CN212206125U - Temperature compensated fiber optic Fabry-Perot high temperature pressure sensor - Google Patents

Abstract

A temperature-compensated optical fiber Fabry-Perot high temperature pressure sensor, the geometry of the single-mode optical fiber is a combination of a first cylinder, a truncated cone and a second cylinder, the outer diameter of the first cylinder is the same as the outer diameter of the small end of the truncated cone, and the second The outer diameter of the cylinder is the same as the outer diameter of the big end of the truncated cone. The core of the first cylindrical section of the single-mode fiber is engraved with a thermal regeneration grating. The first cylindrical section of the single-mode fiber extends from one end of the corundum tube into the corundum tube and is fixed with high temperature resistant glue , so that the thermal regeneration grating is located in the corundum tube, one end of the hollow fiber extends into the corundum tube from the other end of the corundum tube and is fixed with high temperature resistant glue, and there is a gap between the end face of the hollow fiber and the end face of the first cylindrical section of the single mode fiber. Brie-Perot interference cavity, the other end face of the hollow fiber is processed into a bevel. The utility model has the advantages of low cost, simple manufacture, high temperature resistance, etc., solves the problem of differential measurement of temperature and pressure in a high temperature environment, and can be applied to pressure monitoring in a high temperature environment.

Description

Temperature compensated fiber optic Fabry-Perot high temperature pressure sensor

technical field

The utility model belongs to the technical field of optical fiber sensors, in particular to a temperature-compensated optical fiber Fabry-Perot high temperature pressure sensor.

Background technique

Aero-engine is a machine that converts chemical energy into mechanical energy and forms high-speed jet discharge to generate thrust. It is not only suitable for power generation devices, but also refers to the entire machine including power devices. Aero-engines are the "jewel in the crown" of modern industry. , is an important symbol of a country's national defense technology industry. When aero-engines work, the interior usually includes high temperature, high pressure, and violent vibrations accompanied by high load and high speed. It is the most complex and sophisticated industrial product in human history involving multidisciplinary comprehensive systems engineering. Manufacturing difficulty. The real-time monitoring of the operation of each component of the aeroengine during the actual operation is often an important basis for judging the safety, reliability and actual working performance of the engine. Optical fiber high temperature pressure sensor is a rising star of pressure monitoring sensor. Compared with other technologies, optical fiber sensor has incomparable advantages. Optical fiber is a non-electric conductor, suitable for electromagnetic interference environment; optical fiber is made of silica, suitable for high temperature environment; optical fiber measurement can realize non-contact measurement, suitable for installation on the surface of the structure or embedded in the structure body, the impact on the measured structure Small, more realistic reflection of the measurement results; small size, light weight, easy installation; optical fiber sensor has the characteristics of fast response to temperature and pressure, and good linearity of temperature and pressure measurement. In recent years, with the development of optical fiber technology, in view of the high requirements of aero-engine for sensor measurement accuracy and response speed, the application of optical fiber high-temperature pressure sensor to the monitoring of aero-engine temperature and pressure has far-reaching significance for the development of aero-engine.

Utility model content

The technical problem to be solved by the utility model is to provide a temperature-compensated optical fiber Fabry-Perot high-temperature pressure sensor with reasonable design, simple manufacture, low cost, and differential measurement of temperature and pressure in a high-temperature environment.

The technical solution adopted to solve the above technical problems is: the geometric shape of the single-mode optical fiber is a combination of a first cylinder, a truncated cone and a second cylinder, the outer diameter of the first cylinder is the same as the outer diameter of the small end of the truncated cone, and the outer diameter of the second cylinder is the same as the outer diameter of the small end of the truncated cone. The outer diameter of the big end of the round table is the same, and the core of the first cylindrical section of the single-mode fiber is engraved with a thermal regeneration grating. The grating is located in the corundum tube. One end of the hollow fiber extends from the other end of the corundum tube into the corundum tube and is fixed with high temperature resistant glue. There is a gap between the end face of the hollow fiber and the end face of the first cylindrical section of the single mode fiber to form a Fabry Perot Interference cavity, the other end face of the hollow fiber is processed into a bevel.

As a preferred technical solution, the width of the gap between the end face of the hollow-core optical fiber and the end face of the first cylindrical section of the single-mode optical fiber is 15 μm˜80 μm.

