Optical fiber-film high-temperature strain sensor in-situ comparison test system and method

Abstract

The invention discloses an optical fiber-film high-temperature strain sensor in-situ comparison test system and method. The in-situ comparison test system comprises a fiber bragg grating, a Fabry-Perot resonant cavity, a first film strain sensitive grid and a second film strain sensitive grid, wherein the fiber bragg grating and the Fabry-Perot resonant cavity are prepared on an optical fiber; the first film strain sensitive grid and the second film strain sensitive grid are arranged in the same position with the fiber bragg grating and the Fabry-Perot resonant cavity respectively; the two ends of the fiber grating and the two ends of the second film strain sensitive grid prepared in the same position are fixed through high-temperature glue, and the two ends of the Fabry-Perot resonant cavity and the two ends of the first film strain sensitive grid prepared in the same position are fixed through high-temperature glue. The fiber bragg grating-thin film strain sensitive grid strain sensor has the advantages of high temperature resistance, compact structure and the like, meets the strain measurement requirements of high-temperature complex environment fields such as aero-engines and the like, and can be used for comparing three strain test methods, namely a fiber bragg grating-thin film strain sensitive grid strain test method and a Fabry-Perot resonant cavity-thin film strain sensitive grid strain test method in a high-temperature environment at the same position.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber and thin film sensors, and in particular to a co-location comparison test system and method for an optical fiber-thin film high temperature strain sensor. Background Art

[0002] With the increasing demand for strain monitoring in high-temperature environments in aerospace, energy and other fields, the performance of traditional strain sensors in extreme temperature conditions has gradually shown limitations. Conventional metal strain gauges and resistance strain sensors often experience problems such as material thermal expansion, thermoelectric effect and decreased sensing performance in high-temperature environments, which seriously affects the accuracy and stability of strain measurement. Therefore, the development of strain sensors that can work stably for a long time in high-temperature and complex environments has become a technical problem that needs to be solved urgently.

[0003] Fiber optic sensing technology has gradually become a research hotspot for high-temperature strain measurement due to its anti-electromagnetic interference, high temperature resistance, small size, and light weight. In particular, technologies such as fiber gratings and Fabry-Perot resonant cavities have shown great potential in sensing applications under high-temperature environments due to their excellent temperature sensitivity and strain measurement capabilities. However, although fiber optic sensors have shown good performance in high-temperature strain measurement, there are still deficiencies in the existing technology for the co-location comparison test methods between different fiber optic sensors and thin film strain sensitive materials.

[0004] At present, a variety of strain sensor systems (such as fiber Bragg gratings, Fabry-Perot resonant cavities, thin film strain sensitive gratings, etc.) are widely studied for high-temperature strain measurement, but how to effectively combine these sensors with thin film materials and achieve the same-position comparative calibration of the three in a high-temperature environment is still a technical challenge. Especially in complex environments, how to ensure the relative calibration accuracy and consistency between different sensors is the key to ensuring high-precision strain measurement.

[0005] Therefore, how to build a system that can simultaneously realize the co-location comparison and calibration between multiple strain measurement methods such as fiber Bragg grating, Fabry-Perot resonant cavity and thin film strain sensitive grating in high temperature environment has become an important direction of current technological development. The system not only requires basic performance such as high temperature stability, corrosion resistance and high accuracy, but also needs to achieve accurate calibration comparison between different sensors to meet the needs of strain monitoring in high temperature and complex environments such as aircraft engines and gas turbines. Summary of the invention

[0006] To solve the above problems, the present invention provides a co-location comparison test system and method for an optical fiber-thin film high-temperature strain sensor to address the technical problems of insufficient co-location comparison calibration accuracy and poor stability of existing high-temperature strain sensors in high-temperature environments. The system realizes co-location comparison calibration of three strain measurement methods, namely, optical fiber Bragg grating, Fabry-Perot cavity and thin film strain sensitive grating, in high-temperature environments. The system has the characteristics of high temperature resistance, compact structure and high precision, and can meet the strain measurement requirements in high-temperature and complex environments such as aircraft engines and gas turbines.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is:

[0008] A fiber-thin film high temperature strain sensor co-location comparison test system comprises: a fiber grating prepared on an optical fiber, a Fabry-Perot resonant cavity, and a first thin film strain sensitive grating and a second thin film strain sensitive grating co-located with the fiber grating and the Fabry-Perot resonant cavity, respectively.

