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

Abstract

Embodiments of the present invention provide an optical fiber sensor, a method for preparing the same, and an optical fiber sensing device, relating to the field of optical technology. The optical fiber sensor provided by the embodiment of the present invention includes a coupling optical fiber and a 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 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; 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, and 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. The optical fiber sensor, the method for preparing the same, and the optical fiber sensing device provided by the embodiment of the present invention achieve a wide response bandwidth while reducing the difficulty of manufacturing.

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, widely used in lasers, spectroscopy, optical communications, and sensing. The key principle of a Fabry-Perot cavity is to trap light between two mirrors, causing it to reflect multiple times. This increases the number and duration of interactions between light and matter, significantly boosting the energy density within the cavity.

[0003] The optical resonance direction of a traditional Fabry-Perot cavity aligns with the acoustic detection direction. Sound waves reflect within the cavity, reducing the cavity's response bandwidth and rendering it unable to distinguish high-frequency sound waves. While constructing a Bragg grating using multilayer coatings can address this issue to some extent, this approach places extremely high demands on the coating, and the temperatures during coating can damage and deform the cavity's polymer material. Summary of the Invention

[0004] The embodiments of the present invention provide an optical fiber sensor, a preparation method thereof, and an optical fiber sensing device, which avoid the situation where 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. This achieves a wide response bandwidth and reduces 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 first end of the coupling optical fiber, 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 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 includes 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 includes a fixing glue, which is used to fix the coupling optical fiber and the sensing optical fiber on the supporting 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 a fiber optic sensing device, comprising a laser, a detector, and the fiber optic 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 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 the optical fiber sensor provided by any embodiment of the present invention, and the preparation method includes:

[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 includes:

[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 includes:

[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 fiber optic sensor provided by an embodiment of the present invention utilizes an evanescent field to couple a laser beam from a coupling fiber into a sensing fiber. This ensures that the propagation direction of the acoustic wave forms a certain angle with the resonant direction of the laser beam within the Fabry-Perot cavity. This prevents multiple reflections of the acoustic wave within the Fabry-Perot cavity, which can reduce the optical fiber sensor's response bandwidth and render it incapable of detecting high-frequency acoustic waves. The optical fiber sensor has a response bandwidth of up to 100 MHz. Furthermore, by separating the coupling fiber that transmits the laser beam from the sensing fiber, the sensing fiber no longer needs to output laser light. This improves the reflectivity of the reflective films at both ends of the sensing fiber, enhancing the quality factor of the Fabry-Perot cavity while also reducing the difficulty of fabricating the cavity.

[0031] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily 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 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 This is a schematic structural diagram of another sensor provided by an embodiment of the present invention;

[0036] Figure 4 1 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 This 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 This is a flow chart of a processing method for a first optical fiber and a second optical fiber provided by an embodiment of the present invention;

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

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

[0043] In order to enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described 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 making creative efforts should fall within the scope of protection of the present invention.

[0044] It should be noted that the terms "first", "second", etc. in the description 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 numbers 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 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 This 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, which 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, which is located between the first end and the second end of the sensing optical fiber 200, and 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; part of the light 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 1The laser beam is coupled into the sensing fiber 200 from the first end 102 of the coupling fiber 100. When the laser beam propagates to the first coupling point 101, a portion of the laser beam is coupled into the sensing fiber 200. The laser beam coupled into the sensing fiber 200 propagates along the sensing fiber 200. When the laser beam propagates to the first and second ends of the sensing fiber 200, it is reflected by the reflective film 202, thereby propagating back and forth within the sensing fiber 200. Modes that meet the resonance conditions of the Fabry-Perot cavity will constructively interfere during propagation, resulting in resonance. Modes within the laser beam coupled into the sensing fiber 200 that meet the resonance conditions of the Fabry-Perot cavity will resonate within the cavity, and the photon lifetime of these resonant modes will continue to increase. Modes that do not meet the resonance conditions of the Fabry-Perot cavity will be coupled out of the sensing fiber 200 at the second coupling point 201 and return to the coupling fiber 100 for continued transmission. Meanwhile, the laser beam not coupled into the sensing fiber 200 propagates to the second end 103 of the coupling fiber 100. Because the modes that satisfy the resonance conditions of the Fabry-Perot cavity are retained within the sensing fiber 200, these modes will not be temporarily coupled out from the second end 103 of the coupling fiber 100. In the spectrum of the laser beam output from the second end 103 of the coupling fiber 100, the intensities of the modes that satisfy the resonance conditions of the Fabry-Perot cavity will be lower than those of other modes. These modes with lower intensities are the resonant modes of the Fabry-Perot cavity, and the ratio of the intensity of the resonant mode to the intensity of the 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 perturbs the sensing fiber 200, causing the resonant mode of the Fabry-Perot cavity to change. Specifically, the center frequency, linewidth, and extinction ratio of the resonant mode will change accordingly. Therefore, based on the changes in the center frequency, linewidth, and extinction ratio of the resonant mode, the frequency, intensity, and other information of the acoustic wave received by the sensing fiber 200 can be inferred. 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 by 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 fiber optic sensor provided by an embodiment of the present invention utilizes an evanescent field to couple a laser beam from a coupling fiber into a sensing fiber. This ensures that the propagation direction of the acoustic wave forms a certain angle with the resonant direction of the laser beam within the Fabry-Perot cavity. This prevents multiple reflections of the acoustic wave within the Fabry-Perot cavity, which can reduce the optical fiber sensor's response bandwidth and render it incapable of detecting high-frequency acoustic waves. The optical fiber sensor has a response bandwidth of up to 100 MHz. Furthermore, by separating the coupling fiber that transmits the laser beam from the sensing fiber, the sensing fiber no longer needs to output laser light. This improves the reflectivity of the reflective films at both ends of the sensing fiber, enhancing the quality factor of the Fabry-Perot cavity while also reducing the difficulty of fabricating the cavity.

