Optical fiber magnetic field sensor based on a special optical fiber, system and applications

Abstract

The application discloses a special optical fiber based optical fiber magnetic field sensor, a system and application thereof, and relates to the technical field of optical fiber sensing, and comprises a special optical fiber, wherein the special optical fiber comprises: a single-mode optical fiber core for transmitting an optical signal, and a metal wire for generating an induced current; each single-mode optical fiber core is provided with at least one metal wire; a single-mode optical fiber cladding for protecting the single-mode optical fiber core; the single-mode optical fiber cladding wraps the single-mode optical fiber core and the metal wire; the scheme is improved on the basis of a traditional optical fiber structure, and a specially designed optical structure and a magnetic sensitive material are introduced; the special optical fiber containing the metal wire is used to process the optical fiber magnetic field sensor, and then the optical fiber magnetic field sensor can be used to conveniently construct a three-component magnetic field data acquisition system underground, on land, in the air and under the sea; the optical fiber magnetic field sensor has the advantages of small size, light weight, low cost, high temperature resistance, high pressure resistance, no power supply required for the sensor, no electronic devices connected with the optical fiber magnetic field sensor and the like.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing technology, and more specifically to fiber optic magnetic field sensors, systems, and applications based on specially designed optical fibers. Background Technology

[0002] In recent years, magnetic field sensing has played an increasingly important role in many fields such as scientific research and engineering applications. However, the structure and cost of traditional magnetic field sensors based on sensing principles such as the Hall effect, magnetoresistive effect, and fluxgate magnetization still need improvement. Fiber optic magnetic field sensors have attracted increasing attention due to their advantages of light weight, small size, low cost, and remote controllability. Traditional optical fibers, such as those made of quartz, are not easily affected by electromagnetic signals. Therefore, fiber optic magnetic field sensors require specially designed fiber structures and magnetically sensitive materials so that the phase, intensity, frequency, and other physical properties of the light waves in the fiber can be modulated by the ambient magnetic field.

[0003] I. Common Micro / Nano Structures of Magnetic Induction Fiber Optic Sensors

[0004] Because materials such as quartz glass have good electromagnetic signal shielding properties, in order to better realize the sensing and measurement of magnetic fields, fiber optic magnetic field sensors must be combined with specially designed fiber optic structures to adjust the physical parameters such as the frequency, intensity, and phase of light waves, and then detect these changes.

[0005] 1. Sensors based on fiber Bragg gratings (FBG)

[0006] An FBG (Fiber Bragg Gap) is a distributed Bragg reflector in which the refractive index modulation section is periodically distributed on the fiber core. It can reflect light of a specific wavelength while transmitting light of other wavelengths. The effective refractive index of an FBG can be adjusted by changing the fiber cladding stress or reducing the fiber cladding thickness, making magnetic field sensing possible.

[0007] 2. Interferometer-based fiber optic sensor

[0008] Phase changes in optical fibers can be detected using interferometers, and the magnitude of the optical path difference or phase difference between different optical paths within the interferometer determines the sensing sensitivity. This paper specifically discusses several common fiber optic interferometer structures and their optical field modulation characteristics, including MZI (Mach-Zehnder Interferometer), FPI (Fabry-Pérot Interferometer), SI (Sagnac Interferometer), and MI (Michelson Interferometer).

[0009] 3. Sensors based on micro / nano-structured optical fibers

[0010] When light propagates in an optical fiber, an evanescent field forms at the core-cladding interface. This field interacts with the measured material, causing a loss of light energy, which is reflected in a reduction in the output light intensity. This characteristic makes it possible to measure the ambient magnetic field. Micro / nano tapered fibers, D-shaped fibers, and U-shaped fiber structures allow the evanescent field in the fiber to better penetrate into the environment, thereby improving sensor sensitivity.

