CN107861192A - Cone is drawn to combine the method that chemical attack prepares optical fiber F P sensors based on optical fiber - Google Patents

Abstract

The invention provides a method for preparing an optical fiber F-P strain sensor based on optical fiber tapering combined with chemical corrosion. The F-P microstructure on the optical fiber is prepared by the tapering combined with chemical corrosion method to realize the measurement of physical quantities. The core and cladding of the optical fiber become thinner, the change of the measurement cavity length will be more obvious when measuring the strain, and the sensitivity is higher, which is suitable for high-precision measurement; the F-P structure is constructed on the tapered structure to further improve the sensing sensitivity . The optical fiber F-P strain sensor device prepared by the present invention has simple structure, reliable stability, and devices with different cavity lengths can be prepared according to requirements. Realize batch processing of devices.

Description

Method for preparing optical fiber F-P sensor based on optical fiber tapering combined with chemical etching

technical field

The invention relates to the field of optical fiber devices, in particular to a method for an optical fiber F-P sensor made of optical fiber tapering.

Background technique

Optical fiber sensors have many excellent characteristics, which can realize measurement work in complex environments and have a very wide range of application values. It has the characteristics of anti-electromagnetic interference, anti-radiation, high sensitivity, light weight, insulation explosion-proof, corrosion resistance, etc., and the fiber size is small, with good optical transmission performance. Among various types of fiber optic sensors, the most accurate one is the interferometric fiber optic sensor. Among them, the optical fiber F-P sensor has received extensive attention in biomedicine, magnetic field, and micro-electromechanical systems because it only uses one optical fiber and has a simple structure, small size, and large dynamic range.

The traditional manufacturing method has complex procedures and poor repeatability. For the Fabry-Perot cavity, the cavity length needs to be calibrated, which makes the mass production of optical Fabry-Perot difficult, thus limiting the optical fiber Fabry-Perot to a certain extent. The further wide application of Luo sensor. Compared with traditional sensors, fiber optic F-P sensors have many excellent characteristics, such as no electromagnetic interference, wide application range, good stability, good reliability, high resolution, high precision, small size , light weight and other significant advantages.

Optical fiber Fabry-Perot (F-P) sensors mainly include two types: extrinsic type and intrinsic type. The fiber optic F-P sensor with extrinsic structure is composed of an optical fiber and a non-fiber optic element with a reflective surface structure; the processing method of the intrinsic fiber F-P structure is generally made by coating the two ends of the fiber and packaging or docking, but due to The diameter of the optical fiber is on the order of microns. It is difficult to choose the coating material, and the coating is difficult. In addition, it is necessary to accurately control the coated optical fiber and connect the optical fiber to reduce the coupling loss during packaging or docking, and the operation is difficult.

At present, the common F-P cavity preparation methods are: chemical corrosion method, arc discharge method, femtosecond laser preparation method, etc. For the optical fiber F-P sensor formed by femtosecond writing, when the femtosecond laser is focused on the fiber core, the material properties will be changed and the refractive index will be changed, while the surface of the fiber will not be affected in any way. When the optical fiber sensor is prepared by chemical etching, the length of the sensor cavity can be set by controlling the etching time, adjusting the concentration of HF acid solution, setting the etching time, etc., the cost is low, the production is simple, and mass production can be realized in a certain area. .

Therefore, there is a need for a method for fabricating an optical fiber F-P strain sensor with an extrinsic structure based on optical fiber tapering combined with chemical etching.

Contents of the invention

In order to solve the above-mentioned technical problems, the present invention provides a method for preparing an optical fiber F-P strain sensor based on optical fiber tapering combined with chemical corrosion, comprising the following steps:

Step 1: Use ordinary single-mode fiber and place it in a high-precision single-core fusion splicer to taper;

Step 2: Use a cleaver to cut off the tapered ordinary single-mode optical fiber from the middle, and place one end in 40% hydrofluoric acid to corrode for 10 minutes until the corroded optical fiber end face forms a groove;

Step 3: Clean the end face of the corroded optical fiber with residual hydrofluoric acid, and weld it with the other end of the ordinary single-mode optical fiber in a fusion splicer to form an F-P cavity structure, and obtain the structure of the optical fiber F-P strain sensor.

Preferably, in step 1, the length of the tapered optical fiber is 15000 μm-20000 μm, and the corresponding lumbar diameter is 50 μm-100 μm.

Preferably, in step 1, the model of the common single-mode optical fiber is SMF-28, the cladding diameter of the optical fiber is 125 μm, and the core diameter is 9 μm.

Preferably, in step 1, the high-precision single-core welding machine adopts the 80S high-precision single-core welding machine of Japan Fujikura Company.

Among them, in step 2, compared with the cladding of the optical fiber, the core of the optical fiber has higher germanium-doped elements, and the reaction rate with the hydrofluoric acid solution is faster, and after a period of time, grooves will be formed on the end face of the corroded optical fiber. .

