Linear temperature measurement system and method based on single-point enhanced heat source positioning

Abstract

The invention provides a linear temperature measurement system and method based on single-point enhanced heat source positioning, and the system carries out the positioning of an abnormal temperature section through a sensing optical cable, and carries out the positioning of an abnormal cable in the abnormal temperature section through a point-type probe in an optical fiber sensor. Therefore, high-precision positioning of the abnormal temperature of a plurality of long-distance cables arranged side by side is realized.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic temperature measurement technology, specifically relating to a linear temperature measurement system based on single-point enhanced heat source positioning, and also to a linear temperature measurement method based on single-point enhanced heat source positioning. Background Technology

[0002] In modern cable laying applications, especially for power cables buried underground or laid in cable trenches, temperature monitoring of their operating status is of paramount importance. Currently, common temperature monitoring methods include placing point sensors at key locations, using infrared probes, or conducting infrared probe inspections. With the development of fiber optic temperature measurement technology, distributed fiber optic temperature monitoring technology is gradually being widely used in cable and pipeline monitoring. This system relies on the fiber itself as a sensor, possessing the common technical advantages of fiber optics, such as no self-heating and resistance to electromagnetic interference, and can achieve long-distance continuous temperature monitoring along the length of the cable. However, although this technology can identify temperature anomalies in a specific area, its positioning accuracy remains at the "regional level" when monitoring multiple cables simultaneously, failing to accurately determine which specific cable is faulty, still requiring manual on-site inspection for confirmation. Currently, there is a lack of a device that can achieve both long-distance distributed temperature measurement and effectively solve the problems of multi-cable identification and accurate positioning. Summary of the Invention

[0003] The primary objective of this invention is to provide a linear temperature measurement system based on single-point enhanced heat source positioning, thereby addressing the shortcomings of existing technologies in identifying and locating abnormal temperatures of multiple parallel cables laid over long distances with low accuracy.

[0004] A second objective of this invention is to provide a linear temperature measurement method based on single-point enhanced heat source positioning.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A linear temperature measurement system based on single-point enhanced heat source localization includes an optical fiber sensor and a sensing optical cable.

[0007] The fiber optic sensor includes a multi-core fiber segment, several single-core fiber segments, and several point probes; one end of each single-core fiber segment is connected to the multi-core fiber segment, and the other end is connected to the point probe.

[0008] The sensing optical cable includes sensing optical fibers;

[0009] The fiber optic sensor and the sensing cable are coupled into a combined body, such that the combined body is arranged in a trigonometric function waveform along the direction of several cables under test, and each cable under test is fixedly connected to one of the point probes.

[0010] In this invention, the sensing optical cable further includes an end probe; the end probe is coupled to the sensing optical fiber, such that the end probe is positioned at the cable under test. By coupling the end probe to the end of the sensing optical fiber, temperature monitoring at a specific location can be achieved, while simultaneously calibrating the temperature measured by the sensing optical fiber, thereby improving temperature measurement accuracy.

[0011] In this invention, both the point probe and the end probe are gallium arsenide probes.

[0012] In some embodiments of the present invention, the sensing optical fiber is provided with different temperature measurement sections, and a set of point-type optical fiber sensors is set in each temperature measurement section corresponding to the optical fiber sensor. The point-type optical fiber sensor is composed of several single-core optical fiber segments and several point probes. This arrangement can increase the accuracy of abnormal temperature location.

[0013] The present invention also includes a temperature demodulation device, which is connected to a multi-core fiber segment of an optical fiber sensor and to a sensing fiber of a sensing optical cable.

[0014] In some embodiments of the present invention, the temperature demodulation device is provided with a light source module and a spectral demodulation module; the light source module includes a first light source and a second light source, such that the first light source serves as the working light source of the point probe, and the first light source and the second light source are coupled to serve as the overall working light source of the sensing fiber and the end probe.

[0015] Furthermore, the wavelength of the first light source covers the range in which the wavelength of the gallium arsenide crystal changes due to temperature variations; the wavelength of the second light source is in a band outside the wavelength of the first light source.

