Optical fiber sensing structure, pressure sensing system and pressure sensing method

Abstract

The invention discloses an optical fiber sensing structure, a pressure sensing system and a pressure sensing method.The optical fiber sensing structure comprises a sensing optical fiber, a supporting piece and a sensing piece, a sensitization groove is formed in the sensing piece, and the sensing optical fiber is fixed to the supporting piece and the sensing piece and penetrates through the sensitization groove; the elastic modulus of the supporting piece and the sensing piece is larger than that of the sensing optical fiber, and the rigidity of the sensing piece is larger than that of the supporting piece. The pressure sensing system comprises an optical frequency domain reflection measurement module, a data processing module and the optical fiber sensing structure. Through the arrangement, the designed optical fiber sensing structure has relatively high sensitivity, can accurately sense pressure, can resist electromagnetic interference and corrosion, is small in size and strong in anti-interference capability when being applied to an OFDR (Optical Frequency Domain Reflectometer) technology, and can sense the change of the refractive index of each point of the optical fiber, and the internal scattering and back propagation components of the optical fiber are approximately and uniformly distributed along the optical fiber; a spatial resolution of 1 mm or less may be allowed.

Description

Technical Field

[0001] The present invention relates to the field of pressure sensing technology, and in particular to an optical fiber sensing structure, a pressure sensing system and a pressure sensing method based on OFDR technology. Background Art

[0002] The swallowing apparatus is composed of the pharynx, upper esophageal sphincter (UES), esophageal body, and lower esophageal sphincter (LES). The upper 1 / 3 of the esophageal body and its proximal structure are composed of skeletal muscle, while the distal esophageal body and lower esophageal sphincter are composed of smooth muscle. These structures form an integrated system that transports food from the mouth to the stomach and prevents food from refluxing into the esophagus. However, physical obstruction or esophageal motility disorders can affect the function of this system, causing gastric contents to reflux back into the esophagus, causing patients to experience symptoms such as difficulty swallowing, chest pain, or heartburn. For the above-mentioned conditions, accurate pressure testing of the swallowing system is required through medical means to provide a reference for subsequent diagnosis or treatment.

[0003] At present, there are two main types of in vivo manometry catheters in the medical field: water perfusion manometry catheter (WHRM) and solid state manometry catheter (SHRM). Both catheters can be used to diagnose esophageal disorders. Among them, WHRM has multiple perfusion channels inside, each channel has a stable water flow out, and the pressure distribution in the esophagus can be obtained by measuring the water pressure output from each channel. The catheter has low production cost, and the pressure measurement channels and their spacing can be adjusted accordingly according to the human body. It has strong flexibility, but it is mainly used for static pressure measurement and has a slow response. It is also easily affected by the external environment, such as temperature, resulting in insufficient measurement accuracy; SHRM has a micro pressure sensor in each channel, and the pressure change can be directly displayed by the change of the electrical signal on the sensor. The catheter can be used for dynamic monitoring, has a fast response speed, high diagnostic accuracy and is relatively convenient to use, but it is expensive. At the same time, the electrical sensor is easily affected by the external environment, such as temperature and humidity, resulting in insufficient measurement accuracy. In addition, the sensor will be damaged after long-term use, which will also lead to deviations in the measurement results.

[0004] Therefore, when applying the above-mentioned various conventional pressure measurement technologies in the prior art to the body, there are still many problems to be overcome. For example, in scenarios such as the swallowing system where there are interferences from factors such as temperature and humidity, it is often impossible to obtain high-precision measurement results. It cannot be used for pressure detection in scenarios with high precision requirements such as the aforementioned swallowing system. Therefore, it is urgent to design a new sensing structure to solve this problem. Summary of the invention

[0005] In order to solve the defect that the in vivo pressure measuring catheter in the prior art is easily disturbed during measurement and cannot meet the requirements of high-precision measurement, the present invention proposes an optical fiber sensing structure, a pressure sensing system and a pressure sensing method, which can improve the measurement accuracy of in vivo pressure measurement of the swallowing system and the like.

