A high-sensitivity flexible optical fiber sensor and a preparation method thereof

Abstract

The application discloses a high-sensitivity flexible optical fiber sensor and a preparation method thereof, and comprises the following steps: providing first and second quartz single-mode optical fibers; cutting one end of the first and second quartz single-mode optical fibers respectively to obtain first and second smooth quartz optical fiber end faces; providing a flexible single-mode optical fiber, and performing heat treatment, and then cutting two ends to obtain first and second smooth flexible single-mode optical fiber end faces; respectively adhering photoresist on the first and second smooth quartz optical fiber end faces; aligning the first smooth flexible single-mode optical fiber end face with the first smooth quartz optical fiber end face, gradually approaching until the first smooth flexible single-mode optical fiber end face is immersed in the photoresist to perform solidification, and obtaining a first photoresist layer; aligning the second smooth flexible single-mode optical fiber end face with the second smooth quartz optical fiber end face, gradually approaching until the second smooth flexible single-mode optical fiber end face is immersed in the photoresist to perform solidification, and obtaining a second photoresist layer, and the preparation of the high-sensitivity flexible optical fiber sensor is completed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical fiber sensor preparation, in particular to a high-sensitivity flexible optical fiber sensor and a preparation method thereof. BACKGROUND

[0002] In recent years, with the continuous progress and development of science and technology, people have put forward new application requirements for various devices in daily life. Flexible wearable electronic products have attracted great attention due to their wide application in wearable devices, electronic skin, pressure sensors, touch screens, human motion monitoring sensors, and energy sources. Among them, flexible sensors capable of signal monitoring play an important role in the field of intelligent wearable devices, and have broad application prospects in human motion monitoring, health monitoring, human-computer interaction, soft robot, wearable electronic devices, and electronic skin.

[0003] Compared with traditional silicon-based sensors with large rigidity and brittleness, flexible sensors can effectively capture high-quality mechanical signals on curved surfaces and convert them into electrical signals due to their good elasticity and flexibility, so that the flexible sensors have certain sensing performance. However, as people's requirements for flexible sensors become higher and higher, the existing flexible sensors often exhibit significant resistance or current changes under a certain degree of strain, but are not sensitive to small strains in actual applications. In view of the problem of insufficient sensitivity of flexible sensors, researchers have begun to study high-sensitivity flexible sensors.

[0004] In recent years, in order to improve the sensitivity of flexible sensors, researchers have applied various microstructures (such as micropores, microspheres, microcolumns, and micro pyramids) to the electrode layer or dielectric layer to reduce the difficulty of deformation of the flexible sensor, increase the change degree of the electrode plate spacing and the contact area, and thus increase the relative capacitance change rate of the flexible sensor and improve the sensitivity of the flexible sensor. However, the preparation of the above microstructures mostly adopts photolithography technology, and the process of preparing high-sensitivity flexible sensors by using photolithography technology is too complex, so that such high-sensitivity sensors are basically impossible to mass-produce. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the present application provides a high-sensitivity flexible optical fiber sensor and a preparation method thereof, which solves the technical problem that the preparation process of the existing high-sensitivity flexible sensor is too complex and cannot be mass-produced, so as to achieve the purpose of simplifying the preparation process of the high-sensitivity flexible sensor and realizing mass production.

[0006] To solve the above problems, the technical scheme adopted by the present application is as follows:

[0007] A preparation method of a high-sensitivity flexible optical fiber sensor, comprising the following steps:

[0008] providing a first quartz single-mode optical fiber and a second quartz single-mode optical fiber, cutting one end of the first quartz single-mode optical fiber and the second quartz single-mode optical fiber respectively to obtain a first smooth quartz optical fiber end face and a second smooth quartz optical fiber end face;

[0009] providing a flexible single-mode optical fiber, after the flexible single-mode optical fiber is subjected to heat treatment in hot water, cutting two ends of the flexible single-mode optical fiber respectively to obtain a first smooth flexible single-mode optical fiber end face and a second smooth flexible single-mode optical fiber end face;

[0010] attaching photoresist on the first smooth quartz optical fiber end face and the second smooth quartz optical fiber end face respectively;

[0011] aligning the first smooth flexible single-mode optical fiber end face with the first smooth quartz optical fiber end face, and gradually approaching until the first smooth flexible single-mode optical fiber end face is immersed in the photoresist, then using ultraviolet laser to solidify the photoresist between the two end faces to obtain a first photoresist layer;

[0012] aligning the second smooth flexible single-mode optical fiber end face with the second smooth quartz optical fiber end face, and gradually approaching until the second smooth flexible single-mode optical fiber end face is immersed in the photoresist, then using ultraviolet laser to solidify the photoresist between the two end faces to obtain a second photoresist layer, thereby completing the preparation of the high-sensitivity flexible optical fiber sensor.

