An insertion type fiber grating array temperature sensor

Abstract

The application discloses an insertion type fiber grating array temperature sensor, which comprises a fiber grating array, a tail fiber end of the fiber grating array is fixedly inserted on a connector, an inner capillary tube is coated in a gap on the fiber grating array, an outer capillary tube is coated in a gap on the inner capillary tube, a mounting head is sleeved on the outer capillary tube, a protective tube is coated in a gap on the outer capillary tube between the mounting head and the connector, and the two ends of the protective tube are respectively press-bonded with the mounting head and the connector through variable-diameter pressing sleeves. The scheme can be applied to temperature monitoring of key areas under the requirements of high stealth and aerodynamic performance of an airplane. Fiber gratings arranged at intervals on the optical fiber are used as temperature sensitive elements, so that multiple measurement point dense type temperature real-time monitoring can be realized on a structure. Meanwhile, the scheme can be inserted into different pipelines, and is used for networking, so that network space type multiple measurement point dense type temperature real-time monitoring can be realized.

Description

Technical Field

[0001] This invention relates to the field of fiber optic grating sensing technology, and more specifically to an insertable fiber optic grating array temperature sensor. Background Technology

[0002] Currently, when aircraft travel at relatively slow speeds at altitudes of 3,000 to 6,000 meters, icing may occur on areas such as the leading edges of the wings and engine air intakes. This icing alters the aircraft's airfoil, affecting its aerodynamic performance, reducing flight efficiency, and even compromising flight safety. Therefore, it is necessary to activate the onboard de-icing heating system to remove ice from these areas. Currently, both domestic and international approaches combine flight conditions and ice thickness readings from icing detectors to activate the de-icing heating system for heating and de-icing multiple areas. However, the specific de-icing status of the wing and engine air intake leading edges is often poorly monitored, making it difficult to directly assess the effectiveness of the de-icing heating system. Whether the ice in these areas has been completely removed or has been overheated remains to be verified. Therefore, real-time monitoring of temperature changes at the wing and engine air intake leading edges is of paramount importance.

[0003] Traditional electrical temperature sensors require electricity to operate, have poor wave transmission performance and weak resistance to electromagnetic interference, and are therefore unsuitable for temperature monitoring in areas of aircraft structures where stealth requirements are high.

[0004] Fiber optic temperature sensors are passive sensors with superior electromagnetic interference resistance. Furthermore, after being encapsulated with materials that have good wave transmission properties, fiber optic temperature sensors are suitable for temperature monitoring in critical areas of aircraft with high stealth requirements. Currently, most fiber optic temperature sensors used domestically and internationally are installed using surface pressing or bundling methods, which are not suitable for temperature measurement at the leading edge of wings and the leading edge of engine air intakes, where aerodynamic requirements are extremely high. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, this invention provides an insertable fiber optic grating array temperature sensor, which solves the current problem of difficulty in real-time temperature measurement of the leading edge of wing and engine air intake.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An insertable fiber Bragg grating array temperature sensor is provided, comprising a fiber Bragg grating array, the pigtail of the fiber Bragg grating array being fixedly inserted into a connector, an inner capillary covering the gaps on the fiber Bragg grating array, an outer capillary covering the gaps on the inner capillary, a mounting head being fitted onto the outer capillary, a protective tube covering the gaps on the outer capillary located between the mounting head and the connector, and both ends of the protective tube being press-fitted and fixed to the mounting head and the connector respectively by a variable diameter compression sleeve.

[0008] Furthermore, the fiber grating array includes optical fibers and a plurality of fiber gratings spaced on the optical fibers.

[0009] Furthermore, several fiber gratings have different center wavelengths.

[0010] Furthermore, the connector is provided with a socket, and the ends of the inner capillary, outer capillary and protective tube are all fixedly inserted into the socket with fiber polishing adhesive. The pigtail end of the fiber grating array is fixedly inserted into the connector with fiber polishing adhesive.

[0011] Furthermore, the fiber grating array and the inner capillary are made of quartz with a low dielectric constant.

[0012] Furthermore, the outer capillary is made of polyimide with a low dielectric constant.

[0013] Furthermore, the protective pipe is equipped with a protective layer that has bending and tensile strength.

[0014] Furthermore, a tail sleeve is wrapped around the reducing sleeve located between the connector and the protective tube.

