Single cell temperature, pressure and gas composite sensing optical fiber probe and system and application

Abstract

The present invention discloses a single cell temperature, pressure and gas composite sensing optical fiber probe, system and application. Single cell temperature, pressure and gas composite sensing optical fiber probe, temperature and pressure sensing optical fiber probe and gas sensing optical fiber probe; the temperature and pressure sensing optical fiber probe comprises a first single-mode optical fiber, a germanium-doped single-mode optical fiber and a microstructure optical fiber connected in sequence; the germanium-doped single-mode optical fiber is engraved with a commercial single-mode optical fiber Bragg grating for sensing temperature; the microstructure optical fiber is engraved with a pressure-sensitive optical fiber Bragg grating for sensing pressure; the gas sensing optical fiber probe comprises a second single-mode optical fiber and a hollow-core light-guiding optical fiber connected thereto. The battery temperature, pressure and gas quasi-distributed optical fiber sensing system comprises: a sensing module, a demodulation module and a multi-channel optical switch module; the sensing module comprises a plurality of the temperature, pressure and gas single cell composite sensing optical fiber probes. The present invention effectively ensures the safety of the power battery pack by real-time monitoring of the temperature, pressure and gas of the single cell.

Description

Technical Field

[0001] The present invention relates to the field of sensing technology, and in particular to a single cell temperature, pressure and gas composite sensing optical fiber probe, system and application. Background Art

[0002] In the field of battery sensing, key monitoring indicators include operating voltage, temperature, internal pressure, and the types and concentrations of gases generated by electrolyte decomposition. Currently, battery safety monitoring is limited to the surface temperature of the battery. Traditional temperature sensing solutions include: thermocouples, thermistors, acoustic probes, electrochemical impedance spectroscopy, etc. However, these solutions can only sense the shell temperature of the battery surface. Even though the internal center temperature of the battery can be inferred by analyzing the heat conduction model, and the temperature data can be used to infer whether the battery has reached a thermal runaway state and whether the internal pressure of the battery is too high and whether gas is generated, in general, the results of the above sensing solutions are indirect and approximate, and are not very reliable.

[0003] With the promotion and development of new energy, the market size of new energy vehicles is gradually expanding. In new energy vehicles, the power battery pack is the main power source of the vehicle. It is composed of a series of single cells connected in series and parallel, and the total number of battery cells can reach hundreds. At present, the safety inspection of the power battery pack only stays on the temperature of the entire battery module, and does not involve the internal temperature and pressure of each single cell, as well as the CO, CO2 and various VOC gases produced by the decomposition of the electrolyte during thermal runaway, which poses a great safety hazard. Summary of the invention

[0004] In view of the above-mentioned defects of the prior art, the purpose of the present invention is to provide a single cell temperature, pressure and gas composite sensing optical fiber probe and system and application, so as to detect the operating temperature, internal pressure and type and concentration of gas produced by electrolyte decomposition of each single cell in the power battery pack. Optical fiber sensors have significant advantages such as light structure, electromagnetic immunity, long service life and high sensitivity. The advantage of using optical fiber sensing solutions for batteries is that they can be embedded in single cells to measure their internal temperature, pressure, types and concentrations of gases that may be produced while occupying very little internal space of the battery, and will hardly affect the performance of the battery.

[0005] A single cell temperature, pressure and gas composite sensing optical fiber probe comprises a temperature and pressure sensing optical fiber probe and a gas sensing optical fiber probe; the temperature and pressure sensing optical fiber probe comprises a first single-mode optical fiber, a germanium-doped single-mode optical fiber and a microstructure optical fiber which are connected in sequence; the germanium-doped single-mode optical fiber is engraved with a commercial single-mode optical fiber Bragg grating for sensing temperature; the microstructure optical fiber is engraved with a pressure-sensitive optical fiber Bragg grating for sensing pressure; the gas sensing optical fiber probe comprises a second single-mode optical fiber and a hollow-core light-guiding optical fiber which are connected in sequence.

[0006] The pressure sensing optical fiber probe adopts a microstructure optical fiber, including a double-hole optical fiber or a suspended core optical fiber.