[0013] As a preferred embodiment of the present application, when cutting one end of the first quartz single-mode optical fiber and the second quartz single-mode optical fiber respectively, it includes:

[0014] directly cutting one end of the first quartz single-mode optical fiber and the second quartz single-mode optical fiber by using an optical fiber cutter;

[0015] wherein the inclination angle of the optical fiber cutter is controlled within 0.2 degrees, and the length of the cut-off quartz single-mode optical fiber is controlled within 1 cm.

[0016] As a preferred embodiment of the present application, when the flexible single-mode optical fiber is subjected to heat treatment in hot water, it includes:

[0017] immersing the flexible single-mode optical fiber in hot water at 90-100 degrees Celsius for 2-3 minutes.

[0018] As a preferred embodiment of the present application, when cutting two ends of the flexible single-mode optical fiber respectively, it includes:

[0019] directly cutting two ends of the flexible single-mode optical fiber by using a femtosecond laser;

[0020] The pulse energy of the femtosecond laser is controlled within 5-10 uJ, and the cutting angle is controlled within 0.5 degrees.

[0021] As a preferred embodiment of the present application, when the smooth quartz optical fiber end face is adhered with photoresist, it comprises:

[0022] After the photoresist is dropped on the cover glass, the optical fiber fixing tube is clamped by using the vertical displacement platform, and the first quartz single-mode optical fiber and the second quartz single-mode optical fiber are fixed on the optical fiber fixing tube in turn, and the first smooth quartz optical fiber end face and the second smooth quartz optical fiber end face are made to face the direction of advancement of the vertical displacement platform.

[0023] The optical fiber fixing tube is moved by using the vertical displacement platform at a speed of 10-20 um / s, so that the first smooth quartz optical fiber end face and the second smooth quartz optical fiber end face are immersed in the photoresist in turn, and the sequential adhesion of the first smooth quartz optical fiber end face and the second smooth quartz optical fiber end face is completed.

[0024] The photoresist is in a flat convex shape on the cover glass.

[0025] As a preferred embodiment of the present application, when the smooth flexible single-mode optical fiber end face and the smooth quartz optical fiber end face are aligned, it comprises:

[0026] The flexible single-mode optical fiber is fixed on the first three-dimensional displacement platform, and the first smooth flexible single-mode optical fiber end face is made to face the advancement direction of the first three-dimensional displacement platform.

[0027] The first quartz single-mode optical fiber is fixed on the second three-dimensional displacement platform, and the first smooth quartz optical fiber end face is made to face the advancement direction of the second three-dimensional displacement platform.

[0028] After the first smooth flexible single-mode optical fiber end face and the first smooth quartz optical fiber end face are aligned by adjusting the three-dimensional displacement platform, they are gradually approached until the first smooth flexible single-mode optical fiber end face is immersed in the photoresist and is cured.

[0029] The flexible single-mode optical fiber is re-fixed on the first three-dimensional displacement platform, and the second smooth flexible single-mode optical fiber end face is made to face the advancement direction of the first three-dimensional displacement platform.

[0030] The first quartz single-mode optical fiber is removed, the second quartz single-mode optical fiber is fixed on the second three-dimensional displacement platform, and the second smooth quartz optical fiber end face is made to face the advancement direction of the second three-dimensional displacement platform.

[0031] Adjusting the three-dimensional displacement platform to align the second smooth flexible single-mode fiber end face and the second smooth quartz fiber end face, gradually approaching until the second smooth flexible single-mode fiber end face is immersed in the photoresist, and solidifying.

[0032] As a preferred embodiment of the present application, when the photoresist between the two end faces is solidified by ultraviolet laser, it comprises:

[0033] The photoresist between the flexible single-mode fiber and the first and second quartz single-mode fibers is solidified by 365-450 nm ultraviolet laser to obtain the first and second photoresist layers.

