High temperature resistant optical fiber oil level sensor

Abstract

The application discloses a high-temperature-resistant optical fiber lubricating oil level sensor and belongs to the technical field of liquid level measurement. The sensor is composed of an optical fiber sensing array, a heat insulation window structure, a temperature control system and a sensing signal demodulation unit. The optical fiber sensing array adopts high-temperature-resistant special optical fiber, is linearly and closely arranged to form a high-density array, and realizes sub-millimeter level measurement accuracy. The heat insulation window structure adopts double-layer heat insulation design, integrates high-transmittance temperature-resistant base material, inert gas chamber and double sealing components, realizes low-loss transmission of optical signals, efficiently insulates high-temperature oil and gas, and is suitable for narrow installation space. The temperature control system monitors the ambient temperature in real time through the sensor, starts and stops the temperature rising and falling module adaptively, and guarantees stable operation of the demodulation unit under extreme temperature. The sensing signal demodulation unit is provided with an electromagnetic shielding shell, and provides a stable working environment for signal acquisition and processing. The application has the characteristics of high-temperature resistance, strong anti-interference and high precision.

Description

Technical Field

[0001] This invention relates to the field of liquid level detection technology, and specifically to a high-temperature resistant fiber optic lubricating oil level sensor. Background Technology

[0002] In lubrication systems used in aviation, industrial machinery, and other fields, real-time and accurate monitoring of lubricating oil levels is crucial for the safe operation of equipment. These scenarios commonly involve extreme temperatures, strong vibrations, high accelerations, and complex electromagnetic interference, placing stringent requirements on the temperature resistance, interference resistance, and structural stability of lubricating oil level sensors.

[0003] Existing lubricating oil level monitoring technologies have significant limitations: capacitive sensors are susceptible to environmental changes and have short maintenance cycles; hydrostatic sensors are susceptible to vibration and acceleration interference; float-type sensors have low resolution and are prone to jamming in high-viscosity lubricating oils; ultrasonic sensors are susceptible to surface foam, volatile vapors, and acoustic interference; radar sensors are susceptible to electromagnetic interference; interferometric fiber optic sensors are susceptible to vibration interference and require complex demodulation equipment; and fiber Bragg grating sensors are susceptible to vibration interference and have high manufacturing complexity. Furthermore, the isolation structure of ordinary fiber optic sensors has poor sealing performance, allowing high-temperature oil and gas to leak easily, and oil mist easily adheres to the fiber end face, interfering with reflected light signals and affecting measurement accuracy, making it difficult to meet the requirements of actual working conditions. Therefore, there is an urgent need for a high-temperature resistant lubricating oil level sensor that can simultaneously adapt to conditions of strong vibration, high acceleration, and strong electromagnetic interference. Summary of the Invention

[0004] The purpose of this invention is to provide a high-temperature resistant fiber optic lubricating oil level sensor to solve the problems of poor high-temperature resistance, low measurement accuracy, weak vibration resistance, weak anti-interference ability, and insufficient adaptability of traditional lubricating oil level sensors in lubricating oil systems in fields such as aviation and industrial machinery, thereby improving the measurement accuracy and stability of lubricating oil level sensors under complex working conditions.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A high-temperature resistant fiber optic lubricating oil level sensor is installed in the lubricating oil system reservoir via a fixed connector, and includes a sensing signal demodulation unit, a fiber optic sensing array, a heat-insulating window structure, and a temperature control system.

[0007] The sensor signal demodulation unit includes a light source, an image acquisition unit, a signal processing unit, and a voltage output port. The light source generates an optical signal and transmits it to the fiber optic sensor array via a heat-insulating window structure. The image acquisition unit receives the reflected optical signal and converts it into a first electrical signal, which is then sent to the signal processing unit. The signal processing unit calculates the liquid level result based on the received electrical signal and converts it into a second electrical signal, which is then output to an external control system via the voltage output port.

