A fiber-optic misalignment type refractive index sensor based on MXene spray transfer

Abstract

The application belongs to the technical field of optical fiber sensor preparation, and relates to a fiber misplacement type refractive index sensor based on MXene spraying transfer. The sensor introduces a single-mode optical fiber according to light propagation direction distribution, introduces a hollow-core optical fiber, a multimode optical fiber, leads out the hollow-core optical fiber, leads out the single-mode optical fiber and MXene material; the multimode optical fiber is connected through misplacement fusion between the introduced hollow-core optical fiber and the led-out hollow-core optical fiber; the multimode optical fiber comprises a misplacement multimode optical fiber cladding and a misplacement multimode optical fiber core; the MXene material is coated on the surfaces of the introduced hollow-core optical fiber, the misplacement multimode optical fiber cladding and the led-out hollow-core optical fiber; the introduced single-mode optical fiber and the introduced hollow-core optical fiber are aligned and fused; the led-out hollow-core optical fiber and the led-out single-mode optical fiber are aligned and fused. The introduced single-mode optical fiber is used for introducing a light source; the introduced hollow-core optical fiber is used as a light beam expander to excite cladding mode output to the multimode optical fiber; the misplacement multimode optical fiber cladding and the misplacement multimode optical fiber core excite multimode interference effect of the multimode optical fiber through the misplacement structure.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical fiber sensing and sensor preparation, and particularly relates to a light fiber misalignment type refractive index sensor based on MXene spraying transfer. BACKGROUND

[0002] Optical fiber sensors have been widely used in physical, chemical and biological measurement fields due to their high sensitivity, compact structure, fast response speed, anti-electromagnetic interference and long-distance real-time detection advantages. Traditional optical fiber refractive index sensors mostly use a tapered fiber structure. Although this structure can provide high sensitivity, it is not easy to operate and use due to its low mechanical strength, complex manufacturing and other problems.

[0003] In order to improve the sensitivity and stability of the sensor, researchers have proposed a variety of new optical fiber sensor structures in recent years. For example, an optical fiber sensor based on an open cavity Mach-Zehnder interferometer is prepared by a large misalignment fusion splicing technology. By monitoring the wavelength shift of the interference fringes, high-sensitivity solution concentration detection is achieved. The sensor of this structure is not only small, has high repeatability and relatively simple manufacturing process. Another small misalignment optical fiber sensor based on a semi-open cavity structure can simultaneously measure the temperature and salinity under water, and by adjusting the design parameters of the sensor, its sensitivity and stability are improved.

[0004] Current misalignment splicing type optical fiber sensors, such as optical fiber sensors based on open cavity Mach-Zehnder (M-Z) interferometers, use large misalignment fusion splicing technology to achieve high-sensitivity solution concentration detection, but such sensors have problems in actual application, such as being easily affected by temperature changes in complex environments, resulting in a decrease in measurement accuracy. However, these sensors still have some technical challenges when facing complex environments and extreme conditions. First, optical fiber sensors are easily damaged in corrosive environments and need special materials for protection. Second, existing sensors still have room for improvement in terms of sensitivity and stability. For example, although sensors based on open cavity structures have high sensitivity, they are easily affected by environmental temperature changes in actual application, resulting in a decrease in measurement accuracy. Sensors based on semi-open cavity structures perform well in terms of sensitivity, but due to their complex structure and high manufacturing cost, they limit the possibility of their large-scale application.

[0005] The two aforementioned existing sensors need performance improvement in complex environments and extreme conditions that require higher sensitivity and stability. In addition to structural improvements, existing methods for improving sensitivity and stability include coating sensitive materials. MXene is a two-dimensional material with excellent electrical conductivity, mechanical flexibility, and chemical stability, making it an ideal refractive index sensitive material. By uniformly spraying MXene material on the surface of the optical fiber, the refractive index detection accuracy and stability of the sensor can be significantly improved. Compared with traditional coating methods, the MXene coating not only provides higher sensitivity but also has a simpler and more controllable spraying process, better coating uniformity, and effectively avoids measurement errors caused by uneven coating. The MXene coating not only provides high sensitivity but also effectively avoids measurement errors caused by uneven coating, and has excellent corrosion resistance, suitable for various complex detection environments. The optical fiber misalignment type refractive index sensor based on MXene spraying transfer combines the advantages of high sensitivity and high mechanical strength, overcomes the shortcomings of traditional sensors, and has wide application prospects. SUMMARY

[0006] The present application aims to address the technical defects of existing refractive index sensors, which have yet to improve detection sensitivity and stability, and proposes a fiber misalignment type refractive index sensor based on MXene spraying transfer.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions.

[0008] As a first aspect of the present application, a fiber misalignment type refractive index sensor based on MXene spraying transfer is proposed, which has an introduction single-mode optical fiber, an introduction hollow-core optical fiber, a multi-mode optical fiber, an exit hollow-core optical fiber, an exit single-mode optical fiber, and a MXene material layer distributed in the propagation direction of light; the introduction hollow-core optical fiber and the exit hollow-core optical fiber are connected by misalignment fusion splicing to the multi-mode optical fiber;

[0009] The introduction single-mode optical fiber, the multi-mode optical fiber, and the exit single-mode optical fiber all transmit base mode modes; the multi-mode optical fiber transmits base modes and high-order modes; the introduction hollow-core optical fiber and the exit hollow-core optical fiber are both cladding modes;

[0010] The multi-mode optical fiber includes a misalignment multi-mode optical fiber cladding and a misalignment multi-mode optical fiber core;

[0011] The introduction hollow-core optical fiber is a beam expander; the exit hollow-core optical fiber is a mode mixer, which improves the sensitivity of the sensor;

[0012] The multi-mode optical fiber includes a misalignment multi-mode optical fiber cladding and a misalignment multi-mode optical fiber core, has a large core diameter and mode propagation capability, and can effectively excite the cladding mode of the multi-mode optical fiber through the misalignment splicing structure, thereby producing a significant multi-mode interference effect and improving the sensitivity of the sensor.

