Temperature detection system and method

Abstract

The invention discloses a temperature detection system and method. The system comprises a broadband light source, an optical fiber circulator, an optical fiber Fabry-Perot cavity sensor, an optical fiber Mach-Zehnder interference device, a constant temperature box and a spectrograph. The broadband light source, the optical fiber Fabry-Perot cavity sensor and the optical fiber Mach-Zehnder interference device are all connected with the optical fiber circulator; the optical fiber Mach-Zehnder interference device is connected with the spectrograph; a detection cavity of the optical fiber Fabry-Perot cavity sensor is arranged in an environment to be detected; the optical fiber Mach-Zehnder interference device is arranged in the constant temperature box, and the optical fiber Mach-Zehnder interference device is used for being matched with the optical fiber Fabry-Perot cavity sensor to form a first-order vernier effect so as to realize temperature detection of the environment to be detected. According to the temperature detection system provided by the invention, the optical fiber Mach-Zehnder interferometer device provides a stable reference spectrum, so that sensing signals are denser, and high-precision temperature demodulation is realized through small change of wavelength of an inner envelope intersection point.

Description

Technical Field

[0001] The present invention relates to the field of optics and sensing technology, and in particular to a temperature detection system and method. Background Art

[0002] Temperature detection systems use temperature sensors to measure the temperature of the environment being measured. Fiber optic sensing technology is widely used in industries such as industry, aviation, petrochemicals, and medicine, and holds significant application value in temperature sensing. Fiber optic temperature sensors offer advantages such as miniaturization, immunity to electromagnetic interference, corrosion resistance, and the ability to monitor temperature over long distances. Fiber optic temperature sensors based on Fabry-Perot cavities utilize the interference effect of light waves between two reflecting surfaces to monitor temperature. Changes in the temperature of the environment being measured cause changes in the cavity length or the refractive index of the material, resulting in shifts in the interference fringes. By demodulating the shifts in the interference fringes, the temperature change of the environment being measured can be determined. For example, a hollow-core fiber Fabry-Perot cavity temperature sensor uses a single-mode fiber-hollow-core fiber-single-mode fiber structure, using silica or air as the dielectric medium. The reflected light from the two ends of the single-mode fiber is superimposed and interferes, resulting in a reflection signal that primarily depends on the change in the hollow-core fiber cavity length and the refractive index of the silica within the cavity. However, due to the low thermal expansion coefficient of silica, the sensitivity of hollow-core fiber Fabry-Perot cavity temperature sensors is limited.

[0003] Therefore, how to improve the sensitivity of the temperature detection system has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0004] The present invention provides a temperature detection system to solve the technical problem of low sensitivity of existing temperature detection systems and achieve the effect of improving the sensitivity of temperature measurement.

[0005] In a first aspect, the present invention provides a temperature detection system comprising: a broadband light source, a fiber circulator, a fiber Fabry-Perot cavity sensor, a fiber Mach-Zehnder interferometer, a constant temperature chamber, and a spectrometer;

[0006] The broadband light source, the optical fiber Fabry-Perot cavity sensor and the optical fiber Mach-Zehnder interferometer are all connected to the optical fiber circulator;

[0007] The optical fiber Mach-Zehnder interferometer device is connected to the spectrometer;

[0008] The detection cavity of the optical fiber Fabry-Perot cavity sensor is arranged in the environment to be measured;

[0009] The optical fiber Mach-Zehnder interferometer is arranged in the constant temperature box, and the optical fiber Mach-Zehnder interferometer is used to cooperate with the optical fiber Fabry-Perot cavity sensor to form a first-order vernier effect to realize temperature detection of the environment to be measured.

[0010] Preferably, the optical fiber Fabry-Perot cavity sensor comprises a first single-mode optical fiber and a first hollow-core optical fiber connected to each other;

[0011] The internal filler of the first hollow-core optical fiber is polydimethylsiloxane.