[0008] The fiber optic sensing array is located inside the lubricating oil system reservoir. It consists of multiple high-temperature resistant special optical fibers, which are arranged in a linear structure with close proximity along a one-dimensional direction. The end faces of the fiber optic sensing array are ground or polished and have an anti-oil mist coating. The fiber optic sensing array receives optical signals and generates reflected optical signals when it comes into contact with air or lubricating oil. The reflected optical signals are returned to the image acquisition unit through the heat-insulating window structure.

[0009] The temperature control system is thermally coupled to the sensor signal demodulation unit and is used to regulate the operating environment temperature of the sensor signal demodulation unit. The temperature control system includes a temperature sensor, a temperature control unit, a heating module, and a cooling module. The temperature sensor collects the ambient temperature of the sensor signal demodulation unit and transmits it to the temperature control unit. The temperature control unit is connected to both the heating module and the cooling module and has built-in temperature threshold determination logic. When the ambient temperature received by the temperature control unit is lower than a preset low temperature threshold, the heating module is activated to heat the environment around the sensor signal demodulation unit. When the received ambient temperature is higher than a preset high temperature threshold, the cooling module is activated to cool the environment around the sensor signal demodulation unit. This ensures the continuity and accuracy of the optical signal transmission and acquisition by the sensor signal demodulation unit.

[0010] Furthermore, the fixed connector is a flange.

[0011] Furthermore, the high-temperature resistant special optical fiber is selected from one or more of polyimide optical fiber, aluminized high-temperature resistant optical fiber, quartz high-temperature resistant optical fiber, or high-temperature acrylate coated optical fiber; the high-temperature resistant special optical fiber includes a pure quartz fiber core, a fluorine-doped quartz cladding covering the outside of the quartz fiber core, and a high-temperature resistant coating covering the outside of the fluorine-doped quartz cladding.

[0012] Furthermore, the linear structure is provided with a left clamp and a right clamp on both sides, which fastens and fixes the entire array by clamping on both sides. This can effectively constrain the relative position of each fiber unit and prevent it from shifting or misaligning during vibration, assembly or use. The left clamp and the right clamp are made of alloy, ceramic or engineering plastic, and the gap between the clamps is adjustable.

[0013] Furthermore, the heat insulation window structure is a double-layer structure, consisting of two layers of high light transmittance and heat-resistant substrates, an inert gas chamber, and a double sealing component; the high light transmittance and heat-resistant substrates are arranged opposite each other; the inert gas chamber is formed between the two substrates; the double sealing component is located at the edge of the two substrates to seal the chamber and fix the relative position of the two substrates.

[0014] Furthermore, the high-transmittance, high-temperature resistant substrate is selected from one or more of high-temperature resistant glass, ceramic, or sapphire substrate; the dual-sealing component is selected from one or more of fluororubber sealing rings, high-temperature sealants, or metal sealing gaskets.

[0015] Furthermore, the temperature control sensor is selected from one or more of a thermocouple sensor, an NTC thermistor, or a digital temperature sensor; the temperature control unit is selected from one or more of an FPGA chip or a Raspberry Pi; the heating module is selected from one or more of an electric heating wire, a PTC heater, a carbon fiber heating element, or a ceramic heating element; and the cooling module is selected from one or more of a miniature cooling fan, a heat pipe cooling device, a semiconductor refrigeration chip, or a water-cooled heat dissipation assembly.

[0016] Furthermore, the sensor signal demodulation unit is also equipped with an electromagnetic shielding shell, which is made of metal shielding material or electromagnetic shielding composite material through an integral molding process.

[0017] Furthermore, flexible buffer support structures are provided at the connection between the heat insulation window structure and the fixed connector, as well as between the temperature control system and the sensor signal demodulation unit, to offset the impact load generated under vibration conditions.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1. This invention employs high-temperature resistant special optical fibers to construct an optical fiber sensing array, relying on the material properties of the optical fiber to achieve high-temperature tolerance of the sensing array; the sensing signal demodulation unit works in conjunction with the temperature control system through a heat-insulating window to achieve stable temperature control within a preset temperature range. The synergistic effect of the above structures ensures that the sensor as a whole operates stably and reliably in high-temperature environments, thereby solving the core technical problem of traditional sensors being prone to failure in high-temperature environments.