[0015] The beneficial effects of this invention are as follows:

[0016] 1. The fiber grating array temperature sensor in this solution is suitable for temperature monitoring in critical areas of aircraft requiring high stealth and aerodynamic performance. In use, the fiber grating array, inner capillary, and outer capillary are inserted together into the pre-embedded pipe to be measured. It can be fixed to the structure at the pipe port using an installation head, and connected to external monitoring equipment using a connector, thus achieving real-time temperature monitoring. Furthermore, by using several fiber gratings spaced on the optical fiber as temperature-sensitive elements, it enables dense, real-time temperature monitoring of the structure at multiple measurement points. Simultaneously, this solution can be inserted into different pipes for networking and combined use, achieving mesh-like, spatial, multi-point, dense-level real-time temperature monitoring.

[0017] 2. The inner capillary in this design has good rigidity, which protects the fiber Bragg grating array while providing good support for the fiber Bragg grating array temperature sensor, facilitating sensor insertion and installation. The outer capillary has the property of being resistant to repeated bending and is not easily broken, ensuring that the fiber Bragg grating array will not leak out of the outer capillary when the inner capillary cracks under extreme conditions, which is beneficial for the replacement and maintenance of the fiber Bragg grating array temperature sensor.

[0018] 3. This solution uses a material with a low dielectric constant for encapsulation, giving the fiber Bragg grating array temperature sensor good stealth performance; at the same time, it uses a bending and tensile resistant material to encapsulate the part between the connector and the protective tube, giving the fiber Bragg grating array temperature sensor good reliability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the fiber grating array temperature sensor in this solution.

[0020] Figure 2 This is a cross-sectional view of the fiber grating array temperature sensor in this solution.

[0021] Figure 3 for Figure 2 Enlarged view of region I.

[0022] Figure 4 for Figure 2 Enlarged view of region II.

[0023] Figure 5 for Figure 2 Enlarged view of region III.

[0024] Figure 6 This is a schematic diagram of a fiber Bragg grating array.

[0025] Figure 7 This is a schematic diagram of a fiber optic grating array temperature sensor detection system.

[0026] Figure 8 This is a time-domain spectral signal diagram of a fiber Bragg grating array temperature sensor.

[0027] Among them, 1. Fiber Bragg grating array, 2. Inner capillary, 3. Outer capillary, 4. Protective tube, 5. Mounting head, 6. Variable diameter sleeve, 7. Connector, 8. Tail sleeve, 9. Optical fiber, 10. Fiber Bragg grating, 11. Jack, 12. Scanning laser source, 13. Circulator, 14. Photodetector, 15. Host computer. Detailed Implementation

[0028] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0029] like Figures 1 to 6 As shown, the insertable fiber Bragg grating array temperature sensor of this scheme includes a fiber Bragg grating array 1, which includes an optical fiber 9 and several fiber Bragg gratings 10 spaced apart on the optical fiber 9, and the several fiber Bragg gratings 10 have different center wavelengths; the pigtail end of the fiber Bragg grating array 1 is fixed and inserted into the connector 7 by fiber polishing adhesive, and the end face is polished by using special equipment to ensure that its end face has low transmission loss.

[0030] The fiber grating array 1 is covered with an inner capillary tube 2, which prevents the inner capillary tube 2 from constraining the individual fiber gratings 10 on the fiber grating array 1, allowing the fiber grating array 1 to be in a free state within the inner capillary tube 2, so as to avoid affecting the temperature output accuracy due to force. The inner capillary tube 2 is covered with an outer capillary tube 3, and an installation head 5 is fitted on the outer capillary tube 3. The outer capillary tube 3 between the installation head 5 and the connector 7 is covered with a protective tube 4, and the two ends of the protective tube 4 are respectively pressed and fixed to the installation head 5 and the connector 7 by a variable diameter pressure sleeve 6. The variable diameter pressure sleeve 6 between the connector 7 and the protective tube 4 is covered with a tail sleeve 8.

[0031] The connector 7 is provided with a socket 11. The ends of the inner capillary 2, the outer capillary 3 and the protective tube 4 are all fixedly inserted into the socket 11 by optical fiber polishing adhesive. The optical fiber polishing adhesive needs to be heated appropriately during use to improve its curing efficiency.

[0032] Preferably, the fiber Bragg grating array 1 and the inner capillary 2 are made of quartz with a low dielectric constant, and the outer capillary 3 is made of polyimide with a low dielectric constant. A protective layer with bending and tensile strength is provided inside the protective tube 4. This arrangement gives the fiber Bragg grating array 1, the inner capillary 2, and the outer capillary 3 excellent wave transmission and stealth performance. At the same time, the inner capillary 2 has good rigidity, protecting the fiber Bragg grating array 1 while also providing good support for the fiber Bragg grating array temperature sensor, which is conducive to the insertion and installation of the sensor. The outer capillary 3 has the property of being difficult to break even after repeated bending, which can ensure that if the inner capillary 2 becomes brittle in extreme environments, the fiber Bragg grating array 1 will not be released or leaked from the outer capillary 3 covering it, which is conducive to the replacement and maintenance of the fiber Bragg grating array temperature sensor.