[0011] II. Common Magnetic Sensitive Materials for Magnetic Induction Fiber Optic Sensors

[0012] Optical fibers are generally made of materials such as quartz glass and polymers, which inherently possess a certain degree of electromagnetic signal shielding. Therefore, if fiber optic sensors are to be used in magnetic field sensing measurements, magnetically sensitive materials must be introduced into the fiber structure to utilize the sensitivity of these materials to electromagnetic signals, thereby enabling the fiber optic sensor to sense magnetic field signals.

[0013] 1. Magnetohydrodynamic materials

[0014] Magnetofluids are colloidal solutions containing magnetic nanoparticles. When an external magnetic field is applied, the distribution pattern of the magnetic nanoparticles changes with the strength and direction of the external magnetic field. The magnetic particles tend to aggregate into chains along the direction of the magnetic field, and the refractive index of the colloid changes accordingly, thus providing a possibility for optical fiber detection.

[0015] 2. Magnetostrictive materials

[0016] Magnetostrictive materials, under the influence of an external magnetic field, will elongate or shorten in the magnetization direction, with the dimensional change depending on the magnitude and direction of the magnetic flux density. Magnetostrictive materials can be attached to or wrapped around the surface of optical fiber structures to cause changes in the length of the fiber structure under the influence of a magnetic field, thereby altering parameters such as the refractive index of the fiber.

[0017] 3. Magneto-optical materials

[0018] The magneto-optical effect is an optical phenomenon caused by the interaction between a magnetized substance and light. When a beam of linearly polarized light passes through a transparent magneto-optical material, the polarization direction of the transmitted light changes by an angle compared to the polarization direction of the incident light. This material can also be integrated into fiber optic sensing structures through attachment, wrapping, or connection, thereby helping them detect magnetic fields.

[0019] III. Common Applications of Fiber Optic Magnetic Field Sensors

[0020] Fiber optic magnetic field sensor technology is developing rapidly and has broad application prospects, such as in current sensing, multi-dimensional ocean detection, and national defense. Fiber optic magnetic field sensors can also be used as current sensors, geomagnetic sensors, and quasi-distributed magnetic field sensors. Summary of the Invention

[0021] The technical problem to be solved by this invention is that traditional fiber optic magnetic field sensors are not easily affected by electromagnetic signals and are difficult to apply well in special environments such as underground, air, and seabed. The ambient magnetic field cannot modulate the physical characteristics of the light wave in the fiber optic cable, such as the phase, intensity, and frequency. The purpose of this invention is to provide a fiber optic magnetic field sensor, system, and application based on a specially designed fiber optic cable. It improves upon the traditional fiber optic structure by introducing a specially designed fiber optic structure and magnetic sensitive material so that the ambient magnetic field can modulate the physical characteristics of the light wave in the fiber optic cable, such as the phase, intensity, and frequency.

[0022] This invention is achieved through the following technical solution:

[0023] This invention provides a fiber optic magnetic field sensor based on a specially designed optical fiber, comprising:

[0024] Single-mode fiber core, used for transmitting and sensing optical signals;

[0025] Metal wires are used to generate induced current; each single-mode fiber core is equipped with at least one metal wire; the metal wires are low-resistivity metal wires with a resistivity of no more than 0.02Ωm.

[0026] A single-mode fiber cladding is used to protect the single-mode fiber core; the single-mode fiber cladding encloses the single-mode fiber core and the metal wire inside.

[0027] The working principle of this solution is as follows: Although traditional fiber optic magnetic field sensors are not easily affected by electromagnetic signals, they are difficult to apply well in special environments such as underground, air, and seabed. The ambient magnetic field cannot modulate the physical characteristics of the light waves in the fiber optic cable, such as the phase, intensity, and frequency. The purpose of this invention is to provide a fiber optic magnetic field sensor, system, and application based on a specially designed fiber optic cable. It improves upon the traditional fiber optic structure by introducing a specially designed fiber optic structure and magnetically sensitive materials so that the ambient magnetic field can modulate the physical characteristics of the light waves in the fiber optic cable, such as the phase, intensity, and frequency, in special environments such as underground, air, and seabed.

