Optical fiber type temperature chain temperature measurement method and system based on thermosensitive fluorescent material

Abstract

The invention discloses an optical fiber type temperature chain temperature measurement method and system based on a thermosensitive fluorescent material, and belongs to the technical field of temperature measurement. The method comprises the steps that laser pulses are emitted and guided into a main optical fiber through light splitting, and a plurality of sensing units arranged on the main optical fiber at intervals are excited to generate fluorescence; each sensing unit contains a plurality of thermosensitive fluorescent materials, and two characteristic emission wavelengths lambda 1 and lambda 2 are selected. After a fluorescence signal is returned, light splitting and filtering are carried out, and corresponding intensities I (lambda1, T) and I (lambda2, T) are acquired by a photoelectric detector. Through time resolution processing, each sensing unit is positioned according to an optical path difference introduced by an optical path differentiation structure, an intensity ratio is calculated, a nonlinear mapping relation is established in combination with a modified Planck radiation formula, the temperature of each unit is acquired through inversion, and multi-point distributed high-precision temperature measurement is realized. According to the optical fiber type temperature chain temperature measurement method and system based on the thermosensitive fluorescent material, multi-point distributed temperature measurement can be achieved, precision and anti-interference performance are improved, and stability and reliability are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of temperature measurement, and in particular relates to a temperature measurement method and system of an optical fiber temperature chain based on thermosensitive fluorescent materials. Background Art

[0002] Temperature measurement has important technical value in complex environment monitoring, especially the accurate perception of multi-point distributed temperature fields is crucial to research and application in related fields.

[0003] Traditional electrical or contact temperature sensors have significant technical limitations: First, they are mostly single-point measurement modes. If multi-point synchronous monitoring is required, a large number of independent sensors need to be deployed, resulting in a complex system structure, difficult deployment and high maintenance costs; second, they have weak anti-electromagnetic interference capabilities and poor stability in complex environments such as high voltage and strong corrosion, making it difficult to meet long-term continuous monitoring needs.

[0004] Fiber-optic temperature sensing technology has been used due to its resistance to electromagnetic interference and ease of long-distance transmission. However, traditional quartz fiber-optic temperature sensors have problems such as large bending radius, inconvenient installation, and sensitivity to vibration, which limit their deployment applicability in complex environments.

[0005] Fiber optic sensors that use fluorescent materials as temperature sensing media have been a research hotspot in recent years. They use the changes in the optical properties of fluorescent materials with temperature to achieve temperature measurement. However, in existing technologies, the influence of factors such as light source fluctuations and optical fiber transmission loss on temperature measurement accuracy has not been effectively solved, and the long-term stability and adaptability of the system to complex environments still need to be improved, which restricts its practical application in multi-point distributed temperature measurement. Summary of the Invention

[0006] In view of the shortcomings in the related art, the purpose of the present invention is to provide a fiber-optic temperature chain temperature measurement method and system based on thermosensitive fluorescent materials to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions: A temperature measurement method using an optical fiber temperature chain based on a thermosensitive fluorescent material, comprising: S1. Excitation and signal generation steps Laser pulses are emitted and introduced into the main optical fiber after spectroscopic processing, stimulating multiple sensing units spaced axially along the main optical fiber to produce fluorescence signals. Each sensing unit is composed of a structured area on the main optical fiber and a plurality of thermosensitive fluorescent materials coated on its surface. Two of the thermosensitive fluorescent materials are selected, and their characteristic emission wavelengths are λ1 and λ2. S2. Signal transmission and separation steps The fluorescence signal returns along the main optical fiber, is processed by spectrometry, and then guided to the detection module. The interference of the excitation light is filtered out by filtering. At least two photodetectors with different spectral response characteristics collect the fluorescence intensities I(λ1,T) and I(λ2,T) corresponding to the characteristic emission wavelengths λ1 and λ2, respectively. S3, spatial positioning step The fluorescence signal is time-resolved and the spatial position of each sensor unit is determined based on the optical path difference introduced by the optical path difference structure between adjacent sensor units. S4. Temperature inversion step Calculate the intensity ratio based on the fluorescence intensity I(λ1,T) and I(λ2,T) , combined with the modified Planck radiation formula, a nonlinear mapping relationship between intensity ratio and temperature is established, and the temperature information corresponding to each sensing unit is obtained by inversion.

[0008] In some embodiments, in the temperature inversion step S4, the fluorescence intensity I(λ,T) satisfies the modified Planck radiation formula:

[0009] in, C 1 is the first radiation constant, , h is Planck's constant, c is the speed of light, C 2 is the second radiation constant, , k is the Boltzmann constant, is the spectral emissivity of the thermosensitive fluorescent material.