[0049] The fiber optic sensor provided by the present invention supports laser beams from the visible to infrared wavelengths and can be used to detect low-frequency ultrasonic waves in air or high-frequency ultrasonic waves in water. It can also be used as an independent external cavity in the laser field. When detecting low-frequency ultrasonic waves in air, the fiber optic sensor can be left unencapsulated. However, when detecting high-frequency sound waves in water, due to the higher refractive index of water, a low-refractive-index adhesive is required to wrap the optical fiber to ensure total internal reflection of the optical beam within the fiber. Furthermore, encapsulation of the fiber optic sensor protects the fiber from the effects of water flow.

[0050] Optionally, the taper radius of the first and second tapered structures is less than or equal to 1 μm. By heating, melting, and stretching the optical fiber to form the tapered structures, and coupling the tapered structures, optical signals can be transmitted between the different tapered structures. The small size of the tapered region allows for more flexible integration of the sensor into various detection devices without occupying a large 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 This 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] Combine Figure 1 and Figure 2 As shown, Figure 1 The coupling fiber 100 is bent and placed, and the first coupling point 101 is close to the second coupling point 201 of the sensing fiber 200, so that the laser beam can be transmitted between the coupling fiber 100 and the sensing 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 This 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 further includes a supporting structure 500, to which the coupling optical fiber 100 and the sensing optical fiber 200 are both fixed. The supporting structure 500 is used to support the coupling optical fiber 100 and the sensing optical fiber 200. The first coupling point 101 and the second coupling point 201 need to be fixed to the supporting 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. Based on this, the coupling optical fiber 100 and the sensing optical fiber 200 can be partially fixed to the supporting structure 500, or the coupling optical fiber 100 and the sensing optical fiber 200 can be completely fixed to the supporting structure. This embodiment of the present invention does not impose any specific restrictions on the form of the supporting structure 500.

[0054] Optionally, refer to Figure 3 , the sensor also includes a fixing glue ( Figure 3 (Not shown in the figure), the fixing glue is used to fix the coupling fiber 100 and the sensing fiber 200 to the supporting structure 500. The refractive index of the fixing glue is lower than the refractive index of the core of the coupling fiber 100 and the sensing fiber 200. The fixing glue protects the coupling fiber 100 and the sensing fiber 200. Because the refractive index of the fixing glue is lower than the refractive index of the core of the coupling fiber 100 and the sensing fiber 200, the fixing glue does not affect the conditions for total internal reflection of the laser beam in the coupling fiber 100 and the sensing fiber 200, and the laser beam can still propagate in the coupling fiber 100 and the sensing fiber 200.

