High-temperature and high-pressure multi-parameter integrated sensor and system based on fiber misalignment splicing

Abstract

The present invention belongs to the field of optical fiber sensing technology, and discloses a high-temperature and high-pressure multi-parameter integrated sensor and system based on optical fiber misalignment fusion splicing, including a packaging body. A central hole and a cavity for accommodating a transmission optical fiber are provided in the center of the packaging body. The end of the transmission optical fiber is sequentially connected to a temperature detection device and a pressure / sound detection device located in the cavity. The temperature detection device includes an optical fiber Bragg grating, and the pressure / sound detection device includes a single-mode optical fiber, a multi-mode optical fiber, a first hollow capillary optical fiber, and a second hollow capillary optical fiber connected in sequence. The axes of the first hollow capillary optical fiber and the second hollow capillary optical fiber are misaligned and connected to form an open structure. The present invention realizes the composite in-situ synchronous measurement of pressure / sound - temperature multi-parameters, has the advantages of high temperature resistance, small volume, and high test accuracy, and has broad application prospects in the fields of aerospace, petroleum metallurgy, environmental monitoring, etc.

Description

Technical Field

[0001] The present invention relates to an integrated multi-parameter in-situ sensor and system, specifically a high-temperature and high-pressure multi-parameter integrated sensor and system based on fiber optic misalignment fusion splicing, which realizes in-situ pressure / acoustic-temperature multi-parameter sensing through capillary hollow fiber misalignment fusion splicing. Background Art

[0002] In industrial fields such as aerospace, oil exploitation, nuclear energy development, and environmental monitoring, the working process of sensing devices is often accompanied by extreme and complex environmental conditions such as high temperature and high pressure. In such harsh and complex environments, traditional single-parameter sensors can no longer meet the monitoring requirements for the stability and safety of equipment. Especially under the combined action of multiple factors such as high pressure, high temperature, and strong noise, the measurement of a single physical quantity cannot accurately reflect the operating state of the equipment, and the development of multi-parameter synchronous measurement technology is of great significance for improving the reliability and safety of equipment.

[0003] At present, in the field of sensor technology research, relatively rich achievements have been made in the tests for high temperature and high pressure, but it is facing many difficulties in realizing multi-parameter synchronous testing under extreme high-temperature and high-pressure environments and complex conditions, lacking practical and efficient means. Existing sensor systems are often bulky, have slow response speeds, and are easily interfered with in high-temperature environments, making it difficult to achieve accurate measurement. Compared with traditional electrical sensors and optical sensors prepared based on MEMS technology, fiber optic sensors have a smaller volume, lower preparation cost, can withstand high temperatures above 1000 °C, and have stronger environmental adaptability. Therefore, for the harsh environment of high temperature and high pressure, micro-sensors prepared based on optical fibers are an ideal choice. However, single-physical quantity sensors are easily affected by multiple environmental factors in complex environments, have large measurement errors in high-temperature environments, and there is cross-coupling interference between different physical quantities, making it difficult to achieve high-precision measurement. At present, for the multi-physical quantity synchronous measurement technology under high-temperature and high-pressure environments, especially the integrated measurement of three key parameters of pressure, sound, and temperature, there is still a lack of accurate and stable measurement devices.

[0004] Therefore, it is necessary to invent a composite multi-parameter sensor and system that can be used to synchronously detect pressure / acoustic-temperature under high-temperature and high-pressure environments to promote the further development of multi-parameter fine measurement technology in harsh environments. Summary of the Invention

[0005] In order to solve the problem that existing sensors are difficult to achieve synchronous in-situ measurement of pressure / acoustic-temperature in harsh high-temperature and high-pressure environments, the present invention proposes a high-temperature and high-pressure multi-parameter integrated sensor and system based on fiber optic misalignment fusion splicing, which realizes synchronous in-situ measurement of pressure / acoustic-temperature multi-parameters through misaligned optical fibers.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A high-temperature and high-pressure multi-parameter integrated sensor based on fiber misalignment fusion splicing, comprising: a packaging body, a central hole and a cavity for accommodating a transmission fiber are provided in the center of the packaging body, the cavity is located at the end of the central hole and communicates with the outside of the packaging body, the end of the transmission fiber is arranged in the cavity, and the end of the transmission fiber is sequentially connected to a temperature detection device and a pressure / sound detection device located in the cavity; the temperature detection device includes a fiber Bragg grating, and the pressure / sound detection device includes a single-mode fiber, a multi-mode fiber, a first hollow capillary fiber and a second hollow capillary fiber connected in sequence; the central hole diameter of the first hollow capillary fiber is larger than that of the second hollow capillary fiber; the axes of the single-mode fiber, the multi-mode fiber and the first hollow capillary fiber are collinear; the axes of the first hollow capillary fiber and the second hollow capillary fiber are misaligned to form an open structure, and the single-mode fiber, the multi-mode fiber, the first hollow capillary fiber and the second hollow capillary fiber form an FP interferometer for measuring pressure or sound.