Preferably, in step 3, the optical fiber F-P cavity structure is a microcavity formed after the corroded common single-mode fiber end face is relatively fused with the other end of the common single-mode fiber, and the F-P cavity structure includes two reflecting The end face, the reflective end face is a groove formed by the corroded end face of the common single-mode fiber and another groove formed by melting when the other end of the common single-mode fiber is fused, and the two reflective end faces can form a circle.

More preferably, the distance between the two reflective end faces in the F-P cavity structure is 50 μm-6000 μm, and the interference effect is best in this range.

Preferably, the preparation method of the present invention can prepare optical fiber F-P strain sensor devices with different cavity lengths according to requirements.

The present invention has the following beneficial effects:

1. It is prepared by the method of tapering combined with chemical etching, and the preparation method is simple.

2. The prepared extrinsic optical fiber F-P strain sensor device has a simple structure and reliable stability, and devices with different cavity lengths can be prepared according to requirements.

3. Tapering and chemical etching technologies have low cost and high repeatability, and are easy to realize batch processing of devices.

It should be understood that both the foregoing general description and the following detailed description are exemplary illustrations and explanations, and should not be used as limitations on the claimed content of the present invention.

Description of drawings

With reference to the accompanying drawings, more objects, functions and advantages of the present invention will be clarified through the following description of the embodiments of the present invention, wherein:

Fig. 1 shows a schematic diagram of the structure of an optical fiber F-P strain sensor prepared according to the present invention.

Fig. 2 shows a schematic structural diagram of a strain system for testing the performance of the optical fiber F-P strain sensor prepared by the present invention.

Fig. 3 shows the interference spectra of the optical fiber F-P strain sensor prepared according to the present invention under different strains.

Fig. 4 shows a schematic diagram of the wavelength-strain relationship curve obtained after calibration of the optical fiber F-P strain sensor prepared by the present invention.

Detailed ways

The objects and functions of the present invention and methods for achieving the objects and functions will be clarified by referring to the exemplary embodiments. However, the present invention is not limited to the exemplary embodiments disclosed below; it can be implemented in various forms. The essence of the description is only to help those skilled in the relevant art comprehensively understand the specific details of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar components, or the same or similar steps.

Referring to Fig. 1, the present invention provides a kind of method for preparing optical fiber F-P strain sensor based on optical fiber tapering in combination with chemical corrosion, comprising the following steps:

Step 1: Use ordinary single-mode fiber and place it in a high-precision single-core fusion splicer to taper;

Further, the model of the common single-mode optical fiber is SMF-28, the cladding diameter of the optical fiber is 125 μm, and the core diameter is 9 μm.

Further, the length of the tapered optical fiber is 15000 μm-20000 μm, and the corresponding lumbar diameter is 50 μm-100 μm, as shown in (a) of FIG. 1 .

Step 2: Use a cleaver to cut off the tapered optical fiber from the middle, and place one end in 40% hydrofluoric acid for 10 minutes to corrode until the corroded optical fiber end face forms a groove, as shown in Figure 1 (b) shown.

Among them, compared with the cladding, the core of the optical fiber has a higher germanium-doped element, and the reaction rate with the hydrofluoric acid solution is faster. After a period of time, grooves will be formed on the end face of the corroded optical fiber.

Step 3: Clean the remaining hydrofluoric acid from the above-mentioned optical fiber, and weld it with the other end of the common single-mode optical fiber in a fusion splicer to form an F-P cavity structure and obtain the structure of an optical fiber F-P strain sensor. Wherein, the high-precision single-core welding machine adopts the 80S high-precision single-core welding machine of Japan Fujikura Company.

As shown in Figure 1 (c), in step three, the cavity structure of the optical fiber F-P is a microcavity formed after the corroded common single-mode fiber end face is relatively fused with the other end of the common single-mode fiber, and the F-P The cavity structure includes two reflective end faces, the reflective end faces are respectively the groove formed by the corroded common single-mode fiber end face and another groove formed by melting when the other end of the common single-mode fiber is fused. The reflective end faces can form a circle, and the distance between the two reflective end faces in the F-P cavity structure is 50 μm-6000 μm, which is the best interference effect.

Specifically, when the coherent light beam is incident on the microcavity along the large mode field fiber, the light is reflected by the two reflective end faces of the microcavity, returns along the original path, and meets to generate interference.

Specifically, according to the principle of multi-beam interference, the reflection output I _R of the optical FP cavity is

In the formula, is the optical phase, where

Among them, n ₀ is the refractive index of the material in the cavity, R is the reflectivity of both ends, and is the angle between the incident light and the reflection end surface, λ and I ₀ are the wavelength and light intensity of the incident light, respectively, and L is the cavity length of the microcavity , the additional phase π is the phase difference caused by the half-wave loss when light is incident on an optically rarer medium to an optically denser medium.

When the reflectivity R of both ends of the F-P cavity is very low, double-beam interference can be used instead of multi-beam interference, then

From formulas (1), (2) and (3), it can be seen that when the external parameters act on the microcavity, the change of the corresponding external parameters can be deduced through the change of the reflected light intensity, and the purpose of sensing and measurement can be realized.