[0010] In some embodiments, the temperature inversion step S4 specifically includes: S41. Nonlinear mapping relationship derivation steps Substitute the modified Planck radiation formula into the fluorescence intensity ratio formula, and use the temperature range and wavelength range applicable to typical fluorescence temperature measurement to obtain the corrected Planck radiation formula. The approximate conditions of , the nonlinear mapping relationship between intensity ratio and temperature is derived:

[0011] in, A is a constant, , B is a constant, ; S42. Temperature inversion calculation steps based on Relationship, inversion to obtain temperature value: .

[0012] In some embodiments, the S3 spatial positioning step specifically includes: S31, time gate signal generation step Based on the transmission time difference generated by the optical path difference structure between adjacent sensing units, a time gating signal corresponding to each sensing unit is generated, and the trigger delay of the time gating signal matches the preset position of the sensing unit; S32, high-speed sampling and time domain separation steps The fluorescence signal is sampled at a set sampling rate, and the fluorescence signal of each sensor unit is separated using a time-gated signal; S33, spatial position calculation steps According to the transmission speed of light in the optical fiber, the transmission time difference is converted into spatial distance to determine the spatial position of each sensor unit. The spatial distance formula is:

[0013] in, v is the transmission speed of light in the optical fiber, and Δt is the transmission time difference.

[0014] In some embodiments, in step S1, the multiple thermosensitive fluorescent materials coated on the surface of the sensing unit correspond to different sensitive temperature ranges, respectively; the fluorescence signals of the two thermosensitive fluorescent materials selected by each sensing unit within their respective corresponding sensitive temperature ranges can be effectively detected, and the fluorescence intensity of at least one thermosensitive fluorescent material within its sensitive temperature range is significantly higher than that of other thermosensitive fluorescent materials in the sensing unit, so as to form a characteristic response peak within the temperature range.

[0015] An optical fiber temperature chain temperature measurement system based on thermosensitive fluorescent materials, comprising: A main optical fiber is provided with a plurality of sensing units spaced apart along the axial direction. Each sensing unit is composed of an optical waveguide control structure and a plurality of thermosensitive fluorescent materials coated on its surface. Each thermosensitive fluorescent material in the same sensing unit has different temperature response characteristics. An excitation light source unit, which is used to emit laser pulses to the main optical fiber to stimulate each sensing unit to generate a fluorescence signal; A wavelength-selective spectrometer unit, comprising at least two spectrometers, configured to guide laser pulses to the primary optical fiber based on wavelength characteristics and to distribute the fluorescence signals returned by each sensing unit to corresponding detection paths; A filter unit, comprising at least one filter set, arranged in the detection path to filter out interference from the excitation light; A detection unit, comprising at least two photodetectors with different spectral response characteristics, for receiving fluorescence signals of different wavelengths processed by the filter unit; The signal processing unit is used to time-resolve the fluorescence signal to locate each sensing unit, calculate the intensity ratio of the fluorescence signal in different bands, and establish a nonlinear mapping relationship with temperature in combination with the Planck principle, thereby obtaining the temperature information corresponding to each sensing unit.

[0016] In some embodiments, an optical path differentiation structure is provided between adjacent sensing units, and the optical path differentiation structure is used to introduce a resolvable optical path difference between the fluorescence signals of different sensing units, thereby generating a transmission time difference to spatially resolve each sensing unit, wherein the transmission time difference is not less than twice the time resolution accuracy of the signal processing unit and not less than 10ns.

[0017] In some embodiments, the signal processing unit includes: a high-speed data acquisition module, wherein the high-speed data acquisition module is configured to digitally process the fluorescence signal at a set sampling rate; A timing control module, the timing control module is configured to generate a time gating signal corresponding to each sensing unit based on the transmission time difference introduced by the optical path differentiation structure; The temperature calculation module is configured to perform time-domain separation on the digitized fluorescence signal, extract the characteristic signal corresponding to each sensor unit, calculate the intensity ratio of the fluorescence signal in different bands, and establish a nonlinear mapping relationship between the intensity ratio and temperature in combination with the modified Planck radiation formula, and invert to obtain the temperature value at the position of each sensor unit.

[0018] In some embodiments, the signal processing unit further includes a spatial position calculation module, which is configured to convert the transmission time difference into a spatial distance based on the transmission time difference and the transmission speed of light in the optical fiber to calculate the spatial position of each sensing unit.