[0007] The outer end face of the second hollow capillary fiber is subjected to surface roughening treatment by an optical fiber cutter.

[0008] The length of the multi-mode fiber is equal to (2n + 1) / 4 times the length corresponding to one sine path period of light transmission in the multi-mode fiber, where n is a positive integer.

[0009] The fiber Bragg grating is prepared inside the core of the grating fiber by femtosecond laser scanning line by line.

[0010] The high-temperature and high-pressure multi-parameter integrated sensor based on fiber misalignment fusion splicing further includes a packaging handle and a sealing gasket. A threaded hole is provided at the head end of the packaging body. The packaging handle is connected to the head end of the packaging body by a thread and sealed by the sealing gasket; the sealing gasket is arranged between the packaging handle and the packaging body; a fiber hole for allowing the transmission fiber to pass through is provided in the center of the packaging handle.

[0011] The packaging body and the packaging handle are made of zirconia ceramic material, and the material of the sealing gasket is silver or copper.

[0012] A connecting hole is further provided between the threaded hole and the central hole; the diameter of the connecting hole is smaller than that of the threaded hole and is used for setting high-temperature resistant ceramic glue to seal and fix the transmission fiber;

[0013] High-temperature resistant ceramic glue for sealing and fixing the transmission fiber is provided at the head end of the fiber hole of the packaging handle and the end of the central hole of the packaging body.

[0014] An external thread is further provided at the end of the packaging body, and the external thread is used to connect an application interface to fix the sensor.

[0015] In addition, the present invention also provides a high-temperature and high-pressure multi-parameter integrated sensing system based on fiber misalignment fusion splicing, which includes the above-mentioned high-temperature and high-pressure multi-parameter integrated sensor based on fiber misalignment fusion splicing, and also includes a broadband light source, a circulator, a spectral analyzer, a data acquisition board, and a demodulation calculation and display unit. The broadband light beam output by the broadband light source is incident into the transmission fiber of the sensor through the circulator, and the reflected signal in the transmission fiber is sent to the spectral analyzer for spectral signal analysis after passing through the circulator. The spectral signal is collected by the data acquisition board and then sent to the demodulation calculation and display unit for calculation and processing to obtain the pressure and temperature to be measured, or the sound and temperature to be measured.

[0016] The specific method for the demodulation calculation and display unit to perform calculation and processing to obtain the pressure and temperature to be measured, or the sound and temperature to be measured is as follows:

[0017] Extract the interference signal in the spectrum as the pressure sensing signal or the sound sensing signal through the spectral filtering algorithm, and extract the FBG reflection signal in the spectrum as the temperature sensing signal;

[0018] Calculate the spectral peak drift corresponding to the temperature sensing signal and the change in the optical cavity length corresponding to the pressure sensing signal , or calculate the spectral peak drift corresponding to the temperature sensing signal and the interference spectrum drift corresponding to the sound sensing signal ;

[0019] According to the spectral peak drift corresponding to the temperature sensing signal and the change in the optical cavity length corresponding to the pressure sensing signal , calculate the temperature change and the pressure change ; or according to the spectral peak drift corresponding to the temperature sensing signal and the interference spectrum drift corresponding to the sound sensing signal , calculate the temperature change and the sound change ; The calculation formula is:

[0020] ;

[0021] ;

[0022] Among them, represents the temperature change, represents the pressure change, represents the sound change; represents the change in the optical cavity length corresponding to the pressure sensing signal; represents the spectral peak drift corresponding to the temperature sensing signal, caused by temperature change; represents the interference spectral drift of the sound sensing signal, caused by sound changes; respectively represent the sensitivities of the pressure sensing signal to temperature and pressure, respectively represent the sensitivities of the temperature sensing signal to temperature and pressure; respectively represent the sensitivities of the sound sensing signal to temperature and sound, respectively represent the sensitivities of the temperature sensing signal to temperature and sound.

