Ocean temperature and magnetism two-parameter sensor based on optical fiber F-P and SPR and manufacturing method

Abstract

The invention provides an optical fiber F-P (Fabry-Perot) and SPR (Surface Plasmon Resonance)-based ocean temperature-magnetic dual-parameter sensor and a manufacturing method, and relates to the technical field of optical fiber sensing, and the sensor specifically comprises an optical fiber F-P interferometer and an optical fiber SPR sensing structure; according to the optical fiber SPR sensing structure, the surface of a gold-plated single-mode optical fiber is coated with a layer of magnetic fluid to serve as a magnetic field sensing area; in the optical fiber F-P interferometer, an air F-P cavity between two multimode optical fibers is used as a 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, the temperature sensitivity can reach-0.251 nm / DEG C, and temperature crosstalk is overcome through a two-parameter matrix. The device has the advantages of high sensitivity, simple structure, plug and play, wide dynamic measurement range and the like, 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 magnetism dual-parameter sensor based on optical fiber FP and SPR and a manufacturing method thereof. Background Art

[0002] Marine magnetic field monitoring is a key technical requirement in marine geophysical exploration, resource survey and military fields. 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 and have poor stability. In addition, their metal material properties make them susceptible to seawater corrosion, electromagnetic interference and high-voltage environments, and they are difficult to integrate, which limits their application in complex marine scenarios. These problems limit their application in real-time monitoring, and a more efficient, accurate and reliable detection technology is urgently needed.

[0003] As a new type of sensing technology, fiber optic 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. At present, fiber optic magnetic sensors can be divided into three categories: magnetic sensors based on magnetostrictive effect, magnetic sensors based on Faraday effect and magnetic sensors based on magnetic fluid. However, due to the low bonding degree between the coating and the optical fiber, the sensor is easy to fall off due to the magnetostrictive effect, affecting the life and performance of the sensor. Fiber optic magnetic sensors with Faraday effect are greatly affected by the environment and polarization errors. While the MF magnetic sensor makes full use of the refractive index adjustment characteristics, the fiber optic magnetofluid sensor has no moving parts and no mechanical wear, which can significantly improve the sensing performance and service life, and has become a research hotspot in recent years.

[0004] The Chinese invention patent "CN111610471B" proposed a magnetic field and temperature sensor with a metalized fiber Bragg grating cascade FP structure, but the sensor magnetic field sensitivity still needs to be further improved in the design of magnetic field measurement using the FP structure. The Chinese invention patent "CN111123176B" proposed a three-core hollow fiber magnetic field and temperature sensor based on magnetic fluid filling, with glycerol and magnetic fluid filled in the hollow core. The sensor is difficult to manufacture and needs further optimization.

[0005] Therefore, by comparing the above results, it can be found that although interferometric sensors such as optical fiber FP are widely used, their magnetic field detection sensitivity needs to be further improved. The single-parameter optical fiber SPR sensor has excellent magnetic field response characteristics, but it is greatly affected by temperature, which seriously restricts the practical application and further development of the sensor. 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] In view of the shortcomings of the prior art, the present invention provides an ocean temperature and magnetic dual-parameter sensor based on optical fiber FP and SPR and a manufacturing method, which can realize the simultaneous monitoring of ocean magnetic field and seawater temperature. It is simple to manufacture and has high sensitivity. It has certain potential in marine geophysical exploration, resource survey and military fields.

[0007] On the one hand, an ocean temperature and magnetic dual-parameter sensor based on optical fiber FP and SPR specifically includes: an optical fiber FP interferometer and an optical fiber SPR sensing structure; The optical fiber FP interferometer comprises two sections of multimode optical fibers, namely a first multimode optical fiber and a second multimode optical fiber; the first multimode optical fiber and the second multimode optical fiber are connected by a hollow core optical fiber, and the air cavity between the two sections of multimode optical fibers is a temperature sensing cavity; The hollow-core optical fiber is connected to two sections of multimode optical fiber by ultraviolet curing glue, and the inner diameter of the hollow-core optical fiber is 130 microns and the outer diameter is 250 microns; The optical fiber SPR sensing structure is a single-mode optical fiber, the surface of the single-mode optical fiber is coated with a layer of gold film to form a gold-plated optical fiber, and the surface of the gold-plated optical fiber is coated with a layer of magnetic fluid to form a magnetic field sensing area; The air cavity between the first multimode optical fiber and the second multimode optical fiber forms Fabry-Perot interference; the contact surface between the first multimode optical fiber and the air cavity is a first reflection surface, and the contact surface between the air cavity and the second multimode optical fiber is a second reflection surface. The light from the first multimode optical fiber is reflected on the two reflection surfaces respectively, and the two reflected light beams interfere with each other to form FP interference.

