Optical fiber sensor, preparation method thereof and optical fiber sensing device

Abstract

The embodiment of the invention provides an optical fiber sensor, a preparation method thereof and an optical fiber sensing device, and relates to the technical field of optics. The optical fiber sensor provided by the embodiment of the invention comprises a coupling optical fiber and a sensing optical fiber, the first end and the second end of the sensing optical fiber are provided with reflecting films to form a Fabry-Perot cavity; the coupling optical fiber comprises a first tapering structure, the first tapering structure is located between the first end and the second end of the coupling optical fiber, and the first tapering structure comprises a first coupling point; the sensing optical fiber comprises a second tapering structure, the second tapering structure is located between the first end and the second end of the sensing optical fiber, the second tapering structure comprises a second coupling point, and the first coupling point of the coupling optical fiber is coupled with the second coupling point of the sensing optical fiber. According to the optical fiber sensor, the preparation method thereof and the optical fiber sensing device provided by the embodiment of the invention, the wide response bandwidth is realized, and the manufacturing difficulty is reduced at the same time.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to an optical fiber sensor and a preparation method thereof, and an optical fiber sensing device. Background Art

[0002] The Fabry-Perot cavity is a precision sensor structure based on the principle of optical interference, which is widely used in lasers, spectral analysis, optical communications and sensing. The main principle of the Fabry-Perot cavity is to confine light between two mirrors for multiple reflections, thereby increasing the number and time of interactions between light and matter, and greatly improving the energy density in the cavity.

[0003] The optical resonance direction of the traditional Fabry-Perot cavity is consistent with the acoustic detection direction. The acoustic wave will reflect in the cavity, causing the response bandwidth of the Fabry-Perot cavity to become smaller, resulting in the Fabry-Perot cavity being unable to distinguish the wavelength of high-frequency acoustic waves. The use of multi-layer film coating to construct a Bragg grating can solve the above problems to a certain extent, but this solution has extremely high requirements for the coating, and the temperature during coating may cause damage and deformation to the cavity polymer material. Summary of the invention

[0004] The embodiments of the present invention provide an optical fiber sensor and a method for preparing the same, as well as an optical fiber sensing device, which avoid the situation in which multiple reflections of sound waves in a Fabry-Perot cavity cause the response bandwidth of the sensor to become smaller, thereby making it impossible to detect high-frequency sound waves, thereby achieving a wide response bandwidth and reducing the difficulty of manufacturing.

[0005] In a first aspect, an embodiment of the present invention provides an optical fiber sensor, comprising a coupling optical fiber and a sensing optical fiber;

[0006] The first end and the second end of the sensing optical fiber are provided with a reflective film to form a Fabry-Perot cavity;

[0007] The coupling optical fiber includes a first tapered structure, the first tapered structure is located between the first end and the second end of the coupling optical fiber, and the first tapered structure includes a first coupling point;

[0008] The sensing optical fiber includes a second tapered structure, the second tapered structure is located between the first end and the second end of the sensing optical fiber, the second tapered structure includes a second coupling point, and the first coupling point of the coupling optical fiber is coupled to the second coupling point of the sensing optical fiber;

[0009] The laser beam is coupled into the coupling optical fiber from the first end, coupled into the Fabry-Perot cavity through the first coupling point and the second coupling point, and part of the beam in the Fabry-Perot cavity is coupled into the coupling optical fiber through the second coupling point and the first coupling point, and coupled out from the second end of the coupling optical fiber.

[0010] Optionally, the sensing optical fiber is in a straight line shape, the coupling optical fiber is in a bent shape, and the first coupling point is the vertex of the bent shape.

[0011] Optionally, the coupling optical fiber is in a straight line shape, the sensing optical fiber is in a bent shape, and the second coupling point is the vertex of the bent shape.

[0012] Optionally, the optical fiber sensor further comprises a bearing structure, and the coupling optical fiber and the sensing optical fiber are both fixed on the bearing structure.

[0013] Optionally, the sensor further comprises a fixing glue, which is used to fix the coupling optical fiber and the sensing optical fiber on the bearing structure, and the refractive index of the fixing glue is smaller than the refractive index of the core of the coupling optical fiber and the core of the sensing optical fiber.