[0023] The present invention has the following beneficial effects compared with the prior art:

[0024] 1. The present invention proposes a high-temperature and high-pressure multi-parameter integrated sensor and system based on fiber optic misalignment splicing. By setting fiber Bragg gratings in the transmission fiber, temperature detection can be achieved. At the same time, an open-ended Fabry-Perot interferometer (FP interferometer) structure formed by misalignment splicing is used at the end of the transmission fiber to detect pressure signals or sound signals, realizing the integrated integration of pressure / sound detection and temperature detection. The overall sensor is a micro-probe structure, and the sensitive areas are independent of each other, enabling spatio-temporal synchronous measurement of multiple parameters. In addition, the encapsulation structure of the sensor makes the temperature detection part insensitive to pressure or sound signals, ensuring the accuracy of measurement.

[0025] 2. In the present invention, through the reflected signal of the fiber Bragg grating, not only can the real-time temperature be sensed, but also the error in pressure or sound detection under high-temperature environments can be compensated according to the real-time measured temperature signal, improving the accuracy of pressure or sound detection.

[0026] 3. The present invention adopts an open-ended encapsulation structure, ensuring that the sensor has high structural strength and is not easily damaged under high-pressure environments.

[0027] 4. The main body part of the sensor of the present invention is prepared based on quartz materials, which is an integrated structure of homogeneous materials. The same materials have consistent thermal stress changes, ensuring that the sensor can work with high reliability under harsh environments such as high temperature and high pressure. The external encapsulation structure is made of zirconia ceramic materials. The overall sensor can withstand high temperatures of 1000 °C, and has good high-temperature protection effects. The front end of the sensor encapsulation adopts a threaded encapsulation handle, which is convenient for installation, and the encapsulation size can be customized according to actual application requirements, with strong practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the overall structure sectional view of a high-temperature and high-pressure multi-parameter integrated sensor based on fiber optic misalignment splicing provided by an embodiment of the present invention;

[0029] Figure 2 is the structure sectional view of the pressure / sound detection device in an embodiment of the present invention;

[0030] Figure 3 This is the structural sectional view of the temperature detection device in the embodiment of the present invention;

[0031] Figure 4 This is the structural sectional view of the encapsulation main body in the embodiment of the present invention;

[0032] Figure 5 This is the structural sectional view of the encapsulation handle in the embodiment of the present invention;

[0033] Figure 6 This is the structural schematic diagram of a high-temperature and high-pressure multi-parameter integrated sensing system based on fiber optic misalignment splicing provided in the second embodiment of the present invention;

[0034] Figure 7 This is the composite spectrum schematic diagram obtained in the second embodiment of the present invention;

[0035] Figure 8 This is the interference spectrum schematic diagram corresponding to the extracted pressure / sound detection signal;

[0036] Figure 9 This is the spectrum schematic diagram received before and after the temperature change;

[0037] Figure 10 This is the interference spectrum schematic diagram before and after the pressure change;

[0038] Figure 11 This is the interference spectrum schematic diagram before and after the sound change;

[0039] In the figure, 1 - pressure / sound detection unit, 2 - temperature detection unit, 3 - encapsulation main body, 4 - sealing gasket, 5 - encapsulation handle, 6 - transmission optical fiber, 7 - high-temperature resistant ceramic glue, 11 - single-mode optical fiber, 12 - multi-mode optical fiber, 13 - first hollow capillary optical fiber, 14 - second hollow capillary optical fiber, 21 - cladding, 22 - fiber Bragg grating, 23 - core, 31 - cavity, 32 - central hole, 33 - connection hole, 34 - threaded hole, 35 - internal thread, 37 - external thread, 51 - optical fiber hole, 52 - encapsulation external thread, 61 - broadband light source, 62 - circulator, 63 - sensor, 64 - spectrum analyzer, 65 - data acquisition board, 66 - demodulation calculation and display unit. Detailed implementation manners

