An oxygen and oil level dual-parameter sensing monitoring system and method

Abstract

The present application relates to fuel measurement control technical field, specifically, it is a kind of oxygen and oil level dual parameter sensing monitoring system and method;The method first transmits laser signal to reference light path and sensing light path respectively, and obtains reference light path signal and sensing light path signal;Then the output power of reference light path and sensing light path is calculated;Finally, the output power of reference light path and sensing light path is differentially processed, and the differential value is obtained;And according to the differential value, the positional relationship between oil level and sensor installation is judged, and the oxygen concentration is calculated, which can be used as oxygen and oil level signal indicator, and also can realize discrete oil level sensing, and installation is not limited to tank structure;Realize the real-time monitoring of multiple point oil level and oxygen concentration.

Description

Technical Field

[0001] This invention relates to the field of fuel measurement and control technology, and more specifically, to a dual-parameter sensing and monitoring system and method for oxygen and fuel level. Background Technology

[0002] In the face of increasingly complex aviation environments, traditional electrical sensors are subject to significant limitations in application due to their susceptibility to electromagnetic interference, difficulty in installation, and large footprint. They are also limited in harsh environments such as extreme temperatures and complex spaces.

[0003] Aircraft fuel tanks consist of fuselage tanks, wing tanks, and auxiliary tanks. These tanks are numerous and varied in structure, representing a large proportion of the aircraft's total mass. Accurate and reliable fuel monitoring directly impacts flight performance. Existing fuel level sensors and signal transmitters primarily employ capacitive measurement. Even with electromagnetic interference (EMI) protection designs, capacitive fuel level sensors are frequently affected by EMI from various onboard systems, leading to abnormal fuel level signals. To ensure fuel safety, monitoring the oxygen content within the fuel tanks is also crucial. Under all flight conditions, the fuel system must maintain an oxygen volume concentration below 10% in inerted tanks or fuel compartments. Employing fiber optic sensing-based fuel level and oxygen measurement technologies completely eliminates EMI issues and improves sensor stability. Furthermore, fiber optic sensors are passive devices, inherently safe. Using fiber optic cables for signal transmission eliminates the need for electromagnetic shielding like capacitive sensors. Fiber optic cables also offer advantages such as strong environmental resistance, long lifespan, high flexibility, simple wiring, high bandwidth, high transmission speed, and low cost.

[0004] Currently, aircraft manufacturers are placing higher demands on sensor systems in terms of integration, reliability, security, intelligence, and high-speed, high-capacity communication. Fiber optic sensors, with their lightweight, small size, resistance to electromagnetic interference, corrosion resistance, resistance to high and low temperatures, long lifespan, and ease of integration into high-speed, low-latency sensor networks, have become an ideal type of aerospace sensor. Therefore, fuel measurement and control systems based on multi-parameter fiber optic sensors are a requirement for the development of next-generation aerospace technology. Summary of the Invention

[0005] This invention addresses the problems of low sensitivity and inability to simultaneously monitor fuel level and oxygen concentration in existing fuel control systems. It proposes a dual-parameter sensing monitoring system and method for oxygen and fuel level. The method first transmits laser signals to a reference optical path and a sensing optical path respectively, acquiring the signals from both. Then, it calculates the output power of the reference and sensing optical paths. Finally, it performs differential processing on the output power of the reference and sensing optical paths to obtain a difference value. Based on this difference value, it determines the relationship between the fuel level and the sensor's installation position, and calculates the oxygen concentration. This system can function as both an oxygen and fuel level signal transmitter and a discrete fuel level sensor, and its installation is not limited by the fuel tank structure. It achieves real-time monitoring of fuel level and oxygen concentration at multiple points.

[0006] The specific implementation details of this invention are as follows: An oxygen and oil level dual-parameter sensing and monitoring system includes a light source module, a sensing optical path, a reference optical path, a sensing optical path detection module, a reference optical path detection module, a signal processing module, and an optical fiber coupler. The light source module receives a laser signal at its input and its output is connected to the input of the fiber optic coupler. The input of the sensing optical path is connected to the output of the fiber optic coupler, and its output is connected to the input of the sensing optical path detection module. The input of the reference optical path is connected to the output of the fiber optic coupler, and its output is connected to the input of the reference optical path detection module. The input of the signal processing module is connected to the outputs of both the reference optical path detection module and the sensing optical path detection module, and the output of the signal processing module displays the oxygen concentration. The light source module is used to acquire laser signals; The fiber optic coupler is used to split the laser signal into beams and transmit the split laser signals to the sensing optical path and the reference optical path, respectively. The sensing optical path is used to generate a sensing optical path signal based on the laser signal after beam splitting. The reference optical path is used to generate a reference optical path signal based on the split laser signal. The sensing optical path detection module is used to calculate the output power of the sensing optical path based on the sensing optical path signal; The reference optical path detection module is used to calculate the reference optical path output power based on the reference optical path signal; The signal processing module is used to perform differential processing on the output power of the reference optical path and the output power of the sensing optical path to obtain a differential value, determine the positional relationship between the oil level and the sensor based on the differential value, calculate the oxygen concentration based on the positional relationship, and output a concentration signal.

[0007] To better realize the present invention, both the sensing optical path and the reference optical path further include micro-nano fiber structures; The micro / nano fiber structure includes a first fiber flange, a first micro / nano fiber taper region, a second micro / nano fiber taper region, a micro / nano fiber waist region, and a second fiber flange. The input end of the first fiber optic flange is connected to the output end of the fiber optic coupler, and the output end of the first fiber optic flange is connected to the input end of the first micro / nano fiber optic tape region. The input end of the waist region of the micro-nano fiber is connected to the output end of the first micro-nano fiber taper region, and the output end of the waist region of the micro-nano fiber is connected to the input end of the second micro-nano fiber taper region. The output end of the second micro / nano fiber taper region is connected to the input end of the second fiber flange.