[0014] Optionally, the reflective film is a total reflective film, and the thickness of the total reflective film is greater than 50 nm.

[0015] In a second aspect, an embodiment of the present invention provides an optical fiber sensing device, including a laser, a detector, and an optical fiber sensor provided by any embodiment of the present invention;

[0016] The output end of the laser is coupled to the first end of the coupling optical fiber, and the laser is used to emit a laser beam;

[0017] The detector is coupled to the second end of the coupling optical fiber, and the detector is used for converting the optical signal into an electrical signal.

[0018] In a third aspect, an embodiment of the present invention provides a method for preparing an optical fiber sensor, which is applicable to preparing an optical fiber sensor provided by any embodiment of the present invention, and the preparation method comprises:

[0019] preparing two optical fibers, wherein the optical fibers include a first optical fiber and a second optical fiber;

[0020] Cutting both ends of the first optical fiber and both ends of the second optical fiber flat;

[0021] forming a reflective film at both ends of the first optical fiber;

[0022] Tapering the first optical fiber and the second optical fiber;

[0023] The tapered region of the first optical fiber and the tapered region of the second optical fiber are coupled and fixed.

[0024] Optionally, coupling and fixing the first optical fiber and the second optical fiber comprises:

[0025] bending the tapered region of the first optical fiber, and coupling and fixing the bent first optical fiber to the second optical fiber;

[0026] The bending apex of the first optical fiber is coupled to the second optical fiber.

[0027] Optionally, coupling and fixing the first optical fiber and the second optical fiber comprises:

[0028] bending the tapered region of the second optical fiber, and coupling and fixing the bent second optical fiber to the first optical fiber;

[0029] The bending apex of the second optical fiber is coupled to the first optical fiber.

[0030] The optical fiber sensor provided by the embodiment of the present invention uses the evanescent field to couple the laser beam from the coupling optical fiber to the sensing optical fiber, so that the propagation direction of the sound wave forms a certain angle with the resonance direction of the laser beam in the Fabry-Perot cavity, thereby avoiding the situation where the response bandwidth of the optical fiber sensor becomes smaller due to multiple reflections of the sound wave in the Fabry-Perot cavity, thereby being unable to detect high-frequency sound waves. The response bandwidth of the optical fiber sensor can reach hundreds of MHz. In addition, by separating the coupling optical fiber that transmits the laser beam from the sensing optical fiber, the sensing optical fiber does not need to output laser, thereby improving the reflectivity of the reflective film at both ends of the sensing optical fiber, while improving the quality factor of the Fabry-Perot cavity and reducing the difficulty of making the Fabry-Perot cavity.

[0031] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 is a schematic structural diagram of an optical fiber sensor provided by an embodiment of the present invention;

[0034] Figure 2 is a schematic structural diagram of another optical fiber sensor provided by an embodiment of the present invention;

[0035] Figure 3 is a schematic diagram of the structure of another sensor provided by an embodiment of the present invention;

[0036] Figure 4 is a schematic structural diagram of an optical fiber sensing device provided by an embodiment of the present invention;

[0037] Figure 5 is a schematic structural diagram of another optical fiber sensing device provided by an embodiment of the present invention;

[0038] Figure 6 is a flow chart of a method for preparing an optical fiber sensor provided by an embodiment of the present invention;

[0039] Figure 7 is a flow chart of another method for preparing an optical fiber sensor provided by an embodiment of the present invention;

[0040] Figure 8 is a flow chart of a processing method of a first optical fiber and a second optical fiber provided by an embodiment of the present invention;

[0041] Fig. 9 is a flow chart of another method for preparing an optical fiber sensor provided by an embodiment of the present invention;

