Optical fiber sensor system for monitoring temperature

Abstract

The invention provides an optical fiber sensor system for monitoring temperature, and the system comprises an optical fiber sensor of which the end part is provided with a sensitive layer containing a samarium-doped fluorescent material; the excitation light source is used for exciting the sensitive layer to generate a fluorescence signal; the ultraviolet light source is used for irradiating the sensitive layer to reduce trivalent samarium ions into divalent samarium ions; the optical routing assembly is used for coupling output light of the excitation light source and the ultraviolet light source to the optical fiber sensor and directionally transmitting a fluorescence signal returned by the optical fiber sensor; the band-pass filter is used for receiving the fluorescence signal and transmitting a wave band from 600nm to 700nm; and the signal processing unit is used for analyzing the transmitted fluorescence signal and outputting temperature data.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber sensing, and in particular relates to an optical fiber sensor system for monitoring temperature. Background Art

[0002] As a fundamental physical quantity, precise temperature monitoring holds irreplaceable value in industry, medicine, and scientific research. Traditional temperature monitoring methods, such as glass thermometers and thermocouples, while reliable in conventional environments, often exhibit significant limitations in specialized scenarios such as deep-sea high-pressure environments, mine explosion protection, and in-vivo invasive testing. Mechanical thermometers' fragile structures cannot withstand extreme pressures; electronic sensors are prone to explosion risks caused by electric sparks; and non-contact methods like infrared sensors are susceptible to obstruction and emissivity interference from the medium, making them difficult to meet the high-precision requirements of confined spaces.

[0003] The emergence of fiber optic sensing technology has provided a new path for temperature measurement in special environments. With its inherent safety (no electric sparks), anti-electromagnetic interference, corrosion resistance and miniaturization, fiber optic temperature sensors have shown unique advantages in deep-sea exploration, oil and gas well monitoring, minimally invasive medical treatment and other fields. In the existing technology, fiber optic sensors based on the fluorescence principle have been widely studied due to their simple structure, low cost and high sensitivity. This type of sensor uses the law that the optical properties of rare earth doped fluorescent materials change with temperature and realizes temperature inversion by analyzing the fluorescence spectrum. Among them, divalent samarium ions doped with barium fluoride chloride (BaFCl: Sm 2+ ) nanomaterials are regarded as highly potential sensitive materials due to their efficient orange-red fluorescence emission (600-700nm band) and low preparation cost.

[0004] However, the practical application of this material still faces severe challenges. Divalent samarium ions undergo irreversible valence transitions during fluorescence excitation (Sm 2+ →Sm 3+ ), resulting in a significant decay of fluorescence intensity over time. This photobleaching phenomenon is particularly prominent in continuous operation mode, which seriously restricts the long-term stability of the sensor. Although researchers have tried to slow down the oxidation process by optimizing the packaging process or adding a protective layer, the material performance will still deteriorate rapidly in harsh environments such as high humidity and strong radiation. In addition, the existing technology has not yet solved a fundamental contradiction: if the real-time temperature measurement is to be improved, the excitation light power needs to be increased, which in turn accelerates the consumption of divalent samarium ions; if the power is reduced, the decay can be delayed, but the signal-to-noise ratio and response speed are sacrificed.

[0005] It's worth noting that these issues can't be solved simply through material modification. Traditional methods like ion co-doping or surface passivation can extend lifetimes to a limited extent, but often weaken fluorescence efficiency. Complex regeneration circuit designs can also negate the inherent structural simplicity of fiber optic sensors. Summary of the Invention

[0006] To address the shortcomings and deficiencies of existing technologies, the present invention provides a fiber optic temperature sensor system based on dynamic valence state balance. This system solves the signal attenuation problem caused by photooxidation of divalent samarium ions through the synergistic effect of an ultraviolet light source and an excitation light source. Its core innovations include: Dynamically regenerated sensitive layer: The optical fiber end face is coated with a composite layer of barium fluoride and chloride nanoparticles doped with divalent samarium ions. The trivalent samarium ions are reduced to a divalent state through periodic ultraviolet irradiation (wavelength < 300nm) to maintain fluorescence stability. Dual-light source optical architecture: A wavelength division multiplexer couples UV light and excitation light (wavelengths avoid 600-700nm), which are then routed to the probe via a fiber circulator. A bandpass filter (600-700nm transmission band) accurately extracts the fluorescence signal. Anti-interference calibration mechanism: Analyze the ratio of fluorescence peak intensities at 688nm and 643nm to achieve temperature inversion and eliminate the influence of light source fluctuations; High-reliability probe technology: Nanoparticles are synthesized by co-precipitation and solidified on the optical fiber end face in proportion to the polymer matrix.