[0008] To better realize the present invention, the micro-nano fiber structure of the reference optical path further includes a first vacuum flange and a second vacuum flange; The first vacuum flange is disposed between the output end of the fiber optic coupler and the input end of the first fiber optic flange; The second vacuum flange is positioned between the output end of the second fiber optic flange and the input end of the reference optical path detection module.

[0009] To better realize the present invention, the micro-nano fiber structure of the reference optical path is further sealed in a sealing tube by the first vacuum flange and the second vacuum flange; the micro-nano fiber structure of the sensing optical path is disposed in the medium to be measured.

[0010] To better realize the present invention, further, based on the output power of the sensing optical path micro / nano fiber structure in air... P sa With reference optical path output power P r The difference d P a Output power of micro / nano fiber optic structures in fuel for sensing optical paths P sf With reference optical path output power P r The difference d P f Adjust the length of the micro-nano fiber in the micro-nano fiber structure.

[0011] To better realize the present invention, a method for monitoring oxygen and oil level using a dual-parameter sensor is further proposed based on the above-mentioned oxygen and oil level dual-parameter sensor monitoring system, specifically including the following steps: Step S1: The acquired laser signal is transmitted to the reference optical path and the sensing optical path respectively through an optical fiber coupler; Step S2: Obtain the reference optical path signal from the reference optical path and obtain the sensing optical path signal from the sensing optical path; Step S3: Calculate the output power of the reference optical path and the output power of the sensor optical path based on the reference optical path signal and the sensor optical path signal; Step S4: Perform differential processing on the output power of the reference optical path and the output power of the sensing optical path to obtain the differential value; Step S5: Determine the relationship between the oil level and the sensor installation position based on the difference value, and calculate the oxygen concentration based on the position relationship.

[0012] To better realize the present invention, step S4 further includes the following steps: Step S41: Calculate the output power of the reference optical path based on the obtained output optical power of the laser signal, the intrinsic loss of the micro / nano fiber, and the length of the micro / nano fiber. P r ; Step S42: Calculate the output power of the sensing optical path based on the acquired laser signal output power, intrinsic loss of the micro / nano fiber, length of the micro / nano fiber, oxygen concentration of the test medium, and evanescent field proportion of the micro / nano fiber in the test medium. P s ; Step S43: Output power of the reference optical path P r and the output power of the sensing optical path P s Perform difference processing to obtain the difference value Δ P。

[0013] To better realize the present invention, further, the specific operation of step S5 is as follows: if the reference optical path output power P r =0, then the reference optical path is determined to be broken; if the output power of the sensing optical path is 0, then the reference optical path is determined to be broken. P s When the difference value ΔP is 0, the sensing optical path is determined to be broken; if the difference value ΔP is less than 0, the current system is determined to have a signal abnormality; if the difference value ΔP is greater than 0 and less than the difference ΔP between the output power of the reference optical path and the sensing optical path of the micro / nano fiber under 100% oxygen concentration, the .... P crit0 If the current oil level does not exceed the sensor installation position, the oxygen concentration is calculated and a concentration signal is output; if the difference value ΔP is greater than the difference between the output power of the reference optical path and the sensing optical path of the micro-nano optical fiber in the fuel at the upper limit of high temperature, and less than the difference between the output power of the reference optical path and the sensing optical path of the micro-nano optical fiber in the fuel at the lower limit of low temperature, then the current oil level exceeds the sensor installation position and the output signal is abnormal.

[0014] To better implement the present invention, step S42 further includes the following steps: Step S421: Place the micro / nano fiber structure of the sensing optical path in the air. Calculate the output power of the sensing optical path in the air based on the acquired laser signal output power, intrinsic loss of the micro / nano fiber, length of the micro / nano fiber, oxygen concentration in the air, and the evanescent field ratio of the micro / nano fiber in the air. P sa And calculate the output power of the sensing optical path in air. P sa With reference optical path output power P r The difference d P a ; Step S422: Place the micro / nano fiber structure of the sensing optical path in the fuel. Calculate the output power of the sensing optical path in the fuel based on the output optical power of the acquired laser signal, the intrinsic loss of the micro / nano fiber, the length of the micro / nano fiber, the oxygen concentration in the fuel, and the evanescent field ratio of the micro / nano fiber in the fuel. P sf And calculate the output power of the sensing optical path in the fuel. P sf With reference optical path output power P r The difference d P f ; Step S423: Calculate the difference d P a The difference d P f The difference dP is used to adjust the length of the micro-nano fiber in the micro-nano fiber structure.

[0015] To better realize the present invention, further, the specific operation of adjusting the length of the micro-nano fiber in step S423 is as follows: the difference d P The maximum value corresponds to the length of the micro-nano fiber in the micro-nano fiber structure, which is taken as the length of the micro-nano fiber in the micro-nano fiber structure.

[0016] The present invention has the following beneficial effects: (1) The present invention determines the relationship between the oil level and the sensor installation position based on the difference between the output power of the reference optical path and the output power of the sensing optical path, and calculates the oxygen concentration, thereby realizing real-time monitoring of oil level and oxygen concentration at multiple points. (2) This invention can be used as an oxygen and oil level signaler, as well as a discrete oil level sensor, and its installation is not limited by the oil tank structure. It has the characteristics of simple sensing structure, light weight, small size, electromagnetic interference resistance, safety, high and low temperature resistance, easy integration, high accuracy, simple demodulation and fast response. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the dual-parameter sensing and monitoring method for oxygen and oil level provided by the present invention.

[0018] Figure 2 This is a schematic diagram showing the relationship between the evanescent field ratio of micro / nano optical fibers in air and fuel media and the radius of the micro / nano optical fibers provided in this embodiment of the invention.