[0040] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] Example 1

[0042] As Figures 1 - 5 shown, Example 1 of the present invention provides a high temperature and high pressure multi-parameter integrated sensor based on fiber optic misalignment splicing, including: a packaging body 3, a central hole 32 and a cavity 31 for accommodating a transmission fiber 6 are provided in the center of the packaging body 3, the cavity 31 is located at the end of the central hole 32 and communicates with the outside of the packaging body 3, the end of the transmission fiber 6 is arranged in the cavity, and the end of the transmission fiber 6 is sequentially connected to a temperature detection device 2 and a pressure / sound detection device 1 located in the cavity 31; specifically, the temperature detection device 2 includes a fiber Bragg grating 22, and the pressure / sound detection device 1 includes a single-mode fiber 11, a multi-mode fiber 12, a first hollow capillary fiber 13 and a second hollow capillary fiber 14 connected in sequence, the central hole diameter of the first hollow capillary fiber 13 is larger than that of the second hollow capillary fiber 14; the single-mode fiber 11, the multi-mode fiber 12 and the first hollow capillary fiber 13 are collinear; the axes of the first hollow capillary fiber 13 and the second hollow capillary fiber 14 are misaligned and connected to form an open structure.

[0043] In this embodiment, the reflection signal of the fiber Bragg grating 22 is used to detect temperature, and the single-mode fiber 11, the multi-mode fiber 12, the first hollow capillary fiber 13 and the second hollow capillary fiber 14 form an FP interferometer. By measuring the change in the optical cavity length corresponding to the reflection signal of the FP interferometer, the pressure or sound signal can be measured. Among them, the first hollow capillary fiber 13 and the second hollow capillary fiber 14 are laterally misaligned and spliced to form an open sensing structure, such a structure can enhance the interference fringe contrast, and the second hollow capillary fiber 14 provides a microchannel for the medium to enter and exit, which can realize the interactive coupling of the optical signal and the external signal.

[0044] In this embodiment, the fiber Bragg grating 22 is arranged inside the core 23 of the grating fiber at the end of the transmission fiber 6. After each part of the pressure / sound detection device 1 is welded together by arc discharge technology, the single-mode fiber 11 is connected to the grating fiber at the end of the transmission fiber 6 by arc discharge technology, wherein the grating fiber and the single-mode fiber 11 are collinear; in addition, as Figure 3 shown, in this embodiment, the grating fiber includes a cladding 21 and a core 23, and the fiber Bragg grating 22 is prepared by femtosecond laser scanning line by line inside the core 23 of the grating fiber. The fiber Bragg grating 22 has the characteristic of high reflectivity, and the reflectivity is greater than 95%.

[0045] Specifically, in this embodiment, the outer sides of the fiber cores of the single-mode fiber 11 and the multi-mode fiber 12 are provided with a cladding of quartz material but no coating layer; the outer sides of the fiber cores of the first hollow capillary fiber 13 and the second hollow capillary fiber 14 have no cladding and coating layer.

[0046] In this embodiment, by making the diameter of the central through-hole of the first hollow capillary fiber 13 larger than that of the second hollow capillary fiber 14, the air can be stabilized. In addition, the left end face of the second hollow capillary fiber 14 serves as a reflection interface to promote the interference effect of the FP interferometer.

[0047] Specifically, in this embodiment, the outer diameters of the first hollow capillary fiber 13 and the second hollow capillary fiber 14 are the same. Specifically, the outer diameters of the single-mode fiber 11, the multi-mode fiber 12, the first hollow capillary fiber 13, and the second hollow capillary fiber 14 are all 125 μm. The core diameter of the multi-mode fiber 12 is 62.5 μm. The diameter of the central through-hole of the first hollow capillary fiber 13 is 70 μm, and the diameter of the central through-hole of the second hollow capillary fiber 14 is 10 μm. In addition, the diameter of the central through-hole of the second hollow capillary fiber 14 can also be 50 μm or 30 μm.

[0048] Specifically, in this embodiment, the transmission fiber 6 is a common single-mode fiber, and a coating layer is provided on its surface.

[0049] In addition, in this embodiment, the multi-mode fiber 12 functions as a self-focusing collimating lens, which can collimate and focus the transmitted light, facilitating the improvement of the ability to receive reflected light and enhancing the interference intensity of the FP interferometer. The intuitive manifestation is that the contrast of the interference spectrum increases, and the increase in the contrast of the interference spectrum is beneficial to improving the accuracy of signal demodulation. Specifically, the length of the multi-mode fiber 12 is equal to (2n + 1) / 4 times the length corresponding to one sine path period of light transmission in the multi-mode fiber 12, where n is a positive integer. At this time, the divergence angle of the light beam is the smallest and the loss is small, that is, the self-focusing collimation effect of the multi-mode fiber 12 is the best, which can greatly enhance the interference spectrum intensity and improve the ability to receive reflected light.