[0042] Fig.10 This is a flow chart of another processing method of the first optical fiber and the second optical fiber provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the present solution, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0044] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0045] An embodiment of the present invention provides an optical fiber sensor. Figure 1 is a schematic diagram of the structure of an optical fiber sensor provided by an embodiment of the present invention, with reference to Figure 1The light sensor includes a coupling optical fiber 100 and a sensing optical fiber 200; a reflective film 202 is provided at the first end and the second end of the sensing optical fiber 200 to form a Fabry-Perot cavity; the coupling optical fiber 100 includes a first tapered structure, the first tapered structure is located between the first end 102 and the second end 103 of the coupling optical fiber 100, and the first tapered structure includes a first coupling point 101; the sensing optical fiber 200 includes a second tapered structure, the second tapered structure is located between the first end and the second end of the sensing optical fiber 200, the second tapered structure includes a second coupling point 201, and the first coupling point of the coupling optical fiber 100 is coupled to the second coupling point of the sensing optical fiber 200; the laser beam is coupled into the coupling optical fiber from the first end 102 of the coupling optical fiber 100, and is coupled into the Fabry-Perot cavity through the first coupling point and the second coupling point, and part of the beam in the Fabry-Perot cavity is coupled into the coupling optical fiber through the second coupling point 201 and the first coupling point 101, and is coupled out from the second end 103 of the coupling optical fiber 100.

[0046] refer to Figure 1, the laser beam is coupled into the sensing optical fiber 200 from the first end 102 of the coupling optical fiber 100. When the laser beam propagates to the first coupling point 101, part of the laser beam will be coupled into the sensing optical fiber 200. The laser beam coupled into the sensing optical fiber 200 will be transmitted along the sensing optical fiber 200. When the laser beam propagates to the first end and the second end of the sensing optical fiber 200, the laser beam will be reflected by the reflective film 202, and thus propagate back and forth in the sensing optical fiber 200. The modes that meet the resonance condition of the Fabry-Perot cavity will constructively interfere during the propagation process and resonate. The modes that meet the resonance condition of the Fabry-Perot cavity in the laser beam coupled into the sensing optical fiber 200 will resonate in the Fabry-Perot cavity, and the photon lifetime of the resonant mode will continue to extend, while the modes that do not meet the resonance condition of the Fabry-Perot cavity will be coupled out of the sensing optical fiber 200 from the second coupling point 201 and return to the coupling optical fiber 100 to continue to transmit. At the same time, the laser beam that is not coupled into the sensing optical fiber 200 will propagate to the second end 103 of the coupling optical fiber 100. Since the modes satisfying the resonance condition of the Fabry-Perot cavity are retained in the sensing fiber 200, these modes will not be coupled out from the second end 103 of the coupling fiber 100 temporarily. In the spectrum of the laser beam output from the second end 103 of the coupling fiber 100, the intensity of the modes satisfying the resonance condition of the Fabry-Perot cavity will be lower than that of other modes. These modes with lower intensity are the resonance modes of the Fabry-Perot cavity, and the ratio of the intensity of the resonance mode to the intensity of other modes is the extinction ratio. When the second coupling point 201 of the sensing fiber 200 receives an acoustic wave, the acoustic pressure of the acoustic wave will cause a perturbation to the sensing fiber 200, thereby causing the resonance mode of the Fabry-Perot cavity to change, that is, the center frequency, line width and extinction ratio of the resonance mode will change accordingly. Therefore, the frequency, intensity and other information of the acoustic wave received by the sensing fiber 200 can be inferred from the changes in the center frequency, line width and extinction ratio of the resonance mode. At the same time, since the optical fiber sensor receives sound waves at the second coupling point 201 of the sensing optical fiber 200, the sound waves will quickly pass through the sensing optical fiber 200, avoiding multiple reflections of the sound waves in the sensing optical fiber 200 and improving the response capability of the sensing optical fiber 200 to high-frequency sound waves.

[0047] It is understandable that the optical fiber sensor provided in the embodiment of the present invention can be used not only to detect sound waves, but also to detect other physical quantities that may cause perturbations to the sensing optical fiber 200, such as temperature and pressure.

[0048] The optical fiber sensor provided by the embodiment of the present invention uses the evanescent field to couple the laser beam from the coupling optical fiber to the sensing optical fiber, so that the propagation direction of the sound wave forms a certain angle with the resonance direction of the laser beam in the Fabry-Perot cavity, thereby avoiding the situation where the response bandwidth of the optical fiber sensor becomes smaller due to multiple reflections of the sound wave in the Fabry-Perot cavity, thereby being unable to detect high-frequency sound waves. The response bandwidth of the optical fiber sensor can reach hundreds of MHz. In addition, by separating the coupling optical fiber that transmits the laser beam from the sensing optical fiber, the sensing optical fiber does not need to output laser, thereby improving the reflectivity of the reflective film at both ends of the sensing optical fiber, while improving the quality factor of the Fabry-Perot cavity and reducing the difficulty of making the Fabry-Perot cavity.