[0019] Figure 3 This is a schematic diagram showing the relationship between the difference in output power of the micro-nano fiber in air and fuel oil and the length of the micro-nano fiber when the radius of the micro-nano fiber is 250nm, as provided in the embodiments of the present invention.

[0020] Figure 4 This is a schematic diagram showing the relationship between the oxygen concentration detection limit and the length of the micro-nano fiber when the radius of the micro-nano fiber is 250nm, as provided in the embodiments of the present invention.

[0021] Figure 5 This is a schematic diagram showing the relationship between the output power difference of the micro-nano optical fiber in air and fuel oil and the oxygen concentration when the micro-nano optical fiber provided in this embodiment of the invention has a radius of 250nm and a length of 9.5cm.

[0022] Figure 6 This is a schematic diagram of the oxygen and oil level dual-parameter sensing and monitoring system provided in an embodiment of the present invention.

[0023] The components include: 1. Light source module; 2. Fiber optic coupler; 3. Reference optical path; 4. Sensing optical path; 5. Reference optical path detection module; 6. Sensing optical path detection module; 7. Signal processing module; 8. First fiber optic flange; 9. First micro / nano fiber taper region; 10. Second micro / nano fiber taper region; 11. Micro / nano fiber waist region; 12. Second fiber optic flange; 13. First vacuum flange; 14. Second vacuum flange; 15. Sealing tube; 16. Input fiber; 17. First output fiber; 18. Second output fiber; 19. First micro / nano fiber pigtail; 20. Second micro / nano fiber pigtail; 21. Receiver optical transmission fiber. Detailed Implementation

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments, and therefore should not be regarded as a limitation on the scope of protection. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] Example 1: This embodiment proposes a dual-parameter sensing and monitoring system for oxygen and oil level, such as... Figure 1 As shown, it includes a light source module 1, a sensing optical path 4, a reference optical path 3, a sensing optical path detection module 6, a reference optical path detection module 5, a signal processing module 7, and an optical fiber coupler 2. The light source module 1 receives a laser signal at its input end and its output end is connected to the input end of the fiber optic coupler 2; the input end of the sensing optical path 4 is connected to the output end of the fiber optic coupler 2, and the output end of the sensing optical path 4 is connected to the input end of the sensing optical path detection module 6; the input end of the reference optical path 3 is connected to the output end of the fiber optic coupler 2, and the output end of the reference optical path 3 is connected to the input end of the reference optical path detection module 5; the input end of the signal processing module 7 is connected to the output ends of the reference optical path detection module 5 and the sensing optical path detection module 6, and the output end of the signal processing module 7 outputs the oxygen concentration. The light source module 1 is used to acquire laser signals; The fiber coupler 2 is used to split the laser signal and transmit the split laser signal to the sensing optical path 4 and the reference optical path 3 respectively. The sensing optical path 4 is used to generate a sensing optical path signal based on the laser signal after beam splitting. The reference optical path 3 is used to generate a reference optical path signal based on the laser signal after beam splitting; The sensing optical path detection module 6 is used to calculate the sensing optical path output power based on the sensing optical path signal; The reference optical path detection module 5 is used to calculate the reference optical path output power based on the reference optical path signal; The signal processing module 7 is used to perform differential processing on the output power of the optical path and the output power of the sensing optical path to obtain a differential value, and to determine the positional relationship between the oil level and the sensor based on the differential value, and to calculate the oxygen concentration based on the positional relationship, and output a concentration signal.

[0027] Furthermore, both the sensing optical path 4 and the reference optical path 3 include micro / nano fiber structures; The micro / nano fiber structure includes a first fiber flange 8, a first micro / nano fiber taper region 9, a second micro / nano fiber taper region 10, a micro / nano fiber waist region 11, and a second fiber flange 12. The input end of the first fiber optic flange 8 is connected to the output end of the fiber optic coupler 2, and the output end of the first fiber optic flange 8 is connected to the input end of the first micro / nano fiber optic tape region 9. The input end of the waist region 11 of the micro-nano fiber is connected to the output end of the first micro-nano fiber taper region 9, and the output end of the waist region 11 of the micro-nano fiber is connected to the input end of the second micro-nano fiber taper region 10. The output end of the second micro-nano fiber taper region 10 is connected to the input end of the second fiber flange 12.

[0028] To better realize the present invention, the micro-nano fiber structure of the reference optical path 3 further includes a first vacuum flange 13 and a second vacuum flange 14; The first vacuum flange 13 is disposed between the output end of the fiber optic coupler 2 and the input end of the first fiber optic flange 8; The second vacuum flange 14 is disposed between the output end of the second optical fiber flange 12 and the input end of the reference optical path detection module 5.

[0029] Furthermore, the micro-nano fiber structure of the reference optical path 3 is sealed in the sealing tube 15 through the first vacuum flange and the second vacuum flange; the micro-nano fiber structure of the sensing optical path 4 is disposed in the medium to be measured.

[0030] Furthermore, based on the output power of the micro / nano fiber structure of sensing optical path 4 in air... P sa With reference optical path output power P r The difference d P a The output power of the micro / nano fiber optic structure in fuel in sensing optical path 4 P sf With reference optical path output power P r The difference d P f Adjust the length of the micro-nano fiber in the micro-nano fiber structure.

[0031] Working Principle: This embodiment proposes a dual-parameter sensing and monitoring system for oxygen and oil level, including a light source module 1, a sensing optical path 4, a reference optical path 3, a sensing optical path detection module 6, a reference optical path detection module 5, a signal processing module 7, and an optical fiber coupler 2. It can be used as an oxygen and oil level signal transmitter, and can also realize discrete oil level sensing. Moreover, the installation is not limited by the oil tank structure. It has the characteristics of simple sensing structure, light weight, small size, electromagnetic interference resistance, safety, high and low temperature resistance, easy integration, high accuracy, simple demodulation, and fast response.