[0013] The MXene material layer is sprayed and coated on the surface of the sensing area;

[0014] The surface of the sensing area comprises the introduction of a hollow optical fiber, a staggered multi-mode optical fiber cladding and the introduction of a hollow optical fiber surface;

[0015] The MXene material has a unique layered structure, rich surface functional groups, high electrical conductivity, high specific surface area and excellent mechanical structure and stability;

[0016] The spraying has the advantages of efficient production, uniform coating, simple operation, and easy flexible adaptation and control of coating thickness.

[0017] The introduction of the single-mode optical fiber is connected with the introduction of the hollow optical fiber; the introduction of the hollow optical fiber is connected with the staggered multi-mode optical fiber cladding; the staggered multi-mode optical fiber cladding is connected with the introduction of the hollow optical fiber; the introduction of the hollow optical fiber is connected with the introduction of the single-mode optical fiber; the introduction of the hollow optical fiber, the multi-mode optical fiber and the introduction of the single-mode optical fiber; the staggered multi-mode optical fiber cladding is connected with the staggered multi-mode optical fiber core; and the multi-mode optical fiber is connected with the MXene material layer.

[0018] The fusion mode between the introduction of the single-mode optical fiber and the introduction of the hollow optical fiber is alignment fusion.

[0019] The fusion mode between the introduction of the hollow optical fiber and the introduction of the single-mode optical fiber is alignment fusion.

[0020] The introduction of the single-mode optical fiber is used for introducing a light source; the introduction of the hollow optical fiber is used as a light beam expander to excite a cladding mode and output to the multi-mode optical fiber.

[0021] The staggered multi-mode optical fiber cladding and the staggered multi-mode optical fiber core excite the multi-mode interference effect of the multi-mode optical fiber through the staggered structure.

[0022] The introduction of the hollow optical fiber plays a role of mode mixing and uniform distribution, improves the coupling efficiency of the interference mode, the introduction of the single-mode optical fiber 6 outputs an optical signal for subsequent reception, and the refractive index range of the MXene material layer is between 1.68 and 2.5.

[0023] As another aspect of the present application, a preparation method of a fiber staggered refractive index sensor based on MXene spraying transfer is provided, comprising the following steps:

[0024] S1: making a multi-mode optical fiber staggered structure, specifically comprising the following steps:

[0025] S11: stripping the coating of the introduction of the single-mode optical fiber and the introduction of the hollow optical fiber, and then fixing the introduction of the single-mode optical fiber and the introduction of the hollow optical fiber;

[0026] S12: cutting the leading-in single-mode optical fiber and the leading-in hollow-core optical fiber and obtaining flat end faces;

[0027] S13: aligning and discharge-fusing the leading-in single-mode optical fiber and the leading-in hollow-core optical fiber;

[0028] S14: misaligning and fusing one side of the multimode optical fiber with the leading-in hollow-core optical fiber and misaligning and fusing the other side of the multimode optical fiber with the leading-out hollow-core optical fiber in the opposite direction;

[0029] S15: using a fiber fusion machine to align and discharge-fuse the leading-out hollow-core optical fiber with the leading-out single-mode optical fiber;

[0030] Up to now, the multimode optical fiber misalignment structure is prepared from S11 to S15;

[0031] S2: preparing a Ti3C2Tx MXene dispersion liquid;

[0032] S3: spray process transferring the MXene dispersion liquid;

[0033] S31: fixing the multimode optical fiber misalignment structure on a glass slide and then placing the glass slide on a hot stage and heating;

[0034] S32: uniformly spraying the MXene dispersion liquid onto the multimode optical fiber misalignment structure;

[0035] S33: observing whether there is a MXene film on a specific area of the surface and measuring the thickness of the MXene film;

[0036] The uniform spraying in S32 and the measurement of the thickness of the MXene film in S33 are specifically to control the spraying time according to the rate, keep the same rate, and the initial spraying time is 5-10 minutes; after multiple spraying, the actual film thickness is measured, and the subsequent spraying time is adjusted to achieve the required thickness; in the spraying process, in order to obtain the best spraying effect, the distance between the spray gun and the optical fiber sensing structure needs to be kept between 10-15 cm.

[0037] The peeling of the coating of the leading-in single-mode optical fiber and the leading-in hollow-core optical fiber in S11 is peeled using a fiber clamp;

[0038] The cutting of the leading-in single-mode optical fiber and the leading-in hollow-core optical fiber in S12 is cut using an electric fiber cutting knife;

[0039] The aligning and discharge-fusing of the leading-in single-mode optical fiber and the leading-in hollow-core optical fiber in S13 is realized using a fiber fusion machine;

[0040] The misaligning and fusing of the multimode optical fiber with the leading-in hollow-core optical fiber or the leading-out hollow-core optical fiber in S14 is realized using a fiber fusion machine;

[0041] The discharge intensity of the aligned discharge fusion is set to 20 bits in the embodiment of S15.