[0016] Furthermore, the second light source is a pulsed laser light source.

[0017] In some embodiments of the present invention, the temperature demodulation device further includes a data output module, which is connected to the spectral demodulation module.

[0018] The present invention can be improved in the following way, and also includes a wavelength division multiplexer, which couples the first light source and the second light source into the sensing fiber, and when the return light is received, separates the return light of the first light source and the return light of the second light source and demodulates them separately through the spectral demodulation module.

[0019] In some embodiments of the present invention, the optical fiber sensor and the sensing optical fiber are encapsulated as a single unit by an outer sheath, and several connection ends extend from the single-core optical fiber segment and the point probe of the optical fiber sensor.

[0020] A linear temperature measurement method based on single-point enhanced heat source localization includes the following steps:

[0021] S1. Construct a linear temperature measurement system based on single-point enhanced heat source localization, select a temperature measurement section to establish a temperature field model, and deploy fiber optic sensors and sensing optical cables on several cables to be tested.

[0022] S2, a dual-source fiber optic sensor and a sensing optical cable are used to obtain a first spectral signal and a second spectral signal, respectively; the first spectral signal is demodulated to obtain the first temperature of each cable in each temperature measurement section of several cables under test; the second spectral signal is demodulated to obtain the third temperature at a specific location along the sensing optical cable.

[0023] S3. Calculate the distance of the abnormal temperature based on the abnormal temperature information in the third temperature at a specific location along the sensing optical cable, determine the abnormal temperature measurement section, and then locate the abnormal cable within the abnormal temperature measurement section using the first temperature of different cables.

[0024] In this invention, in step S2, the obtained first spectral signal is temperature demodulated to obtain the first temperature at several different temperature measurement points of the cable under test. The specific process is as follows: the first light source is input into the fiber optic sensor to obtain the first spectral signal. The first spectral signal is demodulated according to the pre-calibrated absorption edge-temperature relationship. The absorption edge of the first spectral signal is analyzed to obtain the first temperature.

[0025] Furthermore, the absorption edge of the first spectral signal is specifically analyzed as follows: when light passes through gallium arsenide material, when the photon energy exceeds the energy E of the gallium arsenide bandgap... g At time (T), the material absorbs the photon energy of light, while the remaining light continues to propagate through transmission. The absorption-transmission wavelength boundary λ of its absorption spectrum... g It changes with temperature:

[0026] λ g (T)=hc / E g (T)

[0027] Where h is Planck's constant and c is the speed of light.

[0028] In this invention, step S2 involves temperature demodulation of the second spectral signal to obtain a second temperature at the end of the sensing optical cable and a third temperature at a specific location along the sensing optical cable, including the following steps:

[0029] S201, a dual-source input sensing optical cable coupled with a first source and a second source is used to obtain a second spectral signal, which includes a first spectrum, a second spectrum, and a third spectrum; the first spectrum is obtained from the first source input sensing optical cable, and the second and third spectra are obtained from the second source input sensing optical cable.

[0030] S202. Demodulate the first spectrum according to the pre-calibrated absorption edge-temperature relationship, analyze the absorption edge of the first spectrum to obtain the second temperature; and obtain the third temperature at a specific location along the sensing optical fiber by analyzing the ratio of the second spectrum and the third spectrum according to the pre-calibrated ratio function and temperature relationship.

[0031] In this invention, the ratio function of the second spectrum and the third spectrum

[0032]

[0033] Wherein, the subscript S represents Stokes light and AS represents anti-Stokes light; the system integration coefficient corresponding to the K fiber channel is determined through actual calibration, S is the fiber backscattering factor, v is the frequency of the scattered photon, h is Planck's constant, Δv is the Raman frequency shift, and the absolute value of the difference between the frequencies of the returned second / third spectrum and the incident spectrum is equal to the sum of the two.