[0050] Furthermore, in this embodiment, the outer end face of the second hollow capillary fiber 14 is subjected to surface roughening treatment by an optical fiber cutting tool, which can avoid unnecessary multi-stage interference and improve the signal-to-noise ratio.

[0051] Furthermore, as shown in Figure 1 、 4 、5, a high-temperature and high-pressure multi-parameter integrated sensor based on fiber misalignment splicing in this embodiment further includes a packaging handle 5 and a sealing gasket 4; a threaded hole 34 is provided at the head end of the packaging main body 3, and the packaging handle 5 is connected to the head end of the packaging main body 3 by a thread and sealed by the sealing gasket 4; the sealing gasket 4 is arranged between the packaging handle 5 and the packaging main body 3; a fiber hole 51 for passing the transmission fiber 6 is provided at the center of the packaging handle 5, and a packaging external thread 52 matching the threaded hole 34 is provided at the end.

[0052] Specifically, in this embodiment, the encapsulation body 3 and the encapsulation handle 5 are made of zirconia ceramic material, and the material of the sealing gasket 4 is silver or copper.

[0053] Specifically, as Figure 4 shown, in this embodiment, a connection hole 33 is further provided between the threaded hole 34 and the central hole 32; the diameter of the connection hole 33 is smaller than that of the threaded hole 34 and is used to set the high-temperature resistant ceramic glue 7 to seal and fix the transmission optical fiber 6; in addition, high-temperature resistant ceramic glue 7 for sealing and fixing the transmission optical fiber 6 is provided at the head end of the optical fiber hole 51 of the encapsulation handle 5 and the tail end of the central hole 32 of the encapsulation body 3. Among them, the threaded hole 34, the central hole 32, the connection hole 33 and the cavity 31 are cylindrical holes with coaxial centers. Among them, the diameter of the central hole 32 is slightly larger than that of the transmission optical fiber 6, the diameters of the connection hole 33 and the cavity 31 are larger than that of the central hole 32, the diameter of the threaded hole 34 is larger than that of the connection hole 33, and an internal thread 35 is provided on the inner wall of the threaded hole 34.

[0054] Further, as Figure 4 shown, in this embodiment, an external thread 37 is further provided at the tail end of the encapsulation body 3, and the external thread 37 is used to connect to an application interface to fix the sensor.

[0055] In this embodiment, the working principle of pressure / sound detection is that when light is input through the transmission optical fiber 6, it first passes through the single-mode optical fiber 11, and then passes through the multi-mode optical fiber 12 for beam expansion and collimation and then is transmitted to the end face of the second hollow capillary optical fiber 14 after passing through the first hollow capillary optical fiber 13. Double-beam interference occurs between the end face at the tail end of the multi-mode optical fiber 12 and the head end face of the second hollow capillary optical fiber 14 to form an interference spectrum. The reflected spectrum is received by the multi-mode optical fiber 12 and then propagated to the transmission optical fiber 6 through the single-mode optical fiber 11 and the grating optical fiber. Then, the pressure or sound signal can be demodulated by collecting the interference spectrum. The working principle of pressure sensing or sound detection is as follows:

[0056] 1) Pressure detection principle: When the external pressure where the sensor is located changes, after the air medium enters the cavity 31, it enters the first hollow capillary optical fiber 13 through the micro-channel of the second hollow capillary optical fiber 14, that is, enters the Fabry-Perot cavity, causing the change of the air medium density between the two interference planes, and then causing the change of the air refractive index. When the pressure increases, the change of the air refractive index causes the optical cavity length of the Fabry-Perot cavity to increase correspondingly. When the pressure decreases, the optical cavity length decreases accordingly. The two show a linear relationship, and the period of the interference spectrum is related to the optical cavity length. Therefore, by calibrating the relationship between the optical cavity length and the pressure, the change of the pressure can be detected in real time.

[0057] 2) Sound detection principle: Similarly, sound pressure causes changes in the density of the air medium, which in turn leads to changes in the refractive index of the air inside the Fabry - Perot cavity. Since the magnitude of the influence of sound is relatively small, the sound pressure manifests as a drift in the interference spectrum on the spectrum. The drift amount is linearly proportional to the magnitude of the sound pressure. By calibrating the relationship between the drift amount of the interference spectrum and the sound signal, the detection of the sound signal can be achieved.

