensure that the fiber Bragg grating sensor encapsulation structure is not damaged by external forces and to achieve temperature insulation, reducing the impact of temperature changes on the test results.

[0046] In this embodiment, in order to convert the reflected signal from the fiber Bragg grating sensor 3 received by the sweep frequency demodulator 5 into pressure data and display it as a waveform on the terminal device 4, it is necessary to first use a pressure machine to apply pressure to the five fiber Bragg grating sensors for an experiment. Figure 2 This example illustrates the relationship between the wavelength change of the fiber Bragg grating sensor and the pressure magnitude, obtained experimentally. The experimental conditions were: pressure loading experiments (0-100N, 10N steps) were conducted using a standard press at room temperature (25℃). The system achieved a pressure resolution of 3.8N (0.18%FS) at a sampling frequency of 100Hz, with a repeatability error of <±2%. Figure 2 As shown, the linear correlation coefficient R² of the pressure data fitted by the five fiber Bragg grating sensors 3 ranges from 0.97 (FBG5) to 0.996 (FBG2), which is generally better than the 0.9826 of patent CN105725982A. The linear relationship obtained above can be used to convert the wavelength data received by the sweep frequency demodulator 5 into pressure data on the sole of the foot.

[0047] This invention, based on the fiber Bragg grating (FBG) sensing principle and combined with a FBG ring laser structure 1 to enhance the testing performance of the FBG sensor 3, develops a foot pressure testing insole. The terminal device 4 enhances portability through wireless connectivity. The encapsulated FBG sensor 3 is located at different positions on the insole, enabling monitoring of pressure changes at key points on the sole of the foot during exercise. In practical use, the fiber optic cable 9 is threaded through the rear of the insole, maintaining a certain curvature to prevent breakage. Subsequently, the fiber optic cable 9 is laid along the path from the rear side of the shoe → the outer side of the leg → the waist, maintaining appropriate slack and being fixed throughout, finally connecting to a demodulation system (FBG ring laser structure 1 and frequency sweep demodulator 5) fixed at the waist.

Claims

1. A high-precision plantar pressure monitoring system based on a fiber Bragg grating ring laser structure, characterized in that: include: A fiber grating ring laser structure (1) includes a light source (10), a circulator (6), a coupler (11), an erbium-doped fiber (7), and a wavelength division multiplexer (8); an insole body (2) with a fiber grating sensor (3) for monitoring plantar pressure inside, the fiber grating sensor (3) being connected to the fiber grating ring laser structure (1); a sweep frequency demodulator (5) being connected to the fiber grating ring laser structure (1) via a coupler (11); and a terminal device (4) which, through connection with the sweep frequency demodulator (5), acquires plantar pressure data tested by the fiber grating sensor (3) in the insole body (2) to achieve real-time monitoring of plantar pressure; wherein the fiber grating sensor (3) is encapsulated in different positions of the insole body (2) to obtain pressure data at different positions of the plantar surface.

2. The high-precision plantar pressure monitoring system based on a fiber grating ring laser structure according to claim 1, characterized in that: The fiber grating ring laser structure (1) includes a light source (10), a circulator (6), a coupler (11), an erbium-doped fiber (7), and a wavelength division multiplexer (8). The wavelength division multiplexer (8), the erbium-doped fiber (7), the circulator (6), and the coupler (11) are connected in sequence to form a ring cavity. The light source (10) is connected to the wavelength division multiplexer (8). The working principle of the fiber grating ring laser structure (1) is as follows: First, the pump light generated by the light source (10) enters the ring cavity through the wavelength division multiplexer (8) and excites the erbium-doped fiber (7) to generate laser light. Then, the laser light enters the fiber grating sensor (3) through the circulator (6), and part of the laser light is reflected back into the ring cavity by the fiber grating sensor (3). After that, the laser light is amplified multiple times and finally enters the sweep frequency demodulator (5) through the coupler (11). Finally, the wavelength data is collected by the sweep frequency demodulator (5) and transmitted to the terminal device (4) through a wireless connection to calculate the pressure and realize the real-time monitoring of the plantar pressure.

3. A high-precision plantar pressure monitoring system based on a fiber grating ring laser structure according to claim 1 or 2, characterized in that: The fiber optic grating sensor (3) in the insole body (2) is embedded in the structure of the insole body (2) to ensure effective contact with the sole of the foot and accurate sensing of pressure.

4. The high-precision plantar pressure monitoring system based on a fiber grating ring laser structure according to claim 1, characterized in that: The manufacturing of the insole body (2) includes: Step 1: Make the two parts of the insole body (2); The second step is to carve a groove in one of the parts for placing the fiber optic grating sensor (3) and its fiber optic connector (9); The third step is to place the fiber optic grating sensor (3) and its fiber optic connector (9) into the groove and encapsulate them with epoxy resin. After the resin solidifies, the two parts of the insole body (2) are bonded together.

5. A high-precision plantar pressure monitoring system based on a fiber grating ring laser structure according to claim 4, characterized in that: The number of fiber optic grating sensors (3) is five. They are embedded in five key biomechanical stress points of the foot insole body (2). The five fiber optic grating sensors (3) are distributed according to the biomechanical model of the foot, corresponding to the toe area, the first and fifth metatarsal areas, the lateral arch area and the calcaneal area, respectively. These fiber optic grating sensors are arranged in series to simplify the circuit layout and improve the pressure sensitivity and accuracy of the system.

6. A high-precision plantar pressure monitoring system based on a fiber grating ring laser structure according to claim 4 or 5, characterized in that: The insole body (2) adopts a wooden double-layer structure. The fiber optic grating sensor (3) and its encapsulation structure are placed on the upper surface of the lower insole. The upper insole and the lower insole are bonded together with glue to provide sufficient support and stability, while protecting the fiber optic grating sensor (3) from external pressure.

7. A high-precision plantar pressure monitoring system based on a fiber grating ring laser structure according to claim 1, 2, 4, or 5, characterized in that: The sweep frequency demodulator (5) and the terminal device (4) are wirelessly connected to achieve real-time data transmission and remote monitoring.

8. A high-precision plantar pressure monitoring system based on a fiber grating ring laser structure according to claim 1, 2, 4, or 5, characterized in that: The terminal device (4) includes a data receiving module, a data processing module and a data display module, used to receive wavelength data transmitted by the sweep frequency demodulator (5), convert it into pressure data, and display it on the user interface in real time.

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