[0007] The system exhibits a highly linear temperature response within the measured range of 20°C-80°C, and under a constant temperature environment of 20°C, the fluorescence intensity fluctuates very little within 60 minutes, significantly improving long-term stability.

[0008] The technical solution specifically adopted by the present invention to solve the technical problem is: A fiber optic sensor system for monitoring temperature, comprising: An optical fiber sensor having a sensitive layer containing samarium-doped fluorescent material at its end; an excitation light source, used to excite the sensitive layer to generate a fluorescent signal; an ultraviolet light source, used for periodically or continuously irradiating the sensitive layer at low power to reduce trivalent samarium ions to divalent samarium ions to maintain the balance of samarium ions; an optical routing component, coupling the output light of the excitation light source and the ultraviolet light source to the optical fiber sensor, and directionally transmitting the fluorescent signal returned by the optical fiber sensor; a bandpass filter, receiving the fluorescent signal and transmitting the wavelength range of 600 nm to 700 nm; The signal processing unit analyzes the transmitted fluorescence signal and outputs temperature data.

[0009] Furthermore, the optical routing component includes: a wavelength division multiplexer, wherein a first port thereof is connected to the ultraviolet light source, and a second port thereof is connected to the excitation light source; The optical fiber circulator has a first port connected to the third port of the wavelength division multiplexer, and a second port connected to the optical fiber sensor.

[0010] Furthermore, the wavelength of the ultraviolet light source is less than 300 nm, and the wavelength of the excitation light source is outside the range of 600 nm to 700 nm.

[0011] Furthermore, the sensitive layer comprises divalent samarium ion-doped barium fluoride and chloride nanoparticles dispersed in a polymer matrix.

[0012] Furthermore, the polymer matrix is ​​one of polydimethylsiloxane, polymethyl methacrylate, polycarbonate, and polystyrene.

[0013] Furthermore, the signal processing unit realizes temperature calibration by calculating the ratio of fluorescence peak intensities at wavelengths of 688 nm and 643 nm.

[0014] Furthermore, the irradiation interval of the ultraviolet light source is 30-90 minutes, and the single irradiation time is 1-5 minutes.

[0015] And, a method for preparing a sensitive layer, comprising: Mixing barium salt and samarium salt solutions, wherein the samarium doping molar ratio is 0.5%-10% of the barium salt molar amount; Add ammonium fluoride solution in an amount equimolar to the barium salt to react and form a precipitate of barium fluoride and chloride doped with divalent samarium ions; The precipitate is washed and dried and then mixed with a polymer matrix, wherein the polymer matrix is ​​a mixture of polydimethylsiloxane and a curing agent in a mass ratio of 10:1.

[0016] and, a temperature-sensitive coating: A composite layer comprising barium fluoride and chloride doped divalent samarium ion nanoparticles and a polymer matrix; The composite layer can be peelably attached to the surface of the base film and is used to be attached to the end face of the optical fiber to form a temperature sensor probe.

[0017] And, a method for regenerating a sensitive layer of an optical fiber sensor, comprising: The sensitive layer in the system is subjected to ultraviolet irradiation at a wavelength of less than 300 nm for 1-5 minutes; The fluorescence intensity after regeneration was detected, and irradiation was terminated when the intensity at 688 nm recovered to more than 90% of the initial value.

[0018] Compared with the prior art, the present invention and its preferred embodiments have at least the following beneficial effects: 1. Breakthrough solution to the problem of fluorescence decay By irradiating the sensitive layer with ultraviolet light, the trivalent samarium ions are dynamically reduced to their divalent state, fundamentally overcoming the signal attenuation problem caused by photooxidation of fluorescent materials. This self-regeneration mechanism significantly improves the long-term stability of the system while maintaining high-sensitivity temperature measurement, resolving the industry's pain point of performance degradation during continuous operation of traditional fluorescence sensors.