[0006] The technical solution adopted by the present invention is that the optical fiber sensing structure includes a sensing optical fiber, and also includes a support member and a sensing member fixedly connected to each other, the sensing member is provided with at least one sensitivity enhancement groove, the sensing optical fiber is respectively fixed to the support member and the sensing member, and passes through the sensitivity enhancement groove;

[0007] Wherein, the elastic moduli of the supporting member and the sensing member are both greater than the elastic modulus of the sensing optical fiber, and the stiffness of the sensing member is greater than the stiffness of the supporting member.

[0008] Preferably, a plurality of the sensitivity-enhancing grooves are provided on the sensing element, and the plurality of the sensitivity-enhancing grooves are arranged along the length direction of the sensing optical fiber.

[0009] Preferably, there are two sensing members, and the two sensing members are respectively fixed at two ends of the supporting member.

[0010] Preferably, the support member and the sensor member are both engraved with fixing grooves, and the sensing optical fiber is fixed in the fixing grooves.

[0011] Preferably, it further comprises a packaging structure, wherein the packaging structure packages the sensing optical fiber, the supporting member and the sensing member into one.

[0012] Preferably, the elastic modulus of the packaging structure is smaller than the elastic modulus of the sensing optical fiber.

[0013] The present invention also proposes a pressure sensing system, including an optical frequency domain reflection measurement module, a data processing module, and the optical fiber sensing structure as described above, wherein the optical fiber sensing structure is connected to the optical frequency domain reflection measurement module via an optical fiber, and the optical frequency domain reflection measurement module is signal-connected to the data processing module.

[0014] Preferably, the optical frequency domain reflectometry module comprises a narrow linewidth tunable light source and a photodetector.

[0015] The narrow linewidth tunable light source is connected to a reference light path and a measurement light path through an optical fiber, and the measurement light path is connected to the optical fiber sensing structure.

[0016] The reference optical path and the measuring optical path are connected to the photoelectric detector through a coupler, and the photoelectric detector is signal-connected to the data processing module.

[0017] The present invention also proposes a pressure sensing method, which is applied to the pressure sensing system as described above, and the method comprises:

[0018] Inputting the optical signal of the light source into the sensing optical fiber and the reference optical path simultaneously, and determining the light field of the light source;

[0019] After the position to be tested is compressed, a test signal of the sensing optical fiber at the position to be tested is obtained;

[0020] Obtaining the frequency of a beat signal generated by the beat interference of the test light in the sensing optical fiber and the reference light in the reference optical path, and determining the signal at the compressed position according to the frequency;

[0021] The wavelength drift of the modulated optical signal in the sensing optical fiber is obtained, and the force applied to the sensing optical fiber is calculated based on the wavelength drift.

[0022] Preferably, the wavelength drift of the modulated light signal in the sensing optical fiber is obtained, and the force magnitude of the sensing optical fiber is calculated based on the wavelength drift, specifically: the strain information of the sensing optical fiber is calculated based on the wavelength drift, and then the force magnitude is calculated based on the strain information.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The designed optical fiber sensing structure has high sensitivity and can accurately sense pressure;

[0025] 2. When applied to OFDR technology, it can resist electromagnetic interference, corrosion, small size, and strong anti-interference ability. Its internal scattering and its reverse propagation components are roughly evenly distributed along the optical fiber, and the change of refractive index at each point of the optical fiber can be sensed, allowing a spatial resolution of 1 mm or less;

[0026] 3. There is no need to perform grating operations on the optical fiber, which saves costs, reduces the difficulty of production, and simplifies the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention is described in detail below with reference to the embodiments and accompanying drawings, wherein:

[0028] Figure 1 It is a structural schematic diagram of the optical fiber sensing structure in the present invention;

[0029] Figure 2 is a system diagram of the pressure sensing system of the present invention;

[0030] Figure 3 yes Figure 2 Schematic diagram of the measurement system.

