Ocean Temperature and Magnetic Biparameter Sensor Based on Fiber Optic F-P and SPR and Manufacturing Method

Abstract

The present invention provides an ocean temperature and magnetic dual-parameter sensor based on fiber optic F-P and SPR and a manufacturing method thereof, which relates to the technical field of fiber optic sensing. Specifically, it includes a fiber optic F-P interferometer and a fiber optic SPR sensing structure. Among them, the fiber optic SPR sensing structure wraps a layer of magnetic fluid on the surface of the gold-plated single-mode fiber as the magnetic field sensing area. In the fiber optic F-P interferometer, the air F-P cavity between two multi-mode fibers is used as the temperature sensing area. The sensor realizes high-sensitivity measurement of magnetic field intensity and temperature at the micro-nano level. The magnetic field sensitivity can reach 0.428 nm / Gs, and the temperature sensitivity can reach -0.251 nm / °C. The temperature crosstalk is overcome through the dual-parameter matrix. The present invention has the advantages of high sensitivity, simple structure, plug-and-play, wide dynamic measurement range, etc., and can realize dual-parameter measurement of magnetic field intensity and temperature.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensing technology, and in particular to an ocean temperature and magnetic dual-parameter sensor based on optical fiber F-P and SPR and a manufacturing method thereof. Background Art

[0002] Marine magnetic field monitoring is a key technical requirement in marine geophysical exploration, resource investigation, and the military field. The Hall effect method, electromagnetic induction method, and magnetic deflection method are conventional methods for detecting magnetic fields. However, although traditional electrical magnetic field sensors (such as Hall sensors and fluxgate sensors) have a certain sensitivity, they are bulky, have poor stability, and their metal material properties make them vulnerable to seawater corrosion, electromagnetic interference, and high-pressure environments, and are difficult to integrate, which limits their application in complex marine scenarios. These problems limit their application in real-time monitoring, and there is an urgent need for a more efficient, accurate, and reliable detection technology.

[0003] As a new type of sensing technology, optical fiber sensing technology has become a research hotspot in the field of marine environment detection in recent years due to its advantages such as small size, anti-electromagnetic interference, seawater corrosion resistance, and long-distance transmission. Currently, optical fiber magnetic sensors can be divided into three categories: magnetic sensors based on the magnetostrictive effect, magnetic sensors based on the Faraday effect, and magnetic sensors based on magnetic fluids. However, due to the low bonding degree between the coating and the optical fiber, the sensor is prone to falling off due to the magnetostrictive effect, affecting the life and performance of the sensor. Optical fiber magnetic sensors with the Faraday effect are greatly affected by the environment and polarization errors. While MF magnetic sensors make full use of the refractive index adjustment characteristics, optical fiber magnetic fluid sensors have no moving parts and no mechanical wear, which can significantly improve the sensing performance and service life, and are a research hotspot in recent years.

[0004] Chinese invention patent "CN111610471B" proposes a magnetic field and temperature sensor with a metallized fiber grating cascaded F-P structure, but for the design of using the F-P structure for magnetic field measurement, the magnetic field sensitivity of the sensor still needs to be further improved. Chinese invention patent "CN111123176B" proposes a three-core hollow optical fiber magnetic field and temperature sensor based on magnetic fluid filling, filling glycerol and magnetic fluid in the hollow core, and the sensor manufacturing is difficult and needs further optimization.

[0005] Therefore, by comparing the above achievements, it can be found that although interference-type sensors such as optical fiber F-P are widely used, their magnetic field detection sensitivity needs to be further improved. While single-parameter optical fiber SPR sensors have excellent magnetic field response characteristics, they are greatly affected by temperature interference, which seriously restricts the practical application and further development of the sensors. Therefore, in the field of marine magnetic field monitoring, there are still problems such as low sensitivity and temperature interference. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention provides an ocean temperature and magnetic dual-parameter sensor based on fiber optic F-P and SPR, as well as a manufacturing method thereof, which can simultaneously monitor the ocean magnetic field and seawater temperature, is simple to manufacture, has high sensitivity, and has certain potential in the fields of marine geophysical exploration, resource investigation and military.