[0028] Preferably, the low-resistivity metal wire is copper wire, and the special optical fiber is manufactured to possess characteristics such as high temperature resistance, hydrogen loss resistance, and bend insensitivity, so as to ensure the long-term use of the special optical fiber in special environments such as underground, air, and seabed. The special optical fiber is a high-temperature resistant, hydrogen loss resistant, and bend insensitive special optical fiber.

[0029] A further optimized solution includes a magnetic core, which is a cylindrical magnetic core with a diameter of d and a height of h; a specially made optical fiber is spirally wound around the surface of the magnetic core to form a magnetic field sensing component; the magnetic core is a high-temperature resistant, high-magnetic-flux cylindrical magnetic core.

[0030] The further optimized scheme is that the range of h is 5cm-100cm, and the range of d is 2cm-10cm.

[0031] The further optimized solution also includes: an extinction device and a specially designed fiber composite protective layer;

[0032] The tail end of the specially designed optical fiber is connected to an extinction device;

[0033] The composite protective layer is tightly wrapped around the outer surface of the specially made optical fiber.

[0034] A further optimized solution is that the composite protective layer is a high-temperature and high-strength composite material, including a flexible non-metallic composite material that is resistant to high temperature, high pressure, corrosion, wear, and high insulation.

[0035] A further optimized solution is to assemble three identical magnetic field sensing components in three mutually orthogonal directions to obtain a three-component fiber optic magnetic field sensor.

[0036] When the external magnetic field changes, a changing induced current is generated in the specially made optical fiber tightly wound on the cylindrical magnetic core. When this induced current flows on the metal wire, it generates an electromagnetic force perpendicular to the direction of the induced current flow. This electromagnetic force causes the specially made optical fiber containing the metal wire to undergo corresponding strain, resulting in corresponding changes in the amplitude, phase, frequency, or polarization of the laser pulse propagating in the specially made optical fiber. At this time, the distributed fiber strain sensing (DSS) modem connected to the optical fiber magnetic field sensor can measure the changes in the laser pulse propagating in the specially made optical fiber, thereby demodulating the changes in the external magnetic field of the optical fiber magnetic field sensor.

[0037] This solution also provides a fiber optic magnetic field sensing system based on specialized optical fibers, including a modem and a fiber optic magnetic field sensor based on specialized optical fibers. The fiber optic magnetic field sensing system based on specialized optical fibers is calibrated within a standard alternating magnetic field; the calibration result is used to demodulate the change in the external magnetic field measured by the fiber optic magnetic field sensor.

[0038] This solution also provides applications of fiber optic magnetic field sensors based on special optical fibers, including: modems, metal sleeves, surface logging vehicles, and fiber optic magnetic field sensors based on special optical fibers; in this solution, the modem is a three-channel high-sensitivity DSS modulator / demodulator.

[0039] The three-component fiber optic magnetic field sensor is fixed inside a metal sleeve. Each magnetic field sensing component is connected to the ground logging vehicle via an armored optical cable. The metal sleeve is made of non-magnetic titanium alloy or non-magnetic alloy steel.

[0040] This solution also provides applications of fiber optic magnetic field sensors based on special optical fibers, including: modems, non-metallic magnetic field sensor protection boxes, and fiber optic magnetic field sensors based on special optical fibers.

[0041] The three-component fiber optic magnetic field sensor is fixed inside a non-metallic magnetic field sensor protective box, and each magnetic field sensing component is connected to the modem via armored optical cables. In this solution, the modem is a three-channel high-sensitivity DSS modulator / demodulator.

[0042] This solution also provides applications of fiber optic magnetic field sensors based on special optical fibers, including: modems, well electromagnetic acquisition modules, airborne electromagnetic acquisition stations, seabed electromagnetic acquisition stations, and fiber optic magnetic field sensors based on special optical fibers.

[0043] The three-component fiber optic magnetic field sensor is fixed on a non-metallic pod made of non-magnetic material. The three fiber optic magnetic field sensors are connected to the optical signal input terminal of the airborne three-channel high-sensitivity DSS modulator and demodulator via armored optical cables, thus forming an aviation pod-type fiber optic three-component magnetic field data acquisition system.