[0019] 2. Optical Link Collaborative Optimization The innovative combination of dual light sources (UV + excitation) via a wavelength division multiplexer and fiber circulator, combined with a bandpass filter to precisely extract the 600-700nm wavelength band, effectively separates signal from noise. This architecture simplifies system complexity while ensuring the purity of the fluorescence signal and avoiding the crosstalk issues common in traditional systems.

[0020] 3. Anti-interference temperature calibration mechanism The 688nm and 643nm dual-wavelength fluorescence peak intensity ratio algorithm cleverly eliminates the influence of light source fluctuations and environmental interference. This spectral feature-based calibration method significantly improves the reliability of temperature measurement while maintaining a high response speed.

[0021] 4. Breakthrough in probe technology and environmental adaptability The composite curing process of barium fluoride and chloride-doped samarium ion nanoparticles and a polymer matrix gives the probe excellent mechanical strength and thermal stability. This integrated structure not only maintains the advantages of miniaturization, but also enables it to withstand extreme environments such as high pressure and high humidity, expanding its application in special scenarios such as deep sea and mines.

[0022] 5. Optimize manufacturing and maintenance costs The co-precipitation method for preparing nanoparticles and the simplified dipping and curing process significantly reduce the manufacturing cost of the probe. The introduction of a UV regeneration mechanism further reduces the frequency of sensitive layer replacement, achieving economic benefits throughout the entire life cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments: Figure 1 Schematic diagram of an optical fiber sensor system for temperature monitoring based on fluorescence technology according to an embodiment of the present invention; Figure 2 This is a diagram of a samarium ion-doped barium fluoride and chloride nanomaterial prepared according to an embodiment of the present invention; Figure 3 A fluorescence spectrum obtained from a sensor system according to an embodiment of the present invention; Figure 4 Graph showing the change in the ratio of the fluorescence peak at 688 nm to the fluorescence peak at 643 nm as a function of temperature in an embodiment of the present invention; Figure 5This is a test chart showing the stability of the intensity of the fluorescence at 688 nm generated by the optical fiber sensor system according to an embodiment of the present invention over time. DETAILED DESCRIPTION

[0024] In order to make the features and advantages of the present invention more clearly understood, the following embodiments are given for detailed description: It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those skilled in the art to which this application belongs.

[0025] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0026] To overcome the challenges of existing technologies, the present invention provides a fluorescence-based fiber optic sensor system for temperature monitoring. This system utilizes a mixture of PDMS and barium fluoride-doped samarium ion nanomaterials, integrated into the end face of an optical fiber, and further integrated into the optical fiber sensor system using ultraviolet light. Irradiation of the barium fluoride-doped samarium ion nanomaterial reduces trivalent samarium ions to divalent samarium ions, thus creating a fluorescence-based fiber optic temperature sensor. By periodically irradiating the optical fiber, the ultraviolet light repeatedly reduces trivalent samarium ions to divalent samarium ions, resulting in a highly reliable optical fiber temperature sensor system.

[0027] The fiber optic sensor system for monitoring temperature provided by the present invention has a basic device structure including a fiber optic sensor, a fiber optic spectrometer, an excitation light source, an ultraviolet light source, a wavelength division multiplexer, a fiber optic circulator and a bandpass fiber optic filter.

[0028] Among them, the excitation light source and the ultraviolet light source are connected to one end of the fiber circulator through a wavelength division multiplexer; one end of the fiber circulator is connected to the fiber sensor, and the last port is connected to the fiber grating; the other port of the fiber grating is connected to the fiber spectrometer.

[0029] The wavelength range of the excitation light source used is less than 600nm or greater than 700nm.

[0030] The wavelength of the ultraviolet light source used is less than 300nm.

[0031] The optical fiber sensor used has its end coated with a layer of fluorescent material containing barium fluoride and chloride doped with samarium ions.

[0032] The bandpass optical fiber filter used has an operating range of 600nm-700nm and does not include the wavelength range of the excitation light source.