[0034] In this invention, in step S3, the distance to the abnormal temperature is calculated based on the abnormal temperature information at a specific location along the sensing optical cable. The specific process is as follows: Based on the time t it takes for the return light carrying the abnormal temperature information in the third temperature sensor to reach the temperature demodulation device, the distance L in the sensing optical cable where the abnormal temperature is located can be obtained.

[0035]

[0036] Where n is the refractive index of the optical fiber.

[0037] Furthermore, the distance L to the location of the anomalous temperature is corrected using an average correction factor to obtain the straight-line distance to the anomalous temperature, as detailed below:

[0038]

[0039] Where k is the average elongation coefficient of the wave shape.

[0040]

[0041] Where A is the amplitude of the wave, λ0 is the wavelength of the wave, u is the current position within the period (λ0), and 0≤u≤λ0.

[0042] In this invention, in step S3, the abnormal cable is located by the first temperature of different cables within the abnormal temperature measurement section. The specific process is as follows: fiber optic sensors deployed on different cables within the same temperature measurement section are grouped together. A temperature difference threshold ΔT is set. The temperature difference between each pair of the first temperatures obtained by each fiber optic sensor is retrieved. When the temperature difference between a certain first temperature and the first temperature of other cables exceeds the threshold, it is determined that there is an abnormal temperature cable. The abnormal cable is located based on the comparison result.

[0043] The present invention can also be improved as follows: S3 further includes calibrating the third temperature using the second temperature, and then using the calibrated temperature information to determine the abnormal temperature measurement section. The specific process is as follows: The first temperature of several sets of fiber optic sensors along the line is used as calibration anchor points. At this time, the second temperature of the probe at the end of the sensing fiber can be used as a reference calibration anchor point. Curve fitting is performed along the length of the sensing fiber to generate a temperature calibration deviation curve. The original measurement data of the sensing optical cable is calibrated, thereby realizing the calibration of the third temperature using the second temperature. By calibrating the third temperature, the temperature measurement accuracy is improved.

[0044] The present invention has the following beneficial effects:

[0045] (1) The linear temperature measurement system based on single-point enhanced heat source positioning of the present invention locates the abnormal temperature section through the sensing optical cable, and then locates the abnormal cable in the abnormal temperature section through the midpoint probe of the fiber optic sensor, thereby realizing high-precision positioning of the abnormal temperature of multiple parallel cables over a long distance.

[0046] (2) The present invention is based on a linear temperature measurement method for single-point enhanced heat source location. The cable temperature is measured by fiber optic sensor and sensing cable, thereby realizing the location of abnormal cable temperature. At the same time, the temperature is calibrated and the temperature data processing is optimized to improve the accuracy of abnormal temperature location.

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the linear temperature measurement system based on single-point enhanced heat source positioning of the present invention deployed on the cable under test in a cable trench.

[0049] Figure 2 This is a linear temperature measurement system based on single-point enhanced heat source positioning, as described in Embodiment 1 of the present invention.

[0050] Figure 3 This is Embodiment 2 of the present invention: a linear temperature measurement system based on single-point enhanced heat source localization.

[0051] Figure 4 This is Embodiment 3 of the present invention, a linear temperature measurement system based on single-point enhanced heat source positioning;

[0052] Figure 5 This is a schematic diagram of the linear temperature measurement method based on single-point enhanced heat source positioning according to the present invention.

[0053] The following labels are used in the attached diagram: 1. Temperature demodulation device; 2. Fiber optic sensor; 3. Sensing optical cable; 4. Wavelength division multiplexer; 5. Cable trench; 6. Cable; 101. Light source module; 102. Spectrum demodulation module; 201. Multi-core fiber segment; 202. Single-core fiber segment; 203. Point probe; 301. Sensing fiber; 302. End probe. Detailed Implementation

[0054] This invention provides a linear temperature measurement system and method based on single-point enhanced heat source localization. First, a linear temperature measurement system based on single-point enhanced heat source localization is constructed. Then, a cable temperature field model is established and its distribution is displayed. Different light sources are provided for distributed optical fibers with gallium arsenide (GaAs) point probes and end-coupled GaAs probes. The returned light from each point is demodulated. Abnormal temperature ranges are located through distributed positioning. When an abnormal range exists, the abnormality is determined by checking whether the abnormal temperature is monitored by nearby GaAs probes. If true, the abnormality location and cable information are output. For long-term operation, using the GaAs probe at the end of the distributed optical fiber as a base point, linear fitting is performed using data from multiple sets of GaAs probes along the route to calibrate the distributed optical fiber data.