[0034] The solidification time is controlled at 40-60 seconds.

[0035] A high-sensitivity flexible optical fiber sensor comprises:

[0036] The first quartz single-mode fiber comprises a first smooth quartz fiber end face for transmitting the first incident light of the fundamental mode to the first photoresist layer.

[0037] The first photoresist layer connects the first smooth quartz fiber end face and the first smooth flexible single-mode fiber end face, and excites the first incident light of the fundamental mode into light of high-order mode, which is transmitted to the flexible single-mode fiber.

[0038] The flexible single-mode fiber comprises a first smooth flexible single-mode fiber end face and a second smooth flexible single-mode fiber end face for receiving the light of high-order mode through the first smooth flexible single-mode fiber end face and transmitting to the second photoresist layer.

[0039] The second quartz single-mode fiber comprises a second smooth quartz fiber end face for transmitting the second incident light of the fundamental mode to the second photoresist layer.

[0040] The second photoresist layer connects the second smooth quartz fiber end face and the second smooth flexible single-mode fiber end face, and interferes the second incident light of the fundamental mode with the light of high-order mode.

[0041] As a preferred embodiment of the present application, the flexible single-mode fiber is a polymer material single-mode fiber; the polymer material comprises cycloolefin polymer, polyvinyl chloride and polymethyl methacrylate; the first and second photoresist layers are polypropylene-based photoresist layers.

[0042] As a preferred embodiment of the present application, the length of the flexible single-mode fiber is 5-30 mm; the thickness of the first and second photoresist layers is 300-400 μm.

[0043] Compared with the prior art, the application has the beneficial effects that:

[0044] (1) The flexible optical fiber sensor prepared by the application effectively excites the fundamental mode light into high-order mode light based on the mode field difference of the quartz single-mode optical fiber and the flexible single-mode optical fiber interface, forms inter-mode interference, and has high sensitivity to stress and bending based on the low Young's modulus of the flexible single-mode optical fiber;

[0045] (2) The process for preparing the flexible optical fiber sensor mainly combines femtosecond fiber cutting, glue coating and photocuring polymerization processes, thereby realizing the processing and manufacturing of the high-sensitivity flexible optical fiber sensor, and eliminating the complex steps in the prior art of using photolithography technology for preparation, and facilitating mass production.

[0046] The application will be further described in detail below in combination with the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 - is a preparation method step diagram of the high-sensitivity flexible optical fiber sensor of the embodiment of the application;

[0048] Figure 2 - is a structure schematic diagram of the high-sensitivity flexible optical fiber sensor of the embodiment of the application;

[0049] Figure 3 - is a process schematic diagram of adhering photoresist to the smooth quartz optical fiber end face of the embodiment of the application;

[0050] Figure 4 - is a process schematic diagram of aligning and immersing the flexible single-mode optical fiber end face and the quartz optical fiber end face of the embodiment of the application;

[0051] Figure 5 - is a process actuality diagram of aligning and immersing the flexible single-mode optical fiber end face and the quartz optical fiber end face of the embodiment of the application;

[0052] Figure 6 - is a transmission spectrum diagram of the high-sensitivity flexible optical fiber sensor of the embodiment of the application;

[0053] Figure 7 - is an enlarged diagram of the transmission spectrum of the high-sensitivity flexible optical fiber sensor of the embodiment of the application;

[0054] Figure 8 - is a wavelength and curvature relationship diagram of the high-sensitivity flexible optical fiber sensor of the embodiment of the application.

