Optical fiber sensing structure and sensing system for simultaneous measurement of plantar pressure and temperature distribution

Abstract

This invention discloses a fiber optic sensing structure and system for simultaneously measuring plantar pressure and temperature distribution. The fiber optic sensing structure includes a sensing fiber and an elastic plate. Several periodic grooves are fabricated on the elastic plate as mounting channels, including shallow pressure-sensing fiber channels that can detect pressure at that location and deeper temperature-sensing fiber channels that allow the fiber to approach or contact the sole of the foot but do not sense pressure. The sensing fiber is arranged in an S-shaped pattern. The fiber optic sensing system includes: a detection light source, a first fiber optic coupler, a second fiber optic coupler, a fiber optic circulator, the fiber optic sensing structure, a polarization controller, a third fiber optic coupler, a polarization beam splitter, a first photodetector, a second photodetector, a data acquisition card, a fourth fiber optic coupler, a delay fiber, a fifth fiber optic coupler, a third photodetector, and a signal analysis unit. This invention can simultaneously measure plantar pressure and temperature distribution with high accuracy.

Description

Technical Field

[0001] This invention relates to the field of sensing technology, and in particular to a fiber optic sensing structure and sensing system for simultaneously measuring plantar pressure and temperature distribution. Background Technology

[0002] With socioeconomic development and changes in people's dietary structure, the number of diabetic patients is increasing. If diabetic patients have poor blood sugar control for a long period of time, they are very likely to develop various complications affecting the heart, brain, eyes, kidneys, and feet. Among these, diabetic foot disease is not only one of the most common complications, but also one of the most serious. Diabetic foot disease refers to the infection, ulceration, or tissue destruction in the feet of patients newly diagnosed with diabetes or with a history of diabetes. It is usually accompanied by lower limb neuropathy and / or peripheral arterial disease. In severe cases, patients may even face amputation of toes or limbs.

[0003] Foot pressure and temperature distribution are important indicators of the development and progression of diabetic foot. By detecting the pressure and temperature distribution on the soles of diabetic foot patients, we can assist in the diagnosis of abnormal pressure points and their distribution, and provide a design basis for custom-designed pressure-reducing footwear for patients. This is of great significance for the diagnosis and prevention of diabetic foot. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of this invention is to propose an optical fiber sensing structure and sensing system for simultaneous measurement of plantar pressure and temperature distribution based on an optical time-domain reflectometer.

[0005] A fiber optic sensing structure for simultaneously measuring plantar pressure and temperature distribution includes a sensing fiber and an elastic plate. The sensing fiber is divided into a pressure-measuring fiber and a temperature-measuring fiber depending on its installation location. Several periodic grooves are prepared on the elastic plate as installation channels, including shallower pressure-measuring fiber channels that can sense pressure at that location and deeper temperature-measuring fiber channels that allow the fiber to approach or contact the sole of the foot without sensing pressure. The sensing fiber is laid back and forth in an S-shaped pattern within the pressure-measuring fiber channel, alternating between grooves on one side of the elastic plate. After the sensing fiber reaches the other end of the elastic plate, it is folded back and forth and laid back and forth in the temperature-measuring fiber channel, alternating between grooves.

[0006] The sensing optical fiber comprises a bare fiber section and a temperature-sensing optical cable section; the bare fiber section consists of a standard single-mode optical fiber with the coating removed; the temperature-sensing optical cable is a single-mode optical fiber cable with a metal protective sheath.

[0007] The aforementioned fiber optic sensing structure for simultaneously measuring foot pressure and temperature distribution includes a bare fiber that is pre-stressed and then fixed in the pressure-measuring fiber optic channel with adhesive; and a temperature-sensing fiber optic cable that is adhesively bonded in the temperature-measuring fiber optic channel.

[0008] A fiber optic sensing system for simultaneously measuring plantar pressure and temperature distribution using the aforementioned fiber optic sensing structure includes: a detection light source, a first fiber optic coupler, a second fiber optic coupler, a fiber optic circulator, a fiber optic sensing structure, a polarization controller, a third fiber optic coupler, a polarization beam splitter, a first photodetector, a second photodetector, a data acquisition card, a fourth fiber optic coupler, a time-delay fiber, a fifth fiber optic coupler, a third photodetector, and a signal analysis unit.

[0009] The light emitted by the detection light source, which has a periodic scanning frequency, is split into two parts by the first fiber optic coupler, including sensing light and reference light.

