Absolute temperature measuring device based on random weak reflection grating

Abstract

The invention belongs to the technical field of high-precision real-time high-temperature monitoring, and particularly relates to an absolute temperature measuring device based on a random weak reflection grating, which is characterized in that sweep-frequency light output by a narrow-linewidth tunable laser passes through a main interferometer module and is subjected to real-time temperature sensing through the random weak reflection grating; beat frequency signals are formed through the coupling effect of the optical fiber coupler and are transmitted to the polarization grading photoelectric detector, and real-time data acquisition is carried out through the data acquisition processing module. Sampling of the data collecting and processing module is transmitted to the upper computer for processing through beat frequency signals of the auxiliary interferometer, the upper computer interacts with the data collecting card in real time, data sampling is conducted on signals of the main interferometer in real time through an interpolation resampling method, non-linear noise from a light source is eliminated, and finally the signals of the main interferometer are obtained through an optical frequency domain reflection algorithm. And accurate measurement of temperature distribution is realized. According to the invention, the measurement precision of the sensing system in a high-temperature environment and the anti-interference capability of the system are obviously improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-precision real-time high-temperature monitoring technology, and particularly relates to an absolute temperature measurement device based on a random weak reflection grating. Background Art

[0002] As the most basic physical quantity in daily life, engineering applications, etc., the requirements for temperature measurement technology are getting higher and higher. In various industries such as the national defense industry, oil and gas chemical industry, energy transmission, geological detection, building maintenance, security monitoring, industrial and agricultural production, etc., the technologies for temperature measurement, recording, and control have been greatly tested.

[0003] The basic principle of a temperature measurement device is mainly based on the fact that when the temperature of an object changes, some physical properties of the measurement device will change with the temperature, and then the change in temperature is mapped through the change in physical properties, so as to realize the measurement of temperature. Currently, according to the temperature measurement range, it can be divided into ultra-low temperature, low temperature, normal temperature, medium temperature, high temperature, and ultra-high temperature measurement. Temperature measurement in low temperature and normal temperature is mostly applied to the detection of large buildings such as dams, traffic tunnels, etc., as well as the exploration and excavation of mines; temperature measurement in the medium temperature range.

[0004] Currently, there are mainly two means for temperature measurement. One is an electrical sensor, namely a thermocouple, and the other is to rely on an optical sensor, such as a fiber grating for temperature sensing, etc. The basic structure of a thermocouple temperature sensor includes a measurement end and a reference end. The measurement end is mostly made by welding two materials. After connecting the reference end to a measuring instrument to form a circuit, the thermocouple temperature detector is completed. Currently, there are hundreds of thermocouple technologies. Except for slightly different temperature measurement ranges, thermocouple temperature sensors are mainly limited by their service life. Therefore, in order to extend the service life of thermocouple temperature sensors, it is necessary to perform armored installation outside the thermocouple to isolate the pollution and influence of the test environment on the instrument.

[0005] Compared with thermocouple technology, fiber optic temperature sensors make full use of the advantages of fiber optics such as high bandwidth, low loss, anti-interference, and strong durability. Among them, fiber grating-based temperature sensors are widely used in engineering detection, communication engineering, aerospace and other fields due to their advantages of simultaneous measurement of multiple parameters and easy integration of distributed sensing networks. However, current fiber grating sensors also expose quite a few problems, especially in terms of decoupling, sensitivity, range spread, and environmental adaptability. Therefore, in some high-precision temperature or complex environment detection applications, it is necessary to develop fiber optic temperature sensing technologies with stronger tolerance and wider applicability. Summary of the Invention

[0006] The object of the present invention is to provide an absolute temperature measurement device based on a random weak reflection grating, which is applicable to fields with extremely high requirements for temperature monitoring, such as high-temperature superconductivity, energy, aerospace, nuclear energy, precision manufacturing and other industries, and has the advantages of high sensitivity, strong anti-interference ability, high stability, etc.

[0007] The technical solution adopted by the present invention is specifically as follows:

[0008] An absolute temperature measurement device based on a random weak reflection grating, comprising:

[0009] A swept laser module: comprising a narrow linewidth tunable laser and a 99:1 first optical fiber coupler;

[0010] A temperature sensing module: comprising a random weak reflection fiber grating, a temperature chamber and a temperature sensing probe;

[0011] A main interferometer module: comprising a 99:1 second optical fiber coupler, a circulator, a polarization controller and a polarization grading photodetector;

[0012] An auxiliary interferometer module: comprising a 1:1 third optical fiber coupler, a delay optical fiber, an auxiliary interference optical fiber, a 1:1 fourth optical fiber coupler and a second photodetector;