[0020] 2. This invention utilizes a precision fiber array fabrication process, employing an array design where single optical fibers are linearly and closely arranged along a one-dimensional direction. By precisely controlling the fiber spacing and array straightness, the measurement resolution and spatial positioning accuracy are guaranteed from the structural design level, thereby achieving sub-millimeter level measurement accuracy.

[0021] 3. This invention is equipped with a dedicated temperature control system. By controlling the temperature of the sensing unit and key components within a preset temperature range, it can effectively suppress material aging and optical signal drift caused by extreme temperatures, thereby ensuring the signal stability and measurement accuracy of the sensor under complex working conditions and achieving long-term reliable operation.

[0022] 4. This invention integrates end-face anti-oil mist treatment, double sealing structure and electromagnetic shielding design. Through the synergistic effect of multiple protective structures, it can resist oil mist pollution, vibration shock and electromagnetic interference respectively, thereby significantly improving the sensor's adaptability to complex and harsh working conditions and environmental reliability.

[0023] 5. The invention has a compact overall structure and the heat insulation window has been optimized in size to fit narrow installation spaces. No major modifications to the existing equipment structure are required during installation, thereby reducing engineering application costs and making it widely applicable to lubricating oil system monitoring in many fields such as aviation and industrial machinery.

[0024] In summary, this invention solves the technical problems of existing sensors: capacitive sensors are susceptible to environmental influences and have short maintenance cycles; ultrasonic sensors are susceptible to interference from foam, steam, and acoustics; and radar sensors are susceptible to electromagnetic interference. This invention is adaptable to wide temperature range, strong vibration, and strong electromagnetic interference conditions in scenarios such as aircraft oil tanks and industrial machinery storage tanks, meeting the needs for real-time and accurate monitoring of lubricating oil levels. Attached Figure Description

[0025] Figure 1 This is a block diagram of the overall structure of the high-temperature resistant fiber optic lubricating oil level sensor of the present invention;

[0026] Figure 2 This is a schematic diagram of the fiber optic sensing array in an embodiment.

[0027] Figure 3 This is a schematic diagram of the structure of the heat insulation window in the embodiment;

[0028] Figure 4 This is a structural block diagram of the temperature control system of the present invention.

[0029] Figure label:

[0030] 10 is the adjustment structure, 11 is the upper clamping plate, 12 is the lower clamping plate, 13 is the fiber optic sensing array; 20 is the beam splitter, 21 is the light source, 22 is the high-transmittance and heat-resistant substrate, 23 is the flexible buffer support structure, 24 is the connection structure, 25 is the inert gas, and 26 is the fiber bundle. Detailed Implementation

[0031] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0032] like Figure 1 As shown in the figure, this embodiment provides a high-temperature resistant fiber optic lubricating oil level sensor, which is installed in the lubricating oil system reservoir via a fixing connector. It includes a sensing signal demodulation unit, a fiber optic sensing array, a heat-insulating window structure, and a temperature control system. As an optional implementation, the fixing connector adopts a flange structure and is fixedly connected to the reservoir wall by bolts.

[0033] The sensor signal demodulation unit includes a light source, a beam splitter, a lens group, an image acquisition unit, a signal processing unit, and a voltage output port; wherein:

[0034] The light source uses a 520nm low-power LED. This wavelength matches the photosensitivity of the image acquisition unit, ensuring the sensitivity of image acquisition. The beam splitter uses a cubic beam splitter prism made of K9 glass with a splitting ratio of 50:50, used to separate the incident light from the fiber optic bundle's reflected light. The lens group is used to collimate and focus the beam. The light signal emitted by the light source is collimated by the lens group and then incident on the beam splitter. The beam splitter splits the light signal into two paths: one path is transmitted to the heat-insulating window structure, and the other path serves as a reference light. The reflected light signal returning from the fiber optic sensing array passes through the heat-insulating window structure, is guided by the beam splitter to the lens group, and is then focused by the lens group before being incident on the image acquisition unit. It should be noted that the beam splitter and lens group used in this embodiment are only an exemplary implementation. Those skilled in the art can also use other structures with optical path splitting and coupling functions, such as fiber optic couplers and micro-optical components, as alternatives, all of which fall within the protection scope of this application.

