Optical fiber magnetic field sensor based on F-P interferometer

Abstract

The utility model discloses an optical fiber magnetic field sensor based on an F-P interferometer. The optical fiber magnetic field sensor is composed of a single-mode optical fiber, a capillary glass tube and an annular nickel film. Welding a section of capillary glass tube between two sections of single-mode optical fibers, and plating two layers of superposed annular nickel films on the surface of the capillary glass tube at intervals; when the sensor is placed in an external magnetic field environment, the annular nickel film deforms due to the magnetostriction characteristic of nickel, and the deformation enables the thin inner wall of the capillary glass tube to also deform, so that the cavity length of the interferometer is changed, namely the free spectral range of the F-P interferometer is changed, and finally the reflection spectrum of the sensor drifts; the change of the external magnetic field intensity can be demodulated by recording the drifting of the reflection spectrum of the sensor through the optical fiber spectrometer; the annular nickel films can attract each other due to magnetization of a magnetic field, and the capillary glass tube is easier to deform, so that the change of the cavity length of the interferometer is more obvious, the thin inner wall of the capillary glass tube is easier to deform compared with the thick inner wall of the capillary glass tube, and the sensitivity of the sensor is further improved. The optical fiber magnetic field sensor based on the F-P interferometer has the advantages of being high in sensitivity, resistant to electromagnetic interference, simple to manufacture, compact in structure and the like, and can be used for sensing measurement of magnetic field intensity.

Description

Technical Field

[0001] The utility model belongs to the technical field of optical fiber sensing, and in particular relates to an optical fiber magnetic field sensor based on an FP interferometer. Background Art

[0002] Magnetic field is a basic physical quantity in the natural environment. Magnetic field sensing has important applications in many fields, such as medical testing, industrial manufacturing, electronic communications, military equipment, etc. Traditional magnetic field sensors are usually based on principles such as the Hall effect and magnetoresistance effect, which have the disadvantages of high cost, complex structure, large size, and weak anti-electromagnetic interference ability. In contrast, optical fiber magnetic field sensors have the advantages of low cost, small size, anti-electromagnetic interference, simple structure, and high sensitivity, so they have good application potential in the field of magnetic field sensing. Utility Model Content

[0003] The utility model provides an optical fiber magnetic field sensor based on an FP interferometer to detect the intensity of a magnetic field.

[0004] The technical solution adopted by the utility model is: an optical fiber magnetic field sensor based on FP interferometer, including single-mode optical fiber, capillary glass tube and annular nickel film, characterized in that: a section of capillary glass tube is fused between two sections of single-mode optical fiber, and two layers of overlapping annular nickel film are plated on the surface of the capillary glass tube at intervals. The single-mode optical fiber is G652D type, the capillary glass tube is 125μm in outer diameter, 105μm to 115μm in inner diameter, the length of the capillary glass tube is 300μm to 400μm, the first layer of annular nickel film on the surface of the capillary glass tube has a thickness of 60 to 80nm and a width of 20μm, the second layer of annular nickel film has a thickness of 5μm to 6μm and a width of 20μm, and the interval between each ring of nickel film is 10μm to 20μm.

[0005] The flat end face of the single-mode optical fiber and the end face of the capillary glass tube form an FP interferometer. The light beam is input from the single-mode optical fiber. When the light beam enters the FP interferometer, the light beam is reflected multiple times between the two inner surfaces of the interferometer to form multi-beam interference. After two overlapping annular nickel films are plated on the surface of the capillary glass tube, the nickel film is deformed due to the magnetostrictive properties of nickel under the action of the external magnetic field. This deformation also causes the thin inner wall of the capillary glass tube to deform, thereby changing the cavity length of the interferometer. At the same time, due to the magnetization of the magnetic field, each ring of the annular nickel film can also attract each other, making the change of the interferometer cavity length more obvious, that is, the free spectral range of the FP interferometer changes. When the external magnetic field strength is different, the reflection spectrum of the sensor drifts, so that the sensing measurement of the external magnetic field strength can be realized.

[0006] The beneficial effects of the utility model are:

[0007] 1. This sensor has the advantages of high sensitivity, anti-electromagnetic interference, simple production and compact structure.

[0008] 2. This sensor uses two overlapping annular nickel films. The first annular nickel film acts as a substrate, allowing the second annular nickel film to be plated thicker, thereby improving the sensitivity of the sensor and simplifying the production of the sensor.

[0009] 3. The annular nickel film used in this sensor will deform due to the magnetostrictive property of nickel when there is an external magnetic field. This deformation also causes the inner wall of the capillary glass tube to deform, thereby changing the cavity length of the interferometer, that is, the free spectral range of the interferometer changes, thereby realizing the sensing measurement of the external magnetic field strength.

[0010] 4. The ring-shaped nickel film used in this sensor can attract each other due to the magnetization of the magnetic field, making the change of the interferometer cavity length more obvious. At the same time, the thin inner wall of the capillary glass tube is easier to deform than the thick inner wall, which can further improve the sensitivity of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The utility model will be further described below in conjunction with the accompanying drawings.

[0012] Figure 1 It is a schematic diagram of a fiber optic magnetic field sensor based on FP interferometer.

[0013] In the figure: 1. G652D single-mode optical fiber, 2. capillary glass tube, 3. first layer of annular nickel film, 4. second layer of annular nickel film DETAILED DESCRIPTION

[0014] Figure 1 The schematic diagram of the sensor structure of the utility model is as follows: the first step is to weld a capillary glass tube 2 between two sections of single-mode optical fiber 1, the capillary glass tube has a length of 300μm to 400μm, an outer diameter of 125μm, and an inner diameter of 105μm to 115μm; the second step is to use a coating machine to coat a first layer of annular nickel film 3 on the surface of the capillary glass tube, with a thickness of 60 to 80nm and a width of 20μm, and the interval between each ring of nickel film is 10μm to 20μm; the fourth step is to use a nickel electroplating method to coat an overlapping second layer of annular nickel film 4 on the first layer of annular nickel film 3, with a thickness of 5μm to 6μm and a width of 20μm.

Claims

1. An optical fiber magnetic field sensor based on FP interferometer, comprising a single-mode optical fiber, a capillary glass tube and a ring-shaped nickel film, characterized in that: A section of capillary glass tube is fused between two sections of single-mode optical fiber, and two overlapping annular nickel films are plated on the surface of the capillary glass tube at intervals.

2. The optical fiber magnetic field sensor based on FP interferometer according to claim 1, characterized in that: The single-mode optical fiber used is type G652D, and the capillary glass tube has an outer diameter of 125μm and an inner diameter of 105μm to 115μm.

3. The optical fiber magnetic field sensor based on FP interferometer according to claim 1, characterized in that: The length of the capillary glass tube is 300 μm to 400 μm.

4. The optical fiber magnetic field sensor based on FP interferometer according to claim 1, characterized in that: The first layer of annular nickel film on the surface of the capillary glass tube has a thickness of 60-80nm and a width of 20μm, the second layer of annular nickel film has a thickness of 5μm-6μm and a width of 20μm, and the interval between each ring of nickel film is 10μm-20μm.

Images