[0013] The data acquisition and processing module includes a data acquisition card and a host computer;

[0014] The narrow linewidth tunable laser outputs swept laser to the 99:1 first optical fiber coupler for laser beam splitting. One port is incident on the 1:1 third optical fiber coupler of the auxiliary interferometer module, and the remaining port is incident on the 99:1 second optical fiber coupler of the main interferometer module. Specifically, the "99" port is incident on the 99:1 second optical fiber coupler of the main interferometer module, and the "1" port is incident on the 1:1 third optical fiber coupler of the auxiliary interferometer module;

[0015] The light incident on the main interferometer module is further split by the 99:1 second optical fiber coupler. The light transmitted through one port of the main interferometer is transmitted to the polarization grading photodetector through the polarization controller. Specifically, the light transmitted through the "1" port of the main interferometer is transmitted to the polarization grading photodetector through the polarization controller; the two signals form a beat frequency, and after the polarization beat frequency of the polarization grading photodetector, they are respectively transmitted to the data acquisition card of the data acquisition and processing module;

[0016] The light from the remaining port after further splitting by the 99:1 second optical fiber coupler is incident on the "1" port of the circulator. Specifically, the light from the "99" port is incident on the "1" port of the circulator, and then circulates to the 2 port and enters the random weak reflection fiber Bragg gratings in the temperature sensing probes arranged inside the temperature chamber. The swept-frequency light is transmitted in the random weak reflection fiber Bragg gratings, undergoes weak reflection, and is re-transmitted to the "2" port of the circulator. Then, it reaches the "3" port of the circulator through the action of the circulator, and then is transmitted to the polarization grading photodetector;

[0017] The light from another port after splitting from the narrow linewidth tunable laser is incident on the 1:1 third optical fiber coupler of the auxiliary interferometer module. Among them, one path passes through the delay fiber to simulate the interference length of the sensing fiber optical path of the main interferometer module and is transmitted to the 1:1 fourth optical fiber coupler; the other path of light directly passes through the transmission of the optical fiber path of the auxiliary interference fiber to simulate the interference arm path of the main interferometer, and then is transmitted to the 1:1 fourth optical fiber coupler; the two split beams of light form a beat frequency optical signal through the 1:1 fourth optical fiber coupler and are transmitted to the second photodetector, and then are also transmitted to the data acquisition card;

[0018] The data acquisition card receives the signals from the main interferometer module and the auxiliary interferometer module, and transmits their values to the upper computer for data processing; the upper computer interacts with the data acquisition card to complete functions such as parameter setting, signal transmission, random non-linear jitter phase noise correction, and algorithm compilation, and interpolates the beat frequency signal of the auxiliary interferometer to complete the non-linear noise correction of the narrow linewidth tunable laser, further improving the temperature sensing accuracy of the main interferometer;

[0019] The data acquisition and processing module is based on the optical frequency domain reflectometry algorithm of polarization analysis. It transforms the beat signal obtained by the auxiliary interferometer module to obtain the phase change amount of the light source, and then obtains the optical frequency change amount of the light source through frequency domain transformation. After that, interpolation resampling is used to perform equal optical frequency acquisition on the beat signal obtained by the auxiliary interferometer, using the interpolation as the acquisition points of the main interferometer to collect the signal obtained by the main interferometer, so as to correct the nonlinear noise of the narrow linewidth tunable laser; the optical frequency domain reflectometry algorithm uses frequency domain conversion to convert the compensated beat time domain signal into a frequency domain signal, and obtains the information of the compensated beat signal in the distance domain, so as to extract the frequency components and distance information of the signal. The data acquisition and processing module realizes the temperature sensing of the main interferometer path through the temperature sensing probe 203; uses a polarization grading photodetector to realize the collection of the beat of polarized light in different polarization directions, reducing the influence of polarization fading on temperature sensing; uses the auxiliary interferometer module to correct the nonlinear noise of the swept laser; uses a high-speed acquisition card and a host computer to realize the setting of temperature sensing parameters and the real-time correction of nonlinear noise; uses a random weak reflection fiber grating to replace the traditional periodic fiber grating, and uses the multiple reflections of photons in the disordered medium to realize high-precision absolute temperature sensing and determination, and finally outputs the temperature result.

[0020] Preferably, the narrow linewidth tunable laser has functions of an externally adjustable sweep range and sweep speed;

[0021] The sweep wavelength of the narrow linewidth tunable laser is within the reflection wavelength range of the random weak reflection fiber grating;

[0022] The functions of the 99:1 first fiber coupler and the second fiber coupler are to distribute the swept light energy, perform different energy distributions for the main interferometer and the auxiliary interferometer, and finally form a beat signal.