[0019] In some embodiments, the optical fiber temperature chain temperature measurement system based on thermosensitive fluorescent materials is entirely encapsulated in a sealed housing, and the sealed housing has a waterproof, pressure-resistant, and corrosion-resistant structure.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. The fiber-optic temperature chain temperature measurement method based on thermosensitive fluorescent materials provided by the present invention selects the characteristic wavelength intensity ratio of two thermosensitive fluorescent materials and combines it with the modified Planck radiation formula to derive a nonlinear mapping relationship, effectively eliminating the influence of light source fluctuations and transmission losses; at the same time, it uses the time difference introduced by the optical path difference to achieve spatial positioning, taking into account both temperature measurement accuracy and multi-point resolution capabilities, and is suitable for accurate perception of distributed temperature fields.

[0021] 2. The fiber-optic temperature chain measurement system based on thermosensitive fluorescent materials provided by the present invention integrates multiple sensing units through the main optical fiber, and is equipped with wavelength-selective spectroscopy and dual-channel detection. It has a compact structure and is resistant to electromagnetic interference. The whole is encapsulated in a waterproof and pressure-resistant shell, adapted to the marine environment, and combined with time resolution and space solution modules to achieve low-cost, long-term and stable distributed temperature monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 This is a method flow chart of an embodiment of the optical fiber temperature chain temperature measurement method and system based on thermosensitive fluorescent materials of the present invention; Figure 2 This is a schematic diagram of the system structure of an embodiment of the optical fiber temperature chain temperature measurement method and system based on thermosensitive fluorescent materials of the present invention; Figure 3 A schematic diagram of a typical groove structure of an embodiment of a temperature measurement method and system of an optical fiber temperature chain based on thermosensitive fluorescent materials of the present invention; Figure 4 This is a schematic diagram of another typical groove structure of an embodiment of the optical fiber temperature chain temperature measurement method and system based on thermosensitive fluorescent materials of the present invention; Figure 5 Schematic diagram of the fluorescence emission spectrum of a thermosensitive fluorescent material at 30° C. according to an embodiment of the optical fiber temperature chain temperature measurement method and system based on a thermosensitive fluorescent material of the present invention; Figure 6 Schematic diagram of the fluorescence emission spectrum of a thermosensitive fluorescent material at 20° C. according to an embodiment of the optical fiber temperature chain temperature measurement method and system based on a thermosensitive fluorescent material of the present invention; Figure 7 Schematic diagram of the fluorescence emission spectrum of a thermosensitive fluorescent material at 0°C according to an embodiment of the optical fiber temperature chain temperature measurement method and system based on a thermosensitive fluorescent material of the present invention.

[0023] In the picture: 1. Excitation light source; 2. Spectrum splitter; 3. Sensing unit; 31. Optical waveguide control structure; 32. Thermosensitive fluorescent material; 4. Filter set; 5. Photodetector; 6. Signal processing unit; 7. Main optical fiber. DETAILED DESCRIPTION

[0024] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0025] In the description of the present invention, it should be understood that the terms "center", "transverse", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0026] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediary, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0027] Example 1: See attached Figures 1 to 7 , provides an exemplary embodiment of the optical fiber temperature chain temperature measurement method based on thermosensitive fluorescent materials proposed in the present invention, and the optical fiber temperature chain temperature measurement method based on thermosensitive fluorescent materials includes the following steps: S1. Excitation and signal generation steps The excitation light source 1 emits laser pulses of a specific wavelength, which are then directed into the main optical fiber 7 after spectroscopic processing. This stimulates multiple sensing units 3 spaced axially along the main optical fiber 7 to produce fluorescence signals. Each sensing unit 3 is composed of a structured region on the main optical fiber 7 and a plurality of thermosensitive fluorescent materials 32 coated on its surface. Two of the thermosensitive fluorescent materials 32 are selected, and their characteristic emission wavelengths are λ1 and λ2. S2. Signal transmission and separation steps The fluorescence signal returns along the main optical fiber 7 and is directed to the detection module after spectroscopic processing. The interference of the excitation light is filtered out by filtering. At least two photodetectors 5 with different spectral response characteristics collect the fluorescence intensities I(λ1,T) and I(λ2,T) corresponding to the characteristic emission wavelengths λ1 and λ2 respectively. S3, spatial positioning step Performing time-resolved processing on the fluorescence signal and determining the spatial position of each sensor unit 3 based on the optical path difference introduced by the optical path difference structure between adjacent sensor units 3; S4. Temperature inversion step Calculate the intensity ratio based on the fluorescence intensity I(λ1,T) and I(λ2,T) , combined with the modified Planck radiation formula, a nonlinear mapping relationship between intensity ratio and temperature is established, and the temperature information corresponding to each sensing unit 3 is obtained by inversion.