[0032] Example 2: Based on Example 1 above, this embodiment proposes a dual-parameter sensing and monitoring method for oxygen and oil level, specifically including the following steps: Step S1: The acquired laser signal is transmitted to the reference optical path 3 and the sensing optical path 4 respectively through the fiber optic coupler 2.

[0033] Step S2: Obtain the reference optical path signal from the reference optical path 3 and the sensing optical path signal from the sensing optical path 4.

[0034] Step S3: Calculate the output power of the reference optical path and the output power of the sensor optical path based on the reference optical path signal and the sensor optical path signal.

[0035] Step S4: Perform differential processing on the output power of the reference optical path and the output power of the sensing optical path to obtain the differential value.

[0036] Furthermore, step S4 specifically includes the following steps: Step S41: Calculate the output power of the reference optical path based on the obtained output optical power of the laser signal, the intrinsic loss of the micro / nano fiber, and the length of the micro / nano fiber. P r .

[0037] Step S42: Calculate the output power of the sensing optical path based on the acquired laser signal output power, intrinsic loss of the micro / nano fiber, length of the micro / nano fiber, oxygen concentration of the test medium, and evanescent field proportion of the micro / nano fiber in the test medium. P s .

[0038] Furthermore, step S42 specifically includes the following steps: Step S421: Place the micro / nano fiber structure of the sensing optical path 4 in the air. Calculate the output power of the sensing optical path 4 in the air based on the acquired laser signal output power, intrinsic loss of the micro / nano fiber, length of the micro / nano fiber, oxygen concentration in the air, and the evanescent field ratio of the micro / nano fiber in the air. P sa And calculate the output power of the sensing optical path 4 in air. P saWith reference optical path output power P r The difference d P a ; Step S422: Place the micro / nano fiber structure of the sensing optical path 4 in the fuel. Calculate the output power of the sensing optical path 4 in the fuel based on the acquired laser signal output power, intrinsic loss of the micro / nano fiber, length of the micro / nano fiber, oxygen concentration in the fuel, and evanescent field ratio of the micro / nano fiber in the fuel. P sf And calculate the output power of sensing optical path 4 in fuel. P sf With reference optical path output power P r The difference d P f ; Step S423: Calculate the difference d P a The difference d P f The difference dP is used to adjust the length of the micro-nano fiber in the micro-nano fiber structure.

[0039] Furthermore, the specific operation of adjusting the length of the micro-nano fiber in step S423 is as follows: The difference d... P The maximum value corresponds to the length of the micro-nano fiber in the micro-nano fiber structure, which is taken as the length of the micro-nano fiber in the micro-nano fiber structure.

[0040] Step S43: Output power of the reference optical path P r and the output power of the sensing optical path P s Perform difference processing to obtain the difference value Δ P。

[0041] Step S5: Determine the relationship between the oil level and the sensor installation position based on the difference value, and calculate the oxygen concentration based on the position relationship.

[0042] Further, the specific operation of step S5 is as follows: if the reference optical path output power P r =0, then it is determined that reference optical path 3 is broken; if the output power of the sensing optical path is 0, then it is determined that reference optical path 3 is broken. P s When the difference value ΔP is 0, it is determined that the sensing optical path 4 is broken; if the difference value ΔP is less than 0, it is determined that there is a signal abnormality in the current system; if the difference value ΔP is greater than 0 and less than the difference ΔP between the output power of the reference optical path 3 and the sensing optical path in the micro-nano fiber at 100% oxygen concentration, it is determined that there is a signal abnormality in the current system; P crit0If the current oil level does not exceed the sensor installation position, the oxygen concentration is calculated and a concentration signal is output; if the difference value ΔP is greater than the difference between the output power of the reference optical path 3 and the sensing optical path of the micro-nano optical fiber in the fuel at the upper limit of high temperature, and less than the difference between the output power of the reference optical path 3 and the sensing optical path of the micro-nano optical fiber in the fuel at the lower limit of low temperature, then the current oil level exceeds the sensor installation position and the output signal is abnormal.

[0043] Working principle: In this embodiment, the laser signal is first transmitted to the reference optical path 3 and the sensing optical path 4 respectively, and the reference optical path signal and the sensing optical path signal are acquired; then the output power of the reference optical path and the output power of the sensing optical path are calculated; finally, the output power of the reference optical path and the output power of the sensing optical path are differentially processed to obtain the difference value; and the relationship between the oil level and the sensor installation position is determined based on the difference value, and the oxygen concentration is calculated, realizing real-time monitoring of oil level and oxygen concentration at multiple points.

[0044] The other parts of this embodiment are the same as those in Embodiment 1 above, so they will not be described again.

[0045] Example 3: This embodiment is based on any one of Embodiments 1-2 above, such as Figure 1 As shown, the 3dB fiber coupler 2 is used as an example for illustration.

[0046] The oxygen and oil level dual-parameter sensing and monitoring system proposed in this embodiment comprises a light source module 1, a sensing optical path 4, a reference optical path 3, a sensing optical path detection module 6, a reference optical path detection module 5, a signal processing module 7, and a 1×2 3dB fiber optic coupler 2. The narrow-linewidth probe light emitted from the light source module 1 passes through the 3dB fiber optic coupler 2, splitting the probe light signal into two paths at a 50:50 ratio. One path enters the sensing optical path 4, and the other enters the reference optical path 3. The sensing optical path 4 uses micro-nano optical fiber as its carrier to sense oxygen concentration and oil level signals. The reference optical path 3 uses the same micro-nano optical fiber as the sensing optical path 4 to eliminate the influence of system device and external environmental interference on the sensing signal. The two photoelectric detection modules receive the sensing optical path signal and the reference optical path signal respectively. After photoelectric conversion, the signals enter the signal processing module 7 for differential processing of the sensing optical path signal and the reference optical path signal. By analyzing the magnitude of the output light power after differential processing, the air and fuel medium are determined, and the oil level signal or oxygen concentration signal is further measured.