[0058] Specifically, as Figure 3 shown, in this embodiment, the principle of temperature detection is as follows: When the optical signal enters the transmission optical fiber 6, when the wavelength of the input light is scanned near the central wavelength of the fiber Bragg grating 22, most of the light is reflected at the fiber Bragg grating 22, and a small part of the light is transmitted through the fiber Bragg grating 22. On the spectrum, it is manifested as the formation of an obvious fiber Bragg grating reflection peak, that is, the FBG (fiber Bragg grating) reflection signal. When the temperature changes, the period of the fiber Bragg grating 22 changes, and the central wavelength of the reflection peak in the FBG reflection signal, that is, the spectral peak value, will drift. The drift amount is related to the temperature, so as to sense the real - time temperature.

[0059] Specifically, in this embodiment, the period of the fiber Bragg grating 22 used for temperature sensing is only sensitive to the temperature quantity. Then the temperature sensing signal can perform temperature compensation on the pressure / sound signal sensing signal, thereby improving the accuracy of pressure / sound signal sensing in a high - temperature environment.

[0060] Specifically, as Figure 1 shown, in this embodiment, the fiber Bragg grating 22 for temperature detection and the FP interferometer for pressure / sound detection are connected in series in the optical path, and the two can work simultaneously. When the incident light enters the transmission optical fiber 6, a composite reflection spectrum signal will be formed, specifically, the fiber Bragg grating spectrum is superimposed on the Fabry - Perot interference spectrum. The two can be separated by spectral filtering and then monitored separately to achieve multi - parameter sensing applications. Specifically, when pressure / sound acts on the sensor, it will cause changes in the refractive index of the air in the air cavity inside the FP cavity, and the optical path (optical cavity length) of the light propagating in the FP cavity changes; when temperature acts on the sensor, due to the thermal expansion of the material, the physical cavity length of the FP cavity changes, resulting in a change in the optical path, and the peak wavelength of the reflection spectrum of the fiber Bragg grating 22 also drifts. Therefore, the temperature sensing signal can be used to calibrate and compensate the temperature response of the pressure / sound detection device 1 in the optical path. In addition, the temperature sensing signal is not sensitive to the pressure signal, and its pressure sensitivity is close to zero. When detecting the sound signal, approximate dynamic pressure signal detection can be achieved through algorithm calibration.

[0061] Embodiment 2

[0062] As Figure 6As shown in the figure, Embodiment 2 of the present invention provides a high-temperature and high-pressure multi-parameter integrated sensing system based on fiber optic misalignment splicing, including a sensor 63, where the sensor 63 is a high-temperature and high-pressure multi-parameter integrated sensor based on fiber optic misalignment splicing described in Embodiment 1. It further includes a broadband light source 61, a circulator 62, a spectral analyzer 64, a data acquisition board 65, and a demodulation calculation and display unit 66. The broadband light beam output by the broadband light source 61 is incident on the transmission fiber 6 of the sensor after passing through the circulator 62. The reflected signal in the transmission fiber 6 is output through the circulator 62 and sent to the spectral analyzer 64 for spectral signal analysis. The spectral signal is collected by the data acquisition board 65 and then sent to the demodulation calculation and display unit 66 for calculation and processing to obtain the pressure / sound and temperature to be measured.

[0063] Specifically, in this embodiment, the specific method for the demodulation calculation and display unit 66 to perform calculation and processing to obtain the pressure / sound and temperature to be measured is as follows:

[0064] (1) Extract the interference signal of the FP interferometer in the spectrum as the pressure sensing signal or the sound sensing signal through the spectral filtering algorithm, and extract the FBG reflection signal in the spectrum as the temperature sensing signal;

[0065] (2) Calculate the spectral peak drift corresponding to the temperature sensing signal and the change in the optical cavity length corresponding to the pressure sensing signal , or calculate the spectral peak drift corresponding to the temperature sensing signal and the interference spectrum drift corresponding to the sound sensing signal ;

[0066] (3) According to the spectral peak drift corresponding to the temperature sensing signal and the change in the optical cavity length corresponding to the pressure sensing signal , calculate the temperature change and the pressure change ; or according to the spectral peak drift corresponding to the temperature sensing signal and the interference spectrum drift corresponding to the sound sensing signal , calculate the temperature change and the sound change ; The calculation formula is:

[0067] ; (1)

[0068] ; (2)

[0069] Among them, represents the temperature change, represents the pressure change, represents the sound change; represents the change in the optical cavity length corresponding to the pressure sensing signal, caused by the pressure change; represents the spectral peak drift of the temperature sensing signal, caused by the temperature change; represents the interference spectrum drift amount, caused by the sound change; respectively represent the sensitivities of the pressure sensing signal to temperature and pressure, respectively represent the sensitivities of the temperature sensing signal to temperature and pressure; respectively represent the sensitivities of the sound sensing signal to temperature and sound, respectively represent the sensitivities of the temperature sensing signal to temperature and sound.

