A vector flow velocity sensor based on a multi-core optical fiber

Abstract

This application discloses a vector velocity sensor based on multi-core optical fiber, comprising a transmitting unit, a receiving unit, and a signal processing unit. The transmitting unit provides a light source and enables long-distance communication; the receiving unit transmits, modulates, and converts the light source; and the signal processing unit performs photoelectric signal conversion and demodulation. The fiber optic probe consists of multi-core optical fiber, flexible material, and a rigid crystal. Multiple Fabry-Perot interference structures (F-P) are formed by repeatedly coating the ends of the optical fiber with a stable flexible material and then attaching a rigid crystal to the ends. By demodulating the multiple optical signals sensed by the probe, a relationship between the sensor and the flow velocity is established. The communication module transmits the signals, and the terminal device receives and displays the final flow velocity result. This application, in addition to possessing the advantages of a small size, electromagnetic interference resistance, and corrosion resistance of an all-fiber optic velocity sensor, can simultaneously measure the magnitude and direction of flow velocity, achieving high sensitivity, high integration, high spatial resolution, and long-distance communication for vector velocity measurement.

Description

Technical Field

[0001] This application relates to the field of fiber optic sensing technology, specifically to a vector flow velocity sensor based on multi-core optical fiber. Background Technology

[0002] Flow velocity is an important parameter in modern industrial production, medical equipment, and national defense. It represents the displacement of a liquid or gas per unit time, and instruments in this field are receiving increasing attention, such as ultrasonic flow meters and hot-wire flow meters. Although the technology of these instruments is mature, their accuracy is relatively low, especially in environments such as the ocean, where their resistance to interference is weak.

[0003] With the continuous development and improvement of the optical fiber field, optical fiber sensors have received great attention from research institutions in the field of flow velocity measurement. Compared with traditional measuring instruments, optical fiber sensing technology has advantages such as small size, corrosion resistance, waterproofing, and resistance to electromagnetic interference. Its small size makes it easy to form distributed and array-type sensing measurement networks. It can adapt to the measurement of liquid or gas flow velocity and flow rate in complex environments, and has broad prospects for liquid and gas flow measurement in aerospace high-frequency gas measurement, industry, agriculture, marine, medical and other fields.

[0004] However, current fiber optic flow sensors, such as hot-wire fiber optic flow sensors, differential pressure fiber optic flow sensors, all-fiber FP, and FBG flow sensors, have emerged. Although they have solved the problems of traditional flow sensors being susceptible to corrosion and having poor anti-interference capabilities, none of them have been able to achieve vector sensing of flow velocity. Summary of the Invention

[0005] To address the aforementioned technical challenges, this application utilizes a multi-core optical fiber coated with multiple layers of stable flexible silicone material, and then bonded with a stable high-hardness crystal to construct a Fabry-Perot interferometric flow velocity sensor. This enables highly integrated, high spatial resolution, high sensitivity, corrosion resistance, and electromagnetic interference resistance for flow velocity vector measurement.

[0006] To achieve the above objectives, this application provides a vector flow velocity sensor based on multi-core optical fiber, comprising: a transmitting unit, a receiving unit, and a signal processing unit;

[0007] The transmitting unit is used to provide a light source; the transmitting unit is also used for long-distance transmission;

[0008] The receiving unit is used to modulate an optical signal based on the light source and transmit the optical signal.

[0009] The signal processing unit is used to convert optical signals into electrical signals and demodulate the electrical signals.

[0010] Preferably, the transmitting unit includes: a light source module and a communication module;

[0011] The light source module is used to provide the light source to the receiving unit;

[0012] The communication module is used to transmit the optical signal over long distances.

[0013] Preferably, the receiving unit includes: an optical fiber looper, an optical fiber probe, a multi-core optical fiber fan-in / fan-out device, and a receiving terminal;

[0014] The fiber optic probe is used to receive the light source, sense changes in flow rate, and modulate the optical signal.

[0015] The fiber optic looper is used to transmit the light source to the fiber optic probe, and then transmit the optical signal modulated by the fiber optic probe to the multi-core fiber fan-in and fan-out device.

[0016] The multi-core fiber fan-in / fan-out device is used to transmit the optical signal modulated by the fiber optic probe to the signal processing unit.

[0017] The signal receiving terminal is used to receive signals sent by the communication module and display the flow rate results.

[0018] Preferably, the signal processing unit includes: a photodetector, an A / D data acquisition unit, and a microprocessor;

[0019] The photodetector is used to convert the received optical signal into an analog electrical signal;

[0020] The A / D data acquisition unit is used to acquire the analog electrical signal and convert the analog electrical signal into a digital signal;

[0021] The microprocessor is used to demodulate the digital signal.