[0028] The Planck temperature measurement principle relies on Planck's radiation law, which enables non-contact temperature measurement by analyzing the spectral characteristics of radiation. When a laser pulse excites the thermosensitive fluorescent material 32, the radiation spectrum generated by the electron transitions within the material satisfies the modified Planck radiation formula. In the S4 temperature inversion step, the fluorescence intensity I(λ,T) satisfies the modified Planck radiation formula:

[0029] in, C 1 is the first radiation constant, , h is Planck's constant, c is the speed of light, C 2 is the second radiation constant, , k is the Boltzmann constant, is the spectral emissivity of the thermosensitive fluorescent material 32 (which can be approximately constant when the temperature dependence is weak).

[0030] In the S1 excitation and signal generation step, laser pulses sequentially pass through two beam splitters 2 before entering the main optical fiber 7 and propagating along the fiber to each sensing unit 3. When the laser reaches each sensing unit 3, it excites the thermosensitive fluorescent material 32 to produce a fluorescent signal related to its current temperature. The pulse period is determined by the total length of the main optical fiber 7 to ensure that a single pulse can excite the fluorescent material coated on all structured areas.

[0031] The S4 temperature inversion steps specifically include: S41. Nonlinear mapping relationship derivation steps Substitute the modified Planck radiation formula into the fluorescence intensity ratio formula, and use the temperature range and wavelength range applicable to typical fluorescence temperature measurement to obtain the corrected Planck radiation formula. The approximate conditions of , the nonlinear mapping relationship between intensity ratio and temperature is derived:

[0032] in, A is a constant, , B is a constant, ; S42. Temperature inversion calculation steps based on Relationship, inversion to obtain temperature value: .

[0033] In the S41 nonlinear mapping relationship derivation step, the specific derivation process is to substitute the modified Planck radiation formula into the fluorescence intensity ratio formula to obtain:

[0034] ε 1(λ1,T) is the spectral emissivity of a selected thermosensitive fluorescent material 32 at wavelength λ1 and temperature T, ε 2(λ2,T) is the spectral emissivity of another selected thermosensitive fluorescent material 32 at wavelength λ2 and temperature T; Continue to sort and get:

[0035] When the typical temperature range of fluorescence temperature measurement is -50~150℃ and the wavelength range is 0.4~1.6μm, the following conditions are met:

[0036] Based on this condition, we continue to sort out and obtain:

[0037] Taking the natural logarithm, we obtain:

[0038] Finally, we insert the material / wavelength-dependent constants A Sensitivity factor related to Planck's constant B , we get the final nonlinear mapping relationship between intensity ratio and temperature. The light source fluctuation affects the absolute intensity of I(λ1) and I(λ2), but the ratio R(T) The error is offset, effectively reducing the error.

[0039] In the S42 temperature inversion calculation step, if the calculated T exceeds the range of -50~150℃, an alarm is triggered or other temperature measurement algorithms are used.

[0040] The signal processing unit 6 performs time-resolved analysis and spatial positioning on the received fluorescence signal. Using the time difference of the light pulse propagating in the main optical fiber 7, combined with the known speed of light and optical fiber length, the specific position of each sensor unit 3 is calculated and the corresponding temperature information is extracted. The spatial positioning step S3 specifically includes: S31, time gate signal generation step Based on the transmission time difference caused by the optical path difference structure between adjacent sensing units 3, a time gating signal corresponding to each sensing unit 3 is generated, and the trigger delay of the time gating signal matches the preset position of the sensing unit 3; S32, high-speed sampling and time domain separation steps The fluorescence signal is sampled at a set sampling rate, and the fluorescence signal of each sensor unit 3 is separated using a time-gated signal; S33, spatial position calculation steps According to the transmission speed of light in the optical fiber, the transmission time difference is converted into a spatial distance to determine the spatial position of each sensor unit 3. The spatial distance formula is:

[0041] in, v is the speed of light transmission in optical fiber, v= 2×10 8 m / s, Δt is the transmission time difference.