[0012] Preferably, the optical fiber Mach-Zehnder interferometer device comprises a second single-mode optical fiber, a first multi-mode optical fiber, a second hollow-core optical fiber, a second multi-mode optical fiber and a third single-mode optical fiber connected in sequence;

[0013] The second hollow core optical fiber comprises a hollow core cavity and a hollow core optical fiber cladding;

[0014] The hollow core optical fiber cladding is wrapped outside the hollow core cavity.

[0015] Preferably, the refractive index of the hollow-core optical fiber cladding is greater than the refractive index of the filler in the hollow-core cavity.

[0016] Preferably, the core diameters of the first multimode optical fiber and the second multimode optical fiber are both larger than the diameter of the hollow-core cavity.

[0017] Preferably, the length ratio of the first hollow-core optical fiber to the second hollow-core optical fiber is 1:12.35.

[0018] Preferably, the ratio of the first free spectral range of the optical fiber Fabry-Perot cavity sensor to the second free spectral range of the optical fiber Mach-Zehnder interferometer device is 2:1.

[0019] Preferably, the internal filler of the first hollow-core optical fiber is UV glue or epoxy glue.

[0020] Preferably, the internal filler of the first hollow-core optical fiber is polyimide.

[0021] In a second aspect, the present invention further provides a temperature detection method, using the above-mentioned temperature detection system, the method comprising:

[0022] The broadband light source of the temperature detection system generates an optical signal, and the optical signal is transmitted to the optical fiber Fabry-Perot cavity sensor of the temperature detection system through the optical fiber circulator of the temperature detection system; the detection cavity of the optical fiber Fabry-Perot cavity sensor is set in the environment to be measured;

[0023] The optical signal interferes in the optical fiber Fabry-Perot cavity sensor to generate a first optical interference signal;

[0024] The first optical interference signal is transmitted to the optical fiber Mach-Zehnder interferometer of the temperature detection system through the optical fiber circulator; the optical fiber Mach-Zehnder interferometer is arranged in a constant temperature box of the temperature detection system;

[0025] The first interference signal interferes in the optical fiber Mach-Zehnder interferometer to generate a second optical interference signal;

[0026] The spectrometer of the temperature detection system demodulates the wavelength of the inner envelope intersection of the second optical interference signal to obtain the temperature of the environment to be measured.

[0027] The present invention provides a temperature detection system and method. Compared with the prior art, the embodiments of the present invention have the following advantages:

[0028] (1) The combined design of two fiber Fabry-Perot cavity sensors with similar free spectral ranges and a fiber Mach-Zehnder interferometer device is adopted. The fiber optic Mach-Zehnder interferometer device provides a stable reference spectrum, making the sensing signal more dense, and achieving high-precision temperature demodulation through slight changes in the wavelength of the inner envelope intersection.

[0029] (2) Ability to find the most suitable upgrade version for each device from a massive database of software versions. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic structural diagram of a temperature detection system provided by a preferred embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the optical path of a fiber Fabry-Perot cavity sensor provided by a preferred embodiment of the present invention;

[0032] Figure 3 Schematic diagram of the optical path of a fiber-optic Mach-Zehnder interferometer device provided by a preferred embodiment of the present invention;

[0033] Figure 4 This is a schematic diagram of the steps of a temperature detection method provided by a preferred embodiment of the present invention;

[0034] Reference numerals:

[0035] 1- broadband light source, 2- fiber circulator, 3- fiber Fabry-Perot cavity sensor, 4- fiber Mach-Zehnder interferometer, 5- spectrometer, 31- first single-mode fiber 31, 32- first hollow-core fiber, 33- polydimethylsiloxane, 41- second single-mode fiber, 42- first multimode fiber, 43- second hollow-core fiber, 44- second multimode fiber, 45- third single-mode fiber. DETAILED DESCRIPTION

[0036] The following is a detailed explanation of the embodiments of the present invention in conjunction with the accompanying drawings. The embodiments are provided for illustrative purposes only and cannot be understood as limitations on the present invention. The accompanying drawings are for reference and illustration purposes only and do not constitute a limitation on the scope of patent protection of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In the description of the present invention, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, the meaning of "multiple" is two or more.