[0022] Preferably, the fiber optic probe and the multi-core fiber fan-in / fan-out device are integrated, and the output end of the multi-core fiber fan-in / fan-out device is connected to the interface at one end of the fiber optic looper.

[0023] Preferably, the fiber optic probe is composed of multi-core optical fibers.

[0024] Preferably, a flexible material with stable properties is used to coat the multi-core optical fiber multiple times to form a coated multi-core optical fiber.

[0025] Preferably, a stable rigid crystal is bonded to the end of the coated multi-core optical fiber, forming a highly integrated plurality of Fabry-Perot interference structures with the multi-core optical fiber and the flexible cavity.

[0026] Compared with the prior art, the beneficial effects of this application are as follows:

[0027] This application's fiber optic probe is made of multi-core optical fiber, flexible materials, and a rigid crystal, enabling highly integrated, high spatial resolution, and high-sensitivity flow velocity vector measurement. Utilizing the water-insoluble, stable, and elastic properties of PDMS, this application enhances the probe's sensitivity, making it suitable for harsh environments. Simultaneously, a high-hardness crystal is bonded to the PDMS end, forming multiple highly integrated Fabry-Perot interferometer (FP-cavity) structures with the multi-core optical fiber and PDMS, further increasing the probe's sensitivity. By forming multiple FP-cavity structures within the multi-core optical fiber, the magnitude and direction of the flow velocity can be measured simultaneously, achieving highly integrated, high spatial resolution vector flow velocity measurement. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of this application, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the fiber optic probe structure according to an embodiment of this application;

[0030] Figure 2 This is a schematic diagram of a multi-core optical fiber structure according to an embodiment of this application;

[0031] Figure 3 This is a schematic diagram of an application system according to an embodiment of this application;

[0032] Figure 4 This is a schematic diagram of the sensing probe subjected to flow impact according to an embodiment of this application.

[0033] Explanation of reference numerals in the attached diagram: 1. Fiber optic probe; 2. Multi-core fiber fan-in / fan-out device; 3. Fiber optic looper; 4. Light source; 5. Photodetector; 6. A / D data acquisition unit; 7. Microprocessor; 8. Communication module; 9. Receiving terminal; 101. Multi-core fiber; 102. Flexible material cavity; 103. Crystal; 301-307. Fiber optic looper interface; 501-507. Photodetector interface. Detailed Implementation

[0034] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] In this embodiment, the sensor structure includes a transmitting unit, a receiving unit, and a processing unit.

[0037] The transmitting unit includes a light source 4 and a communication module 8; the receiving unit includes an optical fiber probe 1, a multi-core optical fiber fan-in / fan-out device 2, an optical fiber looper 3, and a receiving terminal 9; the processing unit includes a photodetector 3, an A / D data acquisition unit 6, and a microprocessor 7. The light source 4 provides broadband light to the optical fiber probe 1; the optical fiber probe 1 receives the light, senses changes in flow velocity, and converts these changes into optical signals that are reflected to the optical fiber looper 3; the multi-core optical fiber fan-in / fan-out device 2 connects the optical fibers and transmits the optical signals of flow velocity changes sensed by the optical fiber probe 1 to the optical fiber looper 3; the optical fiber looper 3 transmits the optical signals, passing the light source 4 to the optical fiber probe 1, and then the optical signals of flow velocity changes sensed by the optical fiber probe 1 to the signal processing unit; the photodetector 5 converts the received optical signals into electrical signals; the A / D data acquisition unit 6 samples and acquires electrical signals, converting them into digital signals; the microprocessor 7 processes the digital signals. The communication module 8 sends out the processed signal results for long-distance transmission. The receiving terminal 9 receives the signals sent by the communication module and displays the flow velocity results.

[0038] like Figure 1 The diagram shown is a schematic of the fiber optic probe structure in this embodiment. In this embodiment, a seven-core fiber, polydimethylsiloxane silicon (PDMS), and a silicon carbide crystal are used as examples for specific illustration. A multilayer PDMS cavity 102 is formed by coating the ends of the seven-core fiber with multiple layers of PDMS, where the cladding diameter of the seven-core fiber is 150-152 μm. A silicon carbide crystal 103 is attached to the ends of the PDMS film 102. Since the crystal 103 is completely opaque, it forms multiple Fabry-Perot (FP-cavity) interference structures with excellent reflectivity. Furthermore, according to Hooke's law, because PDMS has good elasticity, the multi-core structure of the seven-core fiber, the PDMS film 102, and the crystal 103 form a spring-like structure, resulting in high integration, high sensitivity, and good spatial resolution for the fiber optic probe 1. It can simultaneously measure the velocity magnitude and direction of fluids, achieving flow velocity vector measurement.