[0042] The length of the single-mode optical fiber, the coreless optical fiber, and the multi-mode optical fiber in S11, S12, S13, S14, and S15 is 0.8-1.2 cm.

[0043] The discharge mode of the misalignment fusion in S14 is a multi-mode optical fiber fusion mode, and the displacement ratio of the misalignment fusion is 30%-80% of the diameter of the multi-mode optical fiber.

[0044] The discharge time of the aligned discharge fusion in S15 is set to 1000-1200 ms.

[0045] S21: 0.7-0.9 g of LiF is added to 9-11 mL of hydrochloric acid with a concentration of 8-10 mol / L, and stirred for 4-6 min to make the LiF fully react with the hydrochloric acid as an etchant of the reaction system;

[0046] S22: 1-1.2 g of Ti3AlC2 MAX powder is slowly added to the etchant and reacted at 35-45°C for 40-50 hours to obtain a reaction mixture;

[0047] The time for adding 1-1.2 g of Ti3AlC2 MAX powder is more than 10 minutes;

[0048] S23: The reaction mixture is centrifuged and washed with deionized water for 3-5 times at a centrifugal speed of 3000-3500 rpm until the pH value of the supernatant is greater than 6 to obtain a product;

[0049] S24: The product is vacuum-filtered on a porous polytetrafluoroethylene membrane to obtain a layered cake-shaped slurry which is then separated;

[0050] The separation obtains a slurry and a solid substance;

[0051] The slurry is Ti3C2Tx, and the solid substance is Ti3AlC2 which is not etched completely;

[0052] S25: 0.1-0.12 g of the slurry is added to 90-110 mL of deionized water or ethanol, and ultrasonically treated in an ice water bath for 45 min to 1 hour to obtain a dispersion liquid;

[0053] S26: The dispersion liquid is centrifuged at 3500-4000 rpm for 25-35 min to remove the multi-layer MXene aggregates to obtain a MXene dispersion liquid which is stored for standby use;

[0054] The heating temperature range in S31 is 90-110°C to accelerate the evaporation of the sprayed liquid and prevent the solution from gathering into water droplets; and the heating time is about 5-8 min.

[0055] S32 said uniform spraying by pouring the MXene dispersion into the spray gun through a small flow uniform spraying and making the MXene dispersion drop in the form of mist on the multimode fiber staggered structure and evaporate quickly, without converging water droplets;

[0056] S33 said surface specific area is the surface of introducing a hollow core fiber, a staggered multimode fiber cladding and leading out a hollow core fiber; said measuring the thickness of the MXene film is measured by a step meter; whether the surface specific area has the MXene film is observed by a metallographic microscope.

[0057] Beneficial effects

[0058] The optical fiber staggered refractive index sensor based on MXene spraying transfer provided by the application has the following beneficial effects compared with the prior art:

[0059] 1. The refractive index sensor uses a leading hollow core fiber as a beam expander and a leading hollow core fiber as a mode mixer, thereby improving the sensitivity of the sensor;

[0060] 2. The refractive index sensor has a staggered multimode fiber, which includes a staggered multimode fiber cladding and a staggered multimode fiber core, has a large core diameter and mode propagation capability, and can effectively excite the cladding mode of the multimode fiber through a staggered splicing structure, thereby producing a significant multimode interference effect and improving the sensitivity of the sensor;

[0061] 3. The refractive index sensor sprays MXene new material on the surface of the sensing area, and MXene has unique layered structure, rich surface functional groups, high electrical conductivity, high specific surface area and excellent mechanical structure and stability; under the joint action of these characteristics, the refractive index sensitivity and stability of the sensor can be significantly improved, and the sensor is suitable for high-precision detection in complex environments;

[0062] 4. The refractive index sensor coated with MXene selects spraying process for MXene material transfer, and the spraying method has significant advantages in efficient production, uniform coating, simple operation, flexible adaptability and control of coating thickness. BRIEF DESCRIPTION OF DRAWINGS

[0063] Figure 1 Structure schematic diagram of the optical fiber staggered refractive index sensor based on MXene spraying transfer;

[0064] Figure 2 Cross-sectional schematic diagram of the staggered fusion splicing structure.

[0065] Illustration:

[0066] 1-introducing single-mode optical fiber, 2-introducing hollow-core optical fiber, 3-misaligned multi-mode optical fiber cladding, 4-misaligned multi-mode optical fiber core, 5-outgoing hollow-core optical fiber, 6-outgoing single-mode optical fiber, 7-MXene material coating area. DETAILED DESCRIPTION

[0067] The preferred embodiments of the present application are described below with reference to the accompanying drawings, so that the technical contents can be more clearly and easily understood. The present application can be embodied in many different forms, and the scope of protection of the present application is not limited to the embodiments mentioned herein. In the drawings, the same components are denoted by the same reference numerals, and components having similar structures or functions are denoted by similar reference numerals. In order to make the drawings clearer, the thickness of some components is appropriately exaggerated in some places in the drawings.