[0055] Explanation of reference numerals: 1, first quartz single-mode optical fiber; 2, first photoresist layer; 3, flexible single-mode optical fiber; 4, second quartz single-mode optical fiber; 5, second photoresist layer; 6, vertical displacement platform; 7, optical fiber fixing tube; 8, cover glass; 9, first three-dimensional displacement platform; 10, second three-dimensional displacement platform; 11, objective lens; 12, quartz single-mode optical fiber; 13, photoresist. DETAILED DESCRIPTION

[0056] The preparation method of the high-sensitivity flexible optical fiber sensor provided by the application comprises the following steps, as shown in the figure: Figure 1 The preparation method of the high-sensitivity flexible optical fiber sensor provided by the application comprises the following steps, as shown in the figure:

[0057] Step S1: provide a first quartz single-mode optical fiber 1 and a second quartz single-mode optical fiber 4, and cut one end of each of the first quartz single-mode optical fiber 1 and the second quartz single-mode optical fiber 4 to obtain a first smooth quartz optical fiber end face and a second smooth quartz optical fiber end face;

[0058] Step S2: provide a flexible single-mode optical fiber 3, heat treat the flexible single-mode optical fiber 3 in hot water, and then cut two ends of the flexible single-mode optical fiber 3 to obtain a first smooth flexible single-mode optical fiber end face and a second smooth flexible single-mode optical fiber end face;

[0059] Step S3: adhere photoresist 13 to the first smooth quartz optical fiber end face and the second smooth quartz optical fiber end face respectively;

[0060] Step S4: align the first smooth flexible single-mode optical fiber end face with the first smooth quartz optical fiber end face, gradually approach until the first smooth flexible single-mode optical fiber end face is immersed in the photoresist 13, and then solidify the photoresist 13 between the two end faces by using ultraviolet laser to obtain a first photoresist layer 2;

[0061] Step S5: align the second smooth flexible single-mode optical fiber end face with the second smooth quartz optical fiber end face, gradually approach until the second smooth flexible single-mode optical fiber end face is immersed in the photoresist 13, and then solidify the photoresist 13 between the two end faces by using ultraviolet laser to obtain a second photoresist layer 5, thereby completing the preparation of the high-sensitivity flexible optical fiber sensor.

[0062] Specifically, the first quartz single-mode optical fiber 1 and the second quartz single-mode optical fiber 4 are bonded to the two ends of the flexible single-mode optical fiber 3 through the first photoresist layer 2 and the second photoresist layer 5 respectively.

[0063] The principle of the present application is that when the light of the base mode is incident on the first photoresist layer 2 through the first quartz single-mode optical fiber 1, high-order mode light is generated, and when the high-order mode light is transmitted to the second photoresist layer 5 through the flexible single-mode optical fiber 3, the high-order mode light will interfere with the light of the base mode transmitted from the second quartz single-mode optical fiber 4. When the high-sensitivity flexible optical fiber sensor of the present application is bent, it will cause the wavelength of its transmission spectrum to drift accordingly, and this principle can be used to measure the bending.

[0064] In the above step S1, when cutting one end of the first quartz single-mode optical fiber 1 and the second quartz single-mode optical fiber 4 respectively, it includes:

[0065] The one end of the first quartz single-mode optical fiber 1 and the second quartz single-mode optical fiber 4 is directly cut by using a fiber cutting knife.

[0066] Among them, the inclination angle of the fiber cutting knife is controlled within 0.2 degrees, and the length of the cut quartz single-mode optical fiber 12 is controlled within 1 cm.

[0067] Specifically, controlling the inclination angle within 0.2 degrees can ensure that a smooth quartz single-mode optical fiber end face is obtained, and controlling the cut length within 1 cm ensures that the quartz single-mode optical fiber 12 is not wasted in the process of obtaining a smooth end face. The fiber cutting knife is suitable for cutting the quartz single-mode optical fiber 12, and the cut fiber end is still smooth after magnified by hundreds of times.

[0068] In the above step S2, when the flexible single-mode optical fiber 3 is placed in hot water for heat treatment, it includes:

[0069] The flexible single-mode optical fiber 3 is immersed in hot water at 90-100 degrees Celsius for 2-3 minutes.

[0070] Specifically, the reason for immersing the flexible single-mode optical fiber 3 in hot water at 90-100 degrees Celsius for heat treatment is that the flexible single-mode optical fiber 3 is more easily cut into a relatively smooth state in a state of thermal expansion.

[0071] In the above step S2, when cutting both ends of the flexible single-mode optical fiber 3 respectively, it includes:

[0072] The both ends of the flexible single-mode optical fiber 3 are directly cut by using a femtosecond laser.

[0073] Among them, the pulse energy of the femtosecond laser is controlled within 5-10 uJ, and the cutting angle is controlled within 0.5 degrees.