[0055] Example 1

[0056] like Figure 1-2 The linear temperature measurement system based on single-point enhanced heat source localization shown includes an optical fiber sensor 2, a sensing optical cable 3, and a temperature demodulation device 1.

[0057] The fiber optic sensor 2 includes a multi-core fiber segment 201, several single-core fiber segments 202, and several point probes 203; each single-core fiber segment 202 is connected at one end to the multi-core fiber segment 201 and at the other end to the point probe 203; the sensing optical cable 3 includes a sensing fiber 301 and an end probe 302; the end probe 302 and the sensing fiber 301 are coupled together. In this embodiment, both the point probe 203 and the end probe 302 are gallium arsenide probes.

[0058] Fiber optic sensor 2 and sensing fiber optic cable 3 are coupled into a single unit, arranged in a trigonometric waveform along the direction of several cables 6 to be tested. The cables 6 are located within cable trench 5, and each cable 6 is fixedly connected to a point probe 203, secured at intervals or with thermally conductive adhesive as needed. Point probes 203 are positioned on several cables 6, the number matching the number of cables 6. The sensing fiber optic cable 3 is longer than or equal to the length of the cables 6, preferably longer. The fiber optic sensor 2 is shorter than the sensing fiber 301, allowing the point probes 203 to be positioned at specific locations before and during the middle section of the sensing fiber 301, with the specific locations determined as needed. An end probe 302 is positioned at the cable 6 to monitor the temperature at a predetermined location at a considerable distance from the cable 6, and also serves as a reference point for calibrating the temperature measurement of the entire sensing fiber 301 within the sensing fiber optic cable 3, improving positioning accuracy.

[0059] Temperature demodulation device 1 is connected to the multi-core fiber segment 201 of fiber optic sensor 2, and also to the sensing fiber 301 of sensing optical cable 3. Temperature demodulation device 1 includes a light source module 101, a spectral demodulation module 102, and a data output module. The light source module 101 includes a first light source and a second light source. The first light source serves as the working light source for the point probe 203 of fiber optic sensor 2 and the end probe 302 of sensing optical cable 3, while the second light source serves as the working light source for the sensing fiber 301. The wavelength of the first light source covers the range of wavelength changes in gallium arsenide crystals due to temperature variations, such as the characteristic wavelength band of 880nm. The second light source is a pulsed laser light source, and its wavelength is outside the wavelength range of the first light source, typically including pulsed laser light sources in the 1550nm band.

[0060] Example 2

[0061] like Figure 3 The linear temperature measurement system based on single-point enhanced heat source positioning shown differs from Embodiment 1 in that it also includes a wavelength division multiplexer 4, which couples the first light source and the second light source into the distributed optical fiber, serving as the working light source for the sensing optical fiber 301 and the end probe 302 as a whole, and demodulates the returned light from the first light source and the second light source separately when the returned light is received.

[0062] Example 3

[0063] like Figure 4The linear temperature measurement system based on single-point enhanced heat source localization shown differs from Embodiment 1 in that multiple sets of fiber optic sensors 2 are provided. The sensing fiber 301 is divided into different temperature measurement sections, such as at the two ends of the cable under test 6, the intermediate joint, and the contact position between the conductor and the fittings, with point probes 203 added as the length of the cable under test 6 increases. Specifically, a set of point fiber optic sensors 2 is set in the corresponding single-core fiber segment 202 of the fiber optic sensor 2 within each temperature measurement section. By setting different temperature measurement sections and fiber optic sensors 2, the accuracy of abnormal temperature localization can be increased.