[0042] In step S1, the multiple thermosensitive fluorescent materials 32 coated on the surface of the sensing unit 3 correspond to different sensitive temperature ranges respectively; the fluorescence signals of the two thermosensitive fluorescent materials 32 selected by each sensing unit 3 within their respective corresponding sensitive temperature ranges can be effectively detected, and the fluorescence intensity of at least one thermosensitive fluorescent material 32 within its sensitive temperature range is significantly higher than that of other thermosensitive fluorescent materials 32 in the sensing unit 3, so as to form a characteristic response peak within the temperature range.

[0043] See attached Figures 5 to 7 , which is a schematic diagram of the fluorescence emission spectra of two thermosensitive fluorescent materials 32 at different temperatures, wherein the solid line curve represents the 30°C sensitive fluorescent material, and the dotted line curve represents the 0°C sensitive fluorescent material. Figure 5 When the temperature is 30℃, the peak height of the solid curve is significantly higher than that of the dotted curve, which shows that the fluorescence intensity of the 30℃ sensitive fluorescent material is dominant at 30℃. Figure 6 When the temperature is 20℃, the peak heights of the two curves are close, reflecting the comprehensive impact of temperature change on the two materials. Figure 7 At a temperature of 0°C, the peak height of the dotted curve is significantly higher than that of the solid curve, indicating that the fluorescence intensity of the 0°C-sensitive fluorescent material is dominant at 0°C. If the type of thermosensitive fluorescent material 32 is increased or a spectrometer is used instead of the photodetector 5, a wider temperature range can be covered and measurement accuracy can be improved.

[0044] In the above-mentioned schematic embodiment, the fiber-optic temperature chain temperature measurement method based on thermosensitive fluorescent materials realizes multi-point, high-precision, and high-stability temperature perception in complex environments by combining the temperature-sensitive characteristics of the thermosensitive fluorescent material 32 with the distributed optical fiber sensing structure; the dual-channel fluorescence detection and intensity ratio algorithm it adopts effectively eliminates the influence of light source fluctuations and optical fiber transmission losses, and significantly improves the robustness and reliability of the system; at the same time, the system has good environmental adaptability, which can meet the needs of distributed temperature field monitoring in different ocean depth environments, and has broad engineering application prospects.

[0045] Example 2: This embodiment provides a fiber-optic temperature chain temperature measurement system based on thermosensitive fluorescent materials, which is applied to the fiber-optic temperature chain temperature measurement method based on thermosensitive fluorescent materials in Example 1. The fiber-optic temperature chain temperature measurement system based on thermosensitive fluorescent materials includes a main optical fiber 7, an excitation light source unit, a wavelength selective spectrometer unit, a filtering unit, a detection unit and a signal processing unit 6.

[0046] The main optical fiber 7 is provided with a plurality of sensing units 3 spaced apart along the axial direction. Each sensing unit 3 is composed of an optical waveguide control structure 31 and a plurality of thermosensitive fluorescent materials 32 coated on its surface. Each thermosensitive fluorescent material 32 of the same sensing unit 3 has different temperature response characteristics. The excitation light source unit is used to emit laser pulses to the main optical fiber 7 to stimulate each sensing unit 3 to generate a fluorescence signal. The excitation light source unit includes an excitation light source 1. In this embodiment, the main optical fiber 7 is a single-mode optical fiber, which is suitable for installation and deployment requirements in different application scenarios. The thermosensitive fluorescent material 32 is a rare earth doped material or an organic fluorescent dye, and its luminous intensity shows a predictable linear or nonlinear relationship with temperature. The plurality of thermosensitive fluorescent materials 32 excite fluorescence of different wavelengths according to different temperatures, so as to achieve high-precision temperature measurement.

[0047] The optical waveguide control structure 31 is a grating structure or a unidirectional groove structure written on the main optical fiber 7. Figure 3 and Figure 4 , illustrating two typical groove structures. In some embodiments, the optical waveguide control structure 31 can adopt a unidirectional groove structure engraved on the surface of the main optical fiber 7, specifically including two typical implementation methods: one is a rectangular groove structure, see the attached Figure 3 The structure consists of a rectangular groove extending along the axial direction of the optical fiber. The groove depth is 1 / 3 to 1 / 2 of the optical fiber diameter, and the groove width matches the grating period (e.g. 500nm to 2μm). It is prepared by femtosecond laser direct writing process. The second is an arc groove structure, see Appendix. Figure 4The groove bottom forms an arc transition, with a curvature radius that matches the outer diameter of the optical fiber, effectively reducing stress concentration. Both groove structures disrupt the total internal reflection condition on the optical fiber surface, enhancing the interaction between the evanescent wave and the thermosensitive fluorescent material 32 in the coating layer. This improves the excitation light coupling efficiency (>80%) and fluorescence collection efficiency (>70%), while also increasing the material attachment surface area (3-5 times greater than on a smooth optical fiber surface), ensuring the temperature response stability of the sensing unit 3.