[0074] Specifically, the pulse energy of the femtosecond laser is controlled to be 5-10 uJ, so that the flexible single-mode optical fiber 3 can be prevented from being damaged due to excessive pulse energy during the cutting process. The cutting angle is controlled to be within 0.5 degrees, so that a smooth flexible single-mode optical fiber end face can be obtained.

[0075] As shown in Figure 3 the step S3, when the photoresist 13 is adhered to the smooth quartz optical fiber end face, the step S3 comprises:

[0076] After the photoresist 13 is dropped on the cover glass 8, the optical fiber fixing tube 7 is clamped by the vertical displacement platform 6, and the first quartz single-mode optical fiber 1 and the second quartz single-mode optical fiber 4 are fixed on the optical fiber fixing tube 7 in sequence, and the first smooth quartz optical fiber end face and the second smooth quartz optical fiber end face are made to face the direction in which the vertical displacement platform 6 advances.

[0077] The optical fiber fixing tube 7 is moved by the vertical displacement platform 6 at a speed of 10-20 um / s, so that the first smooth quartz optical fiber end face and the second smooth quartz optical fiber end face are sequentially immersed in the photoresist 13, and the sequential adhesion of the first smooth quartz optical fiber end face and the second smooth quartz optical fiber end face is completed.

[0078] The photoresist 13 on the cover glass 8 is in a flat convex shape.

[0079] Specifically, the moving speed is controlled to be 10-20 um / s, so that the photoresist 13 on the quartz optical fiber end face can be prevented from being unevenly adhered due to too fast moving speed. Further, the quartz single-mode optical fiber 12 can also be prevented from being damaged due to too fast moving speed.

[0080] Specifically, the photoresist 13 dropped on the cover glass 8 is controlled to be in a flat convex shape, so that the entire quartz optical fiber end face can be immersed in the photoresist 13, thereby obtaining a better adhesion effect.

[0081] As shown in Figure 4 and Figure 5 in the step S4, when the smooth flexible single-mode optical fiber end face and the smooth quartz optical fiber end face are aligned, the step S4 comprises:

[0082] The flexible single-mode optical fiber 3 is fixed on the first three-dimensional displacement platform 9, and the first smooth flexible single-mode optical fiber end face is made to face the advancing direction of the first three-dimensional displacement platform 9.

[0083] The first quartz single-mode optical fiber 1 is fixed on the second three-dimensional displacement platform 10, and the first smooth quartz optical fiber end face is made to face the advancing direction of the second three-dimensional displacement platform 10.

[0084] Adjusting the three-dimensional displacement platform to align the first smooth flexible single-mode fiber end face and the first smooth quartz fiber end face, gradually close until the first smooth flexible single-mode fiber end face is immersed in the photoresist 13, and solidify;

[0085] Re-fix the flexible single-mode fiber 3 on the first three-dimensional displacement platform 9, and make the second smooth flexible single-mode fiber end face face the advancing direction of the first three-dimensional displacement platform 9;

[0086] Remove the first quartz single-mode fiber 1, fix the second quartz single-mode fiber 4 on the second three-dimensional displacement platform 10, and make the second smooth quartz fiber end face face the advancing direction of the second three-dimensional displacement platform 10;

[0087] Adjust the second three-dimensional displacement platform 10 to align the second smooth flexible single-mode fiber end face and the second smooth quartz fiber end face, gradually close until the second smooth flexible single-mode fiber end face is immersed in the photoresist 13, and solidify.

[0088] Specifically, the three-dimensional displacement platform is used to align the left quartz single-mode fiber 12 (i.e. the first quartz single-mode fiber) and the flexible single-mode fiber 3, gradually close until the flexible single-mode fiber 3 is immersed in the photoresist 13, and then the photoresist 13 is directly solidified by ultraviolet laser, and the right quartz single-mode fiber 12 (i.e. the second quartz single-mode fiber) and the flexible single-mode fiber 3 are operated in the same way, so as to complete the whole alignment and solidification process.

[0089] Further, when aligning by using the three-dimensional displacement platform, the objective lens 11 can also be used for magnification, so as to greatly improve the alignment accuracy between the quartz single-mode fiber 12 and the flexible single-mode fiber 3.

