CN206960027U - A kind of fibre optic compression sensor based on micro- ellipsoid air chamber - Google Patents

Abstract

The utility model relates to an optical fiber pressure sensor based on a micro-ellipsoidal air cavity, which belongs to the technical field of optical fiber pressure sensors. It includes a single-mode optical fiber and a pressure-sensitive membrane; the upper end of the single-mode optical fiber is fixedly connected to the lower end of the pressure-sensitive membrane, and an air Fabry-Perot cavity is set at the connection between the single-mode optical fiber and the pressure-sensitive membrane. The materials in the utility model are all silicon dioxide, so that the thermal expansion coefficient of the utility model is the same, avoiding the structural failure caused by the high temperature mismatch of different materials, the temperature crosstalk is small, and the cost is low; the manufacturing process of the sensor head only needs welding, cutting and grinding , the manufacturing process is simple; the confocal Fabry-Perot cavity in this device is compared with the Fabry-Perot cavity produced by the etching process or femtosecond laser in the prior art, the interference cavity loss is small, and the contrast of the interference fringes is high , high demodulation accuracy.

Description

A fiber optic pressure sensor based on micro-ellipsoidal air cavity

technical field

The utility model relates to an optical fiber pressure sensor based on a micro-ellipsoidal air cavity, which belongs to the technical field of optical fiber pressure sensors.

Background technique

Commonly used fiber optic pressure sensors mainly include fiber grating pressure sensors and fiber optic Fabry-Perot pressure sensors. Compared with the fiber grating pressure sensor, the fiber optic Fabry-Perot pressure sensor is more sensitive to the pressure signal generated by the outside world. Different structural parameters can meet the requirements of different measurement ranges and sensitivities. It is resistant to harsh environments and electromagnetic resistance. Drying, small temperature cross-sensitivity and other advantages. It is used in pressure detection in fields such as biomedicine, high temperature and high pressure oil wells, aerospace, bridge detection, etc.

The fiber optic Fabry-Perot pressure sensor has a capillary structure and a diaphragm structure. The capillary structure uses the axial deformation of the capillary to realize the pressure sensing, which can be used for the measurement of a large pressure range, but due to the low sensitivity to pressure sensing, it is not suitable for the measurement requiring high precision. The diaphragm structure uses a pressure-sensitive diaphragm to form a reflective surface of the Fabry-Perot interferometer. When the external pressure acts on the diaphragm, the diaphragm undergoes elastic deformation, so that the cavity of the Fabry-Perot interferometer Long-term change, realizing the perception of pressure, has the advantages of high sensitivity, strong anti-interference ability, good linearity, and large dynamic range.

The optical fiber Fabry-Perot pressure sensor with a diaphragm structure can be composed of a concave cavity on the end face of the optical fiber and a pressure sensitive membrane that deforms under force. The cavity is formed by chemical etching [1,2] and femtosecond laser preparation [3]. The etching control in the chemical etching preparation method is difficult, the cavity shape is difficult to control and the loss in the cavity is large; the femtosecond laser preparation method can precisely control the cavity shape of the interference cavity, but the processing system is expensive. The pressure sensitive membrane in literature [1] is specially treated single crystal silicon, which is anodically bonded with borosilicate optical fiber whose end face has been corroded with a concave cavity to form a sensing head. The manufacturing process of this optical fiber pressure sensor is complex and different materials have different thermal expansion coefficients to temperature. Therefore, when the temperature changes, the sensor head will generate stress due to different thermal expansion and is easily damaged. In the literature [2] [3], the pressure sensitive membrane is made of quartz material, which is welded with the optical fiber with a concave cavity to form the sensing head. The thermal expansion coefficient of this optical fiber pressure sensor is consistent and the structure is stable; the formation of the concave cavity on the end face of the optical fiber and the fusion with the sensitive film require a two-step process; The timing pressure measurement accuracy is not high enough.

[1] Ge Yixian, Wang Tingting, Zhang Chuang, Mao Xiaoli. A miniature optical fiber Fabry-Perot pressure sensor and its manufacturing method, invention patent: 201310524956.7, authorized date: 2015.11;

[2] Yang Chundi, Wang Ming, Ge Yixian, Dai Lihua. Miniature Extrinsic Optical Fiber Fabry-Perot Pressure Sensor [J], Acta Optics Sinica, 2010, 30(5): 1458-1461;

[3] Jiang Lan, Jiang Yi, Wang Peng, Wang Sumei, Liu Da. An optical fiber micro-nano-Farper interferometric pressure sensor and its manufacturing method, patent application number: 201510282041.9.