[0044] The three-component fiber optic magnetic field sensor is fixed on the seabed electromagnetic acquisition station, and each magnetic field sensing component is connected to a modem via armored optical cables. In this scheme, the modem is a three-channel high-sensitivity DSS modulator / demodulator.

[0045] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0046] This invention provides a fiber optic magnetic field sensor, system, and application based on specially designed optical fibers. It improves upon traditional optical fiber structures by introducing a specially designed fiber structure and magnetically sensitive materials. The invention uses specially designed optical fibers containing metal wires to fabricate the fiber optic magnetic field sensor, which can then be used to conveniently construct a three-component magnetic field data acquisition system for downhole, land, air, and seabed applications. This fiber optic magnetic field sensor has advantages such as small size, light weight, low cost, high temperature resistance, high pressure resistance, no need for power supply, and no electronic components connected to the fiber optic magnetic field sensor. It directly measures the three-component magnetic field signals from downhole, land, air, and seabed using a three-channel high-sensitivity DSS modulator / demodulator located far from the fiber optic magnetic field sensor. Attached Figure Description

[0047] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0048] Figure 1 This is a schematic diagram of a specially designed optical fiber structure.

[0049] Figure 2This is a schematic diagram of a fiber optic magnetic field sensor based on a specially designed optical fiber.

[0050] Figure 3 This is a schematic diagram of a three-component fiber optic magnetic field sensor.

[0051] Figure 4 This is a schematic diagram of the downhole application structure of a three-component fiber optic magnetic field sensor.

[0052] Figure 5 This is a schematic diagram of the land application structure of a three-component fiber optic magnetic field sensor.

[0053] Figure 6 This is a schematic diagram of the aerospace application structure of a three-component fiber optic magnetic field sensor.

[0054] Figure 7 This is a schematic diagram of the structure for a three-component fiber optic magnetic field sensor used in an underwater application.

[0055] The attached diagram shows the markings and corresponding component names:

[0056] 1-Special fiber, 2-Single-mode fiber core, 3-Single-mode fiber cladding, 4-Metal wire, 5-Magnetic core, 6-Extinction device, 7-Composite protective layer, 8-Modem, 9-Metal sleeve, 10-Surface logging vehicle, 11-Non-metallic magnetic field sensor protection box, 12-Non-metallic material pod, 13-Submarine electromagnetic acquisition station, 14-Armored optical cable. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0058] Example 1

[0059] This embodiment provides a fiber optic magnetic field sensor based on a specially made optical fiber, including a specially made optical fiber 1, such as... Figure 1 As shown, the specially made optical fiber 1 includes:

[0060] Single-mode fiber core 2, used for transmitting and sensing optical signals;

[0061] Metal wire 4 is used to generate induced current; each single-mode fiber core 2 is equipped with at least one low-resistivity metal wire 4; the resistivity of the metal wire is not greater than 0.02Ωm.

[0062] The single-mode fiber cladding 3 is used to protect the single-mode fiber core 2; the single-mode fiber cladding 3 encloses the single-mode fiber core 2 and the metal wire 4 inside.

[0063] Preferably, the low-resistivity metal wire is copper wire, and the special optical fiber is manufactured to possess characteristics such as high temperature resistance, hydrogen loss resistance, and bend insensitivity, so as to ensure the long-term use of the special optical fiber in special environments such as underground, air, and seabed. The special optical fiber is a high-temperature resistant, hydrogen loss resistant, and bend insensitive special optical fiber.

[0064] It also includes a magnetic core 5, which is a cylindrical magnetic core with a diameter of d and a height of h; the specially made optical fiber 1 is spirally wound around the surface of the magnetic core 5 to form a sensing component; the magnetic core 5 is a high-temperature resistant and high-magnetic-flux cylindrical magnetic core.

[0065] The range of h is 5cm-100cm, and the range of d is 2cm-10cm.