[0049] The optical fiber sensor provided by the embodiment of the present invention supports laser beams from visible light to infrared light bands, can be applied to the detection of low-frequency ultrasonic waves in the air or high-frequency ultrasonic waves in water, and can also be used in the field of lasers as an independent external cavity. When detecting low-frequency ultrasonic waves in the air, the optical fiber sensor does not need to be packaged, but when detecting high-frequency sound waves in water, since the refractive index of water is larger, a low-refractive-index glue is required to wrap the optical fiber to ensure that the light beam can be totally internally reflected in the optical fiber. In addition, packaging the optical fiber sensor can prevent the optical fiber from being affected by water flow.

[0050] Optionally, the taper radius of the first tapered structure and the second tapered structure is less than or equal to 1 μm. The optical fiber is heated, melted, and then stretched to form a tapered structure, and the tapered structures are coupled to each other, so that the transmission of optical signals between different tapered structures can be achieved. The small size of the tapered area allows the sensor to be more flexibly integrated into various detection devices without occupying too much volume.

[0051] refer to Figure 1 Optionally, the sensing optical fiber 200 is in a straight line shape, the coupling optical fiber 100 is in a bent shape, and the first coupling point is the vertex of the bent shape 101. Figure 2 is a schematic diagram of the structure of another optical fiber sensor provided by an embodiment of the present invention, referring to Figure 2 Optionally, the coupling optical fiber 100 is in a straight line shape, the sensing optical fiber 200 is in a bent shape, and the second coupling point 201 is the vertex of the bent shape.

[0052] Combination Figure 1 and Figure 2 As shown, Figure 1 The coupling optical fiber 100 is bent and placed, and the first coupling point 101 is close to the second coupling point 201 of the sensing optical fiber 200, so that the laser beam can be transmitted between the coupling optical fiber 100 and the sensing optical fiber 200. Figure 2 The sensing optical fiber 200 is bent and placed, and the first coupling point 101 is also close to the second coupling point 201 , so that the laser beam can be transmitted between the coupling optical fiber 100 and the sensing optical fiber 200 .

[0053] Figure 3 is a schematic diagram of the structure of another sensor provided by an embodiment of the present invention, referring to Figure 3 The optical fiber sensor also includes a bearing structure 500, and the coupling optical fiber 100 and the sensing optical fiber 200 are both fixed on the bearing structure 500. The bearing structure 500 is used to bear the coupling optical fiber 100 and the sensing optical fiber 200, and the first coupling point 101 and the second coupling point 201 need to be fixed on the bearing structure 500 to ensure that the coupling relationship between the first coupling point 101 and the second coupling point 201 remains unchanged, thereby ensuring that the laser beam can be transmitted between the first coupling point 101 and the second coupling point 201. On this basis, the coupling optical fiber 100 and the sensing optical fiber 200 can be partially fixed on the bearing structure 500, and the coupling optical fiber 100 and the sensing optical fiber 200 can also be completely fixed on the bearing structure. The embodiment of the present invention does not specifically limit the form of the bearing structure 500.

[0054] Optionally, refer to Figure 3 , the sensor also includes a fixing glue ( Figure 3 The fixing glue is used to fix the coupling optical fiber 100 and the sensing optical fiber 200 on the bearing structure 500, and the refractive index of the fixing glue is less than the refractive index of the core of the coupling optical fiber 100 and the core of the sensing optical fiber 200. The fixing glue can protect the coupling optical fiber 100 and the sensing optical fiber 200, and because the refractive index of the fixing glue is less than the refractive index of the core of the coupling optical fiber 100 and the core of the sensing optical fiber 200, the fixing glue will not destroy the condition of total reflection of the laser beam in the coupling optical fiber 100 and the sensing optical fiber 200, and the laser beam can still propagate in the coupling optical fiber 100 and the sensing optical fiber 200.