[0064] Example 4

[0065] A linear temperature measurement method based on single-point enhanced heat source localization includes the following steps:

[0066] S1. Construct a linear temperature measurement system based on single-point enhanced heat source localization, select a temperature measurement section to establish a temperature field model, and deploy fiber optic sensors and sensing optical cables on several cables to be tested.

[0067] The specific process is as follows: Construct the linear temperature measurement system based on single-point enhanced heat source positioning as in Example 3. The data output module selects temperature measurement sections along the length of the cable trench and establishes a segmented temperature field model. Fiber optic sensors and sensing cables are deployed on several cables to be tested. The fiber optic sensors can be evenly distributed in each temperature measurement section or distributed according to important nodes along the cable, such as at the cable end joints, intermediate joints, and conductor-fitting contact points. Point probes are added as the length of the cable increases.

[0068] S2. A dual-source fiber optic sensor and a sensing optical cable are input to obtain a first spectral signal and a second spectral signal, respectively. The first spectral signal is demodulated to obtain the first temperature (actual temperature) of each cable in each temperature measurement section of the cable under test. The second spectral signal is demodulated to obtain the third temperature at a specific location along the sensing optical cable.

[0069] The specific process is as follows:

[0070] The system illuminates the overall light source and inputs the light source into the fiber optic sensor and sensing cable. The fiber optic sensor is a single light source input, only inputting the first light source; the sensing cable is a dual light source coupled input, simultaneously inputting the first and second light sources.

[0071] like Figure 5As shown, the first light source reaches the point probe of the fiber optic sensor. After the point probe absorbs part of the light, it reflects the remaining light back to the spectral demodulation module. During the transmission of the coupled dual light sources in the sensing fiber, scattering occurs continuously. The scattered light is reflected back to the spectral demodulation module, and the remaining light continues to be transmitted until it reaches the end point probe. After the point probe absorbs part of the light, it reflects the remaining light back to the spectral demodulation module.

[0072] The temperature demodulation process of the fiber optic sensor is as follows:

[0073] After the first light source is reflected back by the point probe, it forms the first spectral information on the spectral demodulation module. The first spectral information is demodulated by the pre-calibrated absorption edge-temperature relationship, and the first temperature is obtained by analyzing the absorption edge of the first spectral information.

[0074] The absorption edge is specifically defined as follows: When broadband light passes through a direct bandgap semiconductor such as gallium arsenide (GaAs), some wavelengths of light are absorbed by GaAs, while the remaining light is transmitted. The wavelength boundary between the absorbed and transmitted light is called the absorption edge. When the light from the first light source reaches the GaAs probe at the end of the point fiber optic sensor, the absorption edge of GaAs is defined as: when the photon energy exceeds the GaAs bandgap energy E... g At time (T), the material absorbs the photon energy of light, while the remaining light continues to propagate through transmission. The absorption-transmission wavelength boundary λ of its absorption spectrum... g It changes with temperature:

[0075] λ g (T)=hc / E g (T)

[0076] Where h is Planck's constant, c is the speed of light, and E is the speed of light. g (T) is the bandgap energy.

[0077] E g (T) is related to temperature:

[0078]

[0079] Among them, E g (0) represents the bandgap energy at temperature 0 K, and γ and β are material constants. For gallium arsenide, its E g (0) = 1.522 eV, γ = 5.8 × 10 -4 eV / K, β=300K.

[0080] Then there is,

[0081]

[0082] Therefore, the absorption edge λ g(T) is positively correlated with temperature. As temperature increases, the absorption edge shifts towards longer wavelengths (redshift). Based on actual calibration, the absorption edge of gallium arsenide material at each temperature is obtained, yielding the absorption edge-temperature relationship. The first temperature of several cables in contact with several gallium arsenide sensors is obtained by demodulation based on the pre-calibrated absorption edge-temperature relationship.

[0083] The fiber optic temperature demodulation process is as follows:

[0084] After the dual-source input sensing optical cable of the first and second light sources is coupled, the returned light is processed in the spectral demodulation module by extracting the Raman scattering signal in the returned light, first forming the second and third spectra, and then simultaneously forming the first, second, and third spectra.

