A quasi-distributed all-fiber liquid level sensing device and liquid level and leakage detection method

Abstract

The application relates to the technical field of detection, and discloses a quasi-distributed all-fiber liquid level sensing device and a liquid level and liquid leakage detection method. The sensing device comprises an optical time domain reflection system and a sensitive structure; the sensitive structure comprises a sensing optical fiber, a multi-stage coupler and a multi-stage collimator; the collimator is used for changing incident pulse light into collimated light; each stage of the coupler is used for outputting incident pulse light to the next stage of the coupler and the same stage of the collimator, receiving Rayleigh backscattering signals of the next stage of the coupler, and outputting Rayleigh backscattering light generated by the same stage of the collimator to the previous stage after the Rayleigh backscattering light is superimposed on the Rayleigh backscattering signals; the optical time domain reflection system is used for emitting pulse light to the sensing optical fiber, detecting Rayleigh backscattering signals to obtain Rayleigh backscattering light curves generated by the sensing optical fiber along a line, and identifying the collimator immersed in liquid according to Fresnel reflection peaks on the curves. The application can accurately position the collimator immersed in liquid by using the optical time domain reflection technology and the Fresnel reflection principle of the end surface of the optical fiber.

Description

Technical Field

[0001] This invention relates to the field of measurement technology, and in particular to a quasi-distributed all-fiber liquid level sensing device and a method for detecting liquid level and leakage. Background Technology

[0002] Liquid level sensing technology monitors changes in liquid level by detecting physical quantities such as static pressure, mechanical displacement, and energy changes using sensitive elements. It is applicable to the measurement of liquid levels in various media across systems and industries including petrochemicals, metallurgy, power, pharmaceuticals, water supply and drainage, and environmental protection. It is crucial for key projects related to chemical storage and transportation, oil and gas resource storage and transportation, and water conservancy safety and water resource development, making it an indispensable key technology in the industrial sector.

[0003] Currently, widely used liquid level sensors include capacitive liquid level sensors, float-type liquid level sensors, ultrasonic liquid level sensors, and fiber optic liquid level sensors. Chinese patent CN114485853A discloses a capacitive liquid level gauge. This gauge controls its operation via a main circuit board, using a signal transmitter and receiver to collect the capacitance signal between the top of the gauge and a float that changes with the liquid level. The data is then processed by the main circuit board. This gauge has a complex circuit structure and is susceptible to electromagnetic interference. Chinese patent CN111750957A discloses a float-type liquid level gauge. This gauge is based on the buoyancy of the liquid on the float and the principle of static magnetic fields. When the liquid level rises or falls, the position of the magnetic float changes, causing a change in the electrical quantity of the components connected in series with the circuit, thus reflecting the change in liquid level. This gauge has a complex mechanical structure, is easily damaged, and has low reliability over long-term use. Chinese patent CN215639669 discloses a different type of liquid level gauge. A Chinese patent proposes an ultrasonic level gauge that emits ultrasonic pulses through a transmitter. The sound waves are reflected by the liquid surface and return to the receiver. After photoelectric conversion by a piezoelectric crystal, the liquid level height information can be calculated by the pulse flight time. However, the measurement accuracy of this level gauge is easily affected by environmental temperature, humidity, and airflow, making it difficult to improve its accuracy.

[0004] Fiber optic sensing technology boasts significant advantages such as flexibility, corrosion resistance, water resistance, electromagnetic interference resistance, and the ability to operate without power at the sensing point, gradually becoming a key technology in the information industry. Liquid level sensing based on fiber optic technology offers high sensitivity, electromagnetic interference resistance, and enhanced practicality, making it increasingly the preferred technology in the field of liquid level sensing. Summary of the Invention

[0005] The purpose of this invention is to provide a quasi-distributed all-fiber liquid level sensing device and a liquid level and leakage detection method, so as to achieve liquid level / leakage detection simply and accurately.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A quasi-distributed all-fiber liquid level sensing device includes: an optical time-domain reflectometry system and a sensing structure;

[0008] The sensitive structure includes a sensing fiber, a multi-stage coupler, and a multi-stage collimator. Each stage of the coupler includes two output ends: one connected to the input fiber of the next stage coupler, and the other connected to the collimator fiber of the same stage. The input end of the first stage coupler is connected to the output fiber of the optical time-domain reflectometry system. The sensing fiber connecting the first stage coupler and the optical time-domain reflectometry system, as well as between adjacent couplers, constitutes the backbone fiber. Couplers and collimators connected at the same stage form a first-stage detection end and are located at the same detection position.