[0009] In the present invention, high temperature glue is used to fix the two ends of the fiber Bragg grating and the second thin film strain sensitive grating prepared in the same place, the fiber Bragg grating and the second thin film strain sensitive grating prepared in the same place are used as strain sensitive originals, and the Fabry-Perot resonant cavity is used as a temperature compensation original, so that the co-location comparison calibration of the two strain testing methods of the fiber Bragg grating-thin film strain sensitive grating can be realized at different temperatures. High temperature glue is used to fix the two ends of the Fabry-Perot resonant cavity and the first thin film strain sensitive grating prepared in the same place, the Fabry-Perot resonant cavity and the first thin film strain sensitive grating prepared in the same place are used as strain sensitive originals, and the fiber Bragg grating is used as a temperature compensation original, so that the co-location comparison calibration of the two strain testing methods of the Fabry-Perot resonant cavity-thin film strain sensitive grating can be realized at different temperatures.

[0010] In order to realize the co-location comparison test of three sensors, namely, fiber Bragg grating, Fabry-Perot cavity and thin film strain sensitive grating, the fiber Bragg grating and thin film strain sensitive grating No. 1, the Fabry-Perot cavity and thin film strain sensitive grating No. 2 are integrated in the same position of the optical fiber, namely, the "co-location" area.

[0011] Furthermore, the fiber grating is directly prepared by femtosecond laser direct writing technology, preferably, by femtosecond laser line-by-line writing method.

[0012] Furthermore, the Fabry-Perot resonant cavity is prepared by fusing hollow-core optical fibers at both ends of an optical fiber using a fiber fusion splicer.

[0013] Furthermore, the structure of the No. 1 thin film strain sensitive grid and the No. 2 thin film strain sensitive grid is the same, both of which include multiple vertical grids, which are deposited on the optical fiber in parallel, and a horizontal grid is connected between two adjacent vertical grids, and the horizontal grid is deposited on the optical fiber. The vertical grid and the horizontal grid constitute a continuous structure, and the two ends of the continuous structure are respectively connected to one end of the transition grid, and the other ends of the two transition grids are respectively connected to electrodes. The electrodes are coated with conductive silver glue and connected to platinum wires to measure resistance changes.

[0014] Furthermore, the first thin film strain sensitive grating and the second thin film strain sensitive grating both include an indium tin oxide layer and a platinum layer, wherein the indium tin oxide layer is deposited on the surface of the optical fiber co-located with the fiber grating and the Fabry-Perot resonant cavity, and the platinum layer is deposited on the indium tin oxide layer. The indium tin oxide layer and the platinum layer are deposited by a magnetron sputtering method.

[0015] Furthermore, the optical fiber uses quartz optical fiber and is fixed on the surface of the component to be tested by high-temperature glue.

[0016] The present invention also provides a co-location comparison test method for an optical fiber-thin film high temperature strain sensor, and the co-location comparison test system for the optical fiber-thin film high temperature strain sensor is used for testing.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] Multi-method co-location comparison and calibration can be realized: In a high-temperature environment, the present invention realizes the co-location comparison and calibration of three strain testing methods: fiber Bragg grating-thin film strain sensitive grating, Fabry-Perot resonant cavity-thin film strain sensitive grating, to ensure the consistency and accuracy of the measurement data.

[0019] Excellent high-temperature adaptability: The present invention adopts indium tin oxide layer and platinum layer as strain sensitive materials, which ensures the stability of the sensor in high-temperature environment and meets the application requirements of high-temperature occasions such as aircraft engines and gas turbines.

[0020] Compact structure and high integration: The present invention integrates the fiber Bragg grating, Fabry-Perot resonant cavity and thin film strain sensitive grating in the same position with micron-level precision, with compact structure and convenient installation, and is suitable for complex space occasions.

[0021] In summary, the present invention solves the problems of strain measurement accuracy, stability and multi-sensor method comparison and calibration in high-temperature environments by constructing a co-location comparison test system and method for optical fiber-thin film high-temperature strain sensors, and has important engineering application value and promotion potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0023] Figure 1 A schematic diagram of applying the optical fiber-thin film high temperature strain sensor co-location comparison test system of the present invention to a cantilever arm test;

[0024] In the figure: 1-cantilever beam; 2-optical fiber; 3-Fabry-Perot resonant cavity; 4-optical fiber grating; 5-strain sensitive grating; 6-strain sensitive grating; 7-transverse grating; 8-vertical grating; 9-electrode; 10-transition grating. DETAILED DESCRIPTION

[0025] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0026] like Figure 1 As shown, the present invention proposes a co-location comparison test system for an optical fiber-thin film high temperature strain sensor, the co-location comparison test system comprising: a fiber grating 4 arranged on an optical fiber 2, a Fabry-Perot resonant cavity 3, and a first thin film strain sensitive grating 5 and a second thin film strain sensitive grating 6 co-located with the fiber grating 4 and the Fabry-Perot resonant cavity 3, respectively.