[0035] The image acquisition unit uses an industrial-grade CCD camera with a resolution of 1920×1080 and a frame rate of 40fps to acquire images of the brightness and darkness distribution formed by reflected light signals and convert them into a first electrical signal representing the liquid level height. The signal processing unit uses an FPGA chip to process the received first electrical signal through algorithms such as filtering and noise reduction, and adaptive threshold segmentation, calculating the liquid level data and converting it into a second electrical signal. The voltage output port uses an RS485 interface to output a standard voltage signal of 0–5V to the external control system.

[0036] Furthermore, the sensor signal demodulation unit in this embodiment is also equipped with an electromagnetic shielding shell, which is made of metal shielding material or electromagnetic shielding composite material through an integral molding process. As an optional embodiment, the electromagnetic shielding shell is made of aluminum foil Mylar material to shield external electromagnetic interference and provide a stable working environment for internal components.

[0037] The fiber optic sensor array is installed inside the lubricating oil system reservoir. For example... Figure 2As shown, the fiber optic sensing array consists of multiple high-temperature resistant special optical fibers, which are tightly arranged in a linear structure along a one-dimensional direction. The end faces of the fiber optic sensing array are ground or polished and coated with an anti-oil-mist coating. The fiber optic sensing array receives optical signals and generates reflected optical signals upon contact with air or lubricating oil. The reflected optical signals are returned to the image acquisition unit via a heat-insulating window structure. In this embodiment, the high-temperature resistant special optical fiber is made of polyimide fiber, which consists of a pure quartz core, a fluorine-doped quartz cladding, and a high-temperature resistant coating from the inside out. The total diameter of the fiber is 150 μm, and its temperature resistance range is -55℃ to 215℃, meeting the high-temperature environment requirements of the lubricating oil system reservoir. The fiber optic sensing array consists of 2000 of these high-temperature resistant special optical fibers arranged tightly to form a linear array with a length of 300 mm, suitable for lubricating oil level measurement within a range of 0 to 300 mm. Aluminum alloy clamps are installed on both sides of the array for clamping and fixing. The entire array is fastened and fixed by clamping on both sides to ensure that it can maintain a stable structural shape and reliable measurement performance under complex working conditions.

[0038] The end-face processing technology of the fiber optic sensing array is as follows: rough grinding, fine grinding and polishing are performed in sequence, wherein the rough grinding uses an 800-grit grinding wheel, the fine grinding uses a 2000-grit grinding wheel, and the polishing uses diamond polishing fluid; after processing, the flatness of the end face is detected by an end-face inspection instrument to ensure the stability of the reflected light signal.

[0039] The array is fixed using a high-temperature resistant epoxy adhesive with a temperature resistance of 250℃, preventing structural loosening under high-temperature conditions. Furthermore, the fiber optic end faces are coated with a polytetrafluoroethylene (PTFE) anti-oil-mist coating to reduce interference from oil and gas deposits within the reservoir on the reflected signal. With these configurations, the fiber optic sensing array achieves a resolution better than 0.2 mm and a measurement accuracy better than 0.4 mm.