[0009] Each collimator is used to convert the incident pulse light into collimated light for output.

[0010] Each stage of the coupler is used to split the incident pulse light into two paths and output them to the next stage coupler and the collimator of the same stage, respectively. It is also used to receive the Rayleigh backscattered signal generated by the next stage coupler, and couple the Rayleigh backscattered light generated by the collimator of the same stage into the main optical fiber, superimpose it on the Rayleigh backscattered signal and output it to the previous stage.

[0011] The optical time-domain reflectometry system is used to emit pulsed light into the sensing fiber, detect the Rayleigh backscattered signal to obtain the Rayleigh backscattered light curve generated along the sensing fiber, and identify the collimator currently immersed in the liquid based on the Fresnel reflection peak on the Rayleigh backscattered light curve.

[0012] Optionally, the optical time-domain reflectometry system includes: a laser, a circulator, a photodetector, a data acquisition card, and a host computer processing system;

[0013] The output end of the laser is connected to the input end of the circulator to emit pulsed light, so that Rayleigh backscattered light is generated along the sensing fiber.

[0014] The circulator includes two output terminals, one connected to the first-stage coupler in the sensitive structure and the other connected to the input terminal of the photodetector; the circulator is used to transmit the pulsed light into the sensing fiber and to receive the Rayleigh backscattered signal on the main fiber and output it to the photodetector.

[0015] The input end of the photodetector is electrically connected to the circulator, and the output end is electrically connected to the data acquisition card, for acquiring the Rayleigh backscattered signal and sending it to the data acquisition card;

[0016] The data acquisition card is electrically connected to the laser and the host computer processing system, respectively, and is used to upload the Rayleigh backscatter signal to the host computer processing system and to trigger the laser with a synchronization pulse.

[0017] The host computer processing system is used to demodulate the Rayleigh backscatter signal to obtain the Rayleigh backscatter light curve generated along the sensing fiber, and to identify the collimator currently immersed in the liquid based on the Fresnel reflection peak on the Rayleigh backscatter light curve.

[0018] Optionally, the circulator is connected to the first-stage coupler via a bidirectional EDFA, which is used to bidirectionally amplify the incident pulsed light and the Rayleigh backscattered light signal from the sensitive structure.

[0019] Optionally, the laser is specifically used to emit Gray code-encoded pulses of light.

[0020] Optionally, the optical fiber of the backbone is set perpendicular to the liquid surface of the liquid being measured, and the last stage of the probe is located at the lowest liquid level of the liquid being measured.

[0021] Optionally, the optical time-domain reflectometry system, in its aspect of identifying the collimator currently immersed in the liquid based on the Fresnel reflection peak on the Rayleigh backscattered light curve, is specifically used for:

[0022] Determine the location of the first abrupt change in the Rayleigh backscattered light curve where the Fresnel reflection peak appears;

[0023] Based on the first mutation location, determine the corresponding target probe end where the mutation occurred;

[0024] The current liquid level height of the liquid being measured is determined based on the total length of the main optical fiber and the length and position of the target detection end on the main optical fiber.

[0025] Optionally, the backbone fiber is laid horizontally within the area to be measured, and each probe is located in a different sub-region within the area to be measured.

[0026] Optionally, the optical time-domain reflectometry system, in its aspect of identifying the collimator currently immersed in the liquid based on the Fresnel reflection peak on the Rayleigh backscattered light curve, is specifically used for:

[0027] Determine all abrupt locations on the Rayleigh backscattered light curve where Fresnel reflection peaks appear;

[0028] Based on each mutation location, identify all target probes that have experienced the mutation.