[0090] In the above step S5, when the photoresist 13 between the two end faces is solidified by using the ultraviolet laser, it includes:

[0091] The photoresist between the flexible single-mode fiber 3 and the first quartz single-mode fiber 1 and the second quartz single-mode fiber 4 is directly solidified by using the ultraviolet laser with a wavelength of 365-450 nm, to obtain the first photoresist layer 2 and the second photoresist layer 5;

[0092] The solidification time is controlled to be 40-60 seconds.

[0093] Specifically, the wavelength of the ultraviolet laser is controlled to be 365-450 nm, and the solidification time is controlled to be 40-60 seconds, so as to ensure that the photoresist 13 is fully solidified.

[0094] As Figure 2As shown, the high-sensitivity flexible optical fiber sensor provided by the present application comprises a first quartz single-mode optical fiber 1, a first photoresist layer 2, a flexible single-mode optical fiber 3, a second quartz single-mode optical fiber 4 and a second photoresist layer 5. The first quartz single-mode optical fiber 1 comprises a first smooth quartz optical fiber end face, which is used to transmit first incident light of a fundamental mode to the first photoresist layer 2; the first photoresist layer 2 is used to connect the first smooth quartz optical fiber end face and a first smooth flexible single-mode optical fiber end face, and excite the first incident light of the fundamental mode into light of a high-order mode, which is transmitted to the flexible single-mode optical fiber 3; the flexible single-mode optical fiber 3 comprises the first smooth flexible single-mode optical fiber end face and a second smooth flexible single-mode optical fiber end face, which are used to receive the light of the high-order mode through the first smooth flexible single-mode optical fiber end face and transmit the light to the second photoresist layer 5; the second quartz single-mode optical fiber 4 comprises a second smooth quartz optical fiber end face, which is used to transmit second incident light of the fundamental mode to the second photoresist layer 5; and the second photoresist layer 5 is used to connect the second smooth quartz optical fiber end face and the second smooth flexible single-mode optical fiber end face, and interfere the second incident light of the fundamental mode with the light of the high-order mode.

[0095] Further, the flexible single-mode optical fiber 3 is a polymer material single-mode optical fiber; the polymer material comprises a cyclic olefin polymer, polyvinyl chloride and polymethyl methacrylate; and the first photoresist layer and the second photoresist layer are polypropylene photoresist layers.

[0096] Specifically, the flexible single-mode optical fiber 3 is prepared by using the above polymer material, so that it has a lower Young's modulus, thereby having a higher sensitivity to stress and bending.

[0097] Specifically, the photoresist 13 is selected to be a polypropylene photoresist, which can effectively excite the light of the fundamental mode into the light of the high-order mode.

[0098] Further, the length of the flexible single-mode optical fiber 3 is 5-30 mm; and the thickness of the first photoresist layer 2 and the second photoresist layer 5 is 300-400 μm.

[0099] Specifically, the length of the flexible single-mode optical fiber 3 is controlled to be 5-30 mm, which can ensure that the light of the high-order mode can be transmitted to the second photoresist layer 5 to interfere with the second incident light of the fundamental mode. If the length of the flexible single-mode optical fiber 3 is too long, the light of the high-order mode will be attenuated before being transmitted to the second photoresist layer 5.

[0100] Specifically, the thickness of the photoresist layer is controlled to be 300-400 μm, which can not only ensure that the quartz single-mode optical fiber 12 and the flexible single-mode optical fiber 3 can be fully bonded, but also effectively excite the light of the high-order mode.

[0101] The present application is further explained by the following specific examples:

[0102] The material selected for the flexible single-mode optical fiber 3 is COP optical material, the core diameter is 5um, the cladding diameter is 125um, the thickness of the photoresist 13 after curing is 400um, and the length of the flexible single-mode optical fiber 3 is 20mm.

[0103] Figure 6 is a transmission spectrum diagram of the high-sensitivity flexible optical fiber sensor of the present application, Figure 7 is an enlarged view of the transmission spectrum of the high-sensitivity flexible optical fiber sensor of the present application, and Figure 6 and Figure 7 It can be seen that as the curvature increases, the wavelength of the sensor is blue-shifted. The blue shift of the wavelength of the sensor indicates that the flexible optical fiber sensor of the present application responds to the wavelength by moving towards the short wavelength direction.