[0039] Figure 2 The diagram shows a seven-core fiber structure, consisting of seven fiber cores with a core diameter of 8-8.5μm.

[0040] Figure 3This is a schematic diagram of the application system of the present invention, including an optical fiber probe 1, a multi-core optical fiber fan-in / fan-out device 2, an optical fiber looper 3, a light source module 4, a photodetector 5, an A / D data acquisition unit 6, a microprocessor 7, a communication module 8, and a receiving terminal 9. In implementation, the optical fiber probe 1 and the multi-core optical fiber fan-in / fan-out device 2 are integrated. The output end of the multi-core optical fiber fan-in / fan-out device 2 is connected to one interface of the optical fiber looper 3, and the light source module 4 and the photodetector 5 are connected to two interfaces on the other end of the optical fiber looper 3. The output end of the photodetector 5 is connected to the A / D data acquisition unit 6, and the output end of the A / D data acquisition unit 6 is connected to the microprocessor 7. The signal demodulated by the microprocessor is transmitted through the communication module 8, and the receiving terminal 9 receives the signal and displays the flow rate result.

[0041] The output of the multi-core fiber fan-in / fan-out device 2 is connected in parallel to several fiber loop interfaces 301, 302, 303, 304, 305, 306, and 307 of the corresponding fiber optic looper 3. One end of the fiber optic looper 3 is connected in parallel to the light source module 4, and the other end is connected in parallel to the interfaces 501, 502, 503, 504, 505, 506, and 507 of each photodetector 5. That is, the fiber optic looper 3 is connected to the multi-core fiber fan-in / fan-out device 2, the light source module 4, and the photodetectors 5. The output electrical signal of the photodetectors 5 is connected in parallel to the A / D data acquisition unit 6, and the output of the A / D data acquisition unit 6 is connected to the microprocessor 7 for signal demodulation.

[0042] Combination Figure 1 , Figure 3 and Figure 4 The working principle of this embodiment is described in detail below: The light source emitted by the light source module 4 is input to the multi-core fiber fan-in / fan-out device 2 via the fiber optic looper 3, and then enters the fiber optic probe 1; multiple FP cavity interference structures are formed by the multi-core fiber 101, PDMS, and crystal. A portion of the light is reflected at the end of the fiber, with a light intensity I... a A portion of the light is transmitted through the PDMS cavity, and when it encounters crystal 103, it is completely reflected, with light intensity I. b , and the first part of reflected light I a Interference is formed. The seven interference beams reflected by the fiber optic probe 1 enter the multi-core fiber fan-in / fan-out device 2, and then enter the photodetector 5 respectively, which converts the corresponding light intensity into the magnitude of the current. The electrical signal is then converted into a digital signal by the A / D data acquisition unit 6, and finally demodulated by the microprocessor 7.

[0043] like Figure 1As shown, when the fluid impacts the crystal head-on, the interference light intensity I of the seven FP cavity structures is the same; the PDMS cavity is compressed, and the fluid causes the length L of the PDMS cavity 102 of the fiber optic probe 1 to change, which in turn causes the optical path length of the reflected light from the crystal 103 to change, which in turn causes the interference light intensity I of the seven FP cavity structures to change, and ultimately causes the magnitude of the electrical signal output to the microprocessor 7 to change.

[0044]

[0045] Where I is the intensity of the interference light; I a I b These represent the reflected light intensity from the fiber end face and the reflected light intensity from the crystal, respectively; Δn eff λ is the optical refractive index of PDMS; λ is the wavelength of the light source; and L is the length of the PDMS interference cavity.

[0046] Different flow velocities correspond to different output electrical signals, thus establishing a one-to-one correspondence between flow velocity and electrical signal, thereby completing the sensor flow velocity calibration.

[0047] like Figure 4 As shown, when the fluid impacts the fiber optic probe 1 from the side, the PDMS cavity 102 of the fiber optic probe 1 bends and deforms due to the action of the fluid. Because the degree of bending of the PDMS cavity corresponding to the seven fiber cores is different, the FP cavity lengths L (L1, L2, L3, L4, L5, L6, L7) of the seven fiber cores change differently. Therefore, the optical path length of the reflected light from the crystal 103 corresponding to the seven fiber cores changes differently, and the interference light intensities I (I1, I2, I3, I4, I5, I6, I7) of the seven FP structures change differently.