[0029] Based on the total length of the main optical fiber and the length and position of each target detection end on the main optical fiber, the sub-regions containing liquid media within the measured area are determined.

[0030] A liquid level detection method using any one of the above-described quasi-distributed all-fiber liquid level sensing devices includes:

[0031] The main optical fiber is positioned perpendicular to the surface of the liquid being measured, and the last stage probe is positioned at the lowest liquid level of the liquid being measured.

[0032] A pulsed light is emitted into the sensing fiber, and the Rayleigh backscattered signal generated on the main fiber is detected at the same time. The Rayleigh backscattered light curve generated along the sensing fiber is obtained based on the Rayleigh backscattered signal.

[0033] First, determine the position of the first abrupt change of the Fresnel reflection peak on the Rayleigh backscattered light curve. Then, determine the target probe corresponding to the abrupt change based on the position of the first abrupt change. Finally, determine the current liquid level height of the liquid being measured based on the total length of the main optical fiber and the length position of the target probe on the main optical fiber.

[0034] A method for detecting leakage using a quasi-distributed all-fiber liquid level sensing device as described above, comprising:

[0035] The main optical fiber is laid horizontally within the area to be tested, and each probe is located in a different sub-region within the area to be tested.

[0036] A pulsed light is emitted into the sensing fiber, and the Rayleigh backscattered signal generated on the main fiber is detected at the same time. The Rayleigh backscattered light curve generated along the sensing fiber is obtained based on the Rayleigh backscattered signal.

[0037] First, determine all abrupt changes in the Fresnel reflection peak on the Rayleigh backscattered light curve. Then, determine all target probes corresponding to the abrupt changes based on each abrupt change location. Finally, determine the sub-regions containing liquid media within the measured area based on the total length of the backbone fiber and the length and position of each target probe on the backbone fiber.

[0038] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0039] (1) This invention utilizes optical time-domain reflectometry and the Fresnel reflection principle of the fiber end face. By using the peak intensity and Fresnel reflection peak of the collimator output end in different media, the collimator immersed in the liquid can be accurately located, thereby achieving accurate detection of liquid level and leakage. At the same time, multi-stage collimators are used, and collimators can be installed according to the target resolution, which can realize quasi-distributed sensing.

[0040] (2) The present invention uses an optical time-domain reflectometry system that utilizes Rayleigh backscattered light signals, which has a large signal strength and can realize long-distance liquid level sensing.

[0041] (3) The sensing part of this invention is fully fiber optic and has no electrical components. It can be used in complex and harsh environments, resists electromagnetic interference, and has advantages such as long service life and high reliability. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of the quasi-distributed all-fiber liquid level sensing device provided in an embodiment of the present invention.

[0044] Figure 2 This is a flowchart of a liquid level detection method implemented using a quasi-distributed all-fiber liquid level sensing device, as provided in an embodiment of the present invention.

[0045] Figure 3 A schematic diagram of the vertical liquid level measurement method and measurement results of the quasi-distributed all-fiber liquid level sensing device provided in an embodiment of the present invention;

[0046] Figure 4 This is a flowchart of a leakage detection method implemented using a quasi-distributed all-fiber liquid level sensing device, as provided in an embodiment of the present invention.

[0047] Figure 5 This is a schematic diagram illustrating the liquid leakage measurement method and measurement results of the quasi-distributed all-fiber liquid level sensing device provided in an embodiment of the present invention.

[0048] Figure reference numerals: 1. Optical time domain reflectometry system; 2. Sensitive structure; 11. Laser; 12. Circulator; 13. EDFA; 14. Photodetector; 15. Data acquisition card; 16. Host computer processing system; 21. Sensing fiber; 22. Coupler; 23. Collimator. Detailed Implementation

[0049] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0050] Please see Figure 1 This invention provides a quasi-distributed all-fiber liquid level sensing device, which mainly includes: an optical time-domain reflectometry system 1 and a sensing structure 2.