[0008] On the other hand, the aforementioned method for manufacturing an ocean temperature and magnetic dual parameter sensor based on optical fiber FP and SPR comprises the following steps: Step 1: Cut one end of the first multimode optical fiber with a fiber cleaver, pass the cut hollow-core optical fiber through the first multimode optical fiber, connect it with ultraviolet curing glue, put the connected first multimode optical fiber into the optical fiber fusion splicer, then cut the second multimode optical fiber with a fiber cleaver, put it into the fusion splicer, adjust the advancement distance of the fusion splicer to form an FP cavity between the two sections of multimode optical fiber, and then use ultraviolet curing glue to connect the hollow-core optical fiber and the second multimode optical fiber; during the production process, monitor the reflection spectrum throughout the process. If other spectra except the FP spectrum appear, it is necessary to repeat step 1; Step 2: Melt-connect the second multimode optical fiber to the single-mode optical fiber, use an ion sputtering device to sputter a gold film, and adjust the sputtering time and current of the gold film so that the gold film evenly covers the surface of the single-mode optical fiber; Step 3: Encapsulate the gold-plated single-mode optical fiber with a Teflon tube, leaving a liquid inlet and outlet, inject the magnetic fluid into it using a syringe, and finally seal the inlet and outlet with ultraviolet curing glue.

[0009] The beneficial effects of adopting the above technical solution are: The present invention provides an ocean temperature and magnetic dual parameter sensor based on optical fiber FP and SPR and a manufacturing method thereof, which specifically includes the following beneficial effects:

[0010] (1) A dual-parameter ocean magnetic and temperature sensor based on fiber FP and SPR is proposed, and the temperature is measured using a fiber FP interferometer. The disclosed fiber FP interferometer is made of an air cavity between two sections of multimode optical fiber, and has the advantages of low cost and simple structure.

[0011] (2) A dual-parameter ocean magnetic temperature sensor based on optical fiber FP and SPR is proposed, which uses an optical fiber SPR sensing structure to detect magnetic fields. The disclosed SPR sensing structure is made 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, making the SPR spectrum particularly sensitive to magnetic field changes.

[0012] (3) Experimental results show that the ocean magnetic field and temperature sensitivities of the sensor are 0.428nm / Gs and -0.251nm / ℃ respectively, and it has the potential for high-performance measurement of ocean magnetic field and temperature.

[0013] (4) The FFT method is used to filter the data, which effectively reduces the impact of other interference signals except temperature signals and magnetic field signals, providing a new technical solution for the high-sensitivity monitoring of ocean temperature and magnetism.

[0014] (5) The present invention constructs an FP cavity so that the FP cavity is in direct contact with the seawater, thereby ensuring that the change in seawater temperature can be detected while detecting the ocean magnetic field, thereby achieving the measurement of seawater temperature.

[0015] (6) The sensor uses only a simple splicing of multi-mode optical fiber and single-mode optical fiber to achieve probe-type dual-parameter detection of ocean temperature and magnetism. The manufacturing process of the sensing structure is simple and has high mechanical strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of an ocean temperature and magnetic dual-parameter sensor based on optical fiber FP and SPR in an embodiment of the present invention; Figure 2 A flow chart for making a sensor structure in an embodiment of the present invention; Figure 3 Schematic diagram of the experimental system in the embodiment of the present invention; Figure 4 This is a spectrum diagram of magnetic field strength test in an embodiment of the present invention; Figure 5 for Figure 4 SPR spectra after filtering; Figure 6 for Figure 4 FP interference spectrum after filtering; Figure 7 is a magnetic field intensity response characteristic curve in an embodiment of the present invention; Figure 8 This is a spectrum diagram of seawater temperature test in an embodiment of the present invention; Fig. 9 for Figure 8 SPR spectra after filtering; Fig.10 for Figure 8 FP interference spectrum after filtering; Fig.11 Graph showing the seawater temperature response characteristic in an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0018] On the one hand, a dual-parameter ocean temperature and magnetic sensor based on optical fiber FP and SPR, such as Figure 1 As shown, it specifically includes: fiber FP interferometer, fiber SPR sensing structure; The optical fiber FP interferometer comprises two sections of multimode optical fibers, namely a first multimode optical fiber and a second multimode optical fiber; the first multimode optical fiber and the second multimode optical fiber are connected by a hollow core optical fiber, and the air cavity between the two sections of multimode optical fibers is a temperature sensing cavity; The hollow-core optical fiber is connected to two sections of multimode optical fiber by ultraviolet curing glue, and the inner diameter of the hollow-core optical fiber is 130 microns and the outer diameter is 250 microns; The optical fiber SPR sensing structure is a single-mode optical fiber, the surface of the single-mode optical fiber is coated with a layer of gold film to form a gold-plated optical fiber, and the surface of the gold-plated optical fiber is coated with a layer of magnetic fluid to form a magnetic field sensing area; The air cavity between the first multimode optical fiber and the second multimode optical fiber forms Fabry-Perot interference; the 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 reflection surface, 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 on the two reflection surfaces respectively, and the two reflected lights interfere with each other to form FP interference; the use of FFT and sensitivity matrix reduces the cross-sensitivity between temperature and magnetism, has high sensitivity and good temperature resistance, and is of great significance for realizing ocean magnetic field detection.