[0007] The gas sensing optical fiber probe adopts a bandgap microstructure optical fiber, including a hollow-core photonic crystal optical fiber or a hollow-core anti-resonance optical fiber.

[0008] The side of the hollow-core light-guiding optical fiber is provided with a plurality of through holes for maintaining communication with the external battery gas environment; the end of the hollow-core light-guiding optical fiber is provided with a high-reflectivity structure for returning the signal light of the detection gas.

[0009] A quasi-distributed optical fiber sensing system for battery temperature, pressure and gas comprises: a sensing module, a demodulation module and a multi-channel optical switch module; the sensing module comprises a plurality of the temperature, pressure and gas single-cell composite sensing optical fiber probes; the demodulation module comprises an optical fiber grating demodulator and an optical fiber gas demodulator, the optical fiber grating demodulator is used to demodulate temperature and pressure information, and the optical fiber gas demodulator is used to demodulate gas concentration information; the multi-channel optical switch module comprises a plurality of optical switch devices, which are used to output lasers emitted by different demodulators in the demodulation module to the temperature and pressure sensing optical fiber probe or the gas sensing optical fiber probe of a specific single cell.

[0010] The fiber grating demodulator is based on a wavelength scannable semiconductor laser or a broadband light source and a tunable filter.

[0011] The fiber optic gas demodulator adopts tunable laser absorption spectroscopy technology, and can connect narrow-band lasers corresponding to different gas absorption peaks to the fiber optic gas demodulator through a 1×M optical switch, where M is the number of gas types that need to be monitored.

[0012] The multi-channel optical switch module includes a 1×2 optical switch and a 1×N optical switch. The 1×2 optical switch is a tree-type coupler with one input end and two output ends; the 1×N optical switch is a tree-type coupler with one input end and N output ends, where N is equal to the number of single cells that need to be monitored.

[0013] An application method of the battery temperature, pressure and gas quasi-distributed optical fiber sensing system. When working, two detection lights are respectively started from the built-in light sources of the optical fiber Bragg grating demodulator and the optical fiber gas demodulator, and are combined into one detection light after passing through a 1×2 optical switch, and then divided into multiple detection lights through a 1×N optical switch as the detection light of each group of temperature, pressure and gas sensing optical fiber probes installed inside the single cell. The detection light returned from each group of temperature, pressure and gas sensing optical fiber probes installed inside the single cell is then returned to the optical fiber Bragg grating demodulator or the optical fiber gas demodulator through the 1×N optical switch and the 1×2 optical switch in turn to be analyzed and processed; when the temperature and pressure inside the single cell change, the reflection peak wavelengths of the commercial single-mode optical fiber Bragg grating and the pressure-sensitive optical fiber Bragg grating will drift, and the change of the temperature and pressure signals can be obtained by analyzing the wavelength offset of the two, and the concentration of the corresponding CO, CO2 and multiple VOC gases can be obtained by monitoring the second harmonic amount of the specific wavelength light in the detection light returned by the gas sensing optical fiber probe.

[0014] In an optional embodiment, the length of the germanium-doped single-mode optical fiber is equal to 5 cm, the length of the double-hole optical fiber is equal to 5 cm, the length of the hollow-core light-guiding optical fiber is equal to 10 cm, and the thickness of the reflective film on the end face of the hollow-core light-guiding optical fiber is equal to 10 microns.

[0015] In an optional embodiment, the length of the commercial single-mode fiber Bragg grating and the pressure-sensitive fiber Bragg grating is 3 mm, and the reflection peak wavelength is around 1550 nm.

[0016] Beneficial effects of the present invention:

[0017] The battery temperature, pressure and gas quasi-distributed optical fiber sensing system provided by the present invention monitors the internal temperature, pressure and the type and concentration of the gas generated by the decomposition of the electrolyte of each battery cell in the power battery pack through a multi-channel optical switch module, a sensing module and a demodulation module; monitors the temperature change inside the single cell to determine whether the battery is in a normal working state; monitors the pressure change inside the single cell to determine whether gas is generated inside the battery so as to timely check; monitors the type and concentration of the gas generated inside the single cell to determine the degree of electrolyte decomposition in the battery and the degree to which the battery is in a dangerous state, and gives an alarm in time; and monitors each single cell in real time to determine which single cell has a fault, and then effectively check to avoid endangering the safety of the entire power battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram of a temperature and pressure sensing optical fiber probe according to one embodiment of the present invention.