[0051] Sensitive structure 2 is mainly used to realize liquid detection function, specifically including sensing fiber 21, multi-stage coupler 22 and multi-stage collimator 23.

[0052] Each stage coupler 22 includes two output terminals, one of which is connected to the input optical fiber of the next stage coupler 22, and the other is connected to the optical fiber of the collimator 23 of the same stage; the input terminal of the first stage coupler 22 is connected to the output optical fiber of the optical time domain reflection system 1.

[0053] The sensing fiber 21 can be divided into a main fiber and a branch fiber. The sensing fiber 21 connected between the first-stage coupler 22 and the optical time-domain reflectometry system 1 and between two adjacent couplers 22 constitutes the main fiber. The sensing fiber 21 connected between the same-stage coupler 22 and the collimator 23 constitutes the branch fiber.

[0054] Coupler 22 and collimator 23 connected at the same level form a primary detection end and are located at the same detection position. Based on this, the sensitive structure 2 includes multiple detection ends connected in series.

[0055] Each collimator 23 is used to convert the incident pulsed light into collimated outgoing light.

[0056] Each coupler 22 is used to split the incident pulse light into two paths and output them to the next coupler 22 and the collimator 23 of the same stage, respectively. It is also used to receive the Rayleigh backscattered signal generated by the next coupler 22, and couple the Rayleigh backscattered light generated by the collimator 23 of the same stage into the main optical fiber, superimpose it on the Rayleigh backscattered signal and output it to the previous stage.

[0057] Optical time-domain reflectometry system 1 is used to emit pulsed light into sensing fiber 21, detect Rayleigh backscattered signal to obtain Rayleigh backscattered light curve generated along sensing fiber 21, and identify collimator 23 currently immersed in liquid based on Fresnel reflection peak on Rayleigh backscattered light curve.

[0058] Since the detection end of this embodiment of the invention is implemented using a collimator 23, the collimator 23 will have obvious Fresnel reflection peaks when immersed in liquid, and no Fresnel reflection peaks will be raised when not immersed in liquid (i.e., in air). Therefore, it is possible to accurately determine whether the collimator 23 is immersed in liquid based on the different end-face reflection intensities of the output end of the collimator 23 in air and liquid media. At the same time, this embodiment of the invention uses multi-stage collimators, thus enabling quasi-distributed sensing.

[0059] Specifically, after the optical time-domain reflectometry system 1 emits pulsed light into the sensing fiber 21, the pulsed light will be scattered in the sensing fiber 21, where the intensity P of Rayleigh scattering is... R for:

[0060]

[0061] Where P is the peak power of the pulsed light, α S denoted as Rayleigh scattering coefficient, S as backscattered light power capture factor, W as pulse width, and v as the speed of light in the optical fiber.

[0062] The location L where the scattering occurs can be obtained from the flight time t of the pulsed light generated by laser 11 in the optical fiber. The specific relationship is as follows:

[0063]

[0064] Where n is the refractive index and c is the speed of light in a vacuum.

[0065] After the pulsed light is emitted, the intensity of the Rayleigh scattered light detected on side 1 of the optical time-domain reflectometry system is:

[0066]

[0067] Where P0 is the peak power of the pulsed light, α0 is the attenuation coefficient of the incident light, and α R Let W be the attenuation coefficient of the Rayleigh backscattered light, and W be the pulse width. The Rayleigh backscattering curve along the fiber can then be obtained from the above equation.

[0068] When collimator 23 is immersed in liquid, a significant Fresnel scattering peak will form at its tail end:

[0069]

[0070] Where n1 is the refractive index of the fiber core, and the Fresnel reflection peak intensity is much greater than the Rayleigh scattering intensity.

[0071] Therefore, based on the location of the Fresnel reflection peak on the Rayleigh backscattering curve, the collimator 23 immersed in the liquid can be accurately identified.

[0072] In one optional implementation, the optical temporal reflectance system 1 includes: a laser 11, a circulator 12, a photodetector 14, a data acquisition card 15, and a host computer processing system 16.