[0031] 1. Sensing optical fiber; 2. Support component; 3. Sensing component; 4. Packaging structure. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar components or components with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0033] For the diagnosis of esophageal disorders, the existing in vivo manometry catheters in the medical field at this stage mainly include water perfusion manometry catheters (WHRM) and solid-state manometry catheters (SHRM), but they each have their own shortcomings, especially the inability to obtain high-precision sensing results, and are easily disturbed by factors such as temperature and humidity. Therefore, in recent years, the research on fiber optic sensing in the measurement of gastrointestinal pressure has become a hot topic at home and abroad, mainly based on high-resolution fiber optic manometry technology based on Bragg gratings (FBG). In the existing technology, there are already pressure measurement catheters based on FBG technology, and in vivo experiments have verified that the catheter can work in the digestive tract.

[0034] However, the pressure measuring catheter based on FBG technology needs to write FBGs with equal spacing on the optical fiber. The cost of engraving is higher than that of ordinary optical fiber and the structure is complex, which is not conducive to commercial promotion and application. The optical frequency-domain reflectometry (OFDR) technology mainly used in this application is one of the most advanced distributed sensing technologies at this stage, and it has been widely studied in monitoring temperature and shape. This technology mainly uses a tunable laser as the light source of the system, and uses continuous wave frequency modulation technology to collect the back Rayleigh scattered light signal in the test optical fiber, and realizes interference with a Michelson interferometer or Mach-Zehnder interferometer structure, and then converts the returned interference light signal into an electrical signal to achieve the measurement of external interference. Due to the high sensitivity of optical fiber, anti-electromagnetic interference, corrosion resistance, small size, and strong anti-interference ability, its internal scattering and its reverse propagation component are roughly evenly distributed along the optical fiber, so the change of the refractive index of each point of the optical fiber can be sensed, and a spatial resolution of 1 mm or less can be allowed. Moreover, it does not need to engrave the optical fiber, which reduces the cost and simplifies the structure of the sensor.

[0035] Specifically in one embodiment, the present invention discloses an optical fiber sensing structure, such as Figure 1As shown, it includes a sensing optical fiber 1, and also includes a support member 2 and a sensing member 3 that are fixedly connected. The sensing member 3 is provided with at least one sensitivity enhancement groove. The sensing optical fiber 1 is fixed to the support member 2 and the sensing member 3, respectively, and passes through the sensitivity enhancement groove. The elastic modulus of the support member 2 and the sensing member 3 is greater than the elastic modulus of the sensing optical fiber 1, and the rigidity of the sensing member 3 is greater than the rigidity of the support member 2. By setting the structure of the sensitivity enhancement groove, the sensing accuracy and sensitivity of the sensing optical fiber 1 are improved, and scenes with higher precision requirements can be measured.

[0036] In this embodiment, the support member 2 and the sensing member 3 are both rigid structures with an elastic modulus greater than that of the sensing optical fiber 1 , such as those made by 3D printing, and the specific materials may be 316 stainless steel and aluminum alloy.

[0037] In one embodiment, the stiffness of the support member 2 is lower than that of the sensor member 3. On the one hand, the difference in stiffness can be used to distinguish the sensing area and the supporting area. On the other hand, when it is applied to a pressure measuring catheter, it is also convenient to bend the catheter at the pressure measuring position.

[0038] In one embodiment, the sensing element 3 is provided with a plurality of the sensitivity enhancement grooves, and the plurality of the sensitivity enhancement grooves are arranged along the length direction of the sensing optical fiber 1. Since a plurality of sensitivity enhancement grooves are provided, the sensitivity and measurement accuracy of the sensing optical fiber 1 are further improved. Specifically, the sensitivity enhancement grooves are vertically downwardly opened on the circumferential surface of the sensing element 3, and side wall structures are formed at both ends of each sensitivity enhancement groove, and a side wall structure is spaced between two adjacent sensitivity enhancement grooves.