[0070] In this embodiment, the temperature sensing signal in the sensor is only sensitive to temperature and insensitive to pressure / sound signals, then = 0, = 0. In addition, = . In this embodiment, by calibrating the sensitivity matrix in the above formulas (1) and (2), the temperature change and the pressure change can be calculated by inverse-solving the formula; or the temperature change and the sound change ; this calculation formula realizes the detection error compensation of temperature data for pressure / sound signals and improves the sensing accuracy.

[0071] As Figure 7 shown, it is the composite spectrum collected by the data acquisition board 65 in this embodiment; as Figure 8 shown, it is the schematic diagram of the extracted interference spectrum; as Figure 9 shown, it is the original composite spectrum collected in the experiment and the composite spectrum after the temperature change. It can be seen from Figure 9 that the temperature change will cause an obvious drift in the spectral peak of the FBG reflection signal. Therefore, the temperature change can be demodulated from the spectral peak drift amount of the FBG reflection signal.

[0072] Figure 10 is the schematic diagram of the interference spectrum before and after the pressure change in the embodiment of the present invention; it can be seen from Figure 10 that the pressure change will cause the free spectral range of the interference spectrum to broaden, and the change amount of the optical cavity length can be demodulated from it. Furthermore, the pressure change value can be calculated through formula (1). Figure 11 is the schematic diagram of the interference spectrum before and after the sound change in the embodiment of the present invention; it can be seen from Figure 11 that the sound change will cause an obvious drift in the interference spectrum, and the sound change amount can be calculated according to the drift amount combined with formula (2).

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A high-temperature and high-pressure multi-parameter integrated sensor based on fiber misalignment fusion splicing, characterized in that, Comprising: An encapsulation body (3), a central hole (32) for accommodating a transmission optical fiber (6) and a cavity (31) are provided in the center of the encapsulation body (3). The cavity (31) is located at the end of the central hole (32) and communicates with the outside of the encapsulation body (3). The end of the transmission optical fiber (6) is arranged in the cavity. The end of the transmission optical fiber (6) is sequentially connected to a temperature detection device (2) and a pressure / sound detection device (1) located in the cavity (31); the temperature detection device (2) includes a fiber Bragg grating (22), and the pressure / sound detection device (1) includes a single-mode optical fiber (11), a multi-mode optical fiber (12), a first hollow capillary optical fiber (13) and a second hollow capillary optical fiber (14) connected in sequence; the diameter of the central through hole of the first hollow capillary optical fiber (13) is larger than the diameter of the central through hole of the second hollow capillary optical fiber (14); the axes of the single-mode optical fiber (11), the multi-mode optical fiber (12), and the first hollow capillary optical fiber (13) are collinear; the axes of the first hollow capillary optical fiber (13) and the second hollow capillary optical fiber (14) are misaligned to form an open structure, and the single-mode optical fiber (11), the multi-mode optical fiber (12), the first hollow capillary optical fiber (13) and the second hollow capillary optical fiber (14) form an FP interferometer for measuring pressure or sound.

2. The high-temperature and high-pressure multi-parameter integrated sensor based on fiber misalignment fusion splicing according to claim 1, wherein, The outer end face of the second hollow capillary optical fiber (14) is subjected to surface roughening treatment by an optical fiber cutter.

3. The high-temperature and high-pressure multi-parameter integrated sensor based on fiber misalignment fusion splicing according to claim 1, characterized in that, The length of the multi-mode optical fiber (12) is equal to (2n + 1) / 4 times the length corresponding to one sine path period of light transmission in the multi-mode optical fiber (12), where n is a positive integer.

4. The high-temperature and high-pressure multi-parameter integrated sensor based on fiber misalignment fusion splicing according to claim 1, wherein, The fiber Bragg grating (22) is prepared by femtosecond laser scanning line by line inside the core (23) of the grating optical fiber.