[0068] Embodiment 1

[0069] The present embodiment provides a misaligned refractive index sensor based on MXene spray transfer of optical fiber, as shown in the figure, according to the propagation direction of light, there are introducing single-mode optical fiber 1, introducing hollow-core optical fiber 2, multi-mode optical fiber, outgoing hollow-core optical fiber 5, outgoing single-mode optical fiber 6 and MXene material coating area 7; the introducing hollow-core optical fiber 2 and the outgoing hollow-core optical fiber 5 are misaligned and connected to the multi-mode optical fiber; Figure 1

[0070] The multi-mode optical fiber includes misaligned multi-mode optical fiber cladding 3 and misaligned multi-mode optical fiber core 4.

[0071] The MXene material is coated on the surface of the introducing hollow-core optical fiber 2, the misaligned multi-mode optical fiber cladding 3 and the outgoing hollow-core optical fiber 5.

[0072] The introducing single-mode optical fiber 1 is connected to the introducing hollow-core optical fiber 2; the introducing hollow-core optical fiber 2 is connected to the misaligned multi-mode optical fiber cladding 3; the misaligned multi-mode optical fiber cladding 3 is connected to the outgoing hollow-core optical fiber 5; the outgoing hollow-core optical fiber 5 is connected to the outgoing single-mode optical fiber 6; the introducing hollow-core optical fiber 2, the multi-mode optical fiber and the outgoing hollow-core optical fiber 5 are connected to the outgoing single-mode optical fiber 6; the misaligned multi-mode optical fiber cladding 3 is connected to the misaligned multi-mode optical fiber core 4; and the multi-mode optical fiber is connected to the MXene material layer.

[0073] The misalignment between the introducing single-mode optical fiber 1 and the introducing hollow-core optical fiber 2 is aligned and fused.

[0074] The misalignment between the outgoing hollow-core optical fiber 5 and the outgoing single-mode optical fiber 6 is aligned and fused.

[0075] The introducing single-mode optical fiber 1 is used to introduce a light source.

[0076] The introducing hollow-core optical fiber 2 is used as a light beam expander to excite cladding modes.

[0077] ​The cladding 3 and core 4 of the misaligned multimode optical fiber excite the multimode interference effect of the multimode optical fiber through the misaligned structure.

[0078] The lead-out coreless optical fiber 5 is a mode mixer, which plays a role of mode mixing and uniform distribution, and improves the coupling efficiency of the interference mode.

[0079] The lead-out single-mode optical fiber 6 is the output of the light rays for subsequent receiving of the optical signal.

[0080] The MXene material is a high-refractive-index sensitive material, which increases the refractive index detection sensitivity of the sensor and enhances the stability of the misaligned sensing structure.

[0081] A fiber misalignment type refractive index sensor based on MXene spraying transfer and a manufacturing method thereof, comprising the following steps:

[0082] S1: a multimode optical fiber misalignment structure as shown in Figure 1 is prepared;

[0083] The specific preparation of the misaligned structure comprises the following steps:

[0084] S11: the coating of the lead-in single-mode optical fiber 1 and the lead-in coreless optical fiber 2 is partially stripped using a fiber clamp, and then the lead-in single-mode optical fiber 1 and the lead-in coreless optical fiber 2 are fixed by a fiber clamp;

[0085] S12: the lead-in single-mode optical fiber 1 and the lead-in coreless optical fiber 2 are cut and a flat end face is obtained by using an electrically driven fiber cutting knife;

[0086] S13: the lead-in single-mode optical fiber 1 and the lead-in coreless optical fiber 2 are aligned and discharge fused by using a fiber fusion machine;

[0087] S14: the multimode optical fiber and the lead-in coreless optical fiber 1 are misaligned and fused by using a fiber fusion machine;

[0088] Meanwhile, the other side of the multimode optical fiber is misaligned and displacement fused in the opposite direction by the lead-out coreless optical fiber 5, as shown in Figure 2 .

[0089] S15: finally, the lead-out coreless optical fiber 5 and the lead-out single-mode optical fiber 6 are aligned and discharge fused by using a fiber fusion machine;

[0090] In an embodiment of the present application, the length of the coreless optical fiber and the multimode optical fiber is 0.8-1.2 cm.

[0091] In an embodiment of the present application, the misaligned welding displacement in step S14 is 62.5 μm, the discharge mode is carried out in the multimode optical fiber fusion mode, the discharge intensity is set to 20 bits, and the discharge time is set to 1000 ms.

[0092] S2: Preparation of Ti3C2Tx MXene dispersion liquid;

[0093] S21: 0.7 g of LiF was added to 9 mL of hydrochloric acid with a concentration of 8 mol / L, and stirred for 4 min to make LiF fully react with hydrochloric acid as an etchant of the reaction system;

[0094] S22: 1 g of Ti3AlC2 MAX powder was slowly added to the etchant (the time of addition was more than 10 min). The system was reacted at 35℃ for 40 h to obtain a reaction mixture;

[0095] S23: The reaction mixture was centrifuged with deionized water for 3 times, and the centrifugal speed was 3000 rpm until the pH value of the supernatant was greater than 6;

[0096] S24: The product was vacuum filtered on a porous polytetrafluoroethylene membrane to obtain two layers of cake-shaped slurry, and the slurry (Ti3C2Tx) was separated from the solid (Ti3AlC2 which was not etched completely);