[0040] like Figure 3 As shown, the heat-insulating window structure is a double-layer structure, consisting of two layers of high-transmittance, heat-resistant substrates, an inert gas chamber, and a double-sealing component. The two layers of high-transmittance, heat-resistant substrates are arranged opposite each other, the inert gas chamber is formed between the two substrates, and the double-sealing component is located at the edge of the two substrates, sealing the chamber and fixing the relative position of the two substrates. In this embodiment:

[0041] The high-transmittance, high-temperature-resistant substrate is made of high-temperature-resistant borosilicate glass, 3mm thick, with a light transmittance of ≥92%. It can withstand temperatures up to 250℃ without structural deformation, ensuring low-loss transmission of optical signals. The dual-sealing components include: a fluororubber sealing ring positioned between the high-transmittance, high-temperature-resistant substrate and the reservoir wall, and a high-temperature sealant located at the connection between the high-transmittance, high-temperature-resistant substrate and the optical fiber bundle; this high-temperature sealant is made of silicone and is temperature-resistant up to 220℃. This dual-sealing design ensures no leakage of high-temperature oil and gas within the reservoir.

[0042] The inert gas chamber is filled with nitrogen to prevent condensation or oxidation inside the window from affecting the transmission of optical signals.

[0043] The heat insulation window structure is connected to the fiber optic sensing array and the sensing signal demodulation unit via an optical fiber bundle. The optical fiber bundle is an independent optical transmission component, with one end connected to the fiber optic sensing array and the other end connected to the beam splitter in the sensing signal demodulation unit via a high-transmittance, heat-resistant substrate, thereby enabling the transmission of optical signals between the heat insulation window and the fiber optic sensing array.

[0044] The temperature control system is thermally coupled to the sensor signal demodulation unit and is used to regulate the operating environment temperature of the sensor signal demodulation unit. For example... Figure 4 As shown, the temperature control system includes a temperature sensor, a temperature control unit, a heating module, and a cooling module. Among them:

[0045] The temperature control sensor is used to collect the ambient temperature of the sensing signal demodulation unit and transmit it to the temperature control unit. In this embodiment, the temperature control sensor is a PT100 platinum resistance sensor, with a temperature measurement range covering -50℃ to 300℃ and a measurement accuracy of ±0.5℃.

[0046] The temperature control unit is connected to both the heating module and the cooling module, and it has built-in temperature threshold determination logic. In this embodiment, the temperature control unit uses an STM32F4 series microcontroller, with a preset low-temperature threshold of 0℃ and a high-temperature threshold of 30℃, which can be flexibly calibrated and adjusted according to actual operating conditions. When the ambient temperature received by the temperature control unit is lower than the preset low-temperature threshold, the heating module is activated to heat the system; when the received ambient temperature is higher than the preset high-temperature threshold, the cooling module is activated to cool the system, thereby ensuring the continuity and accuracy of the optical signal transmission and acquisition by the sensor signal demodulation unit.

[0047] The heating module is used to heat the environment surrounding the sensor signal demodulation unit. In this embodiment, a PTC heater is used, with a maximum surface temperature of 175°C. The cooling module is used to cool the environment surrounding the sensor signal demodulation unit. In this embodiment, a semiconductor cooling chip is used.

[0048] It is understood that the temperature control sensor may also be selected from one or more of thermocouple sensors, NTC thermistors, or digital temperature sensors; the temperature control unit may also be selected from one or more of FPGA chips or Raspberry Pi; the heating module may also be selected from one or more of electric heating wires, carbon fiber heating sheets, or ceramic heating elements; and the cooling module may also be selected from one or more of miniature cooling fans, heat pipe cooling devices, or water-cooled cooling components.

[0049] The above temperature control configuration can effectively ensure the continuity and accuracy of optical signal transmission and acquisition in the sensor signal demodulation unit.

[0050] In addition, flexible buffer support structures are provided at the connection points between the heat insulation window structure and the fixed connector, and between the temperature control system and the sensor signal demodulation unit, to offset the impact loads generated under vibration conditions. In this embodiment, the flexible buffer support structure uses silicone rubber gaskets with a thickness of 2mm and a Shore hardness of 40A, and is disposed between each connection interface. As an optional implementation, the flexible buffer support structure can also use spring shock absorbers or polyurethane buffer pads.