[0066] like Figure 2 As shown, the fiber optic magnetic field sensor based on a special optical fiber also includes an extinction device 6 and a composite protective layer 7; the tail end of the special optical fiber 1 is connected to the extinction device 6.

[0067] The composite protective layer 7 is tightly wrapped around the outer surface of the specially made optical fiber.

[0068] The composite protective layer 7 is a high-temperature and high-strength composite material, including a flexible non-metallic composite material that is resistant to high temperature, high pressure, corrosion, wear, and high insulation.

[0069] Example 2

[0070] like Figure 3 As shown, this embodiment uses three identical magnetic sensing components assembled in three mutually orthogonal directions to form a three-component fiber optic magnetic field sensor. This system is calibrated within a standard alternating magnetic field; the calibration result is used to demodulate the change in the external magnetic field measured by the fiber optic magnetic field sensor.

[0071] This embodiment also provides a fiber optic magnetic field sensing system based on specially made optical fibers, including: a modem 8 and a fiber optic magnetic field sensor based on specially made optical fibers according to Embodiment 2. The three magnetic sensing components are connected to the optical signal input terminal of a three-channel high-sensitivity DSS modulator / demodulator in the ground logging vehicle through an armored optical cable containing three high-temperature resistant single-mode optical fibers, thus forming a three-component fiber optic magnetic field data acquisition system in the well.

[0072] This embodiment provides an application of a fiber optic magnetic field sensor based on a specially designed optical fiber, such as... Figure 4 As shown, it includes: modem 8, metal sleeve 9, surface logging vehicle 10, and a fiber optic magnetic field sensor based on a special optical fiber according to embodiment 2;

[0073] The three-component fiber optic magnetic field sensor is fixed inside the metal sleeve 9. Each magnetic field sensing component is connected to the ground logging vehicle 10 through the armored optical cable 14. The metal sleeve 9 is made of non-magnetic titanium alloy or non-magnetic alloy steel. In this embodiment, the modem is a three-channel high-sensitivity DSS modulator / demodulator.

[0074] Example 3

[0075] This embodiment provides an application of a fiber optic magnetic field sensor based on a specially designed optical fiber, characterized in that, as Figure 5 As shown, it includes: a modem 8, a non-metallic magnetic field sensor protection box 11, and a fiber optic magnetic field sensor based on a special optical fiber according to Embodiment 1.

[0076] The three-component fiber optic magnetic field sensor is fixed inside the non-metallic magnetic field sensor protective box 11. Each magnetic field sensing component is connected to the modem 8 via armored optical cable 14, thus forming a ground-based fiber optic three-component magnetic field data acquisition system. The non-metallic magnetic field sensor protective box 11 is made of non-magnetic non-metallic material. In this embodiment, the modem is a three-channel high-sensitivity DSS modulator / demodulator.

[0077] Example 4

[0078] This embodiment provides an application of a fiber optic magnetic field sensor based on a specially designed optical fiber, such as... Figure 6 As shown, it includes: a modem 8, a non-metallic material pod 12, and a fiber optic magnetic field sensor based on a specially made optical fiber according to Embodiment 1;

[0079] Three fiber optic magnetic field sensors, each with a 10 cm diameter and 100 cm long magnetic core, are fixed orthogonally on a non-metallic pod 12. The three fiber optic magnetic field sensors are connected to the optical signal input of an airborne three-channel high-sensitivity DSS modulator / demodulator 8 via an armored optical cable 14 containing three single-mode optical fibers. This constitutes an aviation pod-type fiber optic three-component magnetic field data acquisition system.

[0080] Example 5

[0081] This embodiment provides an application of a fiber optic magnetic field sensor based on a specially designed optical fiber, such as... Figure 7 As shown, it includes: modem 8, seabed electromagnetic acquisition station 13, and an optical fiber magnetic field sensor based on a special optical fiber according to embodiment 1;

[0082] The three-component fiber optic magnetic field sensor is fixed on the seabed electromagnetic acquisition station 13. Each magnetic field sensing component is connected to the modem 8 through the armored optical cable 14. In this embodiment, the modem is a three-channel high-sensitivity DSS modulator / demodulator.