[0007] On the one hand, an ocean temperature and magnetic dual-parameter sensor based on fiber optic F-P and SPR specifically includes: a fiber optic F-P interferometer and a fiber optic SPR sensing structure;

[0008] The fiber optic F-P interferometer includes two sections of multimode fiber, namely the first multimode fiber and the second multimode fiber; the first multimode fiber and the second multimode fiber are connected by a hollow fiber in the middle, and the air cavity between the two sections of multimode fiber is the temperature sensing cavity;

[0009] The hollow fiber and the two sections of multimode fiber are connected by ultraviolet curing glue. The inner diameter of the hollow fiber is 130 microns and the outer diameter is 250 microns;

[0010] The fiber optic SPR sensing structure is a single-mode fiber. A gold film is coated on the surface of the single-mode fiber to form a gold-plated fiber, and a magnetic fluid is coated on the surface of the gold-plated fiber to form a magnetic field sensing area;

[0011] The air cavity between the first multimode fiber and the second multimode fiber forms a Fabry-Perot interference; the contact surface between the first multimode fiber and the air cavity is the first reflection surface, and the contact surface between the air cavity and the second multimode fiber is the second reflection surface. The light from the first multimode fiber is reflected on the two reflection surfaces respectively, and the two reflected lights interfere with each other to form an F-P interference.

[0012] On the other hand, a manufacturing method of the aforementioned ocean temperature and magnetic dual-parameter sensor based on fiber optic F-P and SPR includes the following steps:

[0013] Step 1: Cut one end of the first multimode fiber with a fiber optic cutter, pass the cut and flat hollow fiber through the first multimode fiber, connect it with ultraviolet curing glue, put the connected first multimode fiber into the fiber fusion splicer, and then cut the second multimode fiber with a fiber optic cutter and put it into the fusion splicer. Adjust the advancing distance of the fusion splicer so that an F-P cavity is formed between the two sections of multimode fiber, and then use ultraviolet curing glue to connect the hollow fiber and the second multimode fiber; during the manufacturing process, monitor the reflection spectrum throughout. If there are other spectra except the F-P spectrum, the manufacturing in Step 1 needs to be redone;

[0014] Step 2: Fuse and connect the second multimode fiber and the single-mode fiber, use an ion sputtering instrument to sputter a gold film, and adjust the sputtering time and current of the gold film to make the gold film evenly cover the surface of the single-mode fiber;

[0015] Step 3: Encapsulate the gold-plated single-mode optical fiber with a Teflon tube, leaving an inlet and an outlet. Inject the magnetic fluid into it using a syringe, and finally seal the inlet and outlet with ultraviolet curable glue.

[0016] The beneficial effects of adopting the above technical solutions are as follows:

[0017] The present invention provides an ocean temperature and magnetic dual-parameter sensor based on fiber optic F-P and SPR and a manufacturing method, which specifically includes the following beneficial effects:

[0018] (1) An ocean magnetic and temperature dual-parameter sensor based on fiber optic F-P and SPR is proposed, and the fiber optic F-P interferometer is used for temperature measurement. The disclosed fiber optic F-P interferometer is made by an air cavity between two multi-mode optical fibers, and has advantages such as low cost and simple structure manufacturing.

[0019] (2) An ocean magnetic and temperature dual-parameter sensor based on fiber optic F-P and SPR is proposed, and the fiber optic SPR sensing structure is used for magnetic field detection. The disclosed SPR sensing structure is formed by coating a magnetic fluid on the surface of a gold-plated single-mode optical fiber. The refractive index of the magnetic fluid changes with the magnetic field change, so that the SPR spectrum is particularly sensitive to the magnetic field change.

[0020] (3) Experimental results show that the ocean magnetic field and temperature sensitivities of this sensor are 0.428 nm / Gs and -0.251 nm / °C respectively, and it has the potential for high-performance measurement of the ocean magnetic field and temperature.