[0047] The light source module 1 is connected to the input port of a 1×2 3dB fiber coupler 2. The first output fiber 17 and the second output fiber 18 of the fiber coupler 2 are connected to the first micro-nano fiber pigtails 19 of the reference optical path 3 and the sensing optical path 4 respectively through the first fiber flange 8. The second micro-nano fiber pigtails 20 of the reference optical path 3 and the sensing optical path 4 are connected to the receiving optical transmission fiber 21 of the reference optical path 3 and the sensing optical path 4 respectively through the second fiber flange 12. The receiving optical transmission fiber 21 of the reference optical path 3 is connected to the reference optical path detection module 5, and the receiving optical transmission fiber 21 of the sensing optical path 4 is connected to the sensing optical path detection module 6. The reference optical path detection module 5 and the sensing optical path detection module 6 are connected to the signal processing module 7 respectively.

[0048] The light source module 1 emits a single-mode narrow-linewidth probe laser on the oxygen spectral absorption line, and the 1×2 3dB fiber coupler 2 splits the narrow-linewidth probe laser into the reference optical path 3 and the sensing optical path 4 in a 50:50 ratio.

[0049] The materials of the micro-nano fiber waist region 11, the micro-nano fiber first pigtail 19, the micro-nano fiber second pigtail 20, the micro-nano fiber first cone region 9, and the micro-nano fiber second cone region 10 in the reference optical path 3 and the sensing optical path 4 are all pure silicon.

[0050] In the reference optical path 3, the micro-nano fiber waist region 11, the micro-nano fiber first cone region 9, the micro-nano fiber second cone region 10, the micro-nano fiber first pigtail 19, and the micro-nano fiber second pigtail 20 are sealed in a sealing tube 15 by a first vacuum flange 13 and a second vacuum flange 14. In this embodiment, the sealing tube 15 is a nitrogen-filled sealing tube, which is used to avoid interference of system device fluctuations and external interference on the sensing signal.

[0051] In the aforementioned sensing optical path 4, micro-nano optical fibers are placed in the environment to be tested for oil level signal sensing and oxygen concentration measurement.

[0052] The sensing optical path 4 and the reference optical path 3 have the same structure.

[0053] The optical fiber 21 at the receiving end of the reference optical path 3 and the optical fiber 2 at each port of the optical fiber coupler 2 are all ordinary single-mode optical fibers.

[0054] The micro-nano fibers in the reference optical path 3 and the sensing optical path 4 both meet the single-mode transmission conditions, and the radii of the first micro-nano fiber pigtail 19 and the second micro-nano fiber pigtail 20 are the same as those of ordinary single-mode fibers.

[0055] The radius of the micro / nano fiber should be smaller than the critical fiber radius corresponding to single-mode transmission conditions. At the same time, the radius of the micro / nano fiber is related to the difference in the proportion of the evanescent field of the micro / nano fiber in air and fuel.

[0056] The length of the micro-nano optical fiber is related to the difference in output power between the micro-nano optical fiber in fuel and in air. The optimal length of the micro-nano optical fiber corresponds to the maximum difference in output power between the micro-nano optical fiber in fuel and in air.

[0057] The length and radius of the micro-nano optical fiber can be appropriately adjusted according to the oxygen concentration detection limit requirements and the power requirements for determining the fuel-air interface.

[0058] The signal processing module 7 receives the output power of the reference optical path 3 and the sensing optical path 4, and when the output power of the reference optical path 3... P r =0 or sensor optical path output power P s When Δ = 0, it indicates that the reference optical path 3 is broken or the sensing optical path 4 is broken, respectively; when the output power Δ of the reference optical path 3 and the sensing optical path is broken, it indicates that the reference optical path 3 and the sensing optical path 4 are broken. P = P r - P s When Δ < 0, it indicates that the system output signal is abnormal. P crit0 >Δ P> When the value is 0, it indicates that the oil level has not exceeded the sensor's installation position. The oxygen concentration can then be calculated and a concentration signal output. P crit0 The difference between the output power of the reference optical path 3 and the sensing optical path in micro / nano optical fibers at 100% oxygen concentration; when Δ P crit1 <Δ P< 0Δ P crit2 When the oil level exceeds the sensor's installation position, it indicates that the oil level is above the sensor's installation position; otherwise, the system output signal is abnormal. Here, Δ... P crit1 With Δ P crit2 These represent the difference in output power between the reference optical path 3 and the sensing optical path of the micro-nano optical fiber in the fuel at the upper limit of high temperature and the lower limit of low temperature, respectively.

[0059] Working principle: The oxygen and oil level dual-parameter sensing and monitoring system provided in this embodiment has the characteristics of simple sensing structure, light weight, small size, electromagnetic interference resistance, intrinsic safety, high and low temperature resistance, easy integration, high accuracy, simple demodulation, and fast response. It can be used as an oxygen and oil level signal device, or it can realize discrete oil level sensing through micro-nano fiber array arrangement. Moreover, the installation is not limited by the fuel tank structure, and it is suitable for scenarios with multi-parameter measurement requirements of liquid level and gas molecules, such as aviation fuel measurement and control systems. The elastic modulus is preset to the maximum, and the high-precision measurement of the system is achieved through feedback adjustment.

[0060] The other parts of this embodiment are the same as any one of the above embodiments 1-2, so they will not be described again.

[0061] Example 4: This embodiment is based on any one of embodiments 1-3 above, such as Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown, a micro-nano fiber with a radius of 250 nm is described in detail.

[0062] This embodiment provides a dual-parameter sensing and monitoring method for oxygen and oil level. By determining the output power of micro-nano optical fibers, oil level signal identification and oxygen concentration calculation are performed.