[0083] This invention utilizes a specially designed optical fiber containing metal wires to fabricate an optical fiber magnetic field sensor. This sensor offers advantages such as small size, light weight, low cost, high temperature and high pressure resistance, no need for power supply, and no electronic components connected to it. This facilitates the construction of a three-component magnetic field data acquisition system for downhole, land, air, and seabed applications. The system directly measures the three-component magnetic field signals from downhole, land, air, and seabed locations using a three-channel high-sensitivity DSS modulator / demodulator located away from the optical fiber sensor and a three-component optical fiber magnetic field sensor connected to the tail of an armored optical cable.

[0084] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fiber optic magnetic field sensor based on a specially designed optical fiber, characterized in that, Includes a special optical fiber (1), said special optical fiber (1) comprising: Single-mode fiber core (2) is used for transmitting and sensing optical signals; Metal wire (4) is used to generate induced current; at least one metal wire (4) is provided for each single-mode fiber core (2). The single-mode fiber cladding (3) is used to protect the single-mode fiber core (2); the single-mode fiber cladding (3) encloses the single-mode fiber core (2) and the metal wire (4).

2. The fiber optic magnetic field sensor based on a specially designed optical fiber according to claim 1, characterized in that, It also includes a magnetic core (5), which is a cylindrical magnetic core with a diameter of d and a height of h; the special optical fiber (1) is spirally wound around the surface of the magnetic core (5) to form a magnetic field sensing component.

3. The fiber optic magnetic field sensor based on a specially designed optical fiber according to claim 2, characterized in that, The range of h is 5cm-100cm, and the range of d is 2cm-10cm.

4. A fiber optic magnetic field sensor based on a specially designed optical fiber according to claim 2, characterized in that, It also includes a matting element (6) and a composite protective layer (7); The tail end of the special optical fiber (1) is connected to an extinction device (6). The composite protective layer (7) is tightly wrapped around the surface of the special optical fiber.

5. A fiber optic magnetic field sensor based on a specially designed optical fiber according to claim 4, characterized in that, The composite protective layer (7) is a flexible non-metallic composite material.

6. A fiber optic magnetic field sensor based on a specially designed optical fiber according to claim 2, characterized in that, A three-component fiber optic magnetic field sensor is obtained by assembling three identical magnetic field sensing components in three mutually orthogonal directions.

7. A fiber optic magnetic field sensing system based on specially designed optical fibers, characterized in that, include: The modem (8) and the fiber optic magnetic field sensor based on a special optical fiber as described in any one of claims 1-6.

8. The application of fiber optic magnetic field sensors based on specially designed optical fibers, characterized in that, include: Modem (8), metal sleeve (9), ground logging vehicle (10) and fiber optic magnetic field sensor based on special optical fiber as described in claim 6; The three-component fiber optic magnetic field sensor is fixed inside the metal sleeve (9), and each magnetic field sensing component is connected to the ground logging vehicle (10) through the armored optical cable (14). The metal sleeve (9) is made of non-magnetic titanium alloy or non-magnetic alloy steel.

9. The application of fiber optic magnetic field sensors based on specially designed optical fibers, characterized in that, include: Modem (8), non-metallic magnetic field sensor protection box (11) and fiber optic magnetic field sensor based on special optical fiber as described in claim 6; The three-component fiber optic magnetic field sensor is fixed inside the non-metallic magnetic field sensor protection box (11), and each magnetic field sensing component is connected to the modem (8) through the armored optical cable (14).

10. The application of fiber optic magnetic field sensors based on specially designed optical fibers, characterized in that, include: Modem (8), seabed electromagnetic acquisition station (13) and fiber optic magnetic field sensor based on special optical fiber as described in claim 6; The three-component fiber optic magnetic field sensor is fixed on the seabed electromagnetic acquisition station (13), and each magnetic field sensing component is connected to the modem (8) through the armored optical cable (14).

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