[0037] In the description of the present invention, it should be noted that, unless otherwise expressly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be a communication between the two components. The terms "vertical", "horizontal", "left", "right", "up", "down" and similar expressions used herein are for illustrative purposes only, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] In describing the present invention, it should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0039] The vernier effect is a physical phenomenon that primarily exploits the large-scale shift in alignment caused by small changes in measured values. A similar vernier effect also exists in optics. For example, the reflection or transmission spectrum of a broadband light source after passing through a Fabry-Perot cavity forms a comb spectrum. By adjusting device parameters, the peak spacing can be adjusted, resulting in a comb spectrum with slightly different peak spacing. By detecting the initially aligned and currently aligned peaks, small peak shifts can be amplified and read, improving measurement sensitivity.

[0040] The amplification factor of temperature detection systems based on the optical Vernier effect is limited by the available wavelength range. The first-order harmonic Vernier effect can further increase the amplification factor several times and achieve higher resolution without compromising signal detection and monitoring. The inner envelope of the first-order harmonic Vernier effect differs from the upper envelope typically monitored in the optical Vernier effect, providing a crossover point with wavelength shifts more suitable for sensing.

[0041] In view of this, in an embodiment of the present invention, a temperature detection system is provided. Figure 1 The fiber optic temperature sensor includes: a broadband light source 1, a fiber optic circulator 2, a fiber optic Fabry-Perot cavity sensor 3, a fiber optic Mach-Zehnder interferometer 4, a constant temperature box and a spectrometer 5; the broadband light source, the fiber optic Fabry-Perot cavity sensor 3 and the fiber optic Mach-Zehnder interferometer 4 are all connected to the fiber optic circulator; the fiber optic Mach-Zehnder interferometer 4 is connected to the spectrometer 5; the detection cavity of the fiber optic Fabry-Perot cavity sensor 3 is arranged in the environment to be measured; the fiber optic Mach-Zehnder interferometer 4 is arranged in the constant temperature box, and the fiber optic Mach-Zehnder interferometer 4 is used to cooperate with the fiber optic Fabry-Perot cavity sensor 3 to form a first-order vernier effect to realize temperature detection of the environment to be measured.

[0042] In a preferred embodiment of the present application, light is emitted from a broadband light source, reaches the first port of the fiber optic circulator, and is input into the fiber optic Fabry-Perot cavity sensor 3 through the second port of the fiber optic circulator. Figure 1 As shown, the optical fiber Fabry-Perot cavity sensor 3 includes a first hollow core fiber 32 filled with polydimethylsiloxane 33 and a first single-mode fiber 31. The polydimethylsiloxane 33 is filled in the hollow core cavity of the entire first hollow core fiber 32. The first hollow core fiber 32 and the first single-mode fiber 31 are connected to each other. Figure 2Figure 3 shows a schematic diagram of the optical path of a fiber-optic Fabry-Perot cavity sensor 3. The two reflective surfaces of the fiber-optic Fabry-Perot cavity sensor 3 are the interface between the first single-mode fiber 31 and polydimethylsiloxane 33, and the interface between polydimethylsiloxane 33 and the ambient air to be measured. Light reflected from these two reflective surfaces superimposes and interferes with each other. Polydimethylsiloxane 33 forms a curved surface at the end of the first hollow-core fiber 32. This curved surface expands outward when the temperature rises and contracts inward when the temperature drops. Temperature changes cause polydimethylsiloxane 33 to undergo thermal expansion and thermo-optic effects. The thermal expansion coefficient of polydimethylsiloxane 33 is positive, causing the cavity length formed by polydimethylsiloxane 33 within the first hollow-core fiber 32 to change. The thermo-optic coefficient is negative, causing the refractive index of polydimethylsiloxane 33 to change, resulting in a shift in the interference spectrum. The calibrated sensor adjusts the temperature of the ambient air to be measured based on the wavelength shift length of the interference spectrum.