[0055] Optionally, the reflective film 202 is a fully reflective film, and the thickness of the fully reflective film is greater than 50nm. Since the first end and the second end of the sensing optical fiber 200 do not need to output a laser beam, the first end and the second end of the sensing optical fiber 200 do not need to be plated with a semi-transparent and semi-reflective film. The first end and the second end can be directly plated with a fully reflective film with a reflectivity greater than 99%. Plating a fully reflective film with a higher reflectivity can improve the quality factor of the sensing optical fiber 200, reduce the loss of the resonant mode in the sensing optical fiber 200, and make it easier for the resonant mode to oscillate in the sensing optical fiber 200. Moreover, the fully reflective film at the first end and the second end of the sensing optical fiber 200 has no special requirements for the coating process and the material of the fully reflective film. It only needs to have a thickness greater than 50nm to limit the resonant mode to the sensing optical fiber 200.

[0056] Optionally, the coupling fiber 100 includes a polarization-maintaining fiber, and the sensing fiber 200 includes a polarization-maintaining fiber. In theory, when the light beam propagates in the optical fiber, no birefringence will occur, and the polarization state of the light beam will not change during the propagation process. However, errors in the production process of the optical fiber can cause uneven thickness or bending of the optical fiber, which can cause birefringence of the light beam in the optical fiber. In addition, when the optical fiber is affected by external interference, such as wavelength, curvature or temperature, the light beam in the optical fiber also produces birefringence. After the light beam in the optical fiber has birefringence, the polarization state of the light will become chaotic when the light beam is transmitted in the optical fiber. Polarization-maintaining fiber actively introduces a stronger birefringence phenomenon through structural design to eliminate the birefringence phenomenon caused by optical fiber structural errors and external interference, thereby keeping the polarization state of the laser beam unchanged. Polarization-maintaining fiber can improve the stability of the sensor by maintaining the polarization state of the laser beam unchanged.

[0057] Based on the same inventive concept, an embodiment of the present invention provides an optical fiber sensing device, Figure 4 is a schematic structural diagram of an optical fiber sensing device provided by an embodiment of the present invention, Figure 5 is a schematic diagram of the structure of another optical fiber sensing device provided by an embodiment of the present invention, Figure 4 and Figure 5 As shown, the optical fiber sensing device includes a laser 300, a detector 400 and an optical fiber sensor provided by any embodiment of the present invention; the output end of the laser 300 is coupled to the first end 102 of the coupling optical fiber 100, and the laser 300 is used to emit a laser beam; the detector 400 is coupled to the second end 103 of the coupling optical fiber 100, and the detector 400 is used to convert the optical signal into an electrical signal.

[0058] Combination Figure 4 and Figure 5As shown, after the laser beam is output from the laser 300, it is coupled into the coupling optical fiber 100. When the laser beam propagates to the first coupling point 101, part of the laser beam will be coupled into the sensing optical fiber 200, wherein the mode that meets the resonance condition of the Fabry-Perot cavity will resonate in the Fabry-Perot cavity, and the photon lifetime of the resonant mode will be continuously extended, while the mode that does not meet the resonance condition of the Fabry-Perot cavity will be coupled out of the sensing optical fiber 200 and return to the coupling optical fiber 100 for continued transmission. At the same time, the laser beam that is not coupled into the sensing optical fiber 200 will propagate to the input end of the second end 103 of the coupling optical fiber 100 and be received by the detector 400. Optionally, the detector 400 includes a spectrometer, which can detect the spectrum information of the received laser beam. Since the resonance mode is left in the Fabry-Perot cavity, these modes will not be coupled into the detector 400 temporarily. In the spectrum of the laser beam detected by the detector 400, the intensity of the mode that meets the resonance condition of the Fabry-Perot cavity will be lower than that of other modes. When changes in sound waves, temperature or pressure cause perturbations to the sensing optical fiber 200, the information of the sound waves, temperature or pressure can be inferred by analyzing the changes in the center frequency, line width and extinction ratio of the resonant mode.

[0059] Based on the same inventive concept, an embodiment of the present invention provides a method for preparing an optical fiber sensor, which is applicable to preparing an optical fiber sensor provided by any embodiment of the present invention. Figure 6 is a flowchart of a method for preparing an optical fiber sensor provided by an embodiment of the present invention, with reference to Figure 6 , the preparation method comprises:

[0060] S101. Prepare two optical fibers, where the optical fibers include a first optical fiber and a second optical fiber.