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] Wherein, I1, I2, I3, I4, I5, I6, and I7 represent the interference light intensities of the seven FP structures; I a1 I a2 I a3 Ia4 I a5 I a6 I a7 These represent the reflected light intensities from the end faces of the seven fiber cores of a seven-core optical fiber; I b1 I b2 I b3 I b4 I b5 I b6 I b7 These represent the reflected light intensities of the seven optical paths corresponding to the seven fiber cores in the FP cavity; Δn eff λ is the optical refractive index of PDMS; λ is the wavelength of the light source; L1, L2, L3, L4, L5, L6, and L7 are the FP cavity lengths corresponding to the seven fiber cores.

[0056] The different interference light signals obtained by the seven photodetectors 5 result in different output electrical signal magnitudes. Based on the differences in the seven electrical signals, a three-dimensional spatial coordinate system can be established, forming a numerical relationship between direction, flow velocity magnitude, and the seven electrical signals, thus completing the sensor vector flow velocity calibration.

[0057] The embodiments described above are merely preferred embodiments of this application and are not intended to limit the scope of this application. Any modifications and improvements made to the technical solutions of this application by those skilled in the art without departing from the spirit of this application shall fall within the protection scope defined by the claims of this application.

Claims

1. A vector flow velocity sensor based on multi-core optical fiber, characterized in that, include: Transmitting unit, receiving unit, and signal processing unit; The emitting unit is used to provide a light source; The transmitting unit is also used for long-distance transmission; The transmitting unit includes a light source module and a communication module; the light source module provides a broadband light source for the fiber optic probe; the communication module transmits the demodulated signal for long-distance transmission. The receiving unit is used to modulate and transmit optical signals based on a light source; the receiving unit includes: an optical fiber looper, an optical fiber probe, a multi-core optical fiber fan-in / fan-out device, and a receiving terminal. The fiber optic probe is used to receive light sources, sense changes in flow rate, and convert them into optical signals. The fiber optic probe is composed of multi-core optical fibers. Polydimethylsiloxane silicon is coated multiple times on the multi-core optical fibers to form a coated flexible cavity. A silicon carbide crystal is attached to the end of the coated flexible cavity, forming a highly integrated Fabry-Perot interference structure with the multi-core optical fibers and the flexible cavity. The fiber optic looper is used to transmit optical signals, passing the light source to the fiber optic probe, and then transmitting the optical signal of the fiber optic probe sensing the change in flow to the signal processing unit. The fiber optic probe and the multi-core fiber fan-in fan-out device are integrated. The multi-core fiber fan-in fan-out device is used to interface with the optical looper to transmit the optical signal sensed by the fiber optic probe to the photodetector. The signal receiving terminal is used to receive signals sent by the communication module and display the flow rate results; The signal processing unit is used to convert optical signals into electrical signals and demodulate the electrical signals; The light emitted from the light source module is input to the multi-core fiber fan-in / fan-out device via a fiber optic looper, and then enters the fiber optic probe; several FP cavity interference structures are formed by the multi-core fiber, PDMS, and crystal; a portion of the light is reflected at the fiber end, with a light intensity I. a A portion of the light is transmitted through the PDMS cavity, and when it encounters the crystal, it is completely reflected, with light intensity I... b , and the first part of reflected light I a Interference occurs; The interference light intensities I of the seven FP structures are as follows: in, I 1. I 2. I 3. I 4. I 5. I 6. I 7 represents the interference light intensity of the seven FP structures; I a1 , I a2 , I a3 , I a4 , I a5 , I a6 , I a7 These are the reflected light intensities from the end faces of the seven fiber cores of the seven-core optical fiber; I b1 , I b2 , I b3 , I b4 , I b5 , I b6 , I b7 These represent the reflected light intensities of the seven optical paths corresponding to the seven fiber cores in the FP cavity; The refractive index of PDMS; L1 represents the wavelength of the light source; L2, L3, L4, L5, L6, and L7 are the FP cavity lengths corresponding to the seven fiber cores.

2. The vector flow velocity sensor based on multi-core optical fiber according to claim 1, characterized in that, The signal processing unit includes: a photodetector, an A / D data acquisition card, and a microprocessor; The photodetector is used to convert the received optical signal into an electrical signal; The A / D data acquisition unit is used to acquire the electrical signal and convert it into a digital electrical signal; The microprocessor is used to demodulate the digital electrical signal.

3. The vector flow velocity sensor based on multi-core optical fiber according to claim 2, characterized in that, The fiber optic probe and the multi-core fiber fan-in / fan-out device are integrated, and the output end of the multi-core fiber fan-in / fan-out device is connected to the interface at one end of the fiber optic looper.

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