Utility model content

The technical problem to be solved by the utility model is to overcome the defects of the prior art and provide a fiber optic pressure sensor based on a micro-ellipsoidal air Fabry-Perot cavity with simple manufacturing process and high measurement accuracy. Welding, cutting and grinding processes, and the reflection spectrum has high fringe contrast, sharp troughs, and high pressure measurement accuracy.

In order to achieve the above object, the utility model provides an optical fiber pressure sensor based on a micro-ellipsoidal air cavity, including a single-mode optical fiber and a pressure-sensitive membrane; the upper end of the single-mode optical fiber is fixedly connected to the lower end of the pressure-sensitive membrane, and the single-mode optical fiber An air Fabry-Perot cavity is provided at the connection between the optical fiber and the pressure sensitive membrane.

Preferably, the air Fabry-Perot cavity is a micro-ellipsoid, and the air Fabry-Perot cavity is a confocal cavity.

Preferably, the cavity length of the air Fabry-Perot cavity is 40 μm-50 μm.

Preferably, the thickness of the pressure sensitive film is 6-12 μm.

Preferably, the material of the single-mode optical fiber is silica.

Preferably, the material of the pressure-sensitive membrane is silicon dioxide.

The beneficial effects achieved by the utility model:

The materials in the utility model are all silicon dioxide, so that the thermal expansion coefficient of the utility model is the same, avoiding the structural failure caused by the high temperature mismatch of different materials, the temperature crosstalk is small, and the cost is low; the manufacturing process of the sensor head only needs welding, cutting and grinding , the production process is simple and the realizability is strong;

The sensing head of the sensor is inside the optical fiber, and the measured pressure can directly modulate the characteristic parameters of the light wave in the optical fiber, which can effectively reduce the size of the sensor and reduce the influence of external interference and environmental factors;

The confocal Fabry-Perot cavity in this device, compared with the Fabry-Perot cavity produced by the corrosion process or femtosecond laser in the prior art, has the advantages of small interference cavity loss, high contrast of interference fringes, and good demodulation The advantage of high precision.

Description of drawings

Fig. 1 is the structural diagram of this device;

Fig. 2 is the manufacturing process flowchart of this device;

Fig. 3 is the demodulation system of this device;

Fig. 4 is the experimental result figure of this device;

Fig. 5 is the reflection spectrum of the optical fiber Fabry-Perot pressure sensor that adopts corrosion process to make in the prior art;

Figure 6 is the reflection spectrum of the device.

The meanings of the marks in the attached drawings, 1-single-mode optical fiber; 2-pressure sensitive film; 3-micro-ellipsoidal air Fabry-Perot cavity; 4-reflecting surface one; 5-reflecting surface two; 6-reflecting surface three; 7-electrode; 8-fiber connector; 9-fiber grinding sandpaper.

Detailed ways

The utility model will be further described below in conjunction with the accompanying drawings. The following examples are only used to illustrate the technical solution of the utility model more clearly, but not to limit the protection scope of the utility model.

An optical fiber pressure sensor based on a micro-ellipsoid air cavity, comprising a single-mode optical fiber and a pressure-sensitive membrane; the upper end of the single-mode optical fiber is fixedly connected to the lower end of the pressure-sensitive membrane, and the connection between the single-mode optical fiber and the pressure-sensitive membrane Open the air Fabry-Perot cavity.

Further, the air Fabry-Perot cavity is a micro-ellipsoid, and the air Fabry-Perot cavity is a confocal cavity.

Further, the cavity length of the air Fabry-Perot cavity is 40 μm-50 μm.

Further, the thickness of the pressure sensitive film is 6-12 μm.

Further, the material of the single-mode optical fiber and the pressure-sensitive film is silicon dioxide.

A method for manufacturing an optical fiber pressure sensor based on a micro-ellipsoidal air cavity, comprising the following steps:

Clean the single-mode fiber and photonic crystal fiber after stripping the coating layer of the single-mode fiber and photonic crystal fiber;

Cut the right end face of the single-mode fiber and the left end face of the photonic crystal fiber;

Place the right end face of the single-mode fiber and the left end face of the photonic crystal fiber on both sides of the electrode of the fusion splicer;

The electrode of the fusion splicer discharges several times until the joint of the single-mode fiber and the photonic crystal fiber is fused to form an air Fabry-Perot cavity with a cavity length of 40 μm-50 μm. The discharge of the electrode of the fusion splicer makes the air hole of the photonic crystal fiber collapse to form In the silicon oxide collapse area, the control processing display monitors the cavity length change of the air Fabry-Perot cavity in real time through an optical fiber sensor analyzer;

Cutting the right end face of the photonic crystal fiber perpendicular to the optical axis, leaving only the silicon dioxide collapsed region of the photonic crystal fiber to form a pressure sensitive film;