[0073] The output of laser 11 is connected to the input of circulator 12 to emit pulsed light so that the sensing fiber 21 generates Rayleigh backscattered light along the line.

[0074] The circulator 12 includes two output terminals, one of which is connected to the first-stage coupler 22 in the sensitive structure 2, and the other is connected to the input terminal of the photodetector 14. The circulator 12 is used to transmit pulsed light into the sensing fiber 21, and to receive the Rayleigh backscattered signal on the main fiber and output it to the photodetector 14.

[0075] The input end of the photodetector 14 is electrically connected to the circulator 12, and the output end is electrically connected to the data acquisition card 15, for acquiring Rayleigh backscattered signals and sending them to the data acquisition card 15;

[0076] The data acquisition card 15 is electrically connected to the laser 11 and the host computer processing system 16 respectively, and is used to upload the Rayleigh backscatter signal to the host computer processing system 16 and to trigger the laser 11 with a synchronous pulse.

[0077] The host computer processing system 16 is used to demodulate the Rayleigh backscatter signal to obtain the Rayleigh backscatter light curve generated along the sensing fiber 21, and to identify the collimator 23 currently immersed in the liquid based on the Fresnel reflection peak on the Rayleigh backscatter light curve.

[0078] Based on this, the circulator 12 and the first-stage coupler 22 can be connected by a bidirectional EDFA 13 (Erbium-Doped Fiber Amplifier), which is used to bidirectionally amplify the incident pulse light and the Rayleigh backscattered light signal from the sensitive structure 2 to improve the signal-to-noise ratio.

[0079] Laser 11 can be specifically used to emit Gray code-encoded pulsed light to further improve the signal-to-noise ratio.

[0080] In practical applications, the sensitive structure 2 can be used in different ways depending on the different detection requirements, such as liquid level detection and leakage detection.

[0081] When performing liquid level detection, such as Figure 3As shown, the backbone fiber is positioned perpendicular to the surface of the liquid being measured, and the last stage detector is located at the lowest liquid level. In this case, the optical time-domain reflectometry system 1, in identifying the collimator 23 currently immersed in the liquid based on the Fresnel reflection peak on the Rayleigh backscattered light curve, specifically involves: first determining the location of the first abrupt change in the Fresnel reflection peak on the Rayleigh backscattered light curve; then, based on the first abrupt change location, determining the corresponding target detector where the abrupt change occurred; and finally, based on the total length L of the backbone fiber... all And the length L of the target detection end on the main optical fiber. f Determine the current liquid level L of the liquid being measured. liquid =L all -L f .

[0082] It should be noted that when performing liquid level detection, the total length of the main optical fiber is determined by the total depth of the liquid being measured, while the spacing between the multi-stage couplers 22 is determined by the target resolution and can be designed according to the actual detection accuracy requirements. This invention does not impose specific limitations on this.

[0083] When performing leak detection, such as Figure 5 As shown, the backbone fiber is laid horizontally within the measured area, and each detector end is located in a different sub-region within the measured area. The optical time-domain reflectometry system 1, in identifying the collimator 23 currently immersed in liquid based on the Fresnel reflection peak on the Rayleigh backscattered light curve, is specifically used for: first, determining all abrupt changes in the Fresnel reflection peak on the Rayleigh backscattered light curve; then, based on each abrupt change location, determining all corresponding target detector ends where the abrupt change occurred; and finally, based on the total length of the backbone fiber and the length position of each target detector end on the backbone fiber, determining the sub-regions within the measured area containing the liquid medium.

[0084] Similarly, when performing leakage detection, the total length of the main optical fiber is determined by the area of ​​the measured region, and the spacing between the multi-stage couplers 22 is determined by the target resolution. The more sub-regions formed by the measured region, the more couplers 22 there are, and the higher the detection accuracy.

[0085] Please see Figure 2 and Figure 3 As shown, applying the aforementioned quasi-distributed all-fiber liquid level sensing device, this embodiment of the invention also provides a liquid level detection method, including the following steps:

[0086] Step 101: Set the main optical fiber perpendicular to the surface of the liquid being measured, and position the last stage probe at the lowest liquid level of the liquid being measured.