[0021] (4) The FFT method is used to filter the data, effectively reducing the influence of other interference signals except the temperature signal and the magnetic field signal, and providing a new technical solution for the field of high-sensitivity monitoring of ocean temperature and magnetism.

[0022] (5) By constructing an FP cavity in the present invention, the FP cavity is in direct contact with seawater, ensuring that while detecting the ocean magnetic field, the change of seawater temperature can be detected at the same time, and the measurement of seawater temperature is realized.

[0023] (6) The sensor only uses the simple splicing of multi-mode optical fiber and single-mode optical fiber to realize the probe-type ocean temperature and magnetic dual-parameter detection. The manufacturing process of the sensing structure is simple and has high mechanical strength. Description of the Drawings

[0024] Figure 1 Schematic diagram of the ocean temperature and magnetic dual-parameter sensor based on fiber optic F-P and SPR in the embodiment of the present invention;

[0025] Figure 2 Flow chart of the sensor structure manufacturing in the embodiment of the present invention;

[0026] Figure 3Schematic diagram of the experimental system in the embodiment of the present invention;

[0027] Figure 4 Magnetic field intensity test spectrogram in the embodiment of the present invention;

[0028] Figure 5 is Figure 4 Filtered SPR spectrogram;

[0029] Figure 6 is Figure 4 Filtered FP interference spectrogram;

[0030] Figure 7 Magnetic field intensity response characteristic curve in the embodiment of the present invention;

[0031] Figure 8 Seawater temperature test spectrogram in the embodiment of the present invention;

[0032] Figure 9 is Figure 8 Filtered SPR spectrogram;

[0033] Figure 10 is Figure 8 Filtered FP interference spectrogram;

[0034] Figure 11 Seawater temperature response characteristic curve graph in the embodiment of the present invention. Specific embodiments

[0035] The following combines the drawings and embodiments to further describe in detail the specific embodiments of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0036] On the one hand, an ocean temperature and magnetic dual-parameter sensor based on fiber optic F-P and SPR, as Figure 1 shown, specifically includes: a fiber optic F-P interferometer, a fiber optic SPR sensing structure;

[0037] The fiber optic F-P interferometer includes two sections of multimode fiber, namely the first multimode fiber and the second multimode fiber; the two sections of multimode fiber are connected by a hollow fiber in the middle, and the air cavity between the two sections of multimode fiber is a temperature sensing cavity;

[0038] The hollow fiber is connected to the two sections of multimode fiber by ultraviolet curing glue, and the inner diameter of the hollow fiber is 130 microns and the outer diameter is 250 microns;

[0039] The fiber optic SPR sensing structure is a single-mode fiber, and a gold film is coated on the surface of the single-mode fiber to form a gold-plated fiber, and a magnetic fluid is coated on the surface of the gold-plated fiber to form a magnetic field sensing area;

[0040] An air cavity between the first multimode optical fiber and the second multimode optical fiber forms a Fabry - Perot interference; incident light enters from the first multimode optical fiber. The contact surface between the first multimode optical fiber and the air cavity is the first reflecting surface, and the contact surface between the air cavity and the second multimode optical fiber is the second reflecting surface. Light from the first multimode optical fiber is reflected at the two reflecting surfaces respectively, and the two reflected light beams interfere with each other to form F - P interference; using FFT and the sensitivity matrix reduces the cross - sensitivity between temperature and magnetism, has high sensitivity and good temperature performance, which is of great significance for realizing ocean magnetic field detection.