[0027] In this embodiment, high-temperature glue is used to fix the two ends of the Fabry-Perot resonant cavity 3 and the co-prepared thin film strain sensitive grating 5. The Fabry-Perot resonant cavity 3 and the co-prepared thin film strain sensitive grating 5 are used as strain sensitive elements to monitor the cavity length of the Fabry-Perot resonant cavity 3 and the resistance change of the thin film strain sensitive grating 5. The fiber grating 4 is used as a temperature compensation element to monitor the Bragg wavelength change of the fiber grating 4. The co-prepared calibration of the two strain testing methods of the Fabry-Perot resonant cavity and the thin film strain sensitive grating can be realized at different temperatures.

[0028] In this embodiment, the fiber Bragg grating 4 is 1 mm long and is prepared by a femtosecond laser line-by-line writing method. High-temperature glue is used to fix the fiber Bragg grating 4 and the second thin film strain sensitive grating 6 prepared in the same place at both ends. The fiber Bragg grating 4 and the second thin film strain sensitive grating 6 prepared in the same place are used as strain sensitive elements to monitor the Bragg wavelength change of the fiber Bragg grating 4 and the resistance change of the second thin film strain sensitive grating 6. The Fabry-Perot resonant cavity 3 is used as a temperature compensation element to monitor the change in the cavity length of the Fabry-Perot resonant cavity 3. The co-situ comparative calibration of the two strain testing methods of the fiber Bragg grating-thin film strain sensitive grating can be realized at different temperatures.

[0029] In this embodiment, the Fabry-Perot resonant cavity 3 is prepared by fusing hollow-core optical fibers at both ends of optical fiber 2 using an optical fiber fusion splicer. Specifically, during production, a 1 mm long hollow-core optical fiber is fused at the tail end of optical fiber 2 using an optical fiber fusion splicer, and the hollow-core optical fiber is then fused with the mating optical fiber 2 to form a sealed cavity. The inner diameter of the hollow-core optical fiber is 75 μm and the outer diameter is 125 μm.

[0030] In this embodiment, the first thin film strain sensitive grid 5 and the second thin film strain sensitive grid 6 have the same structure, both of which include a plurality of longitudinal grids 8, which are deposited on the optical fiber 2 in parallel, and a transverse grid 7 is connected between two adjacent longitudinal grids 8, and the transverse grid 7 is deposited on the optical fiber 2. The longitudinal grids 8 and the transverse grids 7 form a continuous S-shaped structure, and the two ends of the continuous S-shaped structure are respectively connected to one end of the transition grid 10, and the other ends of the two transition grids 10 are respectively connected to electrodes 9. The length of the continuous S-shaped structure is 1 mm, the width is 0.11 mm, the width of the longitudinal grid 8 is 0.01 mm, and the distance between the two adjacent longitudinal grids 8 is 0.01 mm, that is, the width of the transverse grid 7. The electrode 9 is coated with conductive silver glue and connected with a platinum wire to measure the resistance change.

[0031] In this embodiment, the first thin film strain sensitive grating 5 and the second thin film strain sensitive grating 6 are made of a composite laminated film of ITO (indium tin oxide) and Pt (platinum), with an overall thickness of 500nm, wherein the thickness of the indium tin oxide layer is 450nm and the thickness of the platinum layer is 50nm. The thin thickness can better transmit the strain of the object under high temperature. The indium tin oxide layer is deposited on the surface of the optical fiber 2 co-located with the fiber grating 4 and the Fabry-Perot resonant cavity 3 by a magnetron sputtering method, and the platinum layer is deposited on the indium tin oxide layer by a magnetron sputtering method.

[0032] In this embodiment, the optical fiber 2 uses a single-mode optical fiber with a core diameter of 9 μm and an outer diameter of 125 μm.