[0063] like Figure 1 The diagram shown is a composition diagram of the oxygen and oil level dual-parameter sensing and monitoring system in this embodiment, including: the sensing system includes a light source module 1, a sensing optical path 4, a reference optical path 3, a sensing optical path detection module 6, a reference optical path detection module 5, a signal processing module 7, and a 1×2 3dB fiber optic coupler 2. The light source module 1 is connected to the input port of the 1×2 3dB fiber coupler 2. The first and second output fiber optic cables of the 1×2 3dB fiber coupler 2 are connected to the first micro-nano fiber pigtails 19 of the reference optical path 3 and the sensing optical path 4 respectively through fiber optic flanges. The second micro-nano fiber pigtails 20 of the reference optical path 3 and the sensing optical path 4 are connected to the receiving optical transmission fiber 21 of the reference optical path 3 and the sensing optical path 4 respectively through the second fiber optic flange 12. The receiving optical transmission fiber 21 of the reference optical path 3 is connected to the reference optical path detection module 5, and the receiving optical transmission fiber 21 of the sensing optical path 4 is connected to the sensing optical path detection module 6. The reference optical path 3 and the sensing optical path module are connected to the signal processing module 7 respectively. The single-mode narrow-linewidth probe laser emitted by the light source module 1 is split into the reference optical path 3 and the sensing optical path 4 in a 50:50 ratio via a 3dB coupler. The output optical power of the reference optical path 3 and the sensing optical path is detected and converted into photoelectric signals by the reference optical path detection module 5 and the sensing optical path detection module 6, respectively. Finally, the signal processing module 7 analyzes and outputs the oil level and oxygen concentration signals based on the output power and differential power of the two optical paths. This embodiment utilizes the difference in loss caused by the evanescent field difference of micro-nano optical fibers in different media environments to identify the oil level, i.e., the fuel / air interface. The strong absorption of oxygen by the specific wavelength strong evanescent field of the micro-nano optical fiber enables the measurement of oxygen concentration.

[0064] This embodiment takes the measurement of oxygen concentration and fuel level in an aircraft fuel tank as an example. In the absorption spectrum of oxygen, the absorption intensity at 760nm is high, and there is no obvious absorption of other molecules at the 760nm wavelength in RP3 aviation fuel. At the same time, the corresponding 760nm single-mode narrow linewidth laser and 760nm detector are relatively mature. Figure 1 The light source module 1 shown is selected as a 760nm single-mode narrow linewidth laser. Its single-mode output characteristics are conducive to the stable long-distance transmission of probe light in optical fiber, and its narrow linewidth characteristics make oxygen measurement at 760nm highly sensitive and selective.

[0065] Micro- and nano-fibers are special optical fibers with diameters on the order of micrometers and nanometers. Their evanescent field directly affects their sensing performance to environmental media; the stronger the evanescent field, the more sensitive they are to the external environment. The evanescent field ratio Γ of micro- and nano-fibers is calculated by the following formula: (1) in, S cladding and S total These represent the longitudinal components of the Poynting vector in the environmental cladding and the longitudinal components of the Poynting vector in the entire micro / nano fiber, respectively.

[0066] like Figure 2 The figure shows the relationship between the evanescent field proportion of micro / nano-fibers in aviation fuel and air and their micro / nano radius. As the radius of the micro / nano-fiber increases, the evanescent field proportion gradually decreases and approaches zero. In this embodiment, the sensitivity of the micro / nano-fiber to external stimuli is characterized by the transmission loss of the probe light within the micro / nano-fiber. The loss introduced by the evanescent field in the micro / nano-fiber is... α Γ (Γ) is a function related to the proportion of the evanescent field Γ. The larger the proportion of the evanescent field, the greater the loss. Therefore, in order to effectively and accurately distinguish between fuel medium and air medium to achieve fuel level identification, the greater the difference in evanescent field between fuel and air, the better. Figure 2 The results show that the difference in evanescent field proportions between fuel oil and air is greatest when the fiber radius is 250 nm. The corresponding evanescent field proportion in the fuel oil-clad micro / nano fiber is 0.93, while that in air is 0.25. According to the theory of single-mode fiber transmission, for a 760 nm transmitted light wave, the radius of the micro / nano fiber must be less than 681.9 nm in fuel oil and less than 275.6 nm in air. Therefore, a fiber radius of 250 nm meets the requirements for single-mode transmission of micro / nano fibers.

[0067] Reference optical path output power P r Output optical power of sensing optical path 4 in fuel P sf Output optical power of sensing optical path 4 in airP sa See the following formula: (2) (3) (4) Among them, P in for Figure 1 The light source module 1 outputs optical power. α 0 represents the intrinsic loss of micro / nano optical fiber. L The length of the micro / nano fiber. C a This refers to the concentration of oxygen in the air. C f = C a / 1000 Oxygen concentration in fuel, Γ f The evanescent field ratio of micro / nano optical fibers in fuel oil, Γ a The evanescent field proportion of micro / nano optical fibers in the air. δ Let be the oxygen absorption coefficient. Therefore, when the micro / nano optical fiber is in fuel oil, the difference between the output power of the reference optical path and the output power of the sensing optical path is d. P a = P r - P sa When the micro / nano optical fiber is in fuel oil, the difference between the output power of the reference optical path and the output power of the sensing optical path is d. P f = P r - P sf When d P a With d P f The difference d P The larger the fiber, the higher its sensitivity to the fuel-air interface. In this embodiment, a pure silicon core micro / nano optical fiber is used. α 0 = 25 dB / m δ =0.2 / m, air refractive index is 1, and RP3 aviation fuel refractive index is 1.39.

[0068] like Figure 3 The figure shows the relationship between the difference in output power of a micro / nano fiber in air and fuel oil and the length of the micro / nano fiber when the fiber radius is 250 nm. Under different oxygen concentrations, d P The maximum value is 7.68mW, which corresponds to a micro / nano fiber length of 9.5cm, which is the optimal micro / nano fiber length for fuel / air interface identification.