[0097] S25: 0.1 g of Ti3C2Tx slurry was added to 90 mL of deionized water or ethanol, and ultrasonic was performed in an ice water bath for 45 min;

[0098] S26: Then the dispersion liquid was centrifuged at 3500 rpm for 25 min to remove the multi-layer MXene aggregates, and the MXene dispersion liquid was obtained and stored in a reagent bottle for standby;

[0099] Step 3: Spray process transfers MXene;

[0100] S31: The optical fiber sensing structure was fixed on a glass slide, which was placed on a hot stage, and the temperature was set to 90℃. Heating was used to accelerate the evaporation of the spray liquid to prevent the solution from gathering into water droplets;

[0101] S32: The prepared MXene dispersion liquid was poured into a spray gun and sprayed at a small flow rate. The standard was that the solution sprayed on the optical fiber sensing structure should drop in the form of mist and evaporate quickly without gathering water droplets by visual observation;

[0102] S33: The spraying effect was observed, whether the MXene film was present in the specific area of the surface was observed by a metallographic microscope, and the thickness was measured by a step instrument.

[0103] Example 2

[0104] The embodiment provides a fiber misalignment type refractive index sensor based on MXene spraying transfer, wherein according to the propagation direction of light, an introduction single-mode optical fiber 1, an introduction hollow optical fiber 2, a multimode optical fiber, an output hollow optical fiber 5, an output single-mode optical fiber 6 and MXene material are distributed; the introduction hollow optical fiber and the output hollow optical fiber are connected through misalignment fusion splicing to connect the multimode optical fiber;

[0105] The multimode optical fiber comprises a misalignment multimode optical fiber cladding 3 and a misalignment multimode optical fiber core 4.

[0106] The MXene material is coated on the surfaces of the introduction hollow optical fiber 2, the misalignment multimode optical fiber cladding 3 and the output hollow optical fiber 5.

[0107] The introduction single-mode optical fiber 1 is connected with the introduction hollow optical fiber 2; the introduction hollow optical fiber 2 is connected with the misalignment multimode optical fiber cladding 3; the misalignment multimode optical fiber cladding 3 is connected with the output hollow optical fiber 5; the output hollow optical fiber 5 is connected with the output single-mode optical fiber 6; the introduction hollow optical fiber 2, the multimode optical fiber and the output hollow optical fiber 5 are connected with the output single-mode optical fiber 6; the misalignment multimode optical fiber cladding 3 is connected with the misalignment multimode optical fiber core 4; and the multimode optical fiber is connected with the MXene material.

[0108] The fusion splicing mode between the introduction single-mode optical fiber 1 and the introduction hollow optical fiber 2 is alignment fusion splicing.

[0109] The fusion splicing mode between the output hollow optical fiber 5 and the output single-mode optical fiber 6 is alignment fusion splicing.

[0110] The introduction single-mode optical fiber 1 is used for introducing a light source.

[0111] The introduction hollow optical fiber 2 serves as a light beam expander and excites cladding modes.

[0112] The misalignment multimode optical fiber cladding 3 and the misalignment multimode optical fiber core 4 excite the multimode interference effect of the multimode optical fiber through a misalignment structure.

[0113] The output hollow optical fiber 5 is a mode mixer and plays a role in mode mixing and uniform distribution, thereby improving the coupling efficiency of interference modes.

[0114] The output single-mode optical fiber 6 is used for outputting light and receiving subsequent optical signals.

[0115] The MXene material is a high-refractive-index sensitive material, which increases the refractive index detection sensitivity of the sensor and enhances the stability of the misalignment sensing structure.

[0116] A fiber misalignment type refractive index sensor based on MXene spraying transfer and a manufacturing method thereof, comprising the following steps:

[0117] S1: manufacturing a fiber misalignment type refractive index sensor based on MXene spraying transfer as shown in the accompanying drawings. Figure 1The multi-mode fiber misalignment structure shown;

[0118] The specific manufacturing of the misalignment structure includes the following steps:

[0119] S11: Partially stripping the coating of the introduced single-mode optical fiber 1 and the introduced coreless optical fiber 2 using the optical fiber clamp, and then fixing the introduced single-mode optical fiber 1 and the introduced coreless optical fiber 2 with the optical fiber clamp;

[0120] S12: Cutting the introduced single-mode optical fiber 1 and the introduced coreless optical fiber 2 using an electrically driven optical fiber cutting knife and obtaining a flat end face;

[0121] S13: Aligning and discharge fusion splicing the introduced single-mode optical fiber 1 and the introduced coreless optical fiber 2 using an optical fiber fusion splicer;

[0122] S14: Misalignment fusion splicing the multi-mode optical fiber and the introduced coreless optical fiber 1 using an optical fiber fusion splicer;

[0123] At the same time, the other side of the multi-mode optical fiber is also misalignment displacement fusion spliced with the introduced coreless optical fiber 5 in the opposite direction;

[0124] S15: Finally, aligning and discharge fusion splicing the introduced coreless optical fiber 5 and the introduced single-mode optical fiber 6 using an optical fiber fusion splicer;

[0125] In an embodiment of the present application, the length of the coreless optical fiber and the multi-mode optical fiber is 0.8-1.2 cm.

[0126] In an embodiment of the present application, the misalignment welding displacement in step S14 is 62.5 μm, the discharge mode adopted is the multi-mode optical fiber fusion mode, the discharge intensity is set to 20 bits, and the discharge time is set to 1100 ms.