[0051] The specific working steps of the above-mentioned high-temperature resistant fiber optic lubricating oil level sensor are as follows:

[0052] After the system starts, the light source is activated, and the light signal emitted by the light source is transmitted to the beam splitter. The beam splitter changes the direction of the light path and couples it into the fiber bundle. The light signal is transmitted to the heat insulation window, passes through the high-transmittance, heat-resistant substrate and the inert gas, and then enters the fiber optic sensing array along the fiber bundle. Reflection occurs at the end face of the fiber optic sensing array—the fiber end face above the liquid level in the reservoir contacts the air, forming strong reflected light, while the fiber end face below the liquid level contacts the lubricating oil, forming weak reflected light. The reflected light returns along the fiber bundle path, passes through the high-transmittance, heat-resistant substrate and the inert gas in sequence, and is transmitted to the beam splitter. The beam splitter changes the direction of the light path again and transmits it to the image acquisition unit. The image acquisition unit acquires the bright and dark distribution image formed by the reflected light, converts the image into an electrical signal, and transmits it to the signal processing unit. The oil level monitoring image processing algorithm module built into the signal processing unit performs preprocessing, including noise reduction and enhancement to improve image quality. After that, the image passes through fiber end face recognition, coordinate positioning, and brightness analysis to distinguish between strong and weak reflected light fibers above and below the liquid level. Self-calibration and self-diagnosis are performed using preset reference signals to eliminate faults and signal anomalies, ensuring accurate and reliable data.

[0053] The results after self-calibration and self-diagnosis verification are used to calculate the liquid level height: combined with the fiber spacing of the fiber optic sensor array of 0.150mm, the current lubricating oil level height in the reservoir is calculated. For example, when the dividing position corresponds to the 100th fiber, the liquid level height is 15mm. Then, the liquid level height result is converted into a second electrical signal and output to the external control system through the voltage output port to complete one lubricating oil level detection.

[0054] The oil level monitoring image processing algorithm module has a processing latency of ≤200ms, enabling real-time continuous monitoring of the lubricating oil level in the reservoir. Meanwhile, the triple protection of the electromagnetic shielding shell, the heat-insulating window structure, and the temperature control system ensures stable operation of the system in a wide temperature range of -55℃ to 215℃, under conditions of strong vibration and strong electromagnetic interference, making it suitable for various equipment requirements such as aircraft and industrial machinery carrying reservoirs.

[0055] In summary, the sensor implemented in this case forms a complete closed loop from signal acquisition, transmission, environmental isolation to stable demodulation through the coordinated operation of the fiber optic sensing array, the heat-insulated window structure, the temperature control system, and the sensor signal demodulation unit. The fiber optic sensing array is composed of several high-temperature resistant optical fibers to ensure measurement accuracy. The heat-insulated window structure achieves efficient light transmission and isolation from high-temperature oil and gas in a narrow space. The temperature control system and the electromagnetic shielding shell work together to create a stable operating environment for the signal processing unit. The organic combination of these four components gives the sensor the characteristics of high temperature resistance, strong anti-interference, and high precision. It can be adapted to wide temperature range, strong vibration, and strong electromagnetic interference conditions in scenarios such as aircraft oil tanks and industrial machinery storage tanks, meeting the requirements for real-time and accurate monitoring of oil levels.