[0033] In this embodiment, the optical fiber 2 is fixed to the surface of the component to be measured by high-temperature glue, such as the high-temperature surface of large mechanical equipment such as gas turbines and steam turbines, and the surface of the area working in high-temperature extreme environments such as metal smelting and oil and gas extraction. After the high-temperature glue is cured, the resistance changes on the No. 1 thin film strain sensitive grating 5 and the No. 2 thin film strain sensitive grating 6 are collected in real time through the data acquisition card to reflect the resistance response caused by the strain on the material surface. At the same time, the spectral analysis equipment is used to collect the cavity length change of the Fabry-Perot resonant cavity 3 and the Bragg wavelength change of the fiber grating 4, and then the strain and temperature conditions of the corresponding material surface are obtained. In order to eliminate the interference of temperature changes on strain measurement in high-temperature environments, the system corrects the data through a pre-calibrated temperature-strain compensation coefficient to ensure that the measurement results can accurately reflect the actual mechanical strain without being affected by temperature fluctuations, thereby effectively improving the accuracy and stability of strain measurement in complex high-temperature environments.

[0034] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A fiber-thin film high temperature strain sensor co-location comparison test system, characterized in that: include: A fiber grating, a Fabry-Perot resonant cavity and a first thin film strain sensitive grating and a second thin film strain sensitive grating which are respectively co-located with the fiber grating and the Fabry-Perot resonant cavity are prepared on the optical fiber.

2. The optical fiber-thin film high temperature strain sensor co-location comparison test system as claimed in claim 1, characterized in that: The fiber grating and the co-prepared No. 2 thin film strain sensitive grating are fixed at both ends with high temperature glue, the fiber grating and the co-prepared No. 2 thin film strain sensitive grating are used as strain sensitive elements, and the Fabry-Perot resonant cavity is used as a temperature compensation element, so as to realize the co-prepared comparison calibration of two strain testing methods of the fiber grating-thin film strain sensitive grating at different temperatures.

3. The optical fiber-thin film high temperature strain sensor co-location comparison test system as claimed in claim 1, characterized in that: The two ends of the Fabry-Perot resonant cavity and the co-prepared No. 1 thin film strain sensitive grating are fixed with high-temperature glue. The Fabry-Perot resonant cavity and the co-prepared No. 1 thin film strain sensitive grating are used as strain sensitive elements, and the optical fiber Bragg grating is used as a temperature compensation element. The co-prepared calibration of two strain testing methods of the Fabry-Perot resonant cavity and the thin film strain sensitive grating is realized at different temperatures.

4. The optical fiber-thin film high temperature strain sensor co-location comparison test system as claimed in claim 1, characterized in that: The fiber grating is directly prepared by femtosecond laser direct writing technology.

5. The optical fiber-thin film high temperature strain sensor co-location comparison test system as claimed in claim 1, characterized in that: The Fabry-Perot resonant cavity is prepared by fusing hollow-core optical fibers at both ends of an optical fiber using an optical fiber fusion splicer.

6. The optical fiber-thin film high temperature strain sensor co-location comparison test system as claimed in claim 1, characterized in that: The structures of the No. 1 thin film strain sensitive grid and the No. 2 thin film strain sensitive grid are the same, both of which include a plurality of longitudinal grids, which are deposited on the optical fiber in parallel, and a transverse grid is connected between two adjacent longitudinal grids, and the transverse grid is deposited on the optical fiber. The longitudinal grids and the transverse grids constitute a continuous structure, and the two ends of the continuous structure are respectively connected to one end of a transition grid, and the other ends of the two transition grids are respectively connected to electrodes.

7. The optical fiber-thin film high temperature strain sensor co-location comparison test system as claimed in claim 1, characterized in that: The first thin film strain sensitive grating and the second thin film strain sensitive grating both include an indium tin oxide layer and a platinum layer. The indium tin oxide layer is deposited on the surface of the optical fiber co-located with the fiber grating and the Fabry-Perot resonant cavity, and the platinum layer is deposited on the indium tin oxide layer.

8. The optical fiber-thin film high temperature strain sensor co-location comparison test system as claimed in claim 1, characterized in that: The optical fiber uses quartz optical fiber and is fixed on the surface of the component to be tested by high-temperature glue.

9. The optical fiber-thin film high temperature strain sensor co-location comparison test system as claimed in claim 4, characterized in that: The electrodes are coated with conductive silver glue and connected with platinum wires to measure resistance changes.

10. A method for co-location comparison of optical fiber-thin film high temperature strain sensors, characterized in that: The test is performed using the optical fiber-thin film high temperature strain sensor co-location comparison test system as described in any one of claims 1 to 9.

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