5. The high-temperature and high-pressure multi-parameter integrated sensor based on fiber misalignment fusion splicing according to claim 1, characterized in that, It further includes an encapsulation handle (5) and a sealing gasket (4). A threaded hole (34) is provided at the head end of the encapsulation body (3). The encapsulation handle (5) is connected to the head end of the encapsulation body (3) by a thread and sealed by the sealing gasket (4); the sealing gasket (4) is arranged between the encapsulation handle (5) and the encapsulation body (3); a fiber hole (51) for the transmission optical fiber (6) to pass through is provided in the center of the encapsulation handle (5).

6. The high-temperature and high-pressure multi-parameter integrated sensor based on fiber misalignment fusion splicing according to claim 5, characterized in that, The encapsulation body (3) and the encapsulation handle (5) are made of zirconia ceramic material, and the material of the sealing gasket (4) is silver or copper.

7. The high-temperature and high-pressure multi-parameter integrated sensor based on fiber misalignment fusion splicing according to claim 5, characterized in that, A connection hole (33) is further provided between the threaded hole (34) and the central hole (32); the diameter of the connection hole (33) is smaller than that of the threaded hole (34) and is used to set a high-temperature resistant ceramic glue (7) to seal and fix the transmission optical fiber (6); High-temperature resistant ceramic glue (7) for sealing and fixing the transmission optical fiber (6) is provided at the head end of the fiber hole (51) of the encapsulation handle (5) and the end of the central hole (32) of the encapsulation body (3).

8. The high-temperature and high-pressure multi-parameter integrated sensor based on fiber misalignment fusion splicing according to claim 1, characterized in that, An external thread (37) is further provided at the end of the encapsulation body (3), and the external thread (37) is used to connect an application interface to fix the sensor.

9. A high-temperature and high-pressure resistant multi-parameter integrated sensing system based on fiber misalignment fusion splicing, characterized in that, An integrated high-temperature and high-pressure multi-parameter sensor based on fiber misalignment fusion according to any one of claims 1 to 8, further comprising a broadband light source (61), a circulator (62), a spectral analyzer (64), a data acquisition board (65), and a demodulation calculation and display unit (66). The broadband light beam output by the broadband light source (61) is incident into the transmission fiber (6) of the sensor after passing through the circulator (62). The reflected signal in the transmission fiber (6) is output by the circulator (62) and sent to the spectral analyzer (64) for analyzing the spectral signal. The spectral signal is collected by the data acquisition board (65) and then sent to the demodulation calculation and display unit (66) for calculation and processing to obtain the pressure and temperature to be measured, or the sound and temperature to be measured.

10. A high-temperature and high-pressure multi-parameter integrated sensing system based on fiber misalignment fusion splicing according to claim 9, characterized in that, The specific method for the demodulation calculation and display unit (66) to perform calculation and processing to obtain the pressure and temperature to be measured, or the sound and temperature to be measured is as follows: Extract the interference signal in the spectrum as the pressure sensing signal or the sound sensing signal through the spectral filtering algorithm, and extract the FBG reflection signal in the spectrum as the temperature sensing signal; Calculate the spectral peak drift corresponding to the temperature sensing signal and the change in the optical cavity length corresponding to the pressure sensing signal or calculate the spectral peak drift corresponding to the temperature sensing signal and the interference spectrum drift amount corresponding to the sound sensing signal ; According to the spectral peak drift corresponding to the temperature sensing signal and the change in the optical cavity length corresponding to the pressure sensing signal , calculate the temperature change and the pressure change ; or according to the spectral peak drift corresponding to the temperature sensing signal and the interference spectrum drift amount corresponding to the sound sensing signal , calculate the temperature change and the sound change ; The calculation formula is: ； ； Among them, represents the temperature change amount, represents the pressure change amount, represents the sound change amount; represents the change amount of the optical cavity length corresponding to the pressure sensing signal; represents the spectral peak drift corresponding to the temperature sensing signal; represents the interference spectral drift amount corresponding to the sound sensing signal; respectively represent the sensitivities of the pressure sensing signal to temperature and pressure, respectively represent the sensitivities of the temperature sensing signal to temperature and pressure; respectively represent the sensitivities of the sound sensing signal to temperature and sound, respectively represent the sensitivities of the temperature sensing signal to temperature and sound.

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