[0039] In one embodiment, there are two sensing components 3, and the two sensing components 3 are respectively fixed at the two ends of the support component 2, and the support component 2 and the sensing component 3 are bonded with medical grade glue. The support component 2 and the sensing component 3 are both engraved with fixing grooves, and the sensing optical fiber 1 is fixed in the fixing grooves, that is, the fixing grooves are also provided on the side wall structure. Preferably, a packaging structure 4 is also included, and the packaging structure 4 packages the sensing optical fiber 1, the support component 2 and the sensing component 3 into one. In order to improve the axial strain capacity of the sensing optical fiber 1, the elastic modulus of the packaging structure 4 is smaller than the elastic modulus of the sensing optical fiber 1. In this embodiment, the packaging structure 4 adopts the American Dow Corning 3145 silicone with good biocompatibility, and the sensing optical fiber 1, the support component 2 and the sensing component 3 are packaged into an integral cylindrical structure.

[0040] It should be noted that there may be differences in different application scenarios, such as in vivo and in vitro, and other applicable materials may be selected for the support member 2, the sensor member 3, and the flexible structure according to the measurement scenario and required conditions.

[0041] The present invention also discloses a pressure sensing system, such as Figure 2-3 As shown, it includes an optical frequency domain reflection measurement module, a data processing module, and the optical fiber sensing structure as described above, wherein the optical fiber sensing structure is connected to the optical frequency domain reflection measurement module via an optical fiber, and the optical frequency domain reflection measurement module is signal-connected to the data processing module.

[0042] In the system, the optical frequency domain reflection measurement module includes a narrow linewidth tunable light source and a photodetector. The narrow linewidth tunable light source is connected to a reference light path and a measurement light path through an optical fiber. The measurement light path is connected to the optical fiber sensing structure. The reference light path and the measurement light path are connected to the photodetector through a coupler, and the photodetector is signal-connected to the data processing module.

[0043] Therefore, when working, the narrow linewidth tunable light source emits a frequency sweep light, which is simultaneously input into the optical fiber sensing structure and the reference optical path through the optical fiber for signal transmission. When the external environment changes and acts on the optical fiber sensing structure, the optical fiber will be strained, and a modulated optical signal will be generated and transmitted back to the data processing module. The data processing module can calculate the pressure in the external environment based on the modulated optical signal and the signal in the reference optical path, thus realizing accurate pressure sensing. Moreover, the whole process has many advantages such as anti-electromagnetic interference, anti-corrosion, small size, and strong anti-interference ability. At the same time, the internal scattering of the optical fiber sensing structure and its reverse propagation components are roughly evenly distributed along the optical fiber, which can sense the change of the refractive index of each point of the optical fiber, and can allow a spatial resolution of 1 mm or less, with extremely high accuracy.

[0044] In order to further illustrate the solution of the present invention, the present invention also discloses a pressure sensing method, which is applied to the pressure sensing system as described above, and the method comprises:

[0045] Inputting the optical signal of the light source into the sensing optical fiber and the reference optical path simultaneously, and determining the light field of the light source;

[0046] After the position to be tested is compressed, a test signal of the sensing optical fiber at the position to be tested is obtained;

[0047] Obtaining the frequency of a beat signal generated by the beat interference of the test light in the sensing optical fiber and the reference light in the reference optical path, and determining the signal at the compressed position according to the frequency;

[0048] Acquiring a wavelength drift of a modulated optical signal in a sensing optical fiber, and calculating a force applied to the sensing optical fiber according to the wavelength drift;

[0049] The wavelength drift of the modulated optical signal in the sensing optical fiber is obtained, and the force magnitude of the sensing optical fiber is calculated according to the wavelength drift, specifically: the strain information of the sensing optical fiber is calculated according to the wavelength drift, and the force magnitude is calculated according to the strain information.