[0048] The wavelength-selective spectrometer unit includes at least two spectrometers 2, which are used to direct laser pulses to the main optical fiber 7 based on their wavelength characteristics and distribute the fluorescence signals returned by each sensor unit 3 to the corresponding detection path. In this embodiment, the spectrometers 2 are wavelength division multiplexers or fiber Bragg grating filters, which separate the excitation light and the fluorescence signal and direct them to the corresponding paths. When the spectrometers 2 of the wavelength-selective spectrometer unit are wavelength division multiplexers, their design wavelengths match the excitation and emission bands of the selected fluorescent material, thereby ensuring effective separation of the excitation light and fluorescence signals.

[0049] The optical filter unit includes at least one filter set 4, positioned in the detection path to filter out interfering excitation light. In this embodiment, filter set 4 is a bandpass filter or edge filter, which further suppresses residual excitation light and enhances the signal-to-noise ratio of the fluorescence signal. In this embodiment, filter set 4 is positioned at the front end of the detection path to filter out interfering excitation light and only allow fluorescence signals within a specific wavelength range to enter the detector.

[0050] The detection unit includes at least two photodetectors 5 with different spectral response characteristics, which are used to receive fluorescence signals of different wavelengths after processing by the filter unit. A signal processing unit 6 is used to time-resolve the fluorescence signals to locate each sensing unit 3. It calculates the intensity ratio of the fluorescence signals in different wavelengths and establishes a nonlinear mapping relationship with temperature based on the Planck principle to obtain temperature information at the location of each sensing unit 3. By performing a ratio calculation on the intensities of two or more fluorescence signals and establishing a nonlinear mapping relationship based on the Planck principle of temperature measurement, the effects of light source fluctuations and fiber optic transmission losses on temperature measurement accuracy can be effectively eliminated.

[0051] In some embodiments, the signal processing unit 6 implements time resolution of the returned fluorescence signal based on optical time domain reflectometry (OTDR) technology, thereby determining the spatial position of each sensing unit 3 and performing temperature demodulation in combination with the fluorescence intensity ratio.

[0052] An optical path differentiation structure is provided between adjacent sensing units 3. This structure is used to introduce a discernible optical path difference between the fluorescence signals of different sensing units 3, thereby generating a difference in transmission time, thereby spatially resolving each sensing unit 3. The transmission time difference must be no less than twice the time resolution accuracy of the signal processing unit 6 and no less than 10 ns. In this embodiment, the optical path differentiation structure is a long-spaced isolation region or optical fiber delay line provided between adjacent sensing units 3. This structure spatially resolves multiple sensing units 3 on the main optical fiber 7 by varying the transmission time of the optical signal.

[0053] The signal processing unit 6 includes a high-speed data acquisition module, a timing control module, and a temperature calculation module. The high-speed data acquisition module is configured to digitally process the fluorescence signal at a set sampling rate. The timing control module is configured to generate a time-gated signal corresponding to each sensing unit 3 based on the transmission time difference introduced by the optical path differentiation structure. The temperature calculation module is configured to perform time domain separation on the digitized fluorescence signal, extract the characteristic signal corresponding to each sensing unit 3, calculate the intensity ratio of the fluorescence signal in different bands, and establish a nonlinear mapping relationship between the intensity ratio and temperature in combination with the modified Planck radiation formula, and invert the temperature value at the position of each sensing unit 3.

[0054] The signal processing unit 6 also includes a spatial position calculation module, which is configured to convert the transmission time difference into a spatial distance based on the transmission time difference and the transmission speed of light in the optical fiber to calculate the spatial position of each sensor unit 3.

[0055] The signal processing unit 6 has high-precision time resolution, enabling both temporal resolution and spatial localization of fluorescence signals, thereby obtaining the specific position and corresponding temperature information of each sensor unit 3. In this embodiment, the signal processing unit 6 has a time resolution accuracy of no less than 5 nanoseconds, and the temperature calculation module has a temperature resolution of no more than 0.1°C. This allows the signal processing unit 6 to achieve nanosecond-level time resolution, accurately localize the spatial position of each sensor unit 3, and invert the temperature value in real time based on the fluorescence intensity ratio-temperature calibration curve corresponding to each sensor unit 3.