[0019] On the other hand, the aforementioned method for making an ocean temperature and magnetic dual parameter sensor based on optical fiber FP and SPR is as follows: Figure 2 As shown, the following steps are included: Step 1: Cut one end of the first multimode optical fiber with a fiber cleaver to ensure that the cut surface is smooth and flat, then pass the cut hollow-core optical fiber through the first multimode optical fiber, use ultraviolet glue to light cure, put the connected first multimode optical fiber into the optical fiber fusion splicer, then cut the second multimode optical fiber with a fiber cleaver to ensure that the cut surface is smooth and flat, put it into the fusion splicer, align the fusion splicer, so that an FP cavity is formed between the two sections of multimode optical fiber, and then connect the hollow-core optical fiber and the second multimode optical fiber through ultraviolet glue light curing; during the production process, monitor the reflection spectrum throughout the process. If other spectra except the FP spectrum appear, it is necessary to repeat step 1; Step 2: Use a fusion splicer to fusion-splice the second multimode optical fiber with the single-mode optical fiber, use an ion sputtering device to sputter a gold film on the single-mode optical fiber, and adjust the sputtering time and current of the gold film so that the gold film evenly covers the surface of the single-mode optical fiber; Step 3: Single-mode optical fiber magnetic fluid packaging: Use Teflon tube to package the gold-plated single-mode optical fiber, leaving the liquid inlet and outlet, use a syringe to inject the magnetic fluid into it, and finally use ultraviolet curing glue to seal the liquid inlet and outlet.

[0020] The test system of the present invention includes a halogen light source that can emit light in the range of 400nm to 2400nm, an ocean spectrometer that can receive light in the range of 400nm to 1100nm, a Y-type fiber jumper, a magnetic field generating device, and a computer. The light emitted by the halogen light source is transmitted to the fiber optic probe through the Y-type fiber jumper, and the reflected light passes through the Y-type fiber jumper again and finally reaches the spectrometer, and then is transmitted to the computer to read the aliased spectrum data, and the FP interference spectrum data and SPR spectrum data are extracted by FFT processing, and the wavelength demodulation method is used to process the data to achieve the simultaneous measurement of temperature and magnetic dual parameters.

[0021] Based on the above preparation process, a cascade sensor was successfully prepared and built. Figure 3The experimental system diagram shown in FIG. It includes a halogen light source that can emit light in the range of 400nm to 2400nm, an ocean spectrometer that receives light in the range of 400nm to 1100nm, a Y-type fiber 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 in the magnetic field generator, the magnetic field strength inside the Helmholtz coil is changed to simulate the change of the ocean magnetic field. The Gaussmeter is used to calibrate the magnetic field strength inside the Helmholtz coil. The spectral range of the halogen light source is 400nm-1100nm, which provides light source for the system. The ocean 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 is transmitted to the fiber optic probe through the Y-type fiber optic patch cord. The reflected light passes through the Y-type fiber optic patch cord again and finally reaches the spectrometer. It is then transmitted to the computer to read the aliased spectrum data. The FP interference spectrum data and SPR spectrum data are extracted using FFT processing. The wavelength demodulation method is used to process the data to achieve simultaneous measurement of temperature and magnetic dual parameters.

[0022] In this embodiment, the magnetic field intensity characteristics and seawater temperature characteristics of the sensing structure are tested.