[0010] The sensing light is split into a first sensing light and a second sensing light by the second fiber coupler; the first sensing light enters the sensing fiber of the fiber sensing structure through the fiber circulator; the second sensing light reaches one of the input ends of the third fiber coupler through the polarization controller; the backscattered signal of the sensing fiber returns through the fiber circulator to the other input end of the third fiber coupler, and generates a sensing mixing signal with the second sensing light.

[0011] The sensing mixing signal is split into a first polarization sensing mixing signal and a second polarization sensing mixing signal by a polarization beam splitter; the first polarization sensing mixing signal and the second polarization sensing mixing signal are detected by the first photodetector and the second photodetector, respectively; the data acquisition card is used to acquire the signals from the first photodetector and the second photodetector.

[0012] The reference light is split into a first reference light and a second reference light by the fourth fiber coupler; the first reference light is directly connected to one of the inputs of the fifth fiber coupler; the second reference light reaches one of the inputs of the fifth fiber coupler through the delay fiber; the first and second reference lights generate a reference mixing signal at the output of the fifth fiber coupler; the generated reference mixing signal is converted into an acquireable electrical signal by the third photodetector and input to the data acquisition card;

[0013] The signal analysis unit is used to analyze and process the sensor data and demodulate the pressure and temperature distribution on the elastic plate.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The detection light source achieves temperature and pressure measurement through a first fiber optic coupler, a second fiber optic coupler, a fiber optic circulator, a sensing fiber, a polarization controller, a third fiber optic coupler, a polarization beam splitter, a first photodetector, a second photodetector, a data acquisition card, a fourth fiber optic coupler, a delay fiber, a fifth fiber optic coupler, a third photodetector, and a signal analysis unit. The wavelength shift of the Rayleigh scattering spectrum at any point on the fiber is positively correlated with the pressure and temperature experienced at that point. Using OFDR (Optical Frequency Domain Reflectometry) technology, the changes in the Rayleigh scattering spectrum at each sensing point along the sensing fiber can be obtained. The light emitted by the detection light source, with a periodically scanning frequency, is split into two parts through the first fiber optic coupler: sensing light and reference light. The sensing light is further split into first sensing light and second sensing light through the second fiber optic coupler.

[0016] The backscattered signal from the sensing fiber returns through the fiber circulator to the other input of the third fiber coupler, where it mixes with the second sensing light to generate a sensing mixed signal. This mixed signal is then split into a first polarization sensing mixed signal and a second polarization sensing mixed signal by a polarization beam splitter. A data acquisition card is used to acquire these two signals. The reference light is split into a first reference light and a second reference light by the fourth fiber coupler. These two lights generate a reference mixed signal at the output of the fifth fiber coupler. This reference mixed signal is used as a sampling clock signal and input to the data acquisition card. A signal analysis unit analyzes and processes the sensing data, demodulating the pressure and temperature distribution on the elastic plate. When adjacent temperature-measuring fiber segments are close to pressure-measuring fiber segments, the temperature measured by the temperature-measuring fiber segment can be used to approximate the temperature of the adjacent pressure-measuring fiber segment, thus obtaining a more accurate pressure measurement value. Attached Figure Description

[0017] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, are illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0018] Figure 1 This is a schematic diagram (top view) of a fiber optic sensing structure for simultaneous measurement of plantar pressure and temperature distribution based on an optical time-domain reflectometer, according to one embodiment of the present invention.

[0019] Figure 2 This is another schematic diagram (cross-sectional view) of the fiber optic sensing structure for simultaneous measurement of plantar pressure and temperature distribution based on an optical time-domain reflectometer, according to one embodiment of the present invention.

[0020] Figure 3 This is a schematic diagram of the structure of an optical fiber sensing system for simultaneously measuring plantar pressure and temperature distribution based on an optical time-domain reflectometer, according to one embodiment of the present invention.

[0021] In the figure, the components are: 1. Linear tunable laser; 2. First fiber coupler; 3. Second fiber coupler; 4. Fourth fiber coupler; 5. Fiber circulator; 6. Polarization controller; 7. Third fiber coupler; 8. Sensing fiber; 9. Polarization beam splitter; 10. First photodetector; 11. Data acquisition card; 12. Delay fiber; 13. Pressure measuring fiber mounting channel; 14. Fifth fiber coupler; 15. Third photodetector; 16. Second photodetector; 17. Signal analysis unit; 18. Elastic plate; 19. Pressure measuring fiber channel; 20. Temperature measuring fiber channel; 21. Foot pad. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0025] Please see Figure 1 , Figure 1 This is a top view of an optical fiber sensing structure for simultaneous measurement of plantar pressure and temperature distribution based on an optical time-domain reflectometer, according to one embodiment of the present invention.