[0033] The fiber optic sensor preparation method used is as follows: (1) Weigh a certain amount of barium chloride, add it to deionized water, and fully dissolve it to form a barium chloride solution; (2) Weigh a certain mass of samarium chloride and add it to the barium chloride solution to form a mixed solution; (3) Weigh the same molar amount of ammonium fluoride as that of barium chloride, add it to deionized water, and fully dissolve it to form an ammonium fluoride solution; (4) Stirring the mixed solution of barium chloride and samarium chloride, slowly adding the ammonium fluoride solution to the mixed solution, and stirring for 2 hours; (5) The precipitate obtained by the reaction is centrifuged and washed 3-5 times, and then dried at a certain temperature to obtain the nanomaterial of barium fluoride and chloride doped with samarium ions; (6) Weigh a certain amount of polydimethylsiloxane and its curing agent (the mass ratio of polydimethylsiloxane and its curing agent is about 10:1) and mix them thoroughly. (7) Weighing a certain weight of barium fluoride and chloride doped samarium ion nanomaterial, adding it to the mixture of polydimethylsiloxane and its curing agent, and stirring and mixing; (8) Cut a section of optical fiber, dip it into the mixture of barium fluoride and chloride doped samarium ion nanomaterial and polydimethylsiloxane, and then place it in a blast drying oven to accelerate solidification.

[0034] The principle of the present invention is as follows: The present invention utilizes a mixture of polydimethylsiloxane (PDMS) and barium fluoride-chloride-doped samarium ion nanomaterials, which are then integrated into the end face of an optical fiber to create a fiber optic sensor probe. A UV light source and an excitation light source are integrated into the input of the fiber optic sensor via a wavelength division multiplexer. The resulting fluorescence signal is then transmitted through a fiber optic circulator and a bandpass fiber filter to a fiber optic spectrometer. During this process, the UV light source reduces trivalent samarium ions to divalent samarium ions, while the light emitted by the excitation light source excites the divalent samarium ions to produce a fluorescence spectrum. While some divalent samarium ions are converted to trivalent samarium ions by the excitation light, the UV light source can also reduce these to divalent samarium ions, achieving a dynamic equilibrium of divalent samarium ions. This invention addresses the issue of divalent samarium ion consumption during excitation light irradiation, ensuring stable fluorescence spectrum output and enabling high-precision temperature monitoring.

[0035] As can be seen from the above, the optical fiber sensor for monitoring temperature of the present invention has the advantages of integration and strong stability.

[0036] The above solution of the present invention is demonstrated and introduced in more detail below through a more specific embodiment: Weigh 0.01 mol of barium chloride, add it to 25 mL of deionized water, stir it thoroughly to dissolve, and form a barium chloride solution; then weigh 0.0001 mol of samarium chloride, add it to the barium chloride solution, stir it thoroughly to dissolve, and form a mixed solution. Weigh 0.01 mol of ammonium fluoride, add it to 25 mL of deionized water, stir it thoroughly to dissolve, and form an ammonium fluoride solution. Use a magnetic stirrer to stir the mixed solution of barium chloride and samarium chloride, slowly add the ammonium fluoride solution to the mixed solution, and stir the reaction for 2 hours. Centrifuge the precipitate obtained by the reaction and wash it 3-5 times, place it in a blast drying oven, and dry it at 80°C for 24 hours to obtain barium fluoride chloride doped samarium ions (BaFCl:Sm 3+ ) of nanomaterials.

[0037] Weigh 1g of polydimethylsiloxane and its curing agent (the mass ratio of polydimethylsiloxane and its curing agent is approximately 10:1) and stir thoroughly. Weigh 0.2g of barium fluoride chloride-doped samarium ion nanomaterial and add it to the polydimethylsiloxane and curing agent mixture and stir to mix. Cut a section of commercial single-mode optical fiber, remove 3cm of plastic from the surface of the fiber with a wire stripper, and use a fiber cleaver to cut off a portion of the fiber to obtain a flush fiber end face. Dip the mixture of barium fluoride chloride-doped samarium ion nanomaterial and polydimethylsiloxane into the fiber end face, and then place it in a forced air drying oven to accelerate solidification. The forced air drying oven temperature is set to 80°C and the heating time is 6 hours.