[0023] Preferably, the function of the polarization controller is to precisely adjust the polarization state of the optical signal in the optical fiber, including the polarization direction, the shape and amplitude of the polarization ellipse; it can reduce polarization-dependent loss, compensate for polarization mode dispersion and optimize the transmission quality of the optical signal;

[0024] The function of the circulator is to allow the optical signal to transmit in a single direction and prevent the propagation of the reverse optical signal;

[0025] The function of the polarization grading photodetector is to adjust the arrangement of optical elements and the polarization response characteristics, realize sensitive detection of different polarization states of light, and provide an accurate polarization information output.

[0026] Preferably, the function of the 1:1 third fiber coupler is to achieve equal power distribution of the input optical signal and the output optical signal through its symmetric structure, ensuring the effective coupling and transmission of the optical signal in the optical fiber system;

[0027] The delay optical fiber adjusts the propagation time of the optical signal in the optical fiber through the selection of a specific length and optical fiber type, and precisely controls the signal delay to meet the system's requirements for auxiliary interferometer signal noise correction;

[0028] The function of the 1:1 fourth optical fiber coupler is to use a symmetric structure to enable the delay optical fiber of the auxiliary interferometer and the interferometric optical fiber to interfere and obtain a beat signal.

[0029] Preferably, the data acquisition card captures the optical intensity data in the main interferometer and the auxiliary interferometer in real time by high-speed sampling and precisely synchronizing the laser output and the reflected signal, and simultaneously performs preliminary data processing to provide high-quality raw data for subsequent interpolation resampling and non-linear noise correction;

[0030] The upper computer, through its connection with the data acquisition card and corresponding hardware devices, is responsible for receiving, storing, and processing the acquisition data from the system, and executing signal analysis and processing algorithms. In addition, the upper computer also provides a user interface for real-time data display and operation control, supports parameter adjustment, experiment monitoring, and result visualization;

[0031] Preferably, the temperature sensing probe, by virtue of the good thermal conductivity of the metal, while ensuring the temperature sensing performance, uses a metal shell to protect the internal random weak reflection grating, and the probe end is fixed and sealed with glue to achieve the complete encapsulation of the probe.

[0032] Preferably, the temperature chamber is used to provide a controllable temperature environment to ensure the stability and repeatability of the temperature sensing probe 203 under different temperature conditions; the temperature chamber precisely adjusts and stabilizes the temperature change around the optical fiber, so that the reflection spectrum characteristics of the random weak reflection grating in the optical fiber change predictably with the temperature change, thereby providing a reliable calibration and test platform for temperature sensing; in this way, the temperature chamber helps to optimize the sensitivity and accuracy of the temperature sensing system and eliminate the interference of external temperature fluctuations on the measurement results.

[0033] Preferably, the random weak reflection fiber grating in the temperature sensing probe forms a weak reflection wave by introducing tiny reflection regions inside the optical fiber and using the interaction between the optical signal and these regions; when the ambient temperature changes, the optical characteristics of the fiber grating also change accordingly; by monitoring the changes in these reflection spectra, the temperature of the environment where the optical fiber is located can be accurately detected. In addition, the random weak reflection fiber grating has a high-sensitivity temperature response ability and can effectively cope with interference in a complex environment to ensure the accuracy of temperature measurement.

[0034] The technical effects achieved by the present invention are:

[0035] The present invention utilizes optical frequency domain reflectometry, light source non-linear compensation technology, polarization fading suppression technology, etc. By using a random weak reflection fiber grating as a temperature sensor device, it realizes high-precision and high-resolution real-time absolute temperature sensing. Compared with traditional temperature sensing schemes, the present invention makes full use of the randomness of the random weak reflection grating for distributed absolute temperature sensing, can achieve accurate measurement of the temperature field in the entire space, and significantly improves the measurement accuracy of the sensing system in a high-temperature environment and the anti-interference ability of the system.

[0036] The present invention subjects the swept-frequency light output by a narrow linewidth tunable laser to real-time temperature sensing through a random weak reflection fiber grating via a main interferometer module. After the coupling action of an optical fiber coupler, a beat signal is formed and transmitted to a polarization-division photodetector, and real-time data acquisition is performed by a data acquisition and processing module. The sampling of the data acquisition and processing module is transmitted to a host computer for processing through the beat signal of an auxiliary interferometer. The host computer interacts with the data acquisition card in real time, and uses the interpolation resampling method to perform real-time data sampling on the main interferometer signal to eliminate the non-linear noise from the light source. The temperature chamber eliminates the influence of external temperature changes on the temperature sensing probe, stabilizes the temperature distribution, and provides an environment for temperature calibration of the temperature sensing probe. At the same time, the change in the temperature of the temperature chamber causes a change in the physical properties of the random weak reflection fiber grating, resulting in a change in the phase of the beat signal of the main interferometer. Finally, through the optical frequency domain reflection algorithm, accurate measurement of the temperature distribution is achieved.