[0019] Figure 2It is a schematic structural diagram of a gas sensing optical fiber probe according to one embodiment of the present invention.

[0020] Figure 3 It is a structural schematic diagram of a battery temperature, pressure and gas quasi-distributed optical fiber sensing system according to one embodiment of the present invention.

[0021] Figure 4 Schematic diagram of the reflection spectra of a commercial single-mode fiber Bragg grating and a pressure-sensitive fiber Bragg grating from a temperature and pressure sensing fiber probe according to an embodiment of the present invention.

[0022] Figure 5 FIG. 1 is a schematic diagram of a second harmonic spectrum from a gas sensing optical fiber probe according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The technical solutions in the examples of the present invention will be described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The terms "first", "second", etc. in the specification and claims of the embodiments of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0026] See also Figure 1 , Figure 1 It is a schematic structural diagram of a temperature and pressure sensing optical fiber probe according to one embodiment of the present invention.

[0027] like Figure 1 As shown, the temperature and pressure sensing optical fiber probe comprises a first single-mode optical fiber 5, a germanium-doped single-mode optical fiber 6, and a microstructure optical fiber 9. A commercial single-mode optical fiber Bragg grating 7 is engraved on the germanium-doped single-mode optical fiber 6, and a pressure-sensitive optical fiber Bragg grating 8 is engraved on the microstructure optical fiber 9. The first single-mode optical fiber 5, the germanium-doped single-mode optical fiber 6, and the microstructure optical fiber 9 are all fused by arc discharge.

[0028] The pressure-sensitive fiber Bragg grating is implemented by microstructure fiber. In this embodiment, the specific microstructure fiber used is a double-hole fiber. In other embodiments, the pressure-sensitive fiber Bragg grating can be implemented by other microstructure fibers (such as suspended core fibers). For ease of understanding, Figure 1 Also shown are a cross section 10 of a germanium-doped single-mode optical fiber and a cross section 11 of a microstructure optical fiber (a double-hole optical fiber in this embodiment).

[0029] Specifically, a commercial single-mode fiber Bragg grating can be written into a germanium-doped single-mode fiber using a mask ultraviolet photolithography method, and a pressure-sensitive fiber Bragg grating can be written into a microstructured fiber. Other methods such as a dual-beam interferometry method can also be used to write a fiber Bragg grating.

[0030] By using masks with different grating pitches, the reflection peak wavelength (also known as the center wavelength) of the inscribed fiber Bragg grating is different. In particular, the center wavelength of the commercial single-mode fiber Bragg grating 7 is λ1, and the center wavelength of the pressure-sensitive fiber Bragg grating 8 is λ2.

[0031] The center wavelength of the fiber Bragg grating will drift due to the influence of ambient temperature, pressure and strain. In this embodiment, since the battery charging and discharging process will generate heat and gas, the center wavelength drift of the fiber Bragg grating is mainly caused by the temperature and pressure inside the battery; since the optical fiber is almost no longer stretched after being fixed near the top position inside the battery, the influence of strain can be ignored. The center wavelength offset of the commercial single-mode fiber Bragg grating 7 and the pressure-sensitive fiber Bragg grating 8 is given by the following formula:

[0032] Δλ1=k1·ΔT+ k2·ΔP…………………………………………(1)

[0033] Δλ2=k3·ΔT+ k4·ΔP…………………………………………(2)