[0104] Figure 8 is a wavelength-curvature relationship diagram of the high-sensitivity flexible optical fiber sensor of the present application, and Figure 8 It can be seen that the sensitivity of the flexible optical fiber sensor of the present application can reach 4951.96nm / m -1 The sensitivity value indicates that the flexible optical fiber sensor of the present application has high bending sensitivity.

[0105] Compared with the prior art, the present application has the following advantages:

[0106] (1) The flexible optical fiber sensor prepared by the present application effectively excites the fundamental mode light into high-order mode light based on the mode field difference of the quartz single-mode optical fiber and the flexible single-mode optical fiber interface, and forms inter-mode interference, and based on the low Young's modulus of the flexible single-mode optical fiber, it has high sensitivity to stress and bending;

[0107] (2) The preparation process of the present application mainly combines femtosecond fiber cutting, glue coating and photo-cured polymerization processes, so as to realize the processing and manufacturing of the high-sensitivity flexible optical fiber sensor, and eliminates the complex steps in the preparation process of the prior art using photolithography technology, which is convenient for mass production.

[0108] The above embodiments are only preferred embodiments of the present application, and cannot be used to limit the scope of protection of the present application. Any non-essential changes and substitutions made by those skilled in the art based on the present application are within the scope of protection of the present application.

Claims

1. A method for preparing a high-sensitivity flexible optical fiber sensor, characterized by, The method comprises the following steps: providing a first quartz single-mode optical fiber and a second quartz single-mode optical fiber, cutting one end of the first quartz single-mode optical fiber and the second quartz single-mode optical fiber respectively to obtain a first smooth quartz optical fiber end face and a second smooth quartz optical fiber end face; providing a flexible single-mode optical fiber, subjecting the flexible single-mode optical fiber to heat treatment in hot water, and then cutting two ends of the flexible single-mode optical fiber respectively to obtain a first smooth flexible single-mode optical fiber end face and a second smooth flexible single-mode optical fiber end face; attaching photoresist on the first smooth quartz optical fiber end face and the second smooth quartz optical fiber end face respectively; aligning the first smooth flexible single-mode optical fiber end face with the first smooth quartz optical fiber end face, gradually approaching until the first smooth flexible single-mode optical fiber end face is immersed in the photoresist, and then solidifying the photoresist between the two end faces by using ultraviolet laser to obtain a first photoresist layer; aligning the second smooth flexible single-mode optical fiber end face with the second smooth quartz optical fiber end face, gradually approaching until the second smooth flexible single-mode optical fiber end face is immersed in the photoresist, and then solidifying the photoresist between the two end faces by using ultraviolet laser to obtain a second photoresist layer, thereby completing the preparation of the high-sensitivity flexible optical fiber sensor; when attaching photoresist on the smooth quartz optical fiber end face, the method comprises: after dropping the photoresist on a cover glass, clamping a fiber fixing tube by using a vertical displacement platform, and fixing the first quartz single-mode optical fiber and the second quartz single-mode optical fiber on the fiber fixing tube in sequence, and making the first smooth quartz optical fiber end face and the second smooth quartz optical fiber end face face the direction in which the vertical displacement platform moves forward; moving the fiber fixing tube at a speed of 10-20 um / s by using the vertical displacement platform, so that the first smooth quartz optical fiber end face and the second smooth quartz optical fiber end face are immersed in the photoresist in sequence, and the sequential attachment of the first smooth quartz optical fiber end face and the second smooth quartz optical fiber end face is completed; wherein the photoresist is in a flat convex shape on the cover glass; wherein when the light of the fundamental mode is incident on the first photoresist layer through the first quartz single-mode optical fiber, light of high-order modes is generated, and when the light of high-order modes is transmitted through the flexible single-mode optical fiber to the second photoresist layer, the light of high-order modes and the light of the fundamental mode transmitted from the second quartz single-mode optical fiber interfere with each other.

2. The method of claim 1, wherein the high sensitivity flexible optical fiber sensor is prepared by the steps of: when cutting one end of the first quartz single-mode optical fiber and the second quartz single-mode optical fiber respectively, the method comprises: directly cutting one end of the first quartz single-mode optical fiber and the second quartz single-mode optical fiber by using a fiber cutting knife; wherein the inclination angle of the fiber cutting knife is controlled within 0.2 degrees, and the length of the cut-off quartz single-mode optical fiber is controlled within 1 cm.