[0037] The present invention provides an absolute temperature sensing scheme based on a random weak reflection grating, which utilizes optical frequency domain reflectometry, light source non-linear compensation technology, polarization fading suppression technology, etc. By using a random weak reflection fiber grating as a temperature sensor device, it realizes high-precision and high-resolution real-time absolute temperature sensing. Compared with traditional temperature sensing schemes, the present invention makes full use of the randomness of the random weak reflection grating for distributed absolute temperature sensing, can achieve accurate measurement of the temperature field in the entire space, and significantly improves the measurement accuracy of the sensing system in a high-temperature environment and the anti-interference ability of the system. Brief Description of the Drawings

[0038] Figure 1 It is a diagram of an absolute temperature sensing scheme based on a random weak reflection grating provided by the present invention;

[0039] Figure 2 It is the grating unit distribution of the random weak reflection fiber grating used in the present invention.

[0040] Figure 3 It is a random fiber grating sub-unit in the present invention.

[0041] In the drawings, the list of components represented by each reference numeral is as follows:

[0042] 101, Narrow linewidth tunable laser; 102, First fiber optic coupler; 103, ; 104, ; 201, Random weak reflection fiber grating; 202, Temperature chamber; 203, Temperature sensing probe; 204, ; 301, Second fiber optic coupler; 302, Circulator; 303, Polarization controller; 304, Polarization grading photodetector; 401, Third fiber optic coupler; 402, Delay fiber; 403, Auxiliary interference fiber; 404, Fourth fiber optic coupler; 405, Second photodetector; 501, Data acquisition card; 502, Host computer. Detailed implementation mode

[0043] In order to make the purpose and advantages of the present invention clearer, the present invention will be specifically described below in conjunction with embodiments. It should be understood that the following text only describes one or several specific implementation modes of the present invention, and does not strictly limit the scope of protection specifically requested by the present invention.

[0044] As Figures 1 - 3 shown, an absolute temperature measurement device based on a random weak reflection grating includes:

[0045] Swept laser module: includes a narrow linewidth tunable laser 101 and a 99:1 first fiber optic coupler 102;

[0046] Temperature sensing module: includes a random weak reflection fiber grating 201, a temperature chamber 202, and a temperature sensing probe 203;

[0047] Main interferometer module: includes a 99:1 second fiber optic coupler 301, a circulator 302, a polarization controller 303, and a polarization grading photodetector 304;

[0048] Auxiliary interferometer module: includes a 1:1 third fiber optic coupler 401, a delay fiber 402, an auxiliary interference fiber 403, a 1:1 fourth fiber optic coupler 404, and a second photodetector 405;

[0049] The data acquisition and processing module includes a data acquisition card 501 and a host computer 502;

[0050] The narrow linewidth tunable laser 101 outputs a swept laser to the 99:1 first fiber optic coupler 102 for laser beam splitting. One port is incident on the 1:1 third fiber optic coupler 401 of the auxiliary interferometer module, and the remaining port is incident on the 99:1 second fiber optic coupler 301 of the main interferometer module. Specifically, the "99" port is incident on the 99:1 second fiber optic coupler 301 of the main interferometer module, and the "1" port is incident on the 1:1 third fiber optic coupler 401 of the auxiliary interferometer module;

[0051] The light incident on the main interferometer module is further split by a 99:1 second fiber optic coupler 301. One path of the light transmitted through a port of the main interferometer passes through a polarization controller 303 and is transmitted to a polarization division photodetector 304. Specifically, the light transmitted through the "1" port of the main interferometer passes through the polarization controller 303 and is transmitted to the polarization division photodetector 304. The two signals form a beat frequency, and after the polarization beat frequency of the polarization division photodetector 304, they are respectively transmitted to the data acquisition card 501 of the data acquisition and processing module.

[0052] The light at the remaining port after the 99:1 second fiber optic coupler 301 further splits is incident on the "1" port of the circulator 302. Specifically, the light at the "99" port is incident on the "1" port of the circulator 302, and then circulates to the 2 port and enters the random weak reflection fiber grating 201 in the temperature sensing probes 203 arranged inside the temperature chamber 202. The swept-frequency light is transmitted in the random weak reflection fiber grating 201, and after weak reflection, it is re-transmitted to the "2" port of the circulator 302. After that, it reaches the "3" port of the circulator 302 through the action of the circulator 302, and then is transmitted to the polarization division photodetector 304.