[0034] In this embodiment, inside the single cell, the germanium-doped single-mode optical fiber 6 and the double-hole optical fiber 9 are both immersed in the electrolyte liquid. When the temperature changes, the sensitivity k1 of the commercial single-mode fiber Bragg grating 7 to temperature and the sensitivity k3 of the pressure-sensitive fiber Bragg grating 8 to temperature are of the same order of magnitude. When the battery is not used normally and part of the electrolyte decomposes to produce gas, the germanium-doped single-mode optical fiber 6 and the double-hole optical fiber 9 will be surrounded or filled with gas (when gas is generated, it will first fill the top of the battery and cause the liquid level of the electrolyte liquid to drop, so the temperature / air pressure sensing optical fiber probe will be exposed to the gas). When the gas inside the battery increases and the air pressure increases, the air pressure of the two air columns inside the double-hole optical fiber 9 will also increase, and the pressure-sensitive fiber Bragg grating 8 will be more significantly affected by the air pressure. Therefore, the sensitivity k4 of the pressure-sensitive fiber Bragg grating 8 to air pressure will be much greater than the sensitivity k2 of the commercial single-mode fiber Bragg grating to air pressure. According to formulas (1) and (2), the respective changes in temperature and air pressure can be calculated:

[0035] ΔP = (k1Δλ2-k3Δλ1) / (k1k4-k2k3)……………………(3)

[0036] ΔT = (k4Δλ1-k2Δλ2) / (k1k4-k2k3)……………………(4).

[0037] See also Figure 2 , Figure 2 It is a schematic structural diagram of a gas sensing optical fiber probe according to one embodiment of the present invention.

[0038] like Figure 2 As shown, the gas sensing optical fiber probe includes a second single-mode optical fiber 12 and a hollow-core light-guiding optical fiber 13. The second single-mode optical fiber 12 and the hollow-core light-guiding optical fiber 13 are fused by arc discharge. There are a plurality of through holes 14 on the hollow-core light-guiding optical fiber, and a high reflectivity structure 15 is provided at the end of the hollow-core light-guiding optical fiber. Figure 2 The hollow-core light-guiding optical fiber cross section 16 and the hollow-core light-guiding optical fiber cross section 17 at the through hole are shown in FIG.

[0039] Among them, hollow-core light-guiding optical fiber refers to an optical fiber whose core layer is an air core. When light waves are transmitted in the air core, there is a certain amount of loss, which is called leaky mode, because the total reflection condition is not met. Since the length of the hollow-core light-guiding optical fiber used is very small, the light energy loss from the leaky mode can be ignored.

[0040] Specifically, a through hole 14 can be punched by femtosecond laser writing, and the through hole is used to maintain communication with the external battery gas environment, so that the gas generated by the decomposition of the electrolyte can be filled into the air core of the hollow-core light-guiding optical fiber. In this embodiment, the number of through holes on the hollow-core light-guiding optical fiber is 3. The high reflectivity structure is used to fold the light path, so that the optical path is doubled. In this embodiment, a layer of reflective film can be coated on the end face of the hollow-core light-guiding optical fiber by spin coating or the like.

[0041] According to the gas absorption spectrum theory, different gas types have different absorption coefficients for different wavelengths of light, which can be used to determine the gas composition in the air core of the hollow-core light-guiding optical fiber 13. In this embodiment, three gases, CO, CO2, and CH4, produced by electrolyte decomposition are taken as examples. According to the Beer-Lambert law:

[0042] A = lg(1 / T) = KLc…………………………………………(5)

[0043] Where A is the absorbance, T is the light transmittance, K is the gas absorption coefficient of light (unit: L / g·cm), L is the length of the gas absorption layer (unit: cm), and c is the gas concentration (unit: g / L).

[0044] In this embodiment, the concentrations of the three gases CO, CO2, and CH4 inside the battery are:

[0045] c i=3,4,5 = lg(1 / T) / 2LK i=3,4,5 …… ...

[0046] According to the HITRAN database, the absorption peak positions of CO, CO2 and CH4 in the near-infrared region are recorded as λ3 (1574nm), λ4 (1645nm) and λ5 (1654nm), respectively, and the corresponding absorption coefficients are recorded as K3, K4 and K5 (unit: L / g·cm), where L is the length of the hollow-core light-guiding fiber. The concentration of the corresponding gas can be calculated by monitoring the transmittance at a specific wavelength.

[0047] The sensitivity of lg(1 / T) corresponding to the concentration c is 2LK. Since the gas absorption coefficient is a certain value, the sensitivity of the sensor can be improved by increasing L. Specifically, the length of the hollow-core light-guiding fiber can be increased or the number of reflections of the light wave in the hollow-core light-guiding fiber can be increased.