[0050] In one embodiment, the method is as follows:

[0051] The light source of the optical frequency domain reflectometry module adopts a narrow linewidth tunable laser, which emits a frequency-sweep light. The light field of the frequency-sweep light is:

[0052]

[0053] Where E0 is the light intensity amplitude, is the phase of the light source, is the phase noise. The expression formula is:

[0054]

[0055] Among them, υ0 is the initial optical frequency of the tunable laser, γ is the sweep rate of the tunable laser, and t is the duration of the light. Therefore, according to formula (1) and formula (2), it can be concluded that the optical field of the optical signal emitted by the tunable laser can be expressed as:

[0056]

[0057] When the sensing optical fiber is subjected to force at z and reflects, there is a time delay difference τ in the process of returning the optical signal in the reference optical path and the measurement optical path. Z In this embodiment, the optical path difference between the optical fiber origin in the measurement optical path and the optical fiber end in the reference optical path can be considered to be zero, so z and τ Z The relationship between can be expressed as:

[0058]

[0059] Where z is the point on the optical fiber where the pressure changes, c is the speed of light in a vacuum, and n g To measure the group refractive index of the optical fiber in the optical path, that is, the group refractive index of the sensing optical fiber in the light sensing structure. Further, the equivalent reflection coefficient at position z is:

[0060]

[0061] In the formula, R z and α represent the reflection coefficient at position z and the attenuation refractive index of the sensing fiber, respectively. Combining equations (3), (4) and (5), we can obtain the test signal at position z, i.e., the optical field at position z:

[0062]

[0063] The frequency of the beat signal generated by the beat interference between the test light in the sensor fiber and the reference light in the reference light path is the difference between the test light and the reference light frequency. b It is expressed as:

[0064]

[0065] Among them, f b is the beat frequency, i.e. the difference between the test light frequency and the reference light frequency; γ is the sweep rate of the tunable laser; n g is the group refractive index of the optical fiber to be tested; z is the position point on the optical fiber that is subjected to pressure change; c is the speed of light in vacuum. Through equations (6) and (7), f is calculated by the acquisition and calculation system. b The value of can represent the position information of the optical fiber position z to be tested:

[0066]

[0067] Among them, f b is the beat frequency, i.e. the difference between the test light frequency and the reference light frequency; γ is the sweep rate of the tunable laser; n g is the group refractive index of the optical fiber to be tested; z is the position point on the optical fiber that is subject to pressure change; c is the speed of light in a vacuum.

[0068] Through the above calculation process, the position information of the z position where the force is applied can be determined. Furthermore, the magnitude information of the pressure needs to be calculated. Specifically, since strain will cause the spectrum in the sensing optical fiber to drift, the wavelength drift value is expressed as:

[0069]

[0070] Where λ and Δλ are the average light wavelength and the wavelength drift of the light, respectively; v and Δυ are the average light frequency and the frequency drift of the light, respectively; the strain calibration constant K is s is a constant, and then after determining the values ​​of the average light frequency and the frequency drift of the light, the strain in the sensing optical fiber can be measured. Subsequently, the magnitude information of the pressure at z can be directly calculated based on the strain information. The strain on the optical fiber is proportional to the force it receives. The force can be directly calculated using the strain according to the corresponding formula. The calculation process can refer to many conventional methods in the prior art, which will not be described in detail in this embodiment. That is, through the above formulas (8) and (9), the force position and force magnitude of the place to be measured are finally determined. When applied to in vivo measurement, the swallowing system can also be accurately tested for pressure, thereby providing a reference for subsequent diagnosis or treatment.

[0071] In the description of this specification, if the terms "embodiment one", "this embodiment", "in an embodiment" and the like appear, it means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in the invention or at least one embodiment or example of the invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example; moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in an appropriate manner.