[0056] Furthermore, in some embodiments, the signal processing unit 6 further includes a fault detection module and a self-healing control module. The fault detection module is configured to monitor the intensity and waveform characteristics of the fluorescence signal from each sensor unit 3. Upon detecting that the signal intensity of a sensor unit 3 has dropped by more than a preset threshold, the self-healing control module determines that the sensor unit 3 has failed. The self-healing control module is configured to, upon the fault detection module determining that a sensor unit 3 has failed, automatically adjust the optical path differential structural parameters of adjacent sensor units 3 to compensate for measurement blind spots and generate fault alarm information, including the fault location and an estimated repair plan.

[0057] In this embodiment, the fiber-optic temperature chain temperature measurement system, based on thermosensitive fluorescent materials, is enclosed within a sealed enclosure that is waterproof, pressure-resistant, and corrosion-resistant. This enclosure's protective properties adapt to the pressure, corrosion, and humidity conditions of varying ocean depths, enabling the system to operate stably and long-term in marine environments. This makes the system suitable for multi-point distributed temperature measurement in complex environments like the ocean.

[0058] In the aforementioned exemplary embodiment, the fiber-optic temperature chain measurement system based on thermosensitive fluorescent materials integrates multiple sensing units through a single main optical fiber, enabling distributed temperature measurement at multiple points along the same fiber. This significantly reduces deployment costs and improves system scalability and practicality. Furthermore, the introduction of thermosensitive fluorescent materials, coupled with dual-channel detection and an intensity ratio method, effectively eliminates interference from light source fluctuations and fiber transmission losses, improving temperature measurement accuracy and system stability. The system boasts a compact structure, strong resistance to electromagnetic interference, and utilizes time-resolved technology for spatial positioning (precisely locating each temperature measurement point without the need for additional sensors). This system is suitable not only for shallow-water detection but also for long-term stable operation in medium-depth waters. It is particularly well-suited for low-cost, refined, distributed temperature field sensing in marine environments.

[0059] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0060] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to preferred embodiments, persons skilled in the art should understand that the specific implementation methods of the present invention may still be modified or some technical features may be replaced by equivalents without departing from the spirit of the technical solutions of the present invention, and all of these should fall within the scope of the technical solutions claimed for protection by the present invention.

Claims

1. A temperature measurement method using an optical fiber temperature chain based on thermosensitive fluorescent materials, characterized in that: include: S1. Excitation and signal generation steps The laser pulse is emitted and introduced into the main optical fiber after spectroscopic processing, stimulating multiple sensing units spaced along the axial direction of the main optical fiber to generate fluorescence signals; each sensing unit is composed of a structured area on the main optical fiber and a variety of thermosensitive fluorescent materials coated on its surface, two of which are selected. Its characteristic emission wavelengths are λ1 and λ2; S2. Signal transmission and separation steps The fluorescence signal returns along the main optical fiber, is directed to the detection module after spectroscopic processing, and is filtered to remove interference from the excitation light. At least two photodetectors with different spectral response characteristics collect the fluorescence intensities I(λ1,T) and I(λ2,T) corresponding to the characteristic emission wavelengths λ1 and λ2, respectively. S3, spatial positioning step performing time-resolved processing on the fluorescence signal and determining the spatial position of each sensing unit based on the optical path difference introduced by the optical path difference structure between adjacent sensing units; S4. Temperature inversion step The intensity ratio is calculated based on the fluorescence intensities I(λ1,T) and I(λ2,T). , combined with the modified Planck radiation formula, a nonlinear mapping relationship between intensity ratio and temperature is established, and the temperature information corresponding to each sensing unit is obtained by inversion.

2. The optical fiber temperature chain temperature measurement method based on thermosensitive fluorescent material according to claim 1, characterized in that: In the S4 temperature inversion step, the fluorescence intensity I(λ,T) satisfies the modified Planck radiation formula: in, C 1 is the first radiation constant, , h is Planck's constant, c is the speed of light, C 2 is the second radiation constant, , k is the Boltzmann constant, is the spectral emissivity of the thermosensitive fluorescent material.

3. The optical fiber temperature chain temperature measurement method based on thermosensitive fluorescent material according to claim 2, characterized in that: The S4 temperature inversion steps specifically include: S41. Nonlinear mapping relationship derivation steps Substitute the modified Planck radiation formula into the fluorescence intensity ratio formula, and use the temperature range and wavelength range applicable to typical fluorescence temperature measurement to obtain the corrected Planck radiation formula. The approximate conditions of , the nonlinear mapping relationship between intensity ratio and temperature is derived: in, A is a constant, , B is a constant, ; S42. Temperature inversion calculation steps based on Relationship, inversion to obtain temperature value: .