[0061] Optionally, the first optical fiber and the second optical fiber are respectively multimode optical fibers or polarization-maintaining optical fibers. Multimode optical fibers can transmit multiple modes, and polarization-maintaining optical fibers can keep the polarization state of the laser beam unchanged.

[0062] S102, cutting both ends of the first optical fiber and both ends of the second optical fiber flat.

[0063] Specifically, the first optical fiber and the second optical fiber are cut short to a length suitable for fixing on the taper fixture, and the coating layers at both ends of the first optical fiber and the second optical fiber are stripped, and the stripped parts are wiped clean with dust-free paper dipped in alcohol. If they are not wiped clean, dust or coating layer stripping materials will absorb the coating material when the reflective film is plated, resulting in uneven end face coating. After wiping clean, use a fiber optic cutter to cut both ends of the first optical fiber and the second optical fiber to obtain a flat end face. After cutting, the end face of the first optical fiber needs to be placed under a microscope to observe whether the end face is flat. An uneven end face will directly affect the coating effect.

[0064] S103, forming a reflective film at both ends of the first optical fiber.

[0065] Specifically, a reflective film is plated on the two end faces of the first optical fiber. The reflective film can be made of silver, copper or other materials that can form a high reflective film on the optical fiber end face. The thickness of the reflective film must be greater than 50nm so that the reflective film can limit the light coupled into the first optical fiber to be continuously reflected in the cavity.

[0066] S104, tapering the first optical fiber and the second optical fiber.

[0067] Specifically, the first optical fiber after coating is already a Fabry-Perot cavity, but because the reflection films at both ends are total reflection films, the first optical fiber cannot couple into the laser beam, so the middle area of ​​the first optical fiber needs to be tapered to obtain a light coupling entrance.

[0068] S105, coupling and fixing the tapered region of the first optical fiber and the tapered region of the second optical fiber.

[0069] Specifically, after the first optical fiber and the second optical fiber are tapered by using an optical fiber taper machine, it is necessary to adjust the positions of the first optical fiber and the second optical fiber so that the tapered regions of the first optical fiber and the second optical fiber can be coupled to each other, so that the laser beam can be transmitted between the first optical fiber and the second optical fiber. The precision five-axis translation stage is controlled to couple the first optical fiber and the second optical fiber, and the transmission spectra of the first optical fiber and the second optical fiber are monitored to lock the optimal coupling point, and then the fixing glue is transferred to the coupling point by micro-transfer technology to fix it on the bearing structure. After the fixing glue is cured, a layer of fixing glue is spread on the glass slide to completely encapsulate it. The encapsulated device is an optical fiber sensor, in which the first optical fiber corresponds to the sensing optical fiber in the light sensor provided in the embodiment of the present invention, and the second optical fiber corresponds to the coupling optical fiber in the light sensor provided in the embodiment of the present invention.

[0070] Figure 7 is a flow chart of another method for preparing an optical fiber sensor provided by an embodiment of the present invention, with reference to Figure 7 , the preparation method comprises:

[0071] S201. Prepare two optical fibers, where the optical fibers include a first optical fiber and a second optical fiber.

[0072] S202, cutting both ends of the first optical fiber and both ends of the second optical fiber flat.

[0073] S203, forming a reflective film at both ends of the first optical fiber.

[0074] S204, tapering the first optical fiber and the second optical fiber.

[0075] S205, bend the tapered region of the first optical fiber, and couple and fix the bent first optical fiber to the second optical fiber; wherein the bending vertex of the first optical fiber is coupled to the second optical fiber.

[0076] Figure 8is a flowchart of a processing method of a first optical fiber and a second optical fiber provided by an embodiment of the present invention, combined with Figure 1 and Figure 8 As shown, Figure 8 The process shown corresponds to Figure 1 The optical fiber sensor shown.

[0077] Fig. 9 is a flowchart of another method for preparing an optical fiber sensor provided by an embodiment of the present invention, with reference to Fig. 9 , the preparation method comprises:

[0078] S301. Prepare two optical fibers, wherein the optical fibers include a first optical fiber and a second optical fiber.