As a preferred technical solution, the core diameter of the single-mode optical fiber is 8.2 μm, and the outer diameter of the first cylinder is 80 μm˜100 μm.

As a preferred technical solution, the hollow fiber has an inner diameter of 5 μm to 40 μm and an outer diameter of 110 μm to 130 μm.

As a preferred technical solution, the length of the grid region of the thermally regenerated grating is 5-15 mm, and the center wavelength is 1553 nm.

As a preferred technical solution, the inner diameter of the corundum tube is 150 μm˜200 μm, and the outer diameter is 300 μm˜500 μm.

As a preferred technical solution, the corundum tube can also be a sapphire tube.

The beneficial effects of the present utility model are as follows:

The utility model encapsulates the first cylindrical section of the single-mode optical fiber in the corundum tube through high-temperature glue, one end of the corundum tube and the hollow optical fiber are bonded by the high-temperature glue, and the end face of the hollow optical fiber nested inside the corundum tube and the end face of the first cylindrical section of the single-mode optical fiber There is a certain distance between them, so as to form a Bri-Perot interference cavity; the thermal regeneration grating is written on the core of the first cylindrical section of the single-mode fiber. The utility model has the advantages of low cost, simple production, high temperature resistance, etc. The problem of differential measurement of temperature and pressure in high temperature environment can be applied to pressure monitoring in high temperature environment.

Description of drawings

Figure 1 is a schematic structural diagram of the present invention.

Detailed ways

The present utility model will be further described in detail below with reference to the accompanying drawings and examples, but the present utility model is not limited to the following embodiments.

Example 1

In FIG. 1 , the temperature-compensated optical fiber Fabry-Perot high-temperature pressure sensor of this embodiment is formed by connecting a hollow-core optical fiber 1 , a corundum tube 2 , and a single-mode optical fiber 3 .

The geometric shape of the single-mode optical fiber 3 is a combination of a first cylinder, a truncated cone, and a second cylinder. The outer diameter of the cylinder is the same, the second cylindrical section is a standard single-mode optical fiber, the core diameter of the single-mode optical fiber 3 is 8.2 μm, and the first cylindrical section of the single-mode optical fiber 3 extends from one end of the corundum tube 2 into the corundum tube 2 and uses high temperature ceramics. It is sealed and fixed by glue. The core of the first cylindrical section of the single-mode fiber 3 located in the corundum tube 2 is engraved with a thermal regeneration grating 4. The length of the grating area is 10mm, and the center wavelength is 1553nm. The inner diameter of the corundum tube 2 is 180μm and the outer diameter is 400μm, one end of the hollow fiber 1 extends from the other end of the corundum tube 2 into the corundum tube 2 and is sealed and fixed with high temperature ceramic glue. , forming a Fabry-Perot interference cavity. The Fabry-Perot interference cavity also isolates the thermal regeneration grating 4 from the influence of pressure. The inner diameter of the hollow fiber 1 is 25 μm and the outer diameter is 120 μm. The other end face of the hollow fiber 1 is The inclined surface prevents the light reflected from the end surface from returning to the original path.

Example 2

In this embodiment, the geometry of the single-mode optical fiber 3 is a combination of a first cylinder, a truncated cone, and a second cylinder. The outer diameter of the first cylinder is the same as the outer diameter of the small end of the truncated cone, the outer diameter of the first cylinder is 80 μm, and the large end of the truncated cone is 80 μm The outer diameter is the same as the outer diameter of the second cylinder. The second cylindrical section is a standard single-mode fiber. The core diameter of the single-mode fiber 3 is 8.2 μm. The first cylindrical section of the single-mode fiber 3 extends from one end of the corundum tube 2 to the corundum tube. 2 is sealed and fixed with high-temperature ceramic glue. The core of the first cylindrical section of the single-mode fiber 3 in the corundum tube 2 is engraved with a thermal regeneration grating 4. The length of the grating area is 5mm, the center wavelength is 1553nm, and the inner diameter of the corundum tube 2 is 150μm, the outer diameter is 300μm, one end of the hollow fiber 1 extends from the other end of the corundum tube 2 into the corundum tube 2 and is sealed and fixed with high temperature ceramic glue, between the end face of the hollow fiber 1 and the end face of the first cylindrical section of the single mode fiber 3 A gap with a width of 45 μm is left to form a Fabry-Perot interference cavity. The inner diameter of the hollow fiber 1 is 5 μm and the outer diameter is 110 μm. The other end face of the hollow fiber 1 is inclined to prevent the light reflected from the end face from returning to the original path.