[0053] The light from another port after splitting from the narrow linewidth tunable laser 101 is incident on a 1:1 third fiber optic coupler 401 of the auxiliary interferometer module. One path passes through a delay fiber 402 to simulate the interference length of the sensing fiber optical path of the main interferometer module and is transmitted to a 1:1 fourth fiber optic coupler 404. The other path of light is directly transmitted through the fiber optic path of the auxiliary interference fiber 403 to simulate the interference arm path of the main interferometer, and then is transmitted to the 1:1 fourth fiber optic coupler 404. The two split beams of light form a beat frequency optical signal through the 1:1 fourth fiber optic coupler 404 and are transmitted to the second photodetector 405, and then are also transmitted to the data acquisition card 501.

[0054] The data acquisition card 501 receives the signals from the main interferometer module and the auxiliary interferometer module and transmits their values to the upper computer 502 for data processing. The upper computer 502 interacts with the data acquisition card 501 to complete functions such as parameter setting, signal transmission, random non-linear jitter phase noise correction, and algorithm compilation, and interpolates the beat frequency signal of the auxiliary interferometer to complete the non-linear noise correction of the narrow linewidth tunable laser 101, further improving the temperature sensing accuracy of the main interferometer.

[0055] The data acquisition and processing module is based on the optical frequency domain reflection algorithm of polarization analysis. It transforms the beat frequency signal obtained by the auxiliary interferometer module to obtain the phase change amount of the light source, and then obtains the optical frequency change amount of the light source through frequency domain transformation. After that, interpolation resampling is used to perform equal optical frequency acquisition on the beat frequency signal obtained by the auxiliary interferometer, and interpolation is used as the acquisition point of the main interferometer to collect the signal obtained by the main interferometer to correct the nonlinear noise of the narrow linewidth tunable laser 101; the algorithm uses frequency domain conversion to convert the compensated beat frequency time domain signal into a frequency domain signal, obtains the information of the compensated beat frequency signal in the distance domain, so as to extract the frequency component and distance information of the signal. The data acquisition and processing module realizes the temperature sensing of the main interferometer path through the temperature sensing probe 203; uses the polarization grading photodetector 304 to realize the collection of the beat frequency of polarized light in different polarization directions and reduce the influence of polarization fading on temperature sensing; uses the auxiliary interferometer module to correct the nonlinear noise of the swept frequency laser; uses the high-speed acquisition card and the upper computer 502 to realize the setting of temperature sensing parameters and the real-time correction of nonlinear noise; uses the random weak reflection fiber grating 201 to replace the traditional periodic fiber grating, and uses the multiple reflections of photons in the disordered medium to realize high-precision absolute temperature sensing and determination, and finally outputs the temperature result.

[0056] In the present invention, the temperature sensing probe (203) is indirectly connected to the data acquisition card 501 through a circulator and a photodetector.

[0057] In the present invention, the core of the data acquisition and processing module is the absolute temperature sensing algorithm of optical frequency domain reflection. The main solution is to perform real-time temperature sensing on the swept frequency light output by the narrow linewidth tunable laser 101 through the main interferometer module with a random weak reflection grating. After the coupling action of the fiber coupler, a beat frequency signal is formed and transmitted to the polarization grading photodetector 304, and real-time data acquisition is performed by the data acquisition and processing module. The sampling of the data acquisition and processing module is transmitted to the upper computer 502 through the beat frequency signal of the auxiliary interferometer for processing. The upper computer 502 interacts with the data acquisition card 501 in real time, and uses the interpolation resampling method to perform real-time data sampling on the main interferometer signal to eliminate the nonlinear noise from the light source. The temperature chamber 202 eliminates the influence of external temperature changes on the temperature sensing probe 203, stabilizes the temperature distribution, and provides an environment for temperature calibration of the temperature sensing probe 203. At the same time, the change in the temperature of the temperature chamber 202 causes a change in the physical properties of the random weak reflection grating, resulting in a phase change in the beat frequency signal of the main interferometer. Finally, through the optical frequency domain reflection algorithm, the accurate measurement of the temperature distribution is realized. This absolute temperature sensing scheme based on the random weak reflection grating, compared with the traditional temperature sensing scheme, makes full use of the randomness of the random weak reflection grating for distributed absolute temperature sensing, can realize the accurate measurement of the full-space temperature field, and significantly improves the measurement accuracy of the sensing system in a high-temperature environment and the anti-interference ability of the system.