[0085] The first light source is reflected back by the end probe to form a first spectrum. The second temperature at the end of the sensing fiber is obtained by analyzing the absorption edge of the first spectrum.

[0086] During the transmission of the second light source in the sensing fiber, the scattered light emitted reaches the spectral demodulation module to form a second spectrum and a third spectrum. The ratio of the second spectrum to the third spectrum is obtained, and the third temperature along the sensing fiber is obtained by analyzing the pre-calibrated ratio-temperature relationship.

[0087] Distributed fiber demodulation specifically involves:

[0088] When light propagates in an optical fiber, light scattering occurs simultaneously, mainly including Rayleigh scattering, Brillouin scattering, and Raman scattering. Raman scattering includes Stokes light and anti-Stokes light. The intensity change of anti-Stokes light is more sensitive to light intensity. Therefore, the system mainly demodulates based on the relationship between anti-Stokes light and temperature change. In actual demodulation, in order to remove the influence of fiber loss on the demodulation result, temperature demodulation is performed using the ratio of the intensity of anti-Stokes light to that of Stokes light.

[0089] Among them, the luminous flux Φ of Stokes light S for

[0090]

[0091] Luminous flux Φ of anti-Tox light AS for

[0092]

[0093] In this system, the subscript S represents Stokes light, AS represents anti-Stokes light, and O represents incident light; the system integration coefficient corresponding to the K fiber channel is determined through actual calibration, S is the fiber backscattering factor, and v is the frequency of the scattered photons. Let α be the incident light flux, α be the average light transmission loss in the optical fiber, and L be the distance the light source travels in the optical fiber.

[0094] In the thermal equilibrium state of an optical fiber, the distribution of molecules at different energy levels follows the Boltzmann distribution.

[0095]

[0096] The temperature T of the Stokes light is modulated by the Boltzmann constant k and the modulation function R. S (T)

[0097]

[0098] The temperature of the anti-Stokes light is related to the modulation function R of the Boltzmann constant k. AS (T)

[0099]

[0100] Where h is Planck's constant, Δv is the Raman frequency shift, and the absolute value of the difference between the frequencies of the returned second / third spectrum and the incident spectrum is equal to h.

[0101] The ratio function of the two

[0102]

[0103] Based on actual calibration, the ratio at each temperature is obtained, resulting in a ratio-temperature relationship. By using the pre-calibrated ratio function's curve as a function of temperature, the third temperature at a specific location along the sensing fiber in the sensing cable is demodulated.

[0104] S3. Calculate the distance of the abnormal temperature based on the abnormal temperature information in the third temperature at a specific location along the sensing optical cable, determine the abnormal temperature measurement section, and then locate the abnormal cable within the abnormal temperature measurement section using the first temperature of different cables.

[0105] The specific process is as follows:

[0106] (1) Locating abnormal temperature zones:

[0107] Based on the time t it takes for the return light carrying the abnormal temperature information to reach the temperature demodulation device, the distance L in the sensing optical cable where the abnormal temperature is located can be obtained.

[0108]

[0109] Where n is the refractive index of the optical fiber.

[0110] Since the actual deployment of sensing optical cables roughly resembles a trigonometric function waveform, the actual locations of anomalies in the cable trenches need to be corrected. The average correction factor method is used for location correction.

[0111]

[0112] Where k is the average elongation coefficient of the wave shape.

[0113]

[0114] Where A is the amplitude of the wave, λ0 is the wavelength of the wave, u is the current position within the period (λ0), and 0≤u≤λ0.

[0115] The calibration can also be based on the actual on-site deployment method, and the obtained position is the location of the third temperature.

[0116] (2) Authenticity diagnosis and abnormal cable location

[0117] When an abnormal temperature is detected in the third temperature range (based on a comparison with the set monitoring value), the location of the third temperature can be obtained through the above method. This will indicate the area of ​​the abnormal temperature on the long-distance cable under test. However, it is still impossible to determine which of the several cables under test has the abnormal temperature.