[0048] Optionally, in order to further improve the detection precision and accuracy and eliminate environmental noise, the gas concentration can be monitored by tunable semiconductor laser absorption spectroscopy (TDLAS). By periodically modulating the injection current, the laser emitted by the tunable diode laser changes rapidly and periodically in a narrow range of wavelengths. When the laser emission wavelength is in the characteristic absorption spectrum range of the gas molecules, a complete gas absorption curve can be obtained. The properties and concentration information of the measured gas can be inferred using the absorption line type, intensity and other parameters of the absorption spectrum. The demodulation algorithm of the TDLAS demodulation part can use wavelength modulation spectroscopy technology. Modulation spectroscopy technology is based on direct absorption detection of the spectrum, superimposed with high-frequency signals for laser modulation, and a phase-locked amplifier is used to demodulate a specific frequency to extract gas absorption information. Since the laser is subjected to high-frequency sinusoidal modulation, the light beam carries the frequency information of the sinusoidal modulation signal. Since the peak of the second harmonic line type is at the center of the spectrum, it is symmetrical about the center of the spectrum. At the same time, among the even harmonics, the second harmonic line intensity is the strongest and easiest to obtain, so the second harmonic is used to detect gas.

[0049] See also Figure 3 , Figure 3 The structure diagram of the battery temperature, pressure and gas quasi-distributed optical fiber sensing system according to one embodiment of the present invention includes a demodulation module 1, a multi-channel optical switch module 2 and a sensor module 3.

[0050] The multi-channel optical switch module 2 includes a 1×2 optical switch and a 1×N optical switch. The 1×N optical switch is a tree-type coupler having one input terminal and N output terminals. In this embodiment, N is equal to the number of single cells to be monitored. The input terminals of the 1×2 optical switch and a 1×N optical switch are connected, so that at a moment, any one of the fiber Bragg grating demodulators or the fiber gas demodulators in the demodulation module 1 can be selected to be connected to any sensing fiber probe of the sensing module 3.

[0051] The sensing module 3 includes a plurality of temperature, pressure and gas composite sensing optical fiber probes installed inside the single cell as shown in the figure, each composite sensing probe includes a temperature and pressure sensing optical fiber probe and a gas sensing optical fiber probe, and the total number is N. Among them, the temperature probe is a commercial single-mode fiber Bragg grating sensor; the pressure probe is a pressure-sensitive fiber Bragg grating, which can be implemented by a microstructure optical fiber such as a double-hole optical fiber and a suspended core optical fiber; the gas probe is a hollow-core light-guiding optical fiber, which can be implemented by a bandgap microstructure optical fiber such as a hollow-core photonic crystal optical fiber and a hollow-core anti-resonance optical fiber.

[0052] The demodulation module 1 includes a fiber Bragg grating demodulator and a fiber gas demodulator. Among them, there are two implementation methods of the fiber Bragg grating demodulator, one is based on a wavelength scannable semiconductor laser, and the other is based on a broadband light source and a tunable filter; the implementation method of the fiber gas demodulator is based on tunable laser absorption spectroscopy technology, and can be connected to narrow-band lasers corresponding to different gas absorption peaks through a 1×M optical switch. M is the number of gas types that need to be monitored. In this embodiment, the number of channels of the demodulation module must be greater than or equal to N. In other embodiments, the number of output channels N of the multi-way optical switch module 2 and the number N of temperature, pressure and gas composite sensing optical fiber probes installed inside the single cell can be adjusted according to the number of batteries.

[0053] In this embodiment, the cladding diameter of the first single-mode optical fiber 5, the second single-mode optical fiber 12, and the germanium-doped single-mode optical fiber 6 used is equal to 125μm, and the core diameter is equal to 9μm; the cladding diameter of the double-hole optical fiber 9 used is equal to 125μm, and the core diameter is equal to 9μm. The diameters of the two air columns are between 20-50μm. The larger the diameter of the air column, the higher the sensitivity of the pressure-sensitive fiber Bragg grating 8 inscribed on the double-hole optical fiber 9 to the air pressure. The cladding diameter of the hollow-core light-guiding optical fiber 13 used is equal to 125μm, and the air core diameter is equal to 9μm. The diameter of the through hole 14 on the hollow-core light-guiding optical fiber should be less than or equal to the air core diameter. In this embodiment, the through hole diameter is equal to 5μm. The length of the germanium-doped single-mode optical fiber 6 used is equal to 5cm, the length of the double-hole optical fiber 9 is equal to 5cm, the length of the hollow-core light-guiding optical fiber 13 is equal to 10cm, and the thickness of the end-face reflective film 15 of the hollow-core light-guiding optical fiber is equal to 10μm. In other embodiments, the diameters and lengths of the germanium-doped single-mode optical fiber 6, the dual-hole optical fiber 9, the hollow-core light-guiding optical fiber 13, and the thickness of the reflective film 15 on the end face of the hollow-core light-guiding optical fiber can be adjusted according to actual needs.