[0026] like Figure 1As shown, the fiber optic sensing structure includes a sensing fiber 8 and an elastic plate 17. The same sensing fiber 8 is used for pressure measurement and temperature measurement depending on its installation position. Several periodic grooves are prepared on the elastic plate 17 as installation channels, including a shallower pressure-sensing fiber channel 18 that can sense pressure at that location, and a deeper temperature-sensing fiber channel 19 that allows the fiber to approach or contact the sole of the foot but does not sense pressure. The installation methods for the pressure-sensing and temperature-sensing fibers are different: the pressure-sensing fiber installed in the shallower groove is fixed in the groove entirely with adhesive after the coating layer has been removed, allowing it to sense the pressure distribution at various points on the elastic plate 18. The fiber segment used for pressure measurement is installed in the pressure-sensing fiber installation channel 13 using adhesive, enabling it to sense the pressure at that location. The fiber segment used for temperature measurement is installed in the temperature-sensing fiber channel 19. The temperature-sensing fiber segment is loosely placed in the groove, surrounded by thermally conductive material, thus being sensitive to temperature but not to pressure.

[0027] Among them, feasible fiber optic cabling methods for sensing include Figure 1 As shown, the pressure-measuring fiber optic segments are sequentially attached to the surface of the elastic plate from one side in an "S-shape" pattern until the other side. The fibers are then folded back 360 degrees and embedded into the periodic grooves in the same "S-shape" pattern. To prevent the fibers from falling out, both ends can be glued to the grooves while the fibers are relaxed. Finally, all grooves are filled with thermally conductive material. Specifically, when adjacent temperature-measuring fiber optic segments are close to pressure-measuring fiber optic segments, the temperature measured by the temperature-measuring fiber optic segment can be used to approximately compensate for the temperature of the adjacent pressure-measuring fiber optic segment, thus obtaining a more accurate pressure measurement value.

[0028] Please see Figure 2 This is a side view of a fiber optic sensing structure for simultaneous measurement of plantar pressure and temperature distribution based on an optical time-domain reflectometer, according to an embodiment of the present invention. Figure 2 As shown, the fiber optic sensing structure includes an elastic plate 17, foot pads 20, a pressure-measuring fiber optic channel 18, and a temperature-measuring fiber optic channel 19. Sensing fibers 8 are laid inside the pressure-measuring fiber optic channel 18 and the temperature-measuring fiber optic channel 19. The foot pads 20 serve to support the entire fiber optic sensing structure during measurement.

[0029] Please see Figure 3 This is a schematic diagram of a fiber optic sensing system for simultaneously measuring plantar pressure and temperature distribution based on an optical time-domain reflectometer, according to an embodiment of the present invention. Figure 3As shown, the sensing system provided in this embodiment includes: a linearly tunable laser 1, a first fiber coupler 2, a second fiber coupler 3, a fiber optic circulator 5, a fiber optic sensing structure (sensing fiber 8), a polarization controller 6, a third fiber coupler 7, a polarization beam splitter 9, a first photodetector 10, a second photodetector 15, a data acquisition card 11, a fourth fiber coupler 4, a delay fiber 12, a fifth fiber coupler 13, a third photodetector 14, and a signal analysis unit 16.

[0030] In this example, the linearly tunable laser 1 is a laser whose output wavelength can be continuously and linearly changed within a certain range. The laser emits light with a periodically scanning frequency, which is split into two parts by the first fiber coupler 2, including sensing light and reference light. The sensing light is split into a first sensing light and a second sensing light by the second fiber coupler 3. The first sensing light enters the sensing fiber 8 of the fiber sensing structure through the fiber optic circulator 5. The second sensing light reaches one of the input ends of the third fiber coupler 7 through the polarization controller 6. The backscattered signal of the sensing fiber 8 returns through the fiber optic circulator 5 to the other input end of the third fiber coupler 7, where it generates a sensing mixing signal with the second sensing light.

[0031] A polarization beam splitter can split an incident light beam into two linearly polarized beams with mutually perpendicular polarization directions. The sensing mixing signal is split into a first polarization sensing mixing signal and a second polarization sensing mixing signal by the polarization beam splitter 9. The first polarization sensing mixing signal and the second polarization sensing mixing signal are converted into electrical signals by the first photodetector 10 and the second photodetector 15, respectively. The signal analysis unit 16 is used to collect the signals from the first photodetector and the second photodetector.