[0041] On the other hand, the foregoing manufacturing method of an ocean temperature - magnetism dual - parameter sensor based on fiber F - P and SPR is as Figure 2 shown, and includes the following steps:

[0042] Step 1: Cut one end of the first multimode optical fiber with an optical fiber cutter to ensure that the cut surface is smooth and flat. Immediately pass the cut and flat hollow optical fiber through the first multimode optical fiber, use ultraviolet glue for light curing, put the connected first multimode optical fiber into an optical fiber fusion splicer. Then cut the second multimode optical fiber with an optical fiber cutter to ensure that the cut surface is smooth and flat, put it into the fusion splicer, and perform fusion splicer collimation to form an F - P cavity between the two multimode optical fibers. Then use ultraviolet glue for light curing to connect the hollow optical fiber and the second multimode optical fiber; during the manufacturing process, monitor the reflection spectrum throughout. If there are other spectra except the F - P spectrum, the manufacturing in Step 1 needs to be redone.

[0043] Step 2: Fusion splice the second multimode optical fiber and the single - mode optical fiber with an optical fiber fusion splicer, and use an ion sputtering instrument to sputter a gold film on the single - mode optical fiber, and adjust the gold film sputtering time and current to make the gold film evenly cover the surface of the single - mode optical fiber.

[0044] Step 3: Encapsulate the single - mode optical fiber with magnetic fluid; encapsulate the gold - plated single - mode optical fiber with a Teflon tube, leaving an inlet and an outlet. Use a syringe to inject magnetic fluid into it, and finally seal the inlet and outlet with ultraviolet curing glue.

[0045] The test system of this invention patent includes a halogen light source with a light emission range of 400nm - 2400nm, an ocean spectrometer with a received spectrum range of 400nm - 1100nm, a Y - type optical fiber jumper, a magnetic field generating device, and a computer. The light emitted by the halogen light source passes through the Y - type optical fiber jumper and is transmitted to the optical fiber probe. The reflected light passes through the Y - type optical fiber jumper again and finally reaches the spectrometer, and then is transmitted to the computer to read the aliased spectrum data. Use FFT processing to extract the F - P interference spectrum data and SPR spectrum data, and use the wavelength demodulation method to process the data to realize the simultaneous measurement of temperature - magnetism dual - parameters.

[0046] Based on the above preparation process, a cascaded sensor was successfully prepared, and a structure asFigure 3 The experimental system diagram shown. It includes a halogen light source with a light source emission range of 400nm - 2400nm, an Ocean Optics spectrometer with a spectral reception range of 400nm - 1100nm, a Y-shaped fiber optic jumper, a gaussmeter, a Helmholtz coil, a magnetic field generator, and a computer. The magnetic field generator and the Helmholtz coil are used to provide a magnetic field environment. By changing the current and voltage magnitudes in the magnetic field generator, the magnetic field intensity inside the Helmholtz coil is changed to simulate the change of the ocean magnetic field. The gaussmeter is used to calibrate the magnetic field intensity inside the Helmholtz coil. The spectral range of the halogen light source is 400nm - 1100nm, which provides light source for the system. The Ocean Optics spectrometer is used to detect the reflection superposition spectrum of the FP interference signal and the SPR signal. The light emitted by the halogen light source passes through the Y-shaped fiber optic jumper and is transmitted to the fiber optic probe. The reflected light passes through the Y-shaped fiber optic jumper again and finally reaches the spectrometer, and then is transmitted to the computer to read the aliased spectral data. The FFT processing is used to extract the F-P interference spectral data and the SPR spectral data, and the wavelength demodulation method is used to process the data to realize the simultaneous measurement of temperature and magnetic parameters.

[0047] In this embodiment, the magnetic field intensity characteristics and seawater temperature characteristics of the sensing structure are tested.