[0023] First, the magnetic field intensity response characteristics of the sensor were tested. While keeping the temperature constant, the magnetic field size was changed and the detection range was 0-361.5Gs. The magnetic field intensity test spectrum of the embodiment of the present invention is shown in FIG. Figure 4 As shown, it is the superposition spectrum of SPR signal and FP interference signal. The magnetic field detection range is 0~361.5Gs. After filtering the superposition spectrum, the SPR spectrum is obtained as shown in Figure 5 As shown, the FP interference spectrum is as follows Figure 6 The corresponding magnetic field intensity response characteristic curve is shown in Figure 7 As shown, the magnetic field sensitivity is 0.428nm / Gs and -0.026nm / Gs, and the linearity is 0.992 and 0.930. Then the temperature response characteristics of the sensor are tested. The magnetic field is kept constant, the temperature is changed, and the detection range is 5℃-50℃. The seawater temperature test spectrum in the embodiment of the present invention is shown in Figure 8 As shown, it is the superposition spectrum of the SPR signal and the FP interference signal. The SPR spectrum obtained after filtering the superposition spectrum is as follows Fig. 9 As shown, the FP interference spectrum is as follows Fig.10 The corresponding temperature response characteristics are shown in Fig.11 As shown, the temperature sensitivities are -1.000 nm / ℃ and -0.251 nm / ℃ respectively, and the linearities can reach 0.994 and 0.996.

[0024] In summary, the cascade sensor in the present invention can measure the ocean magnetic field and temperature simultaneously, has the advantages of high sensitivity, simple structure, and effective filtering of other interference signals, and provides a new technical solution for the field of ocean multi-parameter detection.

[0025] The above description is only a preferred embodiment of the present disclosure and an explanation of the technical principles used. 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 a 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 above features are replaced with (but not limited to) technical features with similar functions disclosed in the embodiments of the present disclosure to form a technical solution.

Claims

1. An ocean temperature and magnetic dual parameter sensor based on optical fiber FP and SPR, characterized in that: Specifically include: Fiber FP interferometer, fiber SPR sensing structure; The optical fiber FP interferometer comprises two sections of multimode optical fibers, namely a first multimode optical fiber and a second multimode optical fiber; the first multimode optical fiber and the second multimode optical fiber are connected by a hollow core optical fiber, and the air cavity between the two sections of multimode optical fibers is a temperature sensing cavity; The optical fiber SPR sensing structure is a single-mode optical fiber.

2. The ocean temperature and magnetic dual parameter sensor based on optical fiber FP and SPR according to claim 1 is characterized in that: The surface of the single-mode optical fiber is coated with a layer of gold film to form a gold-plated optical fiber, and the surface of the gold-plated optical fiber is coated with a layer of magnetic fluid to form a magnetic field sensing area.

3. The ocean temperature and magnetic dual parameter sensor based on optical fiber FP and SPR according to claim 1, characterized in that: The hollow core optical fiber is connected to the two sections of multimode optical fiber through ultraviolet curing glue.

4. The ocean temperature and magnetic dual parameter sensor based on optical fiber FP and SPR according to claim 1, characterized in that: The inner diameter of the hollow core fiber is 130 microns and the outer diameter is 250 microns.

5. The ocean temperature and magnetic dual parameter sensor based on optical fiber FP and SPR according to claim 1, characterized in that: The air cavity between the first multimode optical fiber and the second multimode optical fiber forms Fabry-Perot interference; the contact surface between the first multimode optical fiber and the air cavity is a first reflection surface, and the contact surface between the air cavity and the second multimode optical fiber is a second reflection surface. The light from the first multimode optical fiber is reflected on the two reflection surfaces respectively, and the two reflected light beams interfere with each other to form FP interference.

6. A method for manufacturing an ocean temperature and magnetism dual-parameter sensor based on optical fiber FP and SPR, used for manufacturing the ocean temperature and magnetism dual-parameter sensor based on optical fiber FP and SPR as claimed in claim 1, characterized in that: The following steps are involved: Step 1: Cut one end of the first multimode optical fiber with a fiber cleaver, pass the cut hollow-core optical fiber through the first multimode optical fiber, connect it with ultraviolet curing glue, put the connected first multimode optical fiber into the optical fiber fusion splicer, then cut the second multimode optical fiber with a fiber cleaver, put it into the fusion splicer, adjust the advancement distance of the fusion splicer to form an FP cavity between the two multimode optical fibers, and then use ultraviolet curing glue to connect the hollow-core optical fiber and the second multimode optical fiber; Step 2: Melt-connect the second multimode optical fiber to the single-mode optical fiber, use an ion sputtering device to sputter a gold film, and adjust the sputtering time and current of the gold film so that the gold film evenly covers the surface of the single-mode optical fiber; Step 3: Encapsulate the gold-plated single-mode optical fiber with a Teflon tube, leaving a liquid inlet and outlet, inject the magnetic fluid into it using a syringe, and finally seal the inlet and outlet with ultraviolet curing glue.

7. A method for manufacturing an ocean temperature and magnetic dual parameter sensor based on optical fiber FP and SPR according to claim 6, characterized in that: During the production process of step 1, the reflection spectrum is monitored throughout the process. If other spectra except the FP spectrum appear, step 1 needs to be repeated.

Images