[0087] Step 102: Emit pulsed light to sensing fiber 21 and simultaneously detect the Rayleigh backscattered signal generated on the main fiber. Obtain the Rayleigh backscattered light curve generated along the sensing fiber 21 based on the Rayleigh backscattered signal.

[0088] Step 103: First, determine the first abrupt change position of the Fresnel reflection peak on the Rayleigh backscattered light curve. Then, determine the corresponding target probe end where the abrupt change occurred based on the first abrupt change position. Finally, determine the current liquid level height of the liquid being measured based on the total length of the main optical fiber and the length position of the target probe end on the main optical fiber.

[0089] Please see Figure 4 and Figure 5 As shown, using the aforementioned quasi-distributed all-fiber liquid level sensing device, this embodiment of the invention also provides a leakage detection method, including the following steps:

[0090] Step 201: Lay the backbone fiber horizontally within the area to be tested, with each probe located in a different sub-region within the area to be tested.

[0091] Step 202: Emit pulsed light to sensing fiber 21 and simultaneously detect the Rayleigh backscattered signal generated on the main fiber. Obtain the Rayleigh backscattered light curve generated along the sensing fiber 21 based on the Rayleigh backscattered signal.

[0092] Step 203: First, determine all abrupt changes in the Fresnel reflection peak on the Rayleigh backscattered light curve. Then, determine all target probes that have abrupt changes based on each abrupt change location. Finally, determine the sub-regions with liquid media within the measured area based on the total length of the main fiber and the length and position of each target probe on the main fiber.

[0093] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A quasi-distributed all-fiber liquid level sensing device, characterized in that, include: Optical temporal reflectance system and sensitive structure; The sensitive structure includes a sensing fiber, a multi-stage coupler, and a multi-stage collimator. Each stage of the coupler includes two output ends: one connected to the input fiber of the next stage coupler, and the other connected to the collimator fiber of the same stage. The input end of the first stage coupler is connected to the output fiber of the optical time-domain reflectometry system. The sensing fiber connecting the first stage coupler and the optical time-domain reflectometry system, as well as between adjacent couplers, constitutes the backbone fiber. Couplers and collimators connected at the same stage form a first-stage detection end and are located at the same detection position. Each collimator is used to convert the incident pulse light into collimated light for output. Each stage of the coupler is used to split the incident pulse light into two paths and output them to the next stage coupler and the collimator of the same stage, respectively. It is also used to receive the Rayleigh backscattered signal generated by the next stage coupler, and couple the Rayleigh backscattered light generated by the collimator of the same stage into the main optical fiber, superimpose it on the Rayleigh backscattered signal and output it to the previous stage. The optical time-domain reflectometry system is used to emit pulsed light into the sensing fiber, detect the Rayleigh backscattered signal to obtain the Rayleigh backscattered light curve generated along the sensing fiber, and identify the collimator currently immersed in the liquid based on the Fresnel reflection peak on the Rayleigh backscattered light curve.

2. The quasi-distributed all-fiber liquid level sensing device according to claim 1, characterized in that, The optical time-domain reflectometry system includes: a laser, a circulator, a photodetector, a data acquisition card, and a host computer processing system; The output end of the laser is connected to the input end of the circulator to emit pulsed light, so that Rayleigh backscattered light is generated along the sensing fiber. The circulator includes two output terminals, one connected to the first-stage coupler in the sensitive structure and the other connected to the input terminal of the photodetector; the circulator is used to transmit the pulsed light into the sensing fiber and to receive the Rayleigh backscattered signal on the main fiber and output it to the photodetector. The input end of the photodetector is electrically connected to the circulator, and the output end is electrically connected to the data acquisition card, for acquiring the Rayleigh backscattered signal and sending it to the data acquisition card; The data acquisition card is electrically connected to the laser and the host computer processing system, respectively, and is used to upload the Rayleigh backscatter signal to the host computer processing system and to trigger the laser with a synchronization pulse. The host computer processing system is used to demodulate the Rayleigh backscatter signal to obtain the Rayleigh backscatter light curve generated along the sensing fiber, and to identify the collimator currently immersed in the liquid based on the Fresnel reflection peak on the Rayleigh backscatter light curve.