[0058] Preferably, the narrow linewidth tunable laser 101 has an externally tunable sweep range and sweep speed function;

[0059] The sweep wavelength of the narrow linewidth tunable laser 101 is within the reflection wavelength range of the random weak reflection fiber grating 201;

[0060] The 99:1 first fiber coupler 102 and the second fiber coupler 301 function to distribute the swept optical energy, performing different energy distributions for the main interferometer and the auxiliary interferometer, and finally forming a beat signal.

[0061] Preferably, the polarization controller 303 functions to precisely adjust the polarization state of the optical signal in the optical fiber, including the polarization direction, the shape and amplitude of the polarization ellipse; it can reduce polarization-dependent loss, compensate for polarization mode dispersion and optimize the transmission quality of the optical signal;

[0062] The circulator 302 functions to allow the optical signal to be transmitted in a single direction and prevent the propagation of the reverse optical signal;

[0063] The polarization-division photodetector 304 functions to adjust the arrangement of the optical elements and the polarization response characteristics, realizing sensitive detection of different polarization states of light to provide an accurate polarization information output.

[0064] Preferably, the 1:1 third fiber coupler 401 functions to achieve equal power distribution of the input optical signal and the output optical signal through its symmetric structure, ensuring effective coupling and transmission of the optical signal in the optical fiber system;

[0065] The delay fiber 402 adjusts the propagation time of the optical signal in the optical fiber by selecting a specific length and fiber type, precisely controlling the signal delay to meet the system's requirement for signal noise correction in the auxiliary interferometer;

[0066] The 1:1 fourth fiber coupler 404 functions to use the symmetric structure to interfere the delay fiber 402 of the auxiliary interferometer with the interference fiber to obtain a beat signal.

[0067] Preferably, the data acquisition card 501 captures the light intensity data in the main interferometer and the auxiliary interferometer in real time by high-speed sampling and precisely synchronizing the laser output and the reflection signal, and simultaneously performs preliminary data processing to provide high-quality raw data for subsequent interpolation resampling and non-linear noise correction;

[0068] The host computer 502 is responsible for receiving, storing and processing the acquisition data from the system by connecting to the data acquisition card 501 and the corresponding hardware devices, and executing signal analysis and processing algorithms. In addition, the host computer 502 also provides a user interface for real-time data display and operation control, supporting parameter adjustment, experimental monitoring and result visualization;

[0069] Preferably, the temperature sensing probe 203 makes use of the good thermal conductivity of the metal to protect the internal random weak reflection grating while ensuring the temperature sensing performance. The probe end is fixed and sealed with glue to achieve the complete encapsulation of the probe.

[0070] Preferably, the temperature chamber 202 is used to provide a controllable temperature environment to ensure the stability and repeatability of the temperature sensing probe 203 under different temperature conditions; the temperature chamber 202 precisely adjusts and stabilizes the temperature change around the optical fiber, enabling the reflection spectrum characteristics of the random weak reflection grating in the optical fiber to change predictably with temperature changes, thereby providing a reliable calibration and test platform for temperature sensing; in this way, the temperature chamber 202 helps to optimize the sensitivity and accuracy of the temperature sensing system while eliminating the interference of external temperature fluctuations on the measurement results.

[0071] Preferably, the random weak reflection fiber grating 201 in the temperature sensing probe 203 forms weak reflection waves by introducing tiny reflection regions inside the optical fiber and using the interaction between the optical signal and these regions; when the ambient temperature changes, the optical characteristics of the fiber grating also change accordingly; by monitoring the changes in these reflection spectra, the temperature of the environment where the optical fiber is located can be accurately detected. In addition, the random weak reflection fiber grating 201 has a high-sensitivity temperature response ability and can effectively cope with interference in complex environments to ensure the accuracy of temperature measurement.

[0072] The present invention utilizes optical frequency domain reflectometry, light source non-linearity compensation technology, polarization fading suppression technology, etc. With the random weak reflection fiber grating 201 as the temperature sensing device, it realizes high-precision and high-resolution real-time absolute temperature sensing. Compared with traditional temperature sensing schemes, the present invention makes full use of the randomness of the random weak reflection grating for distributed absolute temperature sensing, can achieve precise measurement of the full-space temperature field, and significantly improves the measurement accuracy of the sensing system in high-temperature environments and the anti-interference ability of the system.