Claims

1. A high-temperature resistant fiber optic lubricating oil level sensor, installed in a lubricating oil system reservoir via a fixed connector, characterized in that, Includes a sensor signal demodulation unit, fiber optic sensor array, thermal insulation window structure, and temperature control system; The sensor signal demodulation unit includes a light source, an image acquisition unit, a signal processing unit, and a voltage output port. The light source generates an optical signal and transmits it to the fiber optic sensor array via a heat-insulating window structure. The image acquisition unit receives the reflected optical signal and converts it into a first electrical signal, which is then sent to the signal processing unit. The signal processing unit calculates the liquid level result based on the received electrical signal and converts it into a second electrical signal, which is then output to an external control system via the voltage output port. The fiber optic sensing array is located inside the lubricating oil system reservoir. It consists of multiple high-temperature resistant special optical fibers, which are arranged in a linear structure with close proximity along a one-dimensional direction. The end faces of the fiber optic sensing array are ground or polished and have an anti-oil mist coating. The fiber optic sensing array receives optical signals and generates reflected optical signals when it comes into contact with air or lubricating oil. The reflected optical signals are returned to the image acquisition unit through the heat-insulating window structure. The temperature control system is thermally coupled to the sensor signal demodulation unit and is used to regulate the operating environment temperature of the sensor signal demodulation unit. The temperature control system includes a temperature sensor, a temperature control unit, a heating module, and a cooling module. The temperature sensor is used to collect the ambient temperature of the sensor signal demodulation unit and transmit it to the temperature control unit. The temperature control unit is connected to both the heating module and the cooling module, and has built-in temperature threshold determination logic. When the ambient temperature received by the temperature control unit is lower than a preset low temperature threshold, the heating module is activated to heat the environment around the sensor signal demodulation unit. When the received ambient temperature is higher than a preset high temperature threshold, the cooling module is activated to cool the environment around the sensor signal demodulation unit.

2. The high-temperature resistant fiber optic lubricating oil level sensor according to claim 1, characterized in that, The fixed connector is a flange.

3. The high-temperature resistant fiber optic lubricating oil level sensor according to claim 1, characterized in that, The high-temperature resistant special optical fiber is selected from one or more of polyimide optical fiber, aluminized high-temperature resistant optical fiber, quartz high-temperature resistant optical fiber, or high-temperature acrylate coated optical fiber; the high-temperature resistant special optical fiber is composed of a pure quartz fiber core, a fluorine-doped quartz cladding covering the outside of the quartz fiber core, and a high-temperature resistant coating covering the outside of the fluorine-doped quartz cladding.

4. The high-temperature resistant fiber optic lubricating oil level sensor according to claim 1, characterized in that, The linear structure is provided with a left clamp and a right clamp on both sides, and the whole array is fastened and fixed by clamping on both sides. The left clamp and the right clamp are made of alloy, ceramic or engineering plastic, and the gap between the clamps is adjustable.

5. The high-temperature resistant fiber optic lubricating oil level sensor according to claim 1, characterized in that, The heat-insulating window structure is a double-layer structure, consisting of two layers of high-transmittance, heat-resistant substrates, an inert gas chamber, and a double-sealing component. The high-transmittance, heat-resistant substrates are arranged opposite each other; the inert gas chamber is formed between the two substrate layers; the double-sealing component is located at the edge of the two substrate layers, sealing the chamber and fixing the relative position of the two substrate layers.

6. The high-temperature resistant fiber optic lubricating oil level sensor according to claim 5, characterized in that, The high-transmittance, high-temperature resistant substrate is selected from one or more of high-temperature resistant glass, ceramic, or sapphire substrate; the dual-sealing component is selected from one or more of fluororubber sealing rings, high-temperature sealants, or metal sealing gaskets.

7. The high-temperature resistant fiber optic lubricating oil level sensor according to claim 1, characterized in that, The temperature control sensor is selected from one or more of thermocouple sensors, NTC thermistors, or digital temperature sensors; the temperature control unit is selected from one or more of FPGA chips or Raspberry Pi; the heating module is selected from one or more of electric heating wires, PTC heaters, carbon fiber heating sheets, or ceramic heating elements; and the cooling module is selected from one or more of miniature cooling fans, heat pipe cooling devices, semiconductor cooling chips, or water-cooled cooling components.

8. The high-temperature resistant fiber optic lubricating oil level sensor according to claim 1, characterized in that, The sensor signal demodulation unit is also equipped with an electromagnetic shielding shell, which is made of metal shielding material or electromagnetic shielding composite material through an integral molding process.

9. The high-temperature resistant fiber optic lubricating oil level sensor according to claim 1, characterized in that, Flexible buffer support structures are provided at the connection between the heat insulation window structure and the fixed connector, as well as between the temperature control system and the sensor signal demodulation unit, to offset the impact load generated under vibration conditions.

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