Example 3

In this embodiment, the geometry of the single-mode optical fiber 3 is a combination of a first cylinder, a truncated cone, and a second cylinder. The outer diameter of the first cylinder is the same as the outer diameter of the small end of the circular truncated cone, the outer diameter of the first cylinder is 100 μm, and the large end of the circular truncated cone is 100 μm. The outer diameter is the same as the outer diameter of the second cylinder. The second cylindrical section is a standard single-mode fiber. The core diameter of the single-mode fiber 3 is 8.2 μm. The first cylindrical section of the single-mode fiber 3 extends from one end of the corundum tube 2 to the corundum tube. 2 is sealed and fixed with high-temperature ceramic glue. The core of the first cylindrical section of the single-mode fiber 3 in the corundum tube 2 is engraved with a thermal regeneration grating 4. The length of the grating area is 15mm, the center wavelength is 1553nm, and the inner diameter of the corundum tube 2 is 200μm, the outer diameter is 500μm, one end of the hollow fiber 1 extends from the other end of the corundum tube 2 into the corundum tube 2 and is sealed and fixed with high temperature ceramic glue, between the end face of the hollow fiber 1 and the end face of the first cylindrical section of the single mode fiber 3 A gap with a width of 45 μm is left to form a Fabry-Perot interference cavity. The inner diameter of the hollow fiber 1 is 40 μm and the outer diameter is 130 μm. The other end face of the hollow fiber 1 is inclined to prevent the light reflected from the end face from returning to the original path.

Example 4

In the above-mentioned Embodiments 1 to 3, the corundum tube 2 is replaced with a sapphire tube, and the connection relationships of other components and components are the same as those of the corresponding embodiments.

The working principle of the present utility model is as follows:

The light enters from the second cylindrical end face of the single-mode fiber, and is reflected by the thermal regeneration grating, the left and right end faces of the hollow fiber, and the first cylindrical end face of the single-mode fiber. Part of the incident light is reflected back through the thermal regeneration grating, and the other part is transmitted through the thermal regeneration grating. The Fabry-Perot interference cavity and the left end face of the hollow fiber, because the left end face of the hollow fiber is chamfered, the reflected light from the end face will not be reflected back to the thermal regeneration grating, which has no effect on the interference spectrum, while the transmitted light in the Fabry-Perot interference The light from the cavity is reflected by the left end face of the hollow fiber and the first cylindrical end face of the single-mode fiber to form two beams of reflected light that interfere with each other and return to the thermal regeneration grating. parameter.

In the Fabry-Perot interference spectrum of the utility model, the central wavelength λ _m of the m-th order interference peak is:

where n is the refractive index of the interference microcavity, L3 is the length _of the closed cavity in the corundum tube, and L2 is the length of the first cylindrical section of the single _- mode fiber in the corundum tube;

When the pressure acts on the Fabry-Perot interference cavity, the pressure sensitivity _Sp of the wavelength shift of the m-th order interference peak is:

In the formula, P is the pressure on the microcavity, A is the cross-sectional area of the optical fiber, and L ₁ is the length of the actual Fabry-Perot interference cavity; it can be seen that the pressure sensitivity Sp and the actual _Fabry -Perot interference cavity length L ₁ is inversely proportional.

When the temperature of the external environment changes, the relationship between the length L ₁ of the Fabry-Perot interference cavity and the temperature change is:

ΔL ₁ =[α _c (L ₂ +L ₁ )-α _f L ₂ ]·ΔT

where ΔL ₁ is the change in the length of the Fabry-Perot interference cavity, α _c is the thermal expansion coefficient of the corundum tube, α _f is the taper of the first cylindrical section of the single-mode fiber, and ΔT is the temperature change;

The wavelength variation of the Fabry-Perot interference microcavity with temperature is expressed as:

where Δλ is the wavelength variation of the Fabry-Perot interference cavity, _λ0 is the initial wavelength, and S _T is the temperature sensitivity of the Fabry-Perot interference cavity;

Since the pressure sensitivity of thermally regenerated gratings is a function of temperature, the change of wavelength with temperature and pressure in the present invention is expressed as follows

where Δλ _i (i=1, 2) is the resonant wavelength shift of the thermal regeneration grating, α _i is the temperature sensitivity of the thermal regeneration grating, k _PTi is the pressure sensitivity of the thermal regeneration grating at different temperatures, b _Pi is the thermal regeneration grating pressure Sensitivity, T ₀ is the initial temperature, ΔT is the temperature change, and ΔP is the pressure change.