[0032] The reference light is split into a first reference light and a second reference light by the fourth fiber coupler 4; the first reference light is directly connected to one of the inputs of the fifth fiber coupler 13; the second reference light reaches one of the inputs of the fifth fiber coupler 13 through the delay fiber 12; the first and second reference lights generate a reference mixing signal at the output of the fifth fiber coupler 13; the generated reference mixing signal is converted into an acquireable electrical signal by the third photodetector 14 and acquired by the data acquisition card 11; the acquired reference mixing signal is used as a sampling clock signal and input to the signal analysis unit 16; the signal analysis unit 16 is used to analyze and process the sensing data and demodulate the pressure and temperature distribution on the elastic plate.

[0033] As can be seen, the fiber optic sensing structure and system proposed in this invention, which simultaneously measures plantar pressure and temperature distribution based on an optical time-domain reflectometer, can simultaneously measure plantar pressure and temperature distribution. Furthermore, the temperature measured by the temperature-measuring fiber segment can be used to approximately compensate for the temperature of the adjacent pressure-measuring fiber segment, thereby obtaining a more accurate pressure measurement value. This has significant effects and importance in assisting the diagnosis of pressure and temperature abnormalities and providing detection data for decompression intervention in diabetic foot patients.

[0034] It should be understood that the above description of the embodiments is quite detailed, but it should not be considered as a limitation on the scope of protection of this invention. Those skilled in the art can make substitutions or modifications under the guidance of this invention without departing from the scope of protection of the claims of this invention, and all such substitutions or modifications fall within the scope of protection of this invention. The scope of protection of this invention should be determined by the appended claims.

Claims

1. A fiber optic sensing structure for simultaneous measurement of plantar pressure and temperature distribution, characterized in that, The system includes sensing optical fibers and an elastic plate. The sensing optical fibers are categorized into pressure-sensing fibers and temperature-sensing fibers based on their installation location. Several periodic grooves are prepared on the elastic plate as installation channels, including shallower pressure-sensing fiber channels that can sense foot pressure and deeper temperature-sensing fiber channels that allow the fiber to approach or contact the foot but without sensing pressure. The sensing optical fibers are laid back and forth in an S-shaped pattern, starting from one side of the elastic plate and alternating between grooves within the pressure-sensing fiber channels. After the sensing optical fibers are laid to the other end of the elastic plate, they are folded back and forth and alternately laid back and forth between grooves within the temperature-sensing fiber channels. The sensing optical fiber comprises a bare fiber section and a temperature-sensing optical cable section; the bare fiber is a standard single-mode optical fiber with the coating removed; the temperature-sensing optical cable is a single-mode optical fiber cable with a metal protective sheath. After the bare fiber is pre-stressed, it is fixed in the pressure-measuring fiber channel with adhesive; the temperature-sensing fiber cable is glued in the temperature-measuring fiber channel.

2. A fiber optic sensing system for simultaneously measuring plantar pressure and temperature distribution using the fiber optic sensing structure according to claim 1, characterized in that, include: The system includes a detection light source, a first fiber optic coupler, a second fiber optic coupler, a fiber optic circulator, a fiber optic sensing structure, a polarization controller, a third fiber optic coupler, a polarization beam splitter, a first photodetector, a second photodetector, a data acquisition card, a fourth fiber optic coupler, a time-delay fiber, a fifth fiber optic coupler, a third photodetector, and a signal analysis unit. The light emitted by the detection light source, which has a periodic scanning frequency, is split into two parts by the first fiber optic coupler, including sensing light and reference light. The sensing light is split into a first sensing light and a second sensing light by the second fiber coupler; the first sensing light enters the sensing fiber of the fiber sensing structure through the fiber circulator; the second sensing light reaches one of the input ends of the third fiber coupler through the polarization controller; the backscattered signal of the sensing fiber returns through the fiber circulator to the other input end of the third fiber coupler, and generates a sensing mixing signal with the second sensing light. The sensing mixing signal is split into a first polarization sensing mixing signal and a second polarization sensing mixing signal by a polarization beam splitter; the first polarization sensing mixing signal and the second polarization sensing mixing signal are detected by the first photodetector and the second photodetector, respectively; the data acquisition card is used to acquire the signals from the first photodetector and the second photodetector. The reference light is split into a first reference light and a second reference light by the fourth fiber coupler; the first reference light is directly connected to one of the inputs of the fifth fiber coupler; the second reference light reaches one of the inputs of the fifth fiber coupler through the delay fiber; the first and second reference lights generate a reference mixing signal at the output of the fifth fiber coupler; the generated reference mixing signal is converted into an acquireable electrical signal by the third photodetector and input to the data acquisition card; The signal analysis unit is used to analyze and process the sensor data and demodulate the pressure and temperature distribution on the elastic plate.

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