[0118] A group of fiber optic sensors deployed on different cables within the same section is used. A temperature difference threshold ΔT is set, and the temperature difference between each pair of first temperatures obtained by each fiber optic sensor is retrieved. When the temperature difference between a certain first temperature and the first temperature of other cables exceeds the threshold, it is determined that there is an abnormal temperature cable, and the source of the abnormal third temperature can be located based on the comparison result.

[0119] (3) Output of Results

[0120] Abnormal temperature sections can be located based on temperature data from sensing optical cables, and abnormal cables can be located based on temperature data from fiber optic sensors. These abnormalities are then displayed simultaneously in the cable temperature field model, making it easier for maintenance personnel to troubleshoot.

[0121] (4) Data calibration

[0122] Point-type fiber optic sensors typically offer higher temperature measurement accuracy and stability than sensing optical cables. However, after prolonged operation, the second light source, being a pulsed laser, may experience aging, potentially leading to temperature demodulation errors. Therefore, the sensing fiber optic temperature is calibrated based on the temperature of the cable detected by the point-type end probe. Specifically:

[0123] In the absence of abnormal temperature alarms, calculate the average temperature {T1} of each group of fiber optic sensors, and read the temperature {T2} of the sensing cable at the location of each group of fiber optic sensors, and calculate the calibration deviation.

[0124] When there is only one fiber optic sensor in each group, the temperature at that point is used directly to calibrate the data of the sensing fiber optic cable.

[0125] Using the first temperature of several sets of fiber optic sensors along the line as calibration anchor points, the second temperature of the point-type end probe of the sensing fiber can be used as a reference calibration anchor point (because it is coupled with the sensing fiber, the temperature difference at the junction of the two is the smallest). Curve fitting is performed along the length of the sensing fiber, such as linear fitting, spline interpolation, etc., to generate a temperature calibration deviation curve, and the original measurement data of the sensing fiber is calibrated, thereby realizing the calibration of the third temperature.

[0126] The above embodiments of the present invention are not intended to limit the scope of protection of the present invention. The implementation of the present invention is not limited thereto. All other modifications, substitutions or alterations made to the above structure of the present invention based on the above content of the present invention, in accordance with ordinary technical knowledge and common practice in the field, without departing from the basic technical idea of ​​the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A linear thermometry system based on single point enhanced heat source localization, characterized in that, The system comprises a fiber sensor and a sensing optical cable; The fiber sensor comprises a multi-core fiber segment, a plurality of single-core fiber segments and a plurality of point probes; one end of each single-core fiber segment is connected to the multi-core fiber segment, and the other end is connected to the point probe; The sensing optical cable comprises a sensing fiber and a terminal probe; the terminal probe and the sensing fiber are coupled to each other, so that the terminal probe is arranged at the cable to be measured; The fiber sensor and the sensing optical cable are coupled into a combination, so that the combination is arranged in a trigonometric function waveform along the trend direction of the cables to be measured, and each cable to be measured is fixedly connected to a point probe.

2. The linear temperature measurement system based on single-point enhanced heat source localization according to claim 1, wherein, The sensing fiber is provided with different temperature measurement segments, and a group of point fiber sensors are arranged in the fiber sensor corresponding to each temperature measurement segment; the point fiber sensor is composed of a plurality of single-core fiber segments and a plurality of point probes.

3. The linear thermometry system based on single-point enhanced heat source localization according to any of claims 1-2, characterized in that, The system further comprises a temperature demodulation device, which is connected to the multi-core fiber segment of the fiber sensor and the sensing fiber of the sensing optical cable; the temperature demodulation device is provided with a light source module and a spectrum demodulation module; the light source module comprises a first light source and a second light source, so that the first light source serves as the working light source of the point probe, and the first light source and the second light source are coupled to serve as the working light source of the whole sensing fiber and terminal probe.