[0069] like Figure 4The graph shows the relationship between the oxygen concentration detection limit in air and the length of the micro / nano fiber when the radius of the micro / nano fiber is 250 nm. When the length of the micro / nano fiber is 17.37 cm, the minimum oxygen concentration detection limit is 1.5584 ppbv. The oxygen concentration detection limit (DL) is related to the NEP of the detection module. Based on the oxygen concentration detection limit requirements, the length of the micro / nano fiber can be appropriately adjusted while ensuring a clear fuel / air interface identification signal.

[0070] like Figure 5 The figure shows the relationship between the output power difference of the micro / nano fiber in air and fuel and the oxygen concentration when the micro / nano fiber radius is 250 nm and the length is 9.5 cm. In this embodiment, the length of the micro / nano fiber is fixed at 9.5 cm and the diameter is 250 nm. The output power difference dP between the micro / nano fiber in air and fuel decreases as the oxygen concentration increases. When the oxygen concentration is 100%, dP is 7.643 mW. Such a large power difference allows for extremely high accuracy of the fuel level, i.e., the fuel / air interface.

[0071] In this embodiment, due to the large dP, the refractive index of the fuel is between 1.3849 and 1.4025 in the high and low temperature environment of -55℃ to 70℃ inside the aircraft fuel tank, corresponding to a proportion of the evanescent field of the micro-nano fiber in the fuel of 0.90 to 0.965. Since the proportion of the evanescent field of the micro-nano fiber in the fuel changes little under high and low temperature conditions, it is insufficient to significantly affect the difference in output power between the micro-nano fiber in fuel and in air.

[0072] like Figure 6 The diagram shows a flowchart of a dual-parameter sensing and monitoring method for oxygen and oil levels. After receiving the output power of the reference optical path and the sensing optical path, the signal processing module 7 receives the output power of the reference optical path. P r =0 or sensor optical path output power P s When Δ = 0, it indicates that the reference optical path 3 is broken or the sensing optical path 4 is broken, respectively; when the output power Δ of the reference optical path and the sensing optical path is broken... P = P r - P s When Δ < 0, it indicates that the system output signal is abnormal. P crit0 >Δ P> When the value is 0, it indicates that the oil level has not exceeded the sensor's installation position. The oxygen concentration can then be calculated and a concentration signal output. P crit0 The difference between the output power of the reference optical path and the sensing optical path of the micro / nano fiber in 100% oxygen concentration; when Δ P crit1 <Δ P< 0ΔP crit2 When the oil level exceeds the sensor's installation position, it indicates that the oil level is above the sensor's installation position; otherwise, the system output signal is abnormal. Here, Δ... P crit1 With Δ P crit2 These represent the difference in output power between the reference optical path 3 and the sensing optical path 4 of the micro-nano optical fiber in the fuel at the upper limit of high temperature and the lower limit of low temperature, respectively.

[0073] Based on the above embodiments, this embodiment can function as an oxygen concentration and oil level signal transmitter, or it can achieve quasi-continuous dual-parameter sensing of oil level and oxygen concentration by arranging micro-nano optical fibers in an array. It has the characteristics of simple sensing structure, simple signal demodulation, fast response, easy integration, and no limitation on the installation environment.

[0074] It should be noted that this embodiment is not limited to dual-parameter sensing of oxygen concentration and fuel level in aviation fuel tanks, but is applicable to gas concentration and liquid level sensing in all gas-liquid stratification.

[0075] The other parts of this embodiment are the same as any one of the embodiments 1-3 above, so they will not be described again.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A dual-parameter sensing and monitoring system for oxygen and oil level, characterized in that, It includes a light source module (1), a sensing optical path (4), a reference optical path (3), a sensing optical path detection module (6), a reference optical path detection module (5), a signal processing module (7), and an optical fiber coupler (2). The light source module (1) receives a laser signal at its input end and its output end is connected to the input end of the fiber coupler (2); the input end of the sensing optical path (4) is connected to the output end of the fiber coupler (2), and the output end of the sensing optical path (4) is connected to the input end of the sensing optical path detection module (6); the input end of the reference optical path (3) is connected to the output end of the fiber coupler (2), and the output end of the reference optical path (3) is connected to the input end of the reference optical path detection module (5); the input end of the signal processing module (7) is connected to the output end of the reference optical path detection module (5) and the output end of the sensing optical path detection module (6), and the output end of the signal processing module (7) outputs the oxygen concentration. The light source module (1) is used to acquire laser signals; The fiber coupler (2) is used to split the laser signal and transmit the split laser signal to the sensing optical path (4) and the reference optical path (3) respectively. The sensing optical path (4) is used to generate a sensing optical path signal based on the laser signal after beam splitting; The reference optical path (3) is used to generate a reference optical path signal based on the laser signal after beam splitting; The sensing optical path detection module (6) is used to calculate the output power of the sensing optical path based on the sensing optical path signal; The reference optical path detection module (5) is used to calculate the reference optical path output power based on the reference optical path signal; The signal processing module (7) is used to perform differential processing on the output power of the reference optical path and the output power of the sensing optical path to obtain a differential value, and to determine the positional relationship between the oil level and the sensor based on the differential value, and to calculate the oxygen concentration based on the positional relationship and output a concentration signal.

2. The oxygen and oil level dual-parameter sensing and monitoring system according to claim 1, characterized in that, Both the sensing optical path (4) and the reference optical path (3) include micro-nano fiber structures; The micro-nano fiber structure includes a first fiber flange (8), a first micro-nano fiber taper region (9), a second micro-nano fiber taper region (10), a micro-nano fiber waist region (11), and a second fiber flange (12). The input end of the first fiber optic flange (8) is connected to the output end of the fiber optic coupler (2), and the output end of the first fiber optic flange (8) is connected to the input end of the first micro-nano fiber optic cone region (9). The input end of the micro-nano fiber waist region (11) is connected to the output end of the first micro-nano fiber taper region (9), and the output end of the micro-nano fiber waist region (11) is connected to the input end of the second micro-nano fiber taper region (10). The output end of the second micro-nano fiber taper region (10) is connected to the input end of the second fiber flange (12).