3. The method of claim 1, wherein the high sensitivity flexible optical fiber sensor is prepared by the steps of: when subjecting the flexible single-mode optical fiber to heat treatment in hot water, the method comprises: immersing the flexible single-mode optical fiber in hot water at 90-100 degrees Celsius for 2-3 minutes.

4. The method of claim 1, wherein the high sensitivity flexible optical fiber sensor is prepared by the steps of: when cutting two ends of the flexible single-mode optical fiber respectively, the method comprises: directly cutting two ends of the flexible single-mode optical fiber by using a femtosecond laser; The pulse energy of the femtosecond laser is controlled to be 5-10 uJ, and the cutting angle is controlled to be within 0.5 degrees.

5. The method of claim 1, wherein the high sensitivity flexible optical fiber sensor is prepared by the steps of: When aligning the smooth flexible single-mode fiber end face and the smooth quartz fiber end face, the method comprises: Fixing the flexible single-mode fiber on a first three-dimensional displacement platform, and making the first smooth flexible single-mode fiber end face face the advancing direction of the first three-dimensional displacement platform; Fixing the first quartz single-mode fiber on a second three-dimensional displacement platform, and making the first smooth quartz fiber end face face the advancing direction of the second three-dimensional displacement platform; After adjusting the three-dimensional displacement platform to align the first smooth flexible single-mode fiber end face and the first smooth quartz fiber end face, gradually approach until the first smooth flexible single-mode fiber end face is immersed in the photoresist and is cured; Re-fixing the flexible single-mode fiber on the first three-dimensional displacement platform, and making the second smooth flexible single-mode fiber end face face the advancing direction of the first three-dimensional displacement platform; Removing the first quartz single-mode fiber, fixing the second quartz single-mode fiber on the second three-dimensional displacement platform, and making the second smooth quartz fiber end face face the advancing direction of the second three-dimensional displacement platform; After adjusting the three-dimensional displacement platform to align the second smooth flexible single-mode fiber end face and the second smooth quartz fiber end face, gradually approach until the second smooth flexible single-mode fiber end face is immersed in the photoresist and is cured.

6. The method of claim 1, wherein the high sensitivity flexible optical fiber sensor is prepared by the steps of: When curing the photoresist between the two end faces by using ultraviolet laser, the method comprises: Curing the photoresist between the flexible single-mode fiber and the first quartz single-mode fiber and the second quartz single-mode fiber by using 365-450 nm ultraviolet laser to obtain the first photoresist layer and the second photoresist layer; The curing time is controlled to be 40-60 seconds.

7. A high-sensitivity flexible optical fiber sensor, characterized by, The method comprises: A first quartz single-mode fiber comprising a first smooth quartz fiber end face, used for transmitting first incident light of a fundamental mode to a first photoresist layer; A first photoresist layer used for connecting the first smooth quartz fiber end face and a first smooth flexible single-mode fiber end face, and exciting the first incident light of the fundamental mode into light of a high-order mode and transmitting the light to a flexible single-mode fiber; The flexible single-mode fiber comprises a first smooth flexible single-mode fiber end face and a second smooth flexible single-mode fiber end face, used for receiving the light of the high-order mode through the first smooth flexible single-mode fiber end face and transmitting the light to a second photoresist layer; A second quartz single-mode fiber comprising a second smooth quartz fiber end face, used for transmitting second incident light of a fundamental mode to a second photoresist layer; A second photoresist layer used for connecting the second smooth quartz fiber end face and the second smooth flexible single-mode fiber end face, and interfering the second incident light of the fundamental mode with the light of the high-order mode.

8. The high-sensitivity flexible optical fiber sensor according to claim 7, characterized in that, The flexible single-mode fiber is a polymer material single-mode fiber; the polymer material comprises a cyclic olefin polymer, polyvinyl chloride, and polymethyl methacrylate; and the first photoresist layer and the second photoresist layer are polypropylene-based photoresist layers.

9. The high-sensitivity flexible optical fiber sensor according to claim 7, characterized in that, The length of the flexible single-mode optical fiber is 5-30 mm; the thickness of the first photoresist layer and the second photoresist layer is 300-400 μm.

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