[0072] In the description of this specification, the terms "connect", "install", "fix", "set", "have", etc. are all understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0073] In the description of this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0074] The above description of the embodiments is to facilitate ordinary technicians in the technical field to understand and apply the technology of this case. People familiar with the technology in this field can obviously easily make various modifications to these examples and apply the general principles described here to other embodiments without creative work. Therefore, this case is not limited to the above embodiments. Modifications to the following situations should all be within the scope of protection of this case: ① A new technical solution implemented based on the technical solution of the present invention and combined with existing common knowledge, the technical effect produced by the new technical solution does not exceed the technical effect of the present invention; ② The equivalent replacement of some features of the technical solution of the present invention by using known technology, the technical effect produced is the same as the technical effect of the present invention; ③ The technical solution of the present invention can be expanded, and the substantive content of the expanded technical solution does not exceed the technical solution of the present invention; ④ The equivalent transformation made by using the contents of the description and drawings of the present invention is directly or indirectly applied to other related technical fields.

Claims

1. A fiber optic sensing structure, comprising a sensing fiber, characterized in that: It also includes a supporting member and a sensing member fixedly connected to each other, wherein the sensing member is provided with at least one sensitivity-enhancing groove, and the sensing optical fiber is respectively fixed to the supporting member and the sensing member and passes through the sensitivity-enhancing groove; Wherein, the elastic moduli of the supporting member and the sensing member are both greater than the elastic modulus of the sensing optical fiber, and the stiffness of the sensing member is greater than the stiffness of the supporting member.

2. The optical fiber sensing structure according to claim 1, characterized in that: A plurality of sensitivity-enhancing grooves are provided on the sensing element, and the plurality of sensitivity-enhancing grooves are arranged along the length direction of the sensing optical fiber.

3. The optical fiber sensing structure according to claim 1, characterized in that: There are two sensing components, and the two sensing components are respectively fixed at two ends of the supporting component.

4. The optical fiber sensing structure according to claim 1, characterized in that: The supporting member and the sensing member are both engraved with fixing grooves, and the sensing optical fiber is fixed in the fixing grooves.

5. The optical fiber sensing structure according to claim 4, characterized in that: It also includes a packaging structure, which packages the sensing optical fiber, the supporting component and the sensing component into one.

6. The optical fiber sensing structure according to claim 5, characterized in that: The elastic modulus of the packaging structure is smaller than the elastic modulus of the sensing optical fiber.

7. A pressure sensing system, characterized in that It includes an optical frequency domain reflection measurement module, a data processing module, and the optical fiber sensing structure according to any one of claims 1 to 6, wherein the optical fiber sensing structure is connected to the optical frequency domain reflection measurement module through an optical fiber, and the optical frequency domain reflection measurement module is signal-connected to the data processing module.

8. The pressure sensing system according to claim 7, wherein: The optical frequency domain reflection measurement module includes a narrow linewidth tunable light source and a photodetector. The narrow linewidth tunable light source is connected to a reference light path and a measurement light path through an optical fiber, and the measurement light path is connected to the optical fiber sensing structure. The reference optical path and the measuring optical path are connected to the photoelectric detector via a coupler, and the photoelectric detector is signal-connected to the data processing module.

9. A pressure sensing method, applied to the pressure sensing system according to claim 7 or 8, characterized in that: The method comprises: Input the light signal of the light source into the sensing optical fiber and the reference optical path at the same time, and determine the light field of the light source; After the position to be tested is pressurized, a test signal of the sensing optical fiber at the position to be tested is obtained; Obtaining the frequency of a beat signal generated by the beat interference of the test light in the sensing optical fiber and the reference light in the reference optical path, and determining the signal at the compressed position according to the frequency; The wavelength drift of the modulated optical signal in the sensing optical fiber is obtained, and the force applied to the sensing optical fiber is calculated based on the wavelength drift.

10. The pressure sensing method according to claim 9, wherein: The wavelength drift of the modulated optical signal in the sensing optical fiber is obtained, and the force of the sensing optical fiber is calculated based on the wavelength drift. Specifically, the strain information of the sensing optical fiber is calculated based on the wavelength drift, and the force is calculated based on the strain information.

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