3. The dual-parameter sensing and monitoring system for oxygen and oil level according to claim 2, characterized in that, The micro-nano fiber structure of the reference optical path (3) also includes a first vacuum flange (13) and a second vacuum flange (14). The first vacuum flange (13) is disposed between the output end of the fiber optic coupler (2) and the input end of the first fiber optic flange (8); The second vacuum flange (14) is located between the output end of the second fiber optic flange (12) and the input end of the reference optical path detection module (5).

4. The oxygen and oil level dual-parameter sensing and monitoring system according to claim 3, characterized in that, The micro-nano fiber structure of the reference optical path (3) is sealed in a sealing tube (15) through the first vacuum flange (13) and the second vacuum flange (14); the micro-nano fiber structure of the sensing optical path (4) is placed in the medium to be measured.

5. The oxygen and oil level dual-parameter sensing and monitoring system according to claim 2, characterized in that, Based on the output power of the micro / nano fiber structure of the sensing optical path (4) in air P sa With reference optical path output power P r The difference d P a The output power of the micro / nano fiber structure of the sensing optical path (4) in fuel P sf With reference optical path output power P r The difference d P f Adjust the length of the micro-nano fiber in the micro-nano fiber structure.

6. A dual-parameter sensing and monitoring method for oxygen and oil level, implemented based on the dual-parameter sensing and monitoring system for oxygen and oil level as described in claim 1, characterized in that, Specifically, the following steps are included: Step S1: The acquired laser signal is transmitted to the reference optical path (3) and the sensing optical path (4) respectively through the fiber optic coupler (2). Step S2: Obtain the reference optical path signal from the reference optical path (3) and obtain the sensing optical path signal from the sensing optical path (4); Step S3: Calculate the output power of the reference optical path and the output power of the sensor optical path based on the reference optical path signal and the sensor optical path signal; Step S4: Perform differential processing on the output power of the reference optical path and the output power of the sensing optical path to obtain the differential value; Step S5: Determine the relationship between the oil level and the sensor installation position based on the difference value, and calculate the oxygen concentration based on the position relationship.

7. The method for dual-parameter sensing and monitoring of oxygen and oil level according to claim 6, characterized in that, Step S4 specifically includes the following steps: Step S41: Calculate the output power of the reference optical path based on the obtained output optical power of the laser signal, the intrinsic loss of the micro / nano fiber, and the length of the micro / nano fiber. P r ; Step S42: Calculate the output power of the sensing optical path based on the acquired laser signal output power, intrinsic loss of the micro / nano fiber, length of the micro / nano fiber, oxygen concentration of the test medium, and evanescent field proportion of the micro / nano fiber in the test medium. P s ; Step S43: Output power of the reference optical path P r and the output power of the sensing optical path P s Perform difference processing to obtain the difference value Δ P。 8. The method for dual-parameter sensing and monitoring of oxygen and oil level according to claim 7, characterized in that, The specific operation of step S5 is as follows: if the reference optical path output power P r =0, then the reference optical path (3) is broken; If the output power of the sensing optical path P s When =0, it is determined that the sensing optical path (4) is broken; If the difference value ΔP is less than 0, it is determined that there is a signal abnormality in the current system; if the difference value ΔP is greater than 0 and less than the difference ΔP between the output power of the reference optical path (3) and the sensing optical path of the micro-nano fiber under 100% oxygen concentration, it is determined that there is a signal abnormality in the current system. P crit0 If the current oil level does not exceed the sensor installation position, the oxygen concentration is calculated and the concentration signal is output; if the difference value ΔP is greater than the difference between the output power of the reference optical path (3) and the sensing optical path (4) of the micro-nano optical fiber in the fuel at the upper limit of high temperature, and less than the difference between the output power of the reference optical path (3) and the sensing optical path (4) of the micro-nano optical fiber in the fuel at the lower limit of low temperature, then the current oil level exceeds the sensor installation position and the output signal is abnormal.

9. The method for dual-parameter sensing and monitoring of oxygen and oil level according to claim 7, characterized in that, Step S42 specifically includes the following steps: Step S421: Place the micro-nano fiber structure of the sensing optical path (4) in the air. Calculate the output power of the sensing optical path (4) in the air based on the acquired laser signal output power, intrinsic loss of the micro-nano fiber, length of the micro-nano fiber, oxygen concentration in the air, and the evanescent field ratio of the micro-nano fiber in the air. P sa And calculate the output power of the sensing optical path (4) in air. P sa With reference optical path output power P r The difference d P a ; Step S422: Set the micro-nano fiber structure of the sensing optical path (4) in the fuel oil. Calculate the output power of the sensing optical path (4) in the fuel oil based on the output optical power of the acquired laser signal, the intrinsic loss of the micro-nano fiber, the length of the micro-nano fiber, the oxygen concentration in the fuel oil, and the evanescent field ratio of the micro-nano fiber in the fuel oil. P sf And calculate the output power of the sensing optical path (4) in the fuel. P sf With reference optical path output power P r The difference d P f ; Step S423: Calculate the difference d P a The difference d P f The difference dP is used to adjust the length of the micro-nano fiber in the micro-nano fiber structure.

10. The method for dual-parameter sensing and monitoring of oxygen and oil level according to claim 9, characterized in that, The specific operation of adjusting the length of the micro-nano fiber in step S423 is as follows: The difference d... P The maximum value corresponds to the length of the micro-nano fiber in the micro-nano fiber structure, which is taken as the length of the micro-nano fiber in the micro-nano fiber structure.

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