[0127] S2: Preparing a Ti3C2Tx MXene dispersion liquid;

[0128] S21: Adding 0.8 g of LiF to 10 mL of hydrochloric acid with a concentration of 9 mol / L, stirring for 5 min, and fully reacting the LiF with the hydrochloric acid as an etchant of the reaction system;

[0129] S22: Slowly adding 1.1 g of Ti3AlC2 MAX powder (the adding time is more than 10 min) to the etchant, and reacting the system at 40°C for 45 h to obtain a reaction mixture;

[0130] S23: Centrifuging and washing the reaction mixture with deionized water 4 times at a centrifugal speed of 3250 rpm until the pH value of the supernatant is greater than 6;

[0131] S24: The product is vacuum filtered on a porous polytetrafluoroethylene membrane to obtain two layers of cake-like slurry and separate the slurry Ti3C2Tx from the solid (Ti3AlC2 not etched completely);

[0132] S25: 0.11 g of Ti3C2Tx slurry is added to 100 mL of deionized water or ethanol, and ultrasonic treatment is performed in an ice water bath for 55 min;

[0133] S26: Then the dispersion is centrifuged at 3750 rpm for 30 min to remove the multi-layer MXene aggregates, and the MXene dispersion is obtained and stored in a reagent bottle for later use;

[0134] Step 3: Spray process transfers MXene;

[0135] S31: The optical fiber sensing structure is fixed on a glass slide and placed on a hot stage with a temperature of 100°C. Heating accelerates the evaporation of the sprayed solution to prevent the solution from gathering into water droplets;

[0136] S32: Pour the prepared MXene dispersion into the spray gun and spray at a small and uniform flow rate. The standard is that the solution sprayed should fall in the form of mist on the optical fiber sensing structure and evaporate quickly without gathering water droplets by visual observation;

[0137] S33: Observe the spraying effect, observe whether there is a MXene film in the specific area of the surface by metallographic microscope, and measure the thickness by step instrument.

[0138] Example 3

[0139] The embodiment provides an optical fiber misalignment type refractive index sensor based on MXene spray transfer, according to the propagation direction of light, there are an introduction single-mode optical fiber 1, an introduction hollow-core optical fiber 2, a multimode optical fiber, an output hollow-core optical fiber 5, an output single-mode optical fiber 6 and a MXene material layer formed in a MXene material coating area 7; the introduction hollow-core optical fiber 2 and the output hollow-core optical fiber 5 are connected with the multimode optical fiber through misalignment fusion splicing;

[0140] The multimode optical fiber comprises a misalignment multimode optical fiber cladding 3 and a misalignment multimode optical fiber core 4.

[0141] The MXene material is coated on the surfaces of the introduction hollow-core optical fiber 2, the misalignment multimode optical fiber cladding 3 and the output hollow-core optical fiber 5.

[0142] The introduction single-mode optical fiber 1 is connected with the introduction hollow-core optical fiber 2; the introduction hollow-core optical fiber 2 is connected with the staggered multimode optical fiber cladding 3; the staggered multimode optical fiber cladding 3 is connected with the outgoing hollow-core optical fiber 5, and the outgoing hollow-core optical fiber 5 is connected with the outgoing single-mode optical fiber 6; the introduction hollow-core optical fiber 2, the multimode optical fiber and the outgoing hollow-core optical fiber 5 are connected with the outgoing single-mode optical fiber 6; the staggered multimode optical fiber cladding 3 is connected with the staggered multimode optical fiber core 4; and the multimode optical fiber is connected with the MXene material.

[0143] The introduction single-mode optical fiber 1 and the introduction hollow-core optical fiber 2 are aligned and fused.

[0144] The fusion mode between the outgoing hollow-core optical fiber 5 and the outgoing single-mode optical fiber 6 is aligned fusion.

[0145] The introduction single-mode optical fiber 1 is used for introducing a light source.

[0146] The introduction hollow-core optical fiber 2 serves as a light beam expander and excites cladding modes.

[0147] The staggered multimode optical fiber cladding 3 and the staggered multimode optical fiber core 4 excite the multimode interference effect of the multimode optical fiber through the staggered structure.

[0148] The outgoing hollow-core optical fiber 5 is a mode mixer, which plays a role in mode mixing and uniform distribution and improves the coupling efficiency of interference modes.

[0149] The outgoing single-mode optical fiber 6 is used for outputting light, so as to receive subsequent optical signals.

[0150] The MXene material layer is a high-refractive-index sensitive material, which increases the refractive index detection sensitivity of the sensor and enhances the stability of the staggered sensing structure.

[0151] A fiber staggered refractive index sensor based on MXene spraying transfer and a manufacturing method thereof, comprising the following steps:

[0152] S1: a multimode optical fiber staggered structure as shown in Figure 1 is prepared;

[0153] The specific preparation of the staggered structure comprises the following steps:

[0154] S11: using a fiber clamp to partially strip the coating of the introduction single-mode optical fiber 1 and the introduction hollow-core optical fiber 2, and then fixing the introduction single-mode optical fiber 1 and the introduction hollow-core optical fiber 2 with a fiber clamp;

[0155] S12: using an electric fiber cutting knife to cut the introduction single-mode optical fiber 1 and the introduction hollow-core optical fiber 2 and obtain a flat end face;

[0156] S13: using a fiber fusion machine to perform aligned discharge fusion between the introduction single-mode optical fiber 1 and the introduction hollow-core optical fiber 2;

[0157] S14: using a fiber fusion machine to misalign and fuse the multimode optical fiber with the introduced coreless optical fiber 1;

[0158] At the same time, the other side of the multimode optical fiber is also misaligned and displaced and fused with the introduced coreless optical fiber 5 in the opposite direction;

[0159] S15: finally, using a fiber fusion machine to align and discharge and fuse the introduced coreless optical fiber 5 with the introduced single-mode optical fiber 6;

[0160] In an embodiment of the present application, the lengths of the coreless optical fiber and the multimode optical fiber are 0.8 cm, and can also be 1 cm or 1.2 cm.