[0043] The internal filler of the first hollow-core optical fiber 32 should be a polymer material with a high thermal expansion coefficient and / or strong thermo-optical effect. UV glue can also be used. After curing, UV glue has good optical transparency, a high thermal expansion coefficient, strong thermo-optical effect, and a refractive index that changes significantly with temperature. Epoxy glue can also be used. Epoxy glue has good stability and thermal expansion coefficient, and is highly sensitive to temperature changes. Polyimide can also be used. Polyimide has high heat resistance and an adjustable refractive index, making it particularly suitable for applications in high-temperature environments.

[0044] In the preferred embodiment of the present application, the interference light reflected from the fiber Fabry-Perot cavity sensor 3 reaches the second port of the fiber circulator again, and is input into the fiber Mach-Zehnder interferometer 4 through the third port of the fiber circulator. Figure 1 As shown, the optical fiber Mach-Zehnder interferometer device 4 includes a second single-mode optical fiber 41, a first multi-mode optical fiber 42, a second hollow-core optical fiber 43, a second multi-mode optical fiber 44 and a third single-mode optical fiber 45 connected in sequence, a hollow-core cavity of the second hollow-core optical fiber 43 and a hollow-core optical fiber cladding, and the hollow-core optical fiber cladding is wrapped outside the hollow-core cavity. The core diameters of the first multi-mode optical fiber 42 and the second multi-mode optical fiber 44 are both larger than the diameter of the hollow-core cavity of the second hollow-core optical fiber 43, and the refractive index of the hollow-core optical fiber cladding is larger than the refractive index of the filler in the hollow-core cavity. The filler in the hollow-core cavity is generally air, and a material with a refractive index not much different from that of air can also be selected as the filler. As shown in FIG. Figure 3The figure shows the optical path of a fiber-optic Mach-Zehnder interferometer 4. Light first passes through a second single-mode fiber 41 before entering a first multimode fiber 42. Because the diameter of the first multimode fiber 42 is larger than the diameter of the hollow core cavity of the second hollow-core fiber 43, some of the light enters the hollow core cavity of the second hollow-core fiber 43, while the remaining light enters the hollow-core fiber cladding. Because the refractive index of the hollow-core fiber cladding is greater than that of the filler in the hollow-core cavity, the light enters the hollow-core fiber cladding, exciting higher-order modes of light. Higher-order modes of light are optical field modes with specific spatial distributions and energy states formed during light transmission or reflection. These optical field modes typically have more complex structures than fundamental modes, including more complex wavefront shapes, higher energy distributions, and more nodes or antinodes.

[0045] In a preferred embodiment of the present invention, the filling material in the hollow core cavity of the second hollow core optical fiber 43 is air, and the refractive index of the hollow core optical fiber cladding should be greater than 1.4, such as quartz glass, with a refractive index of 1.45. However, the refractive index of the hollow core optical fiber cladding should not exceed 2.0, which can ensure the effective propagation of high-order modes without introducing excessive mode loss. If the refractive index of the hollow core optical fiber cladding is too high, it will lead to strong mode loss, thereby affecting the stability of the interference effect. The refractive index of the hollow core optical fiber cladding also needs to ensure that sufficient mode matching is formed at the interface between the second multimode optical fiber 44 and the second hollow core optical fiber 43 to enhance the effect of mode coupling and ensure that the light propagating in the hollow core optical fiber cladding and the light propagating in the hollow core cavity can effectively interfere. The light propagating in the hollow-core fiber cladding and the light propagating in the hollow-core cavity enter the second multimode optical fiber 44. Due to the difference in refractive index between air and the hollow-core optical fiber cladding, the two beams of light produce an interference effect in the second multimode optical fiber 44. Finally, the interfered light enters the spectrometer 5 through the third single-mode optical fiber 45, and the signal of the Fabry-Perot cavity sensor is superimposed on the signal of the optical fiber Mach-Zehnder interferometer 4.

[0046] During the temperature measurement process, the fiber optic Fabry-Perot cavity sensor 3 is placed in the environment to be measured, and the fiber optic Mach-Zehnder interferometer 4 is placed in a constant temperature box. The constant temperature box provides a constant temperature environment, which allows the fiber optic Mach-Zehnder interferometer 4 to provide a specific frequency signal. The fiber optic Mach-Zehnder interferometer 4 is used to cooperate with the fiber optic Fabry-Perot cavity sensor 3 to form a vernier effect to achieve temperature detection of the environment to be measured.