[0038] The connection of the optical fiber sensor system in this embodiment is as follows Figure 1 As shown in the figure, a 213nm laser with a 5mW output power is used as the UV light source, and the output end of the pigtail is connected to port 1 of the wavelength division multiplexer. A 405nm laser is used as the excitation light source, and the output end of the pigtail is connected to port 3 of the wavelength division multiplexer. Port 2 of the wavelength division multiplexer is connected to port 1 of the fiber circulator, and port 2 of the fiber circulator is connected to the tail end of the fiber optic sensor. Port 3 of the fiber circulator is connected to one end of a bandpass fiber filter, and the other end of the bandpass fiber filter is connected to a fiber spectrometer.

[0039] Scanning electron microscopy of prepared barium fluoride and chloride doped samarium ion nanomaterials Figure 2 As shown, the nanoparticles have nanoscale dimensions. Figure 3 This is the fluorescence spectrum obtained from the test. Figure 4 It is the ratio between the peak value of fluorescence at 688nm and the peak value at 643nm under different temperature conditions, and has good monotonicity between 20℃-80℃. Figure 5This is the change in the peak fluorescence at 688nm generated at 20°C over 60 minutes. It can be seen that the ratio changes very little over 60 minutes, indicating that this technical solution can provide a highly stable spectrum.

[0040] It should be noted that, unless otherwise defined, the technical or scientific terms used in the present invention should have the usual meanings understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

[0042] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive various other forms of an optical fiber sensor system for monitoring temperature under the inspiration of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A fiber optic sensor system for monitoring temperature, characterized in that: include: An optical fiber sensor having a sensitive layer containing samarium-doped fluorescent material at its end; an excitation light source, used to excite the sensitive layer to generate a fluorescent signal; an ultraviolet light source for irradiating the sensitive layer to reduce trivalent samarium ions to divalent samarium ions; an optical routing component, coupling the output light of the excitation light source and the ultraviolet light source to the optical fiber sensor, and directionally transmitting the fluorescent signal returned by the optical fiber sensor; a bandpass filter, receiving the fluorescent signal and transmitting the wavelength range of 600 nm to 700 nm; The signal processing unit analyzes the transmitted fluorescence signal and outputs temperature data.

2. The optical fiber sensor system for monitoring temperature according to claim 1, characterized in that: The optical routing assembly comprises: a wavelength division multiplexer, wherein a first port thereof is connected to the ultraviolet light source, and a second port thereof is connected to the excitation light source; The optical fiber circulator has a first port connected to the third port of the wavelength division multiplexer, and a second port connected to the optical fiber sensor.

3. The optical fiber sensor system for monitoring temperature according to claim 1, characterized in that: The wavelength of the ultraviolet light source is less than 300 nm, and the wavelength of the excitation light source is outside the range of 600 nm to 700 nm.

4. The optical fiber sensor system for monitoring temperature according to claim 1, wherein: The sensitive layer comprises barium fluoride and chloride nanoparticles doped with divalent samarium ions and dispersed in a polymer matrix.

5. The optical fiber sensor system for monitoring temperature according to claim 4, characterized in that: The polymer matrix is ​​one of polydimethylsiloxane, polymethyl methacrylate, polycarbonate, and polystyrene.

6. The optical fiber sensor system for monitoring temperature according to claim 1, characterized in that: The signal processing unit realizes temperature calibration by calculating the ratio of fluorescence peak intensity at wavelengths of 688 nm and 643 nm.

7. A temperature-sensitive coating, characterized in that: A composite layer comprising barium fluoride and chloride doped divalent samarium ion nanoparticles and a polymer matrix; The composite layer is attached to the surface of the base film in a peelable manner and is used to be attached to the end face of the optical fiber to form a temperature sensor probe.

8. A method for regenerating a sensitive layer of an optical fiber sensor, characterized in that: include: The sensitive layer in the system of claim 1 is subjected to ultraviolet irradiation at a wavelength of less than 300 nm for 1-5 minutes; The fluorescence intensity after regeneration was detected, and irradiation was terminated when the intensity at 688 nm recovered to more than 90% of the initial value.

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