4. The linear temperature measurement system based on single-point enhanced heat source localization according to claim 3, wherein, The point probe and the terminal probe are both gallium arsenide probes; the wavelength of the first light source covers the range of wavelength change of the gallium arsenide crystal caused by temperature change; the second light source is a pulse laser light source; the wavelength of the second light source is in a wavelength band outside the wavelength of the first light source.

5. The linear temperature measurement system based on single-point enhanced heat source localization according to claim 4, wherein, The system further comprises a wavelength division multiplexer, so that the wavelength division multiplexer couples the first light source and the second light source into the sensing fiber, and separates the return light of the first light source and the second light source when receiving the return light, and respectively demodulates the return light through the spectrum demodulation module.

6. A linear thermometry method based on single point enhanced heat source localization, characterized in that, The system comprises the following steps: S1, constructing a linear temperature measurement system based on single-point enhanced heat source positioning according to any one of claims 1-5, selecting a temperature measurement segment to establish a temperature field model, and arranging fiber sensors and sensing optical cables on a plurality of cables to be measured; S2, inputting the fiber sensor and the sensing optical cable with double light sources to obtain a first spectrum signal and a second spectrum signal respectively; performing temperature demodulation on the obtained first spectrum signal to obtain the first temperature of each different cable in each temperature measurement segment of the cables to be measured; performing temperature demodulation on the second spectrum signal to obtain the third temperature of a specific position along the sensing optical cable; S3, calculating the distance of the abnormal temperature according to the abnormal temperature information in the third temperature of the specific position along the sensing optical cable, determining the abnormal temperature measurement segment, and then positioning the abnormal cable with the first temperature of different cables in the abnormal temperature measurement segment.

7. The linear thermometry method based on single-point enhanced heat source localization according to claim 6, wherein, In S2, the first temperature of different temperature measurement points of the cables to be measured is obtained by performing temperature demodulation on the obtained first spectrum signal, and the specific process is as follows: the first light source is input into the fiber sensor to obtain the first spectrum signal; the first spectrum signal is demodulated according to the pre-calibrated absorption edge-temperature relationship; and the first temperature is obtained by analyzing the absorption edge of the first spectrum signal.

8. The linear thermometry method based on single-point enhanced heat source localization of claim 6, wherein, S2 demodulating the second optical spectrum signal to obtain the second temperature of the sensing cable end and the third temperature of the sensing cable at a specific position along the line, including the following steps: S201, a double light source coupled with the first light source and the second light source inputs the sensing cable to obtain the second optical spectrum signal, the second optical spectrum signal includes the first spectrum, the second spectrum and the third spectrum; the first spectrum is obtained by inputting the sensing cable with the first light source, and the second spectrum and the third spectrum are obtained by inputting the sensing cable with the second light source; S202, demodulating the first spectrum according to the pre-calibrated absorption edge-temperature relationship, analyzing the absorption edge of the first spectrum to obtain the second temperature; through the ratio of the second spectrum and the third spectrum, according to the pre-calibrated ratio function and the temperature relationship, the third temperature of the sensing cable sensing fiber at a specific position along the line is obtained.

9. The linear thermometry method based on single-point enhanced heat source localization according to claim 8, wherein, In S3, the distance of the abnormal temperature is calculated according to the third temperature of the sensing cable at a specific position along the line, and the specific process is as follows: according to the time t of the return light carrying the abnormal temperature information in the third temperature reaching the temperature demodulation device, the distance L of the abnormal temperature in the sensing cable can be obtained Where n is the refractive index of the optical fiber.

10. The linear thermometry method based on single-point enhanced heat source localization according to claim 9, wherein, In S3, the abnormal cable is positioned at different cable first temperature in the abnormal temperature measurement section, and the specific process is as follows: the optical fiber sensors arranged on different cables in the same temperature measurement section are set as a group, a temperature difference threshold ΔT is set, the temperature difference between each first temperature obtained by each optical fiber sensor is searched, when there is a first temperature whose temperature difference with the first temperature of other cables exceeds the threshold, it is determined that there is an abnormal temperature cable, and the abnormal cable is positioned based on the comparison result.

Images