Insert the combination of single-mode optical fiber and pressure-sensitive film into the fiber optic connector, place the upper end of the pressure-sensitive film downward, and grind the reflective surface of the upper end of the pressure-sensitive film with sandpaper until the thickness of the pressure-sensitive film reaches 20-30μm;

Then continue to use sandpaper to grind the upper end reflective surface of the pressure-sensitive membrane, so that the thickness above the air Fabry-Perot cavity, that is, the center of the pressure-sensitive membrane, reaches 6-12 μm. The control and processing display monitors the pressure sensitivity in real time through an optical fiber sensor analyzer. the thickness of the center of the membrane;

Corroding the reflective surface 3 of the pressure sensitive film with hydrofluoric acid, and roughening the reflective surface 3 of the pressure sensitive film.

Further, the distance between the right end face of the single-mode fiber and the left end face of the photonic crystal fiber is 50 μm, and the electrode of the fusion splicer is 20 μm away from the end face of the single-mode fiber; the electrode of the fusion splicer is discharged 6 to 7 times; the right end of the photonic crystal fiber is cut perpendicular to the optical axis to form A silicon dioxide sensitive membrane with a central thickness of 40 μm.

Further, the welding parameters of the welding machine are welding current 7mA, welding time 650ms, and z-axis advancing amount 5 μm.

Further, first use 3 μm sandpaper to grind the reflective surface 3 on the upper end of the pressure sensitive film until the thickness of the center of the pressure sensitive film reaches 20-30 μm; 6-12 μm.

The light wave E ₀ passes through the single-mode optical fiber 1 and is vertically incident on the sensor probe, and is reflected by the three reflection surfaces of reflection surface 1 4 , reflection surface 2 5 , and reflection surface 3 6 respectively, and the three beams of reflected light E ₁ , E ₂ and E ₃ interfere , after the reflective surface 36 is roughened, E ₃ can be ignored, and the reflection spectrum is approximately E ₁ , E ₂ double-beam interference. When the pressure-sensitive film 2 is deformed under pressure, the reflectance spectrum changes, and the applied pressure can be demodulated by tracking the wavelength of the trough of the reflectance spectrum.

The micro-ellipsoidal air Fabry-Perot cavity 3 is a confocal cavity, that is, the radius of curvature of the two concave cavities is equal to the length of the Fabry-Perot cavity. At this time, the loss of the interference cavity is small, and the reflection spectrum interference fringes are more Sharp, greatly improving measurement accuracy.

The optical fiber Fabry-Perot pressure sensor made based on the above method is demodulated using the demodulation system shown in Figure 3, and the result is shown in Figure 4. The pressure sensor provided by this patent has good linearity and repeatability Spend. Under the same experimental conditions, comparing the planar film pressure sensor using the corrosion process in the prior art and the pressure sensor provided by this patent, the respective reflection spectra are shown in Figure 5 and Figure 6 . Reflecting the reflection spectrum contrast of Figure 6 of this device is 30dB, far greater than the 10dB of Figure 5 of the planar membrane pressure sensor of the corrosion process in the prior art, and the sharp trough makes the optical fiber pressure sensor based on the micro-ellipsoidal air cavity proposed by this patent have more High measurement accuracy.

The above is only the preferred embodiment of the utility model, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the utility model, some improvements and deformations can also be made. And deformation should also be regarded as the protection scope of the present utility model.

Claims (6)

1. a kind of fibre optic compression sensor based on micro- ellipsoid air chamber, it is characterised in that including single-mode fiber, presser sensor Film；The single-mode fiber upper end is fixedly connected with the pressure sensitive film lower end, the single-mode fiber, pressure sensitive film connection Place opens up air Fabry-Perot-type cavity.

2. a kind of fibre optic compression sensor based on micro- ellipsoid air chamber according to claim 1, it is characterised in that described Air Fabry-Perot-type cavity is micro- elliposoidal, and the air Fabry-Perot-type cavity is confocal cavity.

3. a kind of fibre optic compression sensor based on micro- ellipsoid air chamber according to claim 1, it is characterised in that described The chamber of air Fabry-Perot-type cavity grows 40 μm -50 μm.

4. a kind of fibre optic compression sensor based on micro- ellipsoid air chamber according to claim 1, it is characterised in that described Presser sensor film thickness is 6-12 μm.

5. a kind of fibre optic compression sensor based on micro- ellipsoid air chamber according to claim 1, it is characterised in that described Single-mode fiber material is silica.

6. a kind of fibre optic compression sensor based on micro- ellipsoid air chamber according to claim 1, it is characterised in that described Presser sensor membrane material is silica.