[0161] In an embodiment of the present application, the misalignment displacement in step S14 is 62.5 μm, as shown in Figure 1 The discharge mode adopted is a multimode optical fiber fusion mode, the discharge intensity is set to 20 bits, and the discharge time is set to 1200 ms.

[0162] S2: preparing a Ti3C2Tx MXene dispersion liquid;

[0163] S21: adding 0.9 g of LiF to 11 mL of hydrochloric acid with a concentration of 10 mol / L, stirring for 6 min, and fully reacting the LiF with the hydrochloric acid as an etchant of the reaction system;

[0164] S22: slowly adding 1.2 g of Ti3AlC2 MAX powder (the adding time is more than 10 min) into the etchant. The system is reacted at 45°C for 50 h to obtain a reaction mixture;

[0165] S23: centrifugally washing the reaction mixture with deionized water for 5 times at a centrifugal speed of 3500 rpm until the pH value of the supernatant is greater than 6;

[0166] S24: vacuum suction filtering the product on a porous polytetrafluoroethylene membrane to obtain two-layer cake-like slurries and separate the slurry (Ti3C2Tx) from the solid substance (Ti3AlC2 which is not etched completely);

[0167] S25: taking 0.12 g of Ti3C2Tx slurry and adding it into 110 mL of deionized water or ethanol, and ultrasonically treating in an ice water bath for 1 h;

[0168] S26: then centrifuging the dispersion liquid at 4000 rpm for 35 min to remove the multi-layer MXene aggregates, so as to obtain a MXene dispersion liquid, which is stored in a reagent bottle for standby use;

[0169] Step 3: spray process transfers MXene;

[0170] S31: Fix the optical fiber sensing structure on the glass slide, place it on the hot stage, and set the temperature to 110℃. Heat to accelerate the evaporation of the sprayed liquid and prevent the solution from gathering into water droplets;

[0171] S32: Pour the prepared MXene dispersion liquid into the spray gun and spray at a small flow rate. The standard is that the solution sprayed should fall in the form of mist on the optical fiber sensing structure and evaporate quickly without gathering water droplets by visual observation;

[0172] S33: Observe the spraying effect, observe whether there is a MXene film on the surface of the specific area by metallographic microscope, and measure the thickness by step instrument.

[0173] It is particularly noted that in step S31, the heating time is about 5 minutes to ensure that the temperature of the optical fiber sensing structure is stable. In step S32, the spraying time is controlled according to the rate, and the same rate is maintained. It is suggested that the initial spraying time is 5-10 minutes. After multiple spraying, the actual film thickness is measured, and the subsequent spraying time is adjusted to achieve the required thickness; in addition, during the operation, the distance between the spray gun and the optical fiber sensing structure is kept between 10-15 cm to obtain the best spraying effect.

[0174] Compared with ordinary optical fiber sensors, the optical fiber misalignment type refractive index sensor based on MXene spraying transfer can greatly reduce the volume of the sensing system while realizing a stable sensing structure, effectively improve the solution refractive index detection sensitivity of the system, and has the advantages of simple structure, easy preparation, small volume, etc. At the same time, the optical fiber solution sensing system has good embedding and stability, and can be deployed in various harsh liquid environments, which has very important significance for improving the performance of the optical fiber liquid sensing system and expanding the refractive index detection coverage of the optical fiber sensing system.

[0175] The embodiment of the application mainly utilizes the core offset generated by the large misalignment splicing of the multimode optical fiber and the single-mode optical fiber, so as to cause the cladding mode excited by the mode field mismatch, and these cladding modes form a stronger evanescent field on the surface of the optical fiber, and the interaction with the external environment is more significant. And the refractive index response law of the MXene coating to the external solution, the refractive index sensitivity of the liquid detection device is effectively improved by misalignment splicing and MXene material. Due to the existence of the MXene misalignment splicing structure, the action effect between the optical field and the liquid medium can be effectively increased.

[0176] As Figure 2As shown, the working process of the fiber misalignment type refractive index sensor based on MXene spraying transfer of the embodiment of the application is as follows: the sensing structure is placed in a detection liquid, signal light output by a broadband light source with a working wave band of 1500-1600 nm is separated by the introduction of a single-mode optical fiber and a coreless optical fiber, and reaches the misalignment multimode optical fiber cladding 3, the misalignment multimode optical fiber core 4 and the MXene coating area 7, respectively, after the action of the cladding evanescent wave light signal and the core light signal and the common action with the liquid medium in this area, the coupling to the lead-out coreless optical fiber occurs mode mixing and realizes uniform distribution of the mode, and finally interference spectrum output is generated in the lead-out single-mode optical fiber.