[0047] In a preferred embodiment of the present application, the length ratio of the first hollow-core fiber 32 to the second hollow-core fiber 43 is 1:12.35. This ratio results in a ratio of 2:1 between the first free spectral range of the fiber-optic Fabry-Perot cavity sensor 3 and the second free spectral range of the fiber-optic Mach-Zehnder interferometer device 4. This results in a first-order harmonic vernier effect in the fiber-optic Fabry-Perot cavity sensor 3 and the fiber-optic Mach-Zehnder interferometer device 4. This first-order harmonic vernier effect mechanism can increase sensor sensitivity by 12 times.

[0048] In a preferred embodiment of the present invention, the first hollow-core fiber 32 of the fiber-optic Fabry-Perot cavity sensor 3 has an inner diameter of 50 microns, an outer diameter of 125 microns, and a length of 160 microns. The first multimode fiber 42 and second multimode fiber 44 of the fiber-optic Mach-Zehnder interferometer 4 have inner diameters of 105 microns and lengths of 1 millimeter. The second hollow-core fiber 43 has a length of 1.8 millimeters. The diameter of the hollow-core cavity is 50 microns, and the outer diameter of the hollow-core fiber cladding is 125 microns. These dimensions produce the best contrast in the interference fringes.

[0049] In a preferred embodiment of the present invention, the spectrometer 5 is configured to obtain the temperature of the environment to be measured by demodulating the wavelength of the inner envelope intersection point generated by the interference light signals of the superimposed fiber Fabry-Perot cavity sensor 3 and the fiber Mach-Zehnder interferometer 4.

[0050] The optical fiber Fabry-Perot cavity sensor 3 is superimposed on the optical fiber Mach-Zehnder interferometer 4 to generate an inner envelope. When the temperature of the measured environment changes, the change in the measured environment temperature is demodulated according to the change in the moving wavelength of the inner envelope intersection.

[0051] For the optical fiber Fabry-Perot cavity sensor 3 and the optical fiber Mach-Zehnder interferometer 4, the interference of light follows the following expression:

[0052]

[0053] Among them, I FPI1 represents the intensity of the interference light, I1 and I2 represent the intensities of the two coherent light beams respectively, n represents the difference in refractive index of the medium through which the two light beams pass, L represents the difference in the distance the two light beams travel, and λ is the wavelength of the light.

[0054] Furthermore, the interference trough of the optical fiber Mach-Zehnder interferometer is:

[0055]

[0056] Wherein, n1 represents the refractive index difference between the hollow-core fiber cladding and the filler in the hollow-core cavity in the optical fiber Mach-Zehnder interferometer device, and L1 is the length of the hollow-core cavity in the optical fiber Mach-Zehnder interferometer device.

[0057] The interference trough of the optical fiber Fabry-Perot cavity sensor 3 is:

[0058]

[0059] Wherein, n2 represents the refractive index of polydimethylsiloxane, which is approximately 1.39, and L2 is the length of the first hollow-core optical fiber in the optical fiber Fabry-Perot interferometer device.

[0060] Furthermore, the first free spectrum of the optical fiber Fabry-Perot cavity sensor 3 is:

[0061]

[0062] Then the second free spectrum of the optical fiber Mach-Zehnder interferometer 4 is:

[0063]

[0064] The intensity of the superimposed spectrum of the second free spectrum and the first free spectrum is:

[0065]

[0066] For simple calculation, considering I1I2≈I3I4, the sum of the last two terms of formula (6) can be simplified to:

[0067]

[0068] When the optical path lengths of the fiber Fabry-Perot cavity sensor 3 and the fiber Mach-Zehnder interferometer 4 are close, the formula (7) It is approximately equal to the reflection spectrum frequency of the optical fiber Fabry-Perot cavity sensor 3 and the optical fiber Mach-Zehnder interferometer 4. The change of the amplitude wavelength of the superimposed spectrum is given by Determined, the free spectral range of the superimposed spectrum is:

[0069]

[0070] First free spectral range (FSR) of the fiber optic Fabry-Perot cavity sensor 3 FPI 4. Second Free Spectral Range (FSR) with Fiber Mach-Zehnder Interferometer MZI If the ratio is 2, the size of the outer envelope intersection of the superimposed spectrum is:

[0071]

[0072] The size of the inner envelope intersection of the superimposed spectrum is:

[0073]

[0074] According to formula (9) and formula (10), the inner envelope amplification coefficient Min is the outer envelope magnification factor M envelope Twice, expressed as:

[0075]

[0076] The first free spectral range FSR of the fiber optic Fabry-Perot cavity sensor 3 FPI 4. Second Free Spectral Range (FSR) with Fiber Mach-Zehnder Interferometer MZI The ratio is 2. It can be deduced that the ratio of the length of the first hollow-core fiber 32 of the optical fiber Fabry-Perot cavity sensor 3 to the length of the second hollow-core fiber 43 of the optical fiber Mach-Zehnder interferometer 4 is 1:12.35. At this point, the optical fiber Fabry-Perot cavity sensor 3 and the optical fiber Mach-Zehnder interferometer 4 produce a first-order harmonic vernier effect.

[0077] In the basic optical vernier effect, the maximum amplification factor is limited by the free spectral range of the upper envelope, where one period should remain within the wavelength range available to the temperature detection system. In the case of the first-order harmonic effect of this application, the maximum amplification factor is not directly limited by the free spectral range of the inner envelope. Even if the period of the upper envelope exceeds the available wavelength range, the inner envelope intersection can still be used to monitor wavelength shifts.

[0078] Based on the temperature detection system, an embodiment of the present invention further provides a temperature detection method. The method adopts the temperature detection system disclosed in the embodiment of the present invention, and the method includes:

[0079] S1, the broadband light source of the temperature detection system generates an optical signal, and transmits the optical signal to the optical fiber Fabry-Perot cavity sensor of the temperature detection system through the optical fiber circulator of the temperature detection system; the detection cavity of the optical fiber Fabry-Perot cavity sensor is set in the environment to be measured;

[0080] S2. The optical signal interferes in the optical fiber Fabry-Perot cavity sensor to generate a first optical interference signal;

[0081] S3, the first optical interference signal is transmitted to the optical fiber Mach-Zehnder interferometer of the temperature detection system through the optical fiber circulator; the optical fiber Mach-Zehnder interferometer is arranged in a constant temperature box of the temperature detection system;

[0082] S4. The first interference signal interferes in the optical fiber Mach-Zehnder interferometer to generate a second optical interference signal;

[0083] S5, the temperature detection system spectrometer demodulates the wavelength of the inner envelope intersection of the second optical interference signal to obtain the temperature of the measured environment.

[0084] In a preferred embodiment of the present invention, a temperature detection system and method are provided, comprising: a broadband light source, a fiber optic circulator, a fiber optic Fabry-Perot cavity sensor, a fiber optic Mach-Zehnder interferometer, a constant temperature chamber, and a spectrometer; the broadband light source, the fiber optic Fabry-Perot cavity sensor, and the fiber optic Mach-Zehnder interferometer are all connected to the fiber optic circulator; the fiber optic Mach-Zehnder interferometer is connected to the spectrometer; the detection cavity of the fiber optic Fabry-Perot cavity sensor is located in the environment to be measured; the fiber optic Mach-Zehnder interferometer is located in the constant temperature chamber, and the fiber optic Mach-Zehnder interferometer is used to cooperate with the fiber optic Fabry-Perot cavity sensor to form a vernier effect to achieve temperature detection of the environment to be measured. The temperature detection system provided in this application adopts a combined design of two fiber optic Fabry-Perot cavity sensors with similar free spectral ranges and a fiber optic Mach-Zehnder interferometer. The fiber optic Mach-Zehnder interferometer device provides a stable reference spectrum, making the sensing signal more concentrated, and achieves high-precision temperature demodulation through slight changes in the wavelength of the inner envelope intersection.