[0054] In this embodiment, the length of the commercial single-mode fiber Bragg grating 7 and the pressure-sensitive fiber Bragg grating 8 is equal to 3 mm, and the reflection peak wavelength is near 1550 nm. Optionally, the reflection peak wavelength λ1 of the commercial single-mode fiber Bragg grating 7 is equal to 1550 nm, and the reflection peak wavelength λ2 of the pressure-sensitive fiber Bragg grating 8 is equal to 1555 nm. In other embodiments, the commercial single-mode fiber Bragg grating 7 and the pressure-sensitive fiber Bragg grating 8 can be designed to have other lengths according to actual needs, and the reflection peak wavelength can be designed to be other reflection peak wavelengths near 1550 nm.

[0055] The temperature and pressure sensing optical fiber probe and the gas sensing optical fiber probe are both located inside the single battery 4 near the top thereof. Their parameters and functions have been clearly described and will not be repeated here.

[0056] The single cell 4 is a lithium-ion power battery, which mainly includes two types: lithium iron phosphate battery and ternary lithium battery. The single cell structure mainly includes two types: cylindrical and rectangular. In this embodiment, the single cell selected is a rectangular ternary lithium battery with an outer size of 200*33*167mm. 3 In other embodiments, the type, shape and size of the battery can be adjusted.

[0057] In this embodiment, a broadband light source is used as the light source of the fiber optic temperature and pressure probe; a narrowband light source is used as the light source of the fiber optic gas probe. Two detection lights are respectively started from the built-in light sources of the fiber optic Bragg grating demodulator and the fiber optic gas demodulator, and are combined into one detection light after passing through a 1×2 optical switch, and then divided into multiple detection lights through a 1×N optical switch as the detection light of each group of temperature, pressure and gas sensing fiber optic probes installed inside the single cell. The detection light returned from each group of temperature, pressure and gas sensing fiber optic probes installed inside the single cell passes through the 1×N optical switch and the 1×2 optical switch in turn, and returns to the fiber optic Bragg grating demodulator or the fiber optic gas demodulator for analysis and processing.

[0058] See also Figure 4 , Figure 4 Schematic diagram of the reflection peak spectra of commercial single-mode fiber Bragg grating and pressure-sensitive fiber Bragg grating from a temperature and pressure sensing fiber probe according to an embodiment of the present invention. Intensity represents the signal light intensity, and Wavelength represents the wavelength of light. Figure 4 As shown in the figure, the reflection peak wavelengths of commercial single-mode fiber Bragg grating and pressure-sensitive fiber Bragg grating are λ1 and λ2 respectively (black solid line in the figure). Due to the changes in internal temperature and pressure during the use of the battery, the reflection peak wavelengths of commercial single-mode fiber Bragg grating and pressure-sensitive fiber Bragg grating are blue-shifted or red-shifted, and the offset is recorded as Δλ1 and Δλ2. The central wavelength position of the fiber Bragg grating after the offset is shown in the gray dotted line in the figure.

[0059] See also Figure 5 , Figure 5 Schematic diagram of gas absorption spectrum of one embodiment of the present invention. Intensity represents the signal light intensity, and Wavelength represents the wavelength of light. In this embodiment, λ3 represents the position of an absorption peak of CO gas in the near-infrared region. The three curves shown in the figure represent the second harmonic curves measured at different CO concentrations. The higher the peak value of the second harmonic, the greater the corresponding CO gas concentration.