3. The quasi-distributed all-fiber liquid level sensing device according to claim 2, characterized in that, The circulator is connected to the first-stage coupler via a bidirectional erbium-doped fiber amplifier (EDFA), which is used to bidirectionally amplify the incident pulsed light and the Rayleigh backscattered light signal from the sensitive structure.

4. The quasi-distributed all-fiber liquid level sensing device according to claim 1, characterized in that, The laser is specifically used to emit Gray code-encoded pulses of light.

5. The quasi-distributed all-fiber liquid level sensing device according to claim 1, characterized in that, The optical fiber in the backbone is set perpendicular to the surface of the liquid being measured, and the last stage of the probe is located at the lowest liquid level of the liquid being measured.

6. The quasi-distributed all-fiber liquid level sensing device according to claim 5, characterized in that, The optical time-domain reflectometry system, in its aspect of identifying the collimator currently immersed in the liquid based on the Fresnel reflection peak on the Rayleigh backscattered light curve, is specifically used for: Determine the location of the first abrupt change in the Rayleigh backscattered light curve where the Fresnel reflection peak appears; Based on the first mutation location, determine the corresponding target probe end where the mutation occurred; The current liquid level height of the liquid being measured is determined based on the total length of the main optical fiber and the length and position of the target detection end on the main optical fiber.

7. The quasi-distributed all-fiber liquid level sensing device according to claim 1, characterized in that, The main optical fiber is laid horizontally within the area being tested, and each probe is located in a different sub-region within the area being tested.

8. The quasi-distributed all-fiber liquid level sensing device according to claim 7, characterized in that, The optical time-domain reflectometry system, in its aspect of identifying the collimator currently immersed in the liquid based on the Fresnel reflection peak on the Rayleigh backscattered light curve, is specifically used for: Determine all abrupt locations on the Rayleigh backscattered light curve where Fresnel reflection peaks appear; Based on each mutation location, identify all target probes that have experienced the mutation. Based on the total length of the main optical fiber and the length and position of each target detection end on the main optical fiber, the sub-regions containing liquid media within the measured area are determined.

9. A liquid level detection method using the quasi-distributed all-fiber liquid level sensing device according to any one of claims 1 to 4, characterized in that, include: The main optical fiber is positioned perpendicular to the surface of the liquid being measured, and the last stage probe is positioned at the lowest liquid level of the liquid being measured. A pulsed light is emitted into the sensing fiber, and the Rayleigh backscattered signal generated on the main fiber is detected at the same time. The Rayleigh backscattered light curve generated along the sensing fiber is obtained based on the Rayleigh backscattered signal. First, determine the position of the first abrupt change of the Fresnel reflection peak on the Rayleigh backscattered light curve. Then, determine the target probe corresponding to the abrupt change based on the position of the first abrupt change. Finally, determine the current liquid level height of the liquid being measured based on the total length of the main optical fiber and the length position of the target probe on the main optical fiber.

10. A method for detecting leakage using the quasi-distributed all-fiber liquid level sensing device according to any one of claims 1 to 4, characterized in that, include: The main optical fiber is laid horizontally within the area to be tested, and each probe is located in a different sub-region within the area to be tested. A pulsed light is emitted into the sensing fiber, and the Rayleigh backscattered signal generated on the main fiber is detected at the same time. The Rayleigh backscattered light curve generated along the sensing fiber is obtained based on the Rayleigh backscattered signal. First, determine all abrupt changes in the Fresnel reflection peak on the Rayleigh backscattered light curve. Then, determine all target probes corresponding to the abrupt changes based on each abrupt change location. Finally, determine the sub-regions containing liquid media within the measured area based on the total length of the backbone fiber and the length and position of each target probe on the backbone fiber.

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