4. The optical fiber temperature chain temperature measurement method based on thermosensitive fluorescent material according to claim 1, characterized in that: The S3 spatial positioning steps specifically include: S31, time gate signal generation step Based on the transmission time difference generated by the optical path difference structure between adjacent sensing units, a time gating signal corresponding to each sensing unit is generated, and the trigger delay of the time gating signal matches the preset position of the sensing unit; S32, high-speed sampling and time domain separation steps Sampling the fluorescence signal at a set sampling rate, and separating the fluorescence signal of each sensing unit using the time gating signal; S33, spatial position calculation steps According to the transmission speed of light in the optical fiber, the transmission time difference is converted into spatial distance to determine the spatial position of each sensing unit. The spatial distance formula is: in, v is the transmission speed of light in the optical fiber, and Δt is the transmission time difference.

5. The optical fiber temperature chain temperature measurement method based on thermosensitive fluorescent material according to claim 1, characterized in that: In step S1, the multiple thermosensitive fluorescent materials coated on the surface of the sensing unit correspond to different sensitive temperature ranges respectively; the fluorescence signals of the two thermosensitive fluorescent materials selected by each sensing unit within their respective corresponding sensitive temperature ranges can be effectively detected, and the fluorescence intensity of at least one thermosensitive fluorescent material within its sensitive temperature range is significantly higher than that of other thermosensitive fluorescent materials in the sensing unit, so as to form a characteristic response peak within the temperature range.

6. An optical fiber temperature chain temperature measurement system based on thermosensitive fluorescent materials, characterized in that: include: A main optical fiber, wherein the main optical fiber is provided with a plurality of sensing units spaced apart along the axial direction, each sensing unit being composed of an optical waveguide control structure and a plurality of thermosensitive fluorescent materials coated on its surface, and each thermosensitive fluorescent material in the same sensing unit having different temperature response characteristics; an excitation light source unit, configured to emit laser pulses to the main optical fiber to stimulate each sensing unit to generate a fluorescence signal; a wavelength-selective spectroscopic unit comprising at least two spectrometers for guiding the laser pulse to the main optical fiber based on wavelength characteristics and distributing the fluorescence signals returned by each sensing unit to corresponding detection paths; A filter unit, comprising at least one filter set, arranged in the detection path to filter out interference from the excitation light; A detection unit, comprising at least two photodetectors with different spectral response characteristics, configured to receive fluorescence signals of different wavelengths processed by the filter unit; A signal processing unit is used to time-resolve the fluorescence signal to locate each sensing unit, calculate the intensity ratio of the fluorescence signal in different bands, and establish a nonlinear mapping relationship with temperature in combination with the Planck principle, thereby obtaining the temperature information corresponding to each sensing unit.

7. The optical fiber temperature chain temperature measurement system based on thermosensitive fluorescent material according to claim 6, characterized in that: An optical path differentiation structure is provided between adjacent sensing units, and the optical path differentiation structure is used to introduce a resolvable optical path difference between the fluorescence signals of different sensing units, thereby generating a transmission time difference to spatially resolve each sensing unit, wherein the transmission time difference is not less than twice the time resolution accuracy of the signal processing unit and not less than 10ns.

8. The optical fiber temperature chain temperature measurement system based on thermosensitive fluorescent material according to claim 7, characterized in that: The signal processing unit includes: a high-speed data acquisition module, wherein the high-speed data acquisition module is configured to digitally process the fluorescence signal at a set sampling rate; a timing control module configured to generate a time gating signal corresponding to each sensing unit based on the transmission time difference introduced by the optical path differentiation structure; A temperature calculation module is configured to perform time-domain separation on the digitized fluorescence signal, extract the characteristic signal corresponding to each sensing unit, calculate the intensity ratio of the fluorescence signal in different bands, and establish a nonlinear mapping relationship between the intensity ratio and temperature in combination with the modified Planck radiation formula to invert the temperature value at each sensing unit position.

9. The optical fiber temperature chain temperature measurement system based on thermosensitive fluorescent material according to claim 8, characterized in that: The signal processing unit further includes a spatial position calculation module, which is configured to convert the transmission time difference into a spatial distance based on the transmission time difference and the transmission speed of light in the optical fiber to calculate the spatial position of each sensing unit.

10. The optical fiber temperature chain temperature measurement system based on thermosensitive fluorescent material according to any one of claims 6 to 9, characterized in that: The entire system is encapsulated in a sealed housing, which has a waterproof, pressure-resistant and corrosion-resistant structure.

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