[0048] First, the magnetic field intensity response characteristics of the sensor are tested. Under the condition of keeping the temperature constant, the magnetic field magnitude is changed, and the detection range is 0 - 361.5 Gs. The magnetic field intensity test spectrogram in the embodiment of the present invention is as Figure 4 shown, which is the superposition spectrum of the SPR signal and the FP interference signal. The magnetic field detection range is 0 - 361.5 Gs. After filtering the superposition spectrum, the obtained SPR spectrogram is as Figure 5 shown, the FP interference spectrogram is as Figure 6 shown, and its corresponding magnetic field intensity response characteristic curve is as Figure 7 shown. The magnetic field sensitivities are 0.428 nm / Gs and -0.026 nm / Gs respectively, and the linearities are 0.992 and 0.930. Then, the temperature response characteristics of the sensor are tested. Keeping the magnetic field constant, the temperature magnitude is changed, and the detection range is 5℃ - 50℃. The seawater temperature test spectrogram in the embodiment of the present invention is as Figure 8 shown, which is the superposition spectrum of the SPR signal and the FP interference signal. After filtering the superposition spectrum, the obtained SPR spectrogram is as Figure 9 shown, the FP interference spectrogram is as Figure 10 shown, and its corresponding temperature response characteristic is as Figure 11 shown. The temperature sensitivities are -1.000 nm / ℃ and -0.251 nm / ℃ respectively, and the linearities can reach 0.994 and 0.996.

[0049] In summary, the cascaded sensor in the present invention can measure the ocean magnetic field and temperature simultaneously, has high sensitivity, a simple structure, and effectively filters out other interference signals, etc., providing a new technical solution for the field of ocean multi-parameter detection.

[0050] The above description is only a preferred embodiment of the present disclosure and an explanation of the technical principles applied. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above inventive concept. For example, the technical solutions formed by mutually replacing the above features with the technical features (but not limited to) disclosed in the embodiments of the present disclosure that have similar functions.

Claims

1. An ocean temperature and magnetic dual-parameter sensor based on fiber optic F-P and SPR, characterized in that, Specifically include: Optical fiber F-P interferometer, optical fiber SPR sensing structure; The optical fiber F-P interferometer includes two sections of multimode optical fibers, namely the first multimode optical fiber and the second multimode optical fiber; the first multimode optical fiber and the second multimode optical fiber are connected by a hollow optical fiber in the middle, and the air cavity between the two sections of multimode optical fibers is the temperature sensing cavity; The optical fiber SPR sensing structure is a single-mode optical fiber; A layer of gold film is coated on the surface of the single-mode optical fiber to form a gold-plated optical fiber, and a layer of magnetic fluid is coated on the surface of the gold-plated optical fiber to form a magnetic field sensing area; The hollow optical fiber and the two sections of multimode optical fibers are connected by ultraviolet curing glue; The inner diameter of the hollow optical fiber is 130 microns, and the outer diameter is 250 microns; The air cavity between the first multimode optical fiber and the second multimode optical fiber forms a Fabry-Perot interference; the contact surface between the first multimode optical fiber and the air cavity is the first reflection surface, and the contact surface between the air cavity and the second multimode optical fiber is the second reflection surface. The light from the first multimode optical fiber is reflected at the two reflection surfaces respectively, and the two reflected lights interfere with each other to form an F-P interference; The ocean temperature and magnetic dual-parameter sensor based on optical fiber F-P and SPR is fabricated by the following method, including the following steps: Step 1: Cut one end of the first multimode optical fiber with an optical fiber cutter, pass the cut and flat hollow optical fiber through the first multimode optical fiber, and connect them with ultraviolet curing glue. Then put the connected first multimode optical fiber into an optical fiber fusion splicer. After that, cut the second multimode optical fiber with an optical fiber cutter and put it into the fusion splicer. Adjust the pushing distance of the fusion splicer to form an F-P cavity between the two sections of multimode optical fibers, and then connect the hollow optical fiber and the second multimode optical fiber with ultraviolet curing glue; Step 2: Melt and connect the second multimode optical fiber and the single-mode optical fiber, and use an ion sputtering instrument to sputter a gold film. Adjust the sputtering time and current of the gold film to make the gold film evenly cover the surface of the single-mode optical fiber; Step 3: Package the gold-plated single-mode optical fiber with a Teflon tube, leaving an inlet and an outlet. Inject magnetic fluid into it with a syringe, and finally seal the inlet and outlet with ultraviolet curing glue; During the manufacturing process of Step 1, monitor the reflection spectrum throughout the process. If there are other spectra besides the F-P spectrum, Step 1 needs to be carried out again.

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