[0079] S302, cutting both ends of the first optical fiber and both ends of the second optical fiber flat.

[0080] S303, forming a reflective film at both ends of the first optical fiber.

[0081] S304, tapering the first optical fiber and the second optical fiber.

[0082] S305, bend the tapered region of the second optical fiber, and couple and fix the bent second optical fiber to the first optical fiber; wherein the bending vertex of the second optical fiber is coupled to the first optical fiber.

[0083] Fig.10 is another flow chart of a processing method of the first optical fiber and the second optical fiber provided by an embodiment of the present invention, combined with Figure 2 and Fig.10 As shown, Fig.10 The process shown corresponds to Figure 2 The optical fiber sensor shown.

[0084] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An optical fiber sensor, characterized in that: Including coupling optical fiber and sensing optical fiber; The first end and the second end of the sensing optical fiber are provided with a reflective film to form a Fabry-Perot cavity; The coupling optical fiber comprises a first tapered structure, the first tapered structure is located between the first end and the second end of the coupling optical fiber, and the first tapered structure comprises a first coupling point; The sensing optical fiber comprises a second tapered structure, the second tapered structure is located between the first end and the second end of the sensing optical fiber, the second tapered structure comprises a second coupling point, the first coupling point of the coupling optical fiber is coupled to the second coupling point of the sensing optical fiber; A laser beam is coupled into the coupling optical fiber from the first end, coupled into the Fabry-Perot cavity through the first coupling point and the second coupling point, and a portion of the beam in the Fabry-Perot cavity is coupled into the coupling optical fiber through the second coupling point and the first coupling point, and coupled out from the second end of the coupling optical fiber.

2. The optical fiber sensor according to claim 1, characterized in that: The sensing optical fiber is in a straight line shape, the coupling optical fiber is in a bent shape, and the first coupling point is the vertex of the bent shape.

3. The optical fiber sensor according to claim 1, characterized in that: The coupling optical fiber is in a straight line shape, the sensing optical fiber is in a bent shape, and the second coupling point is the vertex of the bent shape.

4. The optical fiber sensor according to claim 1, characterized in that: The optical fiber sensor further comprises a bearing structure, and the coupling optical fiber and the sensing optical fiber are both fixed on the bearing structure.

5. The optical fiber sensor according to claim 4, characterized in that: The sensor further comprises a fixing glue, which is used to fix the coupling optical fiber and the sensing optical fiber on the bearing structure, and the refractive index of the fixing glue is smaller than the refractive index of the core of the coupling optical fiber and the core of the sensing optical fiber.

6. The optical fiber sensor according to claim 1, characterized in that: The reflective film is a total reflective film, and the thickness of the total reflective film is greater than 50nm.

7. An optical fiber sensing device, characterized in that: Comprising a laser, a detector and an optical fiber sensor as claimed in any one of claims 1 to 6; The output end of the laser is coupled to the first end of the coupling optical fiber, and the laser is used to emit a laser beam; The detector is coupled to the second end of the coupling optical fiber, and the detector is used to convert the optical signal into an electrical signal.

8. A method for preparing an optical fiber sensor, characterized in that: Suitable for preparing the optical fiber sensor according to any one of claims 1 to 6, the preparation method comprising: preparing two optical fibers, wherein the optical fibers include a first optical fiber and a second optical fiber; Cutting both ends of the first optical fiber and both ends of the second optical fiber flat; forming a reflective film at both ends of the first optical fiber; Tapering the first optical fiber and the second optical fiber; The tapered region of the first optical fiber and the tapered region of the second optical fiber are coupled and fixed.

9. The preparation method according to claim 8, characterized in that: Coupling and fixing the first optical fiber and the second optical fiber comprises: bending the tapered region of the first optical fiber, and coupling and fixing the bent first optical fiber to the second optical fiber; The bending apex of the first optical fiber is coupled to the second optical fiber.

10. The preparation method according to claim 8, characterized in that: Coupling and fixing the first optical fiber and the second optical fiber comprises: bending the tapered region of the second optical fiber, and coupling and fixing the bent second optical fiber to the first optical fiber; The bending apex of the second optical fiber is coupled to the first optical fiber.

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