[0073] In the present invention, the swept-frequency light output by the narrow linewidth tunable laser 101 undergoes real-time temperature sensing through the main interferometer module via the random weak reflection fiber grating 201. Through the coupling effect of the fiber coupler, a beat signal is formed and transmitted to the polarization-division photodetector 304, where real-time data acquisition is performed by the data acquisition and processing module. The sampling of the data acquisition and processing module is transmitted to the host computer 502 for processing through the beat signal of the auxiliary interferometer. The host computer 502 interacts with the data acquisition card 501 in real time. Using the interpolation resampling method, data sampling is performed on the main interferometer signal in real time to eliminate the non-linear noise from the light source. The temperature chamber 202 eliminates the influence of external temperature changes on the temperature sensing probe 203, stabilizes the temperature distribution, and provides an environment for temperature calibration of the temperature sensing probe 203. At the same time, the change in the temperature of the temperature chamber 202 causes a change in the physical properties of the random weak reflection fiber grating 201, resulting in a change in the phase of the beat signal of the main interferometer. Finally, through the optical frequency domain reflectometry algorithm, the accurate measurement of the temperature distribution is achieved.

[0074] The present invention provides an absolute temperature sensing scheme based on a random weak reflection grating. By using optical frequency domain reflectometry technology, light source non-linear compensation technology, polarization fading suppression technology, etc., with the random weak reflection fiber grating 201 as the temperature sensor device, high-precision and high-resolution real-time absolute temperature sensing is achieved. Compared with traditional temperature sensing schemes, the present invention makes full use of the randomness of the random weak reflection grating for distributed absolute temperature sensing, can achieve accurate measurement of the full-space temperature field, and significantly improves the measurement accuracy of the sensing system in high-temperature environments and the anti-interference ability of the system.

[0075] Figure 2 The figure shows a schematic diagram of the multi-core fiber sensing area. Periodic random weak reflection units are etched inside the multi-core fiber. The double-core fiber is partially coated with a humidity-sensitive material. The coated part of the fiber is sensitive to humidity. The internal multi-core fiber tracks the spectral drift caused by changes in humidity and temperature through machine learning. Through the comparison and separation algorithm, the separation detection and high-precision sensing of temperature and humidity are achieved.

[0076] Figure 3 The figure is a schematic diagram of the random weak reflection unit of the multi-core fiber. By using the randomness of the etching period, high-sensitivity sensing is achieved.

[0077] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention. The structures, devices, and operation methods not specifically described and explained in the present invention, unless otherwise specifically stated and limited, are implemented according to the conventional means in this field.

Claims

1. An absolute temperature measurement device based on a random weak reflection grating, characterized in that: Including: Swept laser module: including a narrow linewidth tunable laser (101) and a first fiber optic coupler (102); Temperature sensing module: including a random weak reflection fiber grating (201), a temperature chamber (202), and a temperature sensing probe (203); Main interferometer module: including a second fiber optic coupler (301), a circulator (302), a polarization controller (303), and a polarization grading photodetector (304); Auxiliary interferometer module: including a third fiber optic coupler (401), a delay fiber (402), an auxiliary interference fiber (403), a fourth fiber optic coupler (404), and a second photodetector (405); The data acquisition and processing module includes a data acquisition card (501) and a host computer (502); The narrow linewidth tunable laser (101) outputs swept laser to the first fiber optic coupler (102) for laser beam splitting. One port is incident on the third fiber optic coupler (401) of the auxiliary interferometer module, and the remaining ports are incident on the second fiber optic coupler (301) of the main interferometer module; The light incident on the main interferometer module is further split by the second fiber optic coupler (301). One of the light beams transmitted through a port of the main interferometer passes through the polarization controller (303) and is transmitted to the polarization grading photodetector (304). The two signals form a beat frequency. After the polarization beat frequency of the polarization grading photodetector (304), they are respectively transmitted to the data acquisition card (501) of the data acquisition and processing module; The light from the remaining port after further splitting by the second fiber optic coupler (301) is incident on the "1" port of the circulator (302), then circulates to the "2" port and enters the random weak reflection fiber grating (201) in the temperature sensing probe (203) arranged inside the temperature chamber (202). The swept light is transmitted in the random weak reflection fiber grating (201), and after weak reflection, it is re-transmitted to the "2" port of the circulator (302). Then, through the action of the circulator (302), it reaches the "3" port of the circulator (302), and then is transmitted to the polarization grading photodetector (304); The light from another port after beam splitting from the narrow linewidth tunable laser (101) is incident on the third fiber optic coupler (401) of the auxiliary interferometer module. Among them, one path passes through the delay fiber (402) to simulate the interference length of the sensing fiber optical path of the main interferometer module and is transmitted to the fourth fiber optic coupler (404); the other path of light is directly transmitted through the optical fiber path of the auxiliary interference fiber (403) to simulate the interference arm path of the main interferometer, and then is transmitted to the fourth fiber optic coupler (404); the two split light beams form a beat frequency optical signal through the fourth fiber optic coupler (404), are transmitted to the second photodetector (405), and then are also transmitted to the data acquisition card (501); The data acquisition card (501) receives the signals from the main interferometer module and the auxiliary interferometer module, and transmits their numerical values to the host computer (502) for data processing; The data acquisition and processing module is based on the optical frequency domain reflection algorithm of polarization analysis. It transforms the beat frequency signal obtained by the auxiliary interferometer module to obtain the phase change amount of the light source, and then obtains the optical frequency change amount of the light source through frequency domain transformation. After that, interpolation resampling is used to perform equal optical frequency acquisition on the beat frequency signal obtained by the auxiliary interferometer, and interpolation is used as the acquisition point of the main interferometer to collect the signal obtained by the main interferometer, so as to correct the nonlinear noise of the narrow linewidth tunable laser (101). The optical frequency domain reflection algorithm uses frequency domain conversion to convert the compensated beat frequency time domain signal into a frequency domain signal, and obtains the information of the compensated beat frequency signal in the distance domain, so as to extract the frequency component and distance information of the signal. The data acquisition and processing module realizes the temperature sensing of the main interferometer path through the temperature sensing probe (203); uses the polarization grading photodetector (304) to realize the collection of the beat frequency of polarized light in different polarization directions, and reduces the influence of polarization fading on temperature sensing; uses the auxiliary interferometer module to correct the nonlinear noise of the swept frequency laser; uses the high-speed acquisition card and the upper computer (502) to realize the setting of temperature sensing parameters and the real-time correction of nonlinear noise; uses a random weak reflection fiber grating to replace the traditional periodic fiber grating, and uses the multiple reflections of photons in the disordered medium to realize high-precision absolute temperature sensing and determination, and finally outputs the temperature result.