[0177] The model of each device in the embodiments of the application is not limited unless otherwise specified, and any device that can complete the above functions can be used.

[0178] Those skilled in the art can understand that the drawings are only schematic diagrams of a preferred embodiment, and the above-mentioned serial numbers of the embodiments of the application are only for description, and do not represent the advantages and disadvantages of the embodiments.

[0179] The above-mentioned is only a preferred embodiment of the application, and does not limit the application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A fiber optic misaligned refractive index sensor based on MXene spray transfer, characterized in that, The optical fiber includes an introduction single-mode fiber, an introduction coreless fiber, a multimode fiber, an exit coreless fiber, an exit single-mode fiber, and an MXene material layer distributed along the direction of light propagation; the introduction coreless fiber and the exit coreless fiber are connected to the multimode fiber by staggered fusion splicing. The multimode fiber includes a misaligned multimode fiber cladding and a misaligned multimode fiber core. The MXene material layer is coated on the surface of the introduced coreless fiber, the cladding of the misaligned multimode fiber, and the surface of the led-out coreless fiber. The introduced single-mode fiber is connected to the introduced coreless fiber; the introduced coreless fiber is connected to the misaligned multimode fiber cladding; the misaligned multimode fiber cladding is connected to the exiting coreless fiber, and the exiting coreless fiber is connected to the exiting single-mode fiber; the introduced coreless fiber, multimode fiber, and exiting coreless fiber are connected to the exiting single-mode fiber; the misaligned multimode fiber cladding is connected to the misaligned multimode fiber core. The misaligned multimode fiber cladding and misaligned multimode fiber core stimulate the multimode interference effect of the multimode fiber through the misaligned structure. The misaligned fusion splicing uses a multimode fiber fusion splicing mode, and the displacement ratio of the misaligned fusion splicing is 30% to 80% of the multimode fiber diameter.

2. The fiber misalignment refractive index sensor based on MXene spray transfer according to claim 1, characterized in that, The fusion splicing method between the introduced single-mode fiber and the introduced coreless fiber is alignment fusion splicing.

3. The fiber misalignment refractive index sensor based on MXene spray transfer according to claim 1, characterized in that, The splicing method between the coreless optical fiber and the single-mode optical fiber is alignment splicing.

4. The fiber optic misaligned refractive index sensor based on MXene spray transfer according to claim 1, characterized in that, The single-mode fiber is used to introduce the light source; the coreless fiber is used as a beam expander, applying the excitation cladding mode, and outputting to the multimode fiber.

5. The fiber optic misaligned refractive index sensor based on MXene spray transfer according to claim 1, characterized in that, The single-mode fiber outputs an optical signal for subsequent reception, and the refractive index of the MXene material layer is between 1.68 and 2.

5.

6. A method for fabricating a fiber optic misaligned refractive index sensor based on MXene spray transfer, characterized in that, Includes the following steps: S1: Fabricate the multimode fiber misalignment structure, which includes the following steps: S11: Strip the coatings from the introduced single-mode fiber and the introduced coreless fiber, and then fix the introduced single-mode fiber and the introduced coreless fiber. S12: Cutting and introducing single-mode fiber and coreless fiber to obtain a flat end face; S13: Align and discharge splice the single-mode fiber and the coreless fiber. S14: The multimode optical fiber includes a misaligned multimode optical fiber cladding and a misaligned multimode optical fiber core; The introduced coreless fiber is connected to the misaligned multimode fiber cladding; the misaligned multimode fiber cladding is connected to the led-out coreless fiber, and one side of the multimode fiber is misaligned and fused with the introduced coreless fiber, while the other side of the multimode fiber is misaligned and fused with the led-out coreless fiber in the opposite direction. S15: Align and discharge splice the coreless fiber and the single-mode fiber. Thus, from S11 to S15, a multimode fiber misalignment structure was fabricated; S2: Preparation of Ti3C2Tx MXene dispersion; S3: Transfer of MXene dispersion during spraying process; S31: Fix the multimode fiber misalignment structure onto the glass slide, and then place the glass slide on a hot stage for heating. S32: Spray MXene dispersion onto the multimode fiber misalignment structure at a uniform speed; S33: Observe whether there is an MXene film in a specific area of ​​the surface and measure the thickness of the MXene film; S32 describes uniform spraying and S33 describes measuring the thickness of the MXene film. Specifically, the spraying time is controlled according to the rate, maintaining the same rate and the initial spraying time is 5 to 10 minutes. After multiple sprayings, the actual film thickness is measured, and subsequent spraying times are adjusted to achieve the required thickness. The discharge mode used in the misaligned fusion splicing described in S14 is a multimode fiber fusion splicing mode, and the displacement distance of the misaligned fusion splicing is 60-65 μm.

7. The method for fabricating a fiber optic misaligned refractive index sensor based on MXene spray transfer according to claim 6, characterized in that, To achieve the best spraying effect during uniform speed spraying, it is necessary to ensure that the distance between the spray gun and the fiber optic sensing structure is maintained between 10 and 15 cm.

8. The method for fabricating a fiber misaligned refractive index sensor based on MXene spray transfer according to claim 7, characterized in that, The lengths of the single-mode optical fiber, coreless optical fiber, and multimode optical fiber mentioned in S11, S12, S13, S14, and S15 are 0.8 to 1.2 cm.

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