[0055] Optionally, the reflective film 202 is a fully reflective film having a thickness greater than 50 nm. Since the first and second ends of the sensing optical fiber 200 do not need to output a laser beam, the first and second ends of the sensing optical fiber 200 do not need to be coated with a semi-transparent, semi-reflective film. Instead, the first and second ends can be directly coated with a fully reflective film having a reflectivity greater than 99%. Coating with a fully reflective film having a higher reflectivity can improve the quality factor of the sensing optical fiber 200, reduce the loss of the resonant mode within the sensing optical fiber 200, and make it easier for the resonant mode to oscillate within the sensing optical fiber 200. Furthermore, the fully reflective films at the first and second ends of the sensing optical fiber 200 have no special requirements for the coating process or the material of the fully reflective films; they only need to have a thickness greater than 50 nm to confine the resonant mode within 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, birefringence will not occur when the light beam propagates in the optical fiber, and the polarization state of the light beam will not change during propagation. However, errors in the optical fiber production process can cause uneven thickness or bending of the optical fiber, which can cause birefringence in 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 exhibits birefringence, the polarization state of the light becomes chaotic when the light beam propagates in the optical fiber. Polarization-maintaining fiber actively introduces stronger birefringence through structural design to eliminate birefringence caused by optical fiber structural errors and external interference, thereby maintaining the polarization state of the laser beam unchanged. Polarization-maintaining fiber maintains the polarization state of the laser beam unchanged, which can improve the stability of the sensor.

[0057] Based on the same inventive concept, an embodiment of the present invention provides a fiber optic sensing device, Figure 4 is a structural diagram of an optical fiber sensing device provided by an embodiment of the present invention, Figure 5 This 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] Combine Figure 4 and Figure 5As shown, after being output from laser 300, a laser beam is coupled into coupling fiber 100. When the laser beam propagates to first coupling point 101, a portion of the laser beam is coupled into sensing fiber 200. Modes that meet the resonance conditions of the Fabry-Perot cavity resonate within the cavity, extending the photon lifetime of these resonant modes. Modes that do not meet the resonance conditions of the Fabry-Perot cavity are coupled out of sensing fiber 200 and return to coupling fiber 100 for continued transmission. Meanwhile, the laser beam not coupled into sensing fiber 200 propagates to the input end of second end 103 of coupling fiber 100 and is received by detector 400. Detector 400 optionally includes a spectrometer that can detect spectral information of the received laser beam. Because the resonant modes are retained within the Fabry-Perot cavity, these modes are temporarily prevented from coupling into detector 400. In the spectrum of the laser beam detected by detector 400, the intensity of the modes that meet the resonance conditions of the Fabry-Perot cavity is lower than that of other modes. When changes in sound waves, temperature or pressure cause perturbations to the sensing optical fiber 200, information about the sound waves, temperature or pressure can be inferred by analyzing 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 This is a flow chart 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 maintain 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, cut the first and second optical fibers to a length suitable for fixing on the taper fixture, and strip the coating from both ends of the first and second optical fibers. Use dust-free paper dampened with alcohol to clean the stripped areas. If not wiped clean, dust or coating strips will absorb the coating material during reflective coating, resulting in uneven coating on the end faces. After wiping clean, use a fiber cleaver to cut both ends of the first and second optical fibers to obtain smooth end faces. After cutting, place the end face of the first optical fiber under a microscope to observe whether the end face is smooth. 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 coating is applied to both end faces of the first optical fiber. The reflective coating can be made of silver, copper, or other materials that can form a highly reflective coating on the optical fiber end face. The thickness of the reflective coating must be greater than 50 nm so that the reflective coating can confine the light coupled into the first optical fiber to continuously reflect within the cavity.

[0066] S104: Taper 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 reflective 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 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 supporting structure. After the fixing glue is cured, a layer of fixing glue is spread on the glass slide for complete encapsulation. The packaged device is an optical fiber sensor, wherein 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: Cut 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 apex of the first optical fiber is coupled to the second optical fiber.

[0076] Figure 8This is a flowchart of a processing method for 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 fiber optic sensor shown.

[0077] Figure 9 This 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 9 , the preparation method comprises:

[0078] S301. Prepare two optical fibers, where 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 apex of the second optical fiber is coupled to the first optical fiber.

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

[0084] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. An optical fiber sensor, characterized in that: Including coupling fiber and sensing 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 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; 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; 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 light 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, wherein 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, wherein 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, wherein 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 includes a fixing glue, which is used to fix the coupling optical fiber and the sensing optical fiber on the supporting structure. 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, wherein The reflective film is a total reflective film, and the thickness of the total reflective film is greater than 50 nm.

7. A fiber optic sensing device, characterized in that: comprising a laser, a detector and the optical fiber sensor according to 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 is used for converting an 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 includes: 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 includes: 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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