Referring to Fig. 2, it is a strain system for testing the performance of an optical fiber F-P strain sensor. The system test system includes a broadband light source 1, an optical fiber circulator 2, an equal-intensity beam 3, an optical fiber F-P strain sensor 4 prepared by the present invention, and an optical fiber sensor Analyzer 5, the optical fiber F-P strain sensor 4 is pasted on the equal strength beam 3, and connected to the optical fiber sensor analyzer 5 through the optical fiber circulator 2.

Among them, the spectrometer adopts the optical fiber sensor analyzer produced by Yokogawa Company.

Wherein, the broadband light source 1 is used to provide test signals for the optical fiber F-P sensor.

In this experiment, the reflection spectrum is collected by the optical fiber sensing analyzer 5 , specifically, the reflection interference spectrum generated by the optical fiber F-P cavity is transmitted to the optical fiber sensing analyzer 5 through the optical fiber circulator 2 . Wherein, the optical fiber F-P strain sensor 4 is pasted on the equal-intensity beam 3, and the equal-intensity beam 3 can be used to change the magnitude of the strain force. Specifically, the equal-strength beam 3 also includes a base and a spiral micrometer head. When the spiral micrometer head rotates, the base will deform, causing stress changes in the F-P cavity attached to the base. Among them, the relationship between the rotation distance of the spiral micrometer head and the bending degree of the substrate has been calibrated.

See Figure 3, which is the reflectance spectrum obtained in this experiment. It can be seen from the figure that when the external temperature or pressure changes, the reflectance spectral lines will shift, and the three spectral lines are respectively when the strain is 50με, 100με, and 150με. The interference spectrum of the fiber optic F-P sensor in the range of 1520nm to 1610nm. Therefore, the strain resistance of the sensor prepared by the invention is good, and the structure is feasible.

Referring to Figure 4, by calibrating the optical fiber F-P strain sensor, within the strain range of 50-400με, applying strain at intervals of 50με, recording the wavelength of the corresponding strain, and obtaining the wavelength-strain relationship curve, it can be seen from the figure that: The linearity is 99.8%, and the sensitivity is 5.82pm/με, indicating that the sensor has good linearity and high sensitivity, and is suitable for high-precision measurement.

The present invention prepares the F-P microstructure on the optical fiber by tapering and chemical corrosion method to realize the measurement of physical quantity, the fiber core and cladding of the optical fiber after tapering become thinner, and the change of the measurement cavity length will be more obvious when measuring the strain, and then Higher sensitivity, suitable for high-precision measurement; constructing F-P structure on the tapered structure will further improve the sensing sensitivity. The optical fiber F-P strain sensor device prepared by the present invention has simple structure, reliable stability, and devices with different cavity lengths can be prepared according to requirements. The preparation method is simple, and the cost of tapering and chemical etching technology is low, the repeatability is high, and the device is easy to realize. batch processing.

Other embodiments of the invention will be apparent to and understood by those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The description and examples are considered exemplary only, with the true scope and spirit of the invention defined by the claims.

Claims (7)

1. a kind of draw cone to combine the method that chemical attack prepares optic fiber F-Pstrain sensor based on optical fiber, comprise the following steps：

S1：Using general single mode fiber, place it in and cone is drawn in high-precision single heat sealing machine；

S2：With cutter the general single mode fiber after boring will be drawn to be cut off from centre, and wherein one end is placed in 40% hydrofluoric acid Middle corrosion 10 minutes, until the fiber end face being corroded forms groove；

S3：The above-mentioned fiber end face being corroded is cleaned into residual hydrofluoric acid, and with the general single mode fiber other end in heat sealing machine Welding, F-P cavity structure is formed, obtains optic fiber F-Pstrain sensor device.

2. the method according to claim 1 for preparing optic fiber F-Pstrain sensor, it is characterised in that in S1, after drawing cone Optical fiber length be 15000 μm -20000 μm, corresponding a diameter of 50 μm -100 μm of lumbar vertebrae.

3. the method according to claim 1 for preparing optic fiber F-Pstrain sensor, it is characterised in that in S1, the light Fine cladding diameter is 125 μm, and core diameter is 9 μm.

4. the method according to claim 1 for preparing optic fiber F-Pstrain sensor, it is characterised in that the general single mode The model SMF-28 of optical fiber, the high-precision single heat sealing machine are melted using the 80S high accuracy singles of Japanese Fujikura companies Pick.

5. the method according to claim 1 for preparing optic fiber F-Pstrain sensor, it is characterised in that in S3, the light Fine F-P cavity structure is that will be formed after the welding relative with the general single mode fiber other end of the general single mode fiber end face corroded Microcavity, the F-P cavity structure includes two reflection end faces, and the reflection end face is respectively the general single mode fiber that has been corroded Another to be formed groove is melted when the groove of end face formation and the general single mode fiber other end welding, it is described two anti- Circle can be formed by penetrating end face.

6. the method according to claim 5 for preparing optic fiber F-Pstrain sensor, it is characterised in that the F-P cavity structure In two reflection end faces distances be 50 μm -6000 μm.

7. the method according to claim 1 for preparing optic fiber F-Pstrain sensor, it is characterised in that the light being prepared Fine F-P strain transducers device can prepare different cavity length as requested.