[0085] Each embodiment in this specification is described in a progressive manner, and the same or similar parts of each embodiment can be directly referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. It should be noted that the various technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0086] The above-described embodiments merely represent several preferred implementations of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art can make several improvements and substitutions without departing from the technical principles of the present invention, and such improvements and substitutions should also be considered within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be based on the scope of protection of the claims.

Claims

1. A temperature detection system, characterized in that: include: Broadband light sources, fiber circulators, fiber Fabry-Perot cavity sensors, fiber Mach-Zehnder interferometers, thermostats, and spectrometers; The broadband light source, the optical fiber Fabry-Perot cavity sensor and the optical fiber Mach-Zehnder interferometer are all connected to the optical fiber circulator; The optical fiber Mach-Zehnder interferometer device is connected to the spectrometer; The detection cavity of the optical fiber Fabry-Perot cavity sensor is arranged in the environment to be tested; The optical fiber Mach-Zehnder interferometer is arranged in the constant temperature box, and the optical fiber Mach-Zehnder interferometer is used to cooperate with the optical fiber Fabry-Perot cavity sensor to form a first-order vernier effect to realize temperature detection of the environment to be measured.

2. The temperature detection system according to claim 1, characterized in that: The optical fiber Fabry-Perot cavity sensor comprises a first single-mode optical fiber and a first hollow-core optical fiber connected to each other; The internal filler of the first hollow core optical fiber is polydimethylsiloxane.

3. The temperature detection system according to claim 2, characterized in that: The optical fiber Mach-Zehnder interferometer device comprises a second single-mode optical fiber, a first multi-mode optical fiber, a second hollow-core optical fiber, a second multi-mode optical fiber and a third single-mode optical fiber connected in sequence; The second hollow core optical fiber comprises a hollow core cavity and a hollow core optical fiber cladding; The hollow core optical fiber cladding is wrapped outside the hollow core cavity.

4. The temperature detection system according to claim 3, characterized in that: The refractive index of the hollow core optical fiber cladding is greater than the refractive index of the filler in the hollow core cavity.

5. The temperature detection system according to claim 3, characterized in that: The core diameters of the first multimode optical fiber and the second multimode optical fiber are both larger than the diameter of the hollow core cavity.

6. The temperature detection system according to claim 3, characterized in that: The length ratio of the first hollow-core optical fiber to the second hollow-core optical fiber is 1:12.

35.

7. The temperature detection system according to claim 6, characterized in that: The ratio of the first free spectral range of the optical fiber Fabry-Perot cavity sensor to the second free spectral range of the optical fiber Mach-Zehnder interferometer device is 2:

1.

8. The temperature detection system according to claim 2, characterized in that: The internal filler of the first hollow-core optical fiber is UV glue or epoxy glue.

9. The temperature detection system according to claim 2, characterized in that: The internal filler of the first hollow core optical fiber is polyimide.

10. A temperature detection method, characterized in that: Using the temperature detection system according to any one of claims 1 to 9, the method comprises: The broadband light source of the temperature detection system generates an optical signal, and the optical signal is transmitted to the optical fiber Fabry-Perot cavity sensor of the temperature detection system through the optical fiber circulator of the temperature detection system; the detection cavity of the optical fiber Fabry-Perot cavity sensor is arranged in the environment to be tested; The optical signal interferes in the optical fiber Fabry-Perot cavity sensor to generate a first optical interference signal; The first optical interference signal is transmitted to the optical fiber Mach-Zehnder interferometer of the temperature detection system through the optical fiber circulator; the optical fiber Mach-Zehnder interferometer is arranged in a constant temperature box of the temperature detection system; The first interference signal interferes in the optical fiber Mach-Zehnder interferometer to generate a second optical interference signal; The spectrometer of the temperature detection system demodulates the wavelength of the inner envelope intersection of the second optical interference signal to obtain the temperature of the environment to be measured.

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