[0033] The working principle of this solution will be explained in detail below:

[0034] The inserted fiber Bragg grating array temperature sensor in this scheme is based on fiber Bragg grating sensing technology. When the fiber Bragg grating 10 is affected by the ambient temperature, its spectral time-domain signal undergoes a phase shift: a red shift occurs when the temperature rises, and a blue shift occurs when the temperature falls. Several fiber Bragg gratings 10 on the fiber Bragg grating array 1 temperature sensor have different center wavelengths, each sensitive to a specific wavelength signal of the transmitted broadband optical signal. The demodulation system demodulates the acquired reflected spectral signal to obtain the wavelength value of each fiber Bragg grating 10. These wavelength values ​​are then processed to establish a relationship between temperature and the wavelength values ​​of the fiber Bragg grating 10. In practical applications, by monitoring the wavelength values ​​of the fiber Bragg grating 10, the temperature of its surrounding environment can be obtained in real time, thereby achieving temperature monitoring at multiple points on the surface of the structure.

[0035] In use, the fiber grating array 1, inner capillary 2, and outer capillary 3 can be inserted together into the pre-embedded pipe to be tested. Then, the mounting head 5 is fixedly connected to the structure at the port of the pre-embedded pipe using screws. The connector 7 is connected to the scanning light source fiber demodulator to obtain the spectral signals of all fiber grating 10 measurement points in the channel. After the signals are processed by modules such as sampling, filtering, and amplification, they are uploaded to the host computer 15 for digital signal processing, thereby calculating the wavelength of the grating and the ambient temperature, which in turn guides the anti-icing system to work accurately and efficiently.

[0036] The principle of spectral detection in this scheme will be explained in detail below:

[0037] like Figure 7 As shown, the scanning laser source type fiber optic demodulator includes a C-band scanning laser source 12, a circulator 13, a photodetector 14, and a host computer 15. The laser emitted from the scanning laser source 12 first passes through the circulator 13 and enters the fiber grating array 1 temperature sensor in this scheme. When the laser propagates to each fiber grating 10 within the fiber grating array 1 temperature sensor, the reflected signal enters the circulator 13, and finally enters the photodetector 14 through another port of the circulator 13. The photodetector 14 collects the interference spectrum signal and sends it to the host computer 15. The collected spectrum signal is shown in the figure. Figure 8 As shown, the host computer 15 performs calculations on the spectral time-domain diagram to obtain the center wavelength value λ of each fiber grating 10.

[0038] According to fiber optic grating sensing technology, the formula for calculating the temperature at 10 measuring points using n fiber gratings is:

[0039]

[0040] Where Δλ is the difference between the real-time center wavelength value λ of the fiber optic grating 10 and the center wavelength value λ0 of the grating under zero-degree conditions; ai is the coefficient of the multiple term, which can be obtained through calibration.

[0041] In summary, this solution can monitor the temperature at each measuring point by measuring the wavelength value of the fiber optic grating 10 in real time.

Claims

1. An in-line fiber Bragg grating array temperature sensor, characterized by, The application relates to a fiber grating array, a tail fiber end of the fiber grating array is fixedly inserted on a connector, an inner capillary is coated on the fiber grating array in gaps, an outer capillary is coated on the inner capillary in gaps, a mounting head is sleeved on the outer capillary, a protective tube is coated on the outer capillary between the mounting head and the connector in gaps, and the two ends of the protective tube are respectively press-bonded with the mounting head and the connector through variable-diameter press sleeves. The material of the fiber grating array and the inner capillary is quartz with low dielectric constant, the material of the outer capillary is polyimide with low dielectric constant, and the protective tube is internally provided with a protective layer with bending resistance and tensile resistance.

2. The insertion fiber grating array temperature sensor according to claim 1, wherein, The fiber grating array comprises optical fibers and a plurality of fiber gratings which are arranged on the optical fibers in gaps.

3. The insertion fiber grating array temperature sensor according to claim 2, wherein, The plurality of fiber gratings have different central wavelengths.

4. The insertion fiber grating array temperature sensor according to claim 1, wherein, The connector is provided with a socket, the end portions of the inner capillary, the outer capillary and the protective tube are fixedly inserted in the socket through optical fiber grinding glue, and the tail fiber end of the fiber grating array is fixedly inserted on the connector through optical fiber grinding glue.

5. The insertion fiber grating array temperature sensor according to claim 1, wherein, A tail protective sleeve is coated on the variable-diameter press sleeve between the connector and the protective tube.

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