2. The absolute temperature measurement device based on a random weak reflection grating according to claim 1, wherein: The narrow linewidth tunable laser (101) has functions of external adjustable sweep range and sweep speed. The sweep wavelength of the narrow linewidth tunable laser (101) is within the reflection wavelength range of the random weak reflection fiber grating (201). The functions of the first fiber coupler (102) and the second fiber coupler (301) are to distribute the swept frequency optical energy, and perform different energy distributions for the main interferometer and the auxiliary interferometer, and finally form a beat frequency signal.

3. The absolute temperature measurement device based on a random weak reflection grating according to claim 1, characterized in that: The function of the polarization controller (303) is to precisely adjust the polarization state of the optical signal in the optical fiber, including the polarization direction, the shape and amplitude of the polarization ellipse. The function of the circulator (302) is to allow the optical signal to be transmitted in a single direction and prevent the propagation of the reverse optical signal. The function of the polarization grading photodetector (304) is to adjust the arrangement of optical elements and the polarization response characteristics to realize sensitive detection of different polarization light states.

4. The absolute temperature measurement device based on a random weak reflection grating according to claim 1, characterized in that: The function of the third fiber coupler (401) is to achieve equal power distribution of the input optical signal and the output optical signal through its symmetric structure. The delay optical fiber (402) adjusts the propagation time of the optical signal in the optical fiber by selecting a specific length and fiber type, and precisely controls the signal delay. The function of the fourth fiber coupler (404) is to use the symmetric structure to interfere the delay optical fiber 402 of the auxiliary interferometer with the interference optical fiber to obtain a beat frequency signal.

5. The absolute temperature measurement device based on a random weak reflection grating according to claim 1, wherein: The data acquisition card (501) accurately synchronizes the output of the laser and the reflection signal through high-speed sampling, and captures the optical intensity data in the main interferometer and the auxiliary interferometer in real time, and at the same time performs preliminary data processing. The host computer (502), by connecting with the data acquisition card 501 and corresponding hardware devices, is responsible for receiving, storing and processing the acquisition data from the system, and executing signal analysis and processing algorithms.

6. The absolute temperature measurement device based on a random weak reflection grating according to claim 1, wherein: The temperature sensing probe (203) uses a metal shell to protect the internal random weak reflection grating, and the end of the probe is fixed and sealed with glue.

7. The absolute temperature measurement device based on a random weak reflection grating according to claim 1, characterized in that: The temperature chamber (202) is used to provide a controllable temperature environment; the temperature chamber (202) precisely adjusts and stabilizes the temperature change around the optical fiber, so that the reflection spectrum characteristics of the random weak reflection grating in the optical fiber change predictably with the temperature change.

8. The absolute temperature measurement device based on a random weak reflection grating according to claim 1, characterized in that: The random weak reflection fiber grating (201) in the temperature sensing probe 203 forms weak reflection waves by introducing tiny reflection regions inside the optical fiber and utilizing the interaction between the optical signal and these regions; when the ambient temperature changes, the optical characteristics of the fiber grating also change accordingly; by monitoring the changes in these reflection spectra, the temperature of the environment where the optical fiber is located is detected.

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