Claims

1. A single cell temperature, pressure and gas composite sensing optical fiber probe, characterized in that: Including temperature and pressure sensing optical fiber probes and gas sensing optical fiber probes; The temperature and pressure sensing optical fiber probe comprises a first single-mode optical fiber, a germanium-doped single-mode optical fiber, and a microstructure optical fiber connected in sequence; the germanium-doped single-mode optical fiber is engraved with a commercial single-mode optical fiber Bragg grating for sensing temperature; the microstructure optical fiber is engraved with a pressure-sensitive optical fiber Bragg grating for sensing pressure; The gas sensing optical fiber probe comprises a second single-mode optical fiber and a hollow-core light-guiding optical fiber connected to each other; The microstructured optical fiber of the temperature and pressure sensing optical fiber probe comprises a double-hole optical fiber or a suspended core optical fiber; The gas sensing optical fiber probe adopts a bandgap microstructure optical fiber, including a hollow-core photonic crystal optical fiber or a hollow-core anti-resonance optical fiber.

2. The composite sensing optical fiber probe according to claim 1, characterized in that: The hollow-core light-guiding optical fiber is provided with a plurality of through holes on its side for maintaining communication with the external battery gas environment; A high reflectivity structure is provided at the end of the hollow-core light-guiding optical fiber for returning the signal light of the detection gas.

3. A battery temperature, pressure and gas quasi-distributed optical fiber sensing system, characterized in that: include: Sensing module, demodulation module and multi-channel optical switch module; The sensing module comprises a plurality of single cell temperature, pressure and gas composite sensing optical fiber probes as claimed in claim 1 or 2; The demodulation module includes a fiber grating demodulator and a fiber gas demodulator, wherein the fiber grating demodulator is used to demodulate temperature and pressure information, and the fiber gas demodulator is used to demodulate gas concentration information; The multi-channel optical switch module includes a plurality of optical switch devices, which are used to output the lasers emitted by different demodulators in the demodulation module to the temperature and pressure sensing optical fiber probe or the gas sensing optical fiber probe of a specific single cell.

4. The battery temperature, pressure and gas quasi-distributed optical fiber sensing system according to claim 3 is characterized in that: The fiber grating demodulator is based on a wavelength scannable semiconductor laser or a broadband light source and a tunable filter.

5. The battery temperature, pressure and gas quasi-distributed optical fiber sensing system according to claim 3 is characterized in that: The fiber optic gas demodulator adopts tunable laser absorption spectroscopy technology, and can connect narrow-band lasers corresponding to different gas absorption peaks to the fiber optic gas demodulator through a 1×M optical switch, where M is the number of gas types that need to be monitored.

6. The battery temperature, pressure and gas quasi-distributed optical fiber sensing system according to claim 3 is characterized in that: The multi-channel optical switch module includes a 1×2 optical switch and a 1×N optical switch. The 1×2 optical switch is a tree-type coupler with one input end and two output ends; the 1×N optical switch is a tree-type coupler with one input end and N output ends, where N is equal to the number of single cells that need to be monitored.

7. An application method of the battery temperature, pressure and gas quasi-distributed optical fiber sensing system according to claim 6, characterized in that: During operation, two detection lights start from the built-in light sources of the fiber Bragg grating demodulator and the fiber gas demodulator respectively, are combined into one detection light after passing through a 1×2 optical switch, and are then divided into multiple detection lights through a 1×N optical switch as the detection light of each group of temperature, pressure and gas sensing fiber probes installed inside the single cell. The detection light returned from each group of temperature, pressure and gas sensing fiber probes installed inside the single cell passes through the 1×N optical switch and the 1×2 optical switch in turn and returns to the fiber Bragg grating demodulator or the fiber gas demodulator for analysis and processing; when the temperature and pressure inside the single cell change, the reflection peak wavelengths of the commercial single-mode fiber Bragg grating and the pressure-sensitive fiber Bragg grating will drift. The changes in the temperature and pressure signals are obtained by analyzing the wavelength offsets of the two. The concentrations of the corresponding CO, CO2 and various VOC gases can be obtained by monitoring the second harmonic amount of the specific wavelength light in the detection light returned by the gas sensing fiber probe.

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