Since the Fabry-Perot interference cavity is sensitive to temperature and pressure, and the thermal regeneration grating encapsulated in the corundum tube has high response to temperature and low response to pressure, the structure of the present invention can utilize the sensitivity coefficient matrix to achieve high sensitivity Pressure measurement and temperature compensation.

When the pressure and temperature of the external environment change at the same time, the wavelength shifts of the Fabry-Perot interference cavity and thermal regeneration grating are:

Δλ _FP =S _P ·ΔP′+S _T ·ΔT′

Δλ _i =b _Pi ·ΔP′+α _i ·ΔT′

In the formula, ΔP′ is the actual total change of pressure, ΔT′ is the actual total change of temperature, Δλ _FP is the wavelength shift of the Fabry-Perot interference cavity, Δλ′ _i is the wavelength shift of the thermal regeneration grating, S _P and b _Pi are the pressure sensitivities of the FP cavity and RFBG, respectively, and S _T and α _i are the temperature sensitivities of the FP cavity and RFBG, respectively.

The coefficient matrix for temperature compensation is:

The utility model realizes the simultaneous distinction and measurement of temperature and pressure parameters at a temperature above 1100°C.

Claims (7)

1. a temperature-compensated optical fiber Fabry-Perot high temperature pressure sensor, characterized in that: the geometry of the single-mode optical fiber (3) is the combination of the first cylinder, the truncated cone and the second cylinder, and the first cylinder outer diameter is the same as the second cylinder. The outer diameter of the small end of the truncated cone is the same, the outer diameter of the second cylinder is the same as the outer diameter of the large end of the truncated cone, the core of the first cylindrical section of the single-mode optical fiber (3) is engraved with a thermal regeneration grating, and the first cylindrical section of the single-mode optical fiber (3) is engraved with a thermal regeneration grating. Extend from one end of the corundum tube (2) into the corundum tube (2) and fix it with high temperature resistant glue, so that the thermal regeneration grating is located in the corundum tube (2), and one end of the hollow fiber (1) extends from the other end of the corundum tube (2). One end extends into the corundum tube (2) and is fixed with high temperature resistant glue. There is a gap between the end face of the hollow fiber (1) and the end face of the first cylindrical section of the single-mode fiber (3) to form a Fabry-Perot interference cavity. The other end face of the optical fiber (1) is processed into an inclined face. 2. The temperature-compensated optical fiber Fabry-Perot high temperature pressure sensor according to claim 1, characterized in that: between the end face of the hollow-core optical fiber (1) and the end face of the first cylindrical section of the single-mode optical fiber (3) The gap width is 15 μm to 80 μm. 3. The temperature-compensated optical fiber Fabry-Perot high temperature pressure sensor according to claim 1, wherein the core diameter of the single-mode optical fiber (3) is 8.2 μm, and the outer diameter of the first cylinder is 80 μm~ 100μm. 4. The temperature-compensated optical fiber Fabry-Perot high temperature pressure sensor according to claim 1 or 2, wherein the hollow fiber (1) has an inner diameter of 5 μm to 40 μm and an outer diameter of 110 μm to 130 μm. 5 . The temperature-compensated optical fiber Fabry-Perot high temperature pressure sensor according to claim 1 , wherein the grid region length of the thermally regenerated grating is 5-15 mm, and the center wavelength is 1553 nm. 6 . 6 . The temperature-compensated optical fiber Fabry-Perot high temperature pressure sensor according to claim 1 , wherein the corundum tube ( 2 ) has an inner diameter of 150 μm to 200 μm and an outer diameter of 300 μm to 500 μm. 7 . 7. The temperature-compensated optical fiber Fabry-Perot high temperature pressure sensor according to claim 1 or 6, characterized in that: the corundum tube (2) can also be a sapphire tube.

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