CN107607889B - Li-Fi-based all-optical transmission magnetic field detection system - Google Patents
Li-Fi-based all-optical transmission magnetic field detection system Download PDFInfo
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- CN107607889B CN107607889B CN201710801306.0A CN201710801306A CN107607889B CN 107607889 B CN107607889 B CN 107607889B CN 201710801306 A CN201710801306 A CN 201710801306A CN 107607889 B CN107607889 B CN 107607889B
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Abstract
The invention provides a Li-Fi-based all-optical transmission magnetic field detection system, and relates to the technical field of optical fiber sensors. The invention comprises an optical fiber directional coupler, an LD light source, a magnetic field sensor, matching fluid and a Li-Fi module. A fiber optic directional coupler configured as a 2 x 2 fiber optic directional coupler having a first port to a fourth port. The LD light source is used for emitting modulated laser with preset frequency to the magnetic field detection system, and the output end of the LD light source is connected with the first port. And the magnetic field sensor is connected with the second port through the Y-shaped optical fiber body and is used for detecting the strength of a magnetic field. The Li-Fi module comprises a Li-Fi transmitting unit and a Li-Fi receiving unit, the Li-Fi transmitting unit is connected with the third port through a matching grating, and the Li-Fi receiving unit is connected with the photoelectric detector so as to establish a wireless transmission network between the photoelectric detector and the magnetic field sensor. The invention works under the full light excitation, does not generate interference to the magnetic field to be measured, has small volume and is suitable for narrow space.
Description
Technical Field
The invention relates to the technical field of optical fiber sensors, in particular to a Li-Fi-based all-optical transmission magnetic field detection system.
Background
The existing magnetic field sensor is mainly based on the mechanisms of Hall effect, magnetoresistance effect, fluxgate effect, tunneling effect, nuclear magnetic resonance effect and the like, the traditional magnetic field sensors all need to be excited by electric signals, and the magnetic field generated by the excitation of the electric signals can interfere with the detected magnetic field, so that the further improvement of the detection precision of the sensor is limited. The traditional magnetic field sensor is large in size and difficult to detect the magnetic field in a narrow space. The optical fiber magnetic field sensor does not influence an electromagnetic field to be measured, has the advantages of corrosion resistance, light weight, small size and the like, and is favorable for application in the fields of aviation and aerospace and narrow spaces. The optical fiber cantilever beam magnetic field sensor combines the characteristics of the optical fiber magnetic field sensor and the cantilever beam, and has the advantages of miniaturization, easy realization of multi-point distributed detection, remote detection, high precision, low power consumption, full optical transmission and the like.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a Li-Fi-based all-optical transmission magnetic field detection system.
In particular, the invention provides a Li-Fi-based all-optical transmission magnetic field detection system, which comprises:
a fiber optic directional coupler configured as a 2 x 2 fiber optic directional coupler having a first port to a fourth port;
the LD light source is used for emitting modulated laser with preset frequency to the magnetic field detection system, and the output end of the LD light source is connected with the first port;
the magnetic field sensor is connected with the second port through the Y-shaped optical fiber body and used for detecting the strength of a magnetic field;
the matching fluid is connected with the fourth port to prevent Fresnel reflection;
the Li-Fi module comprises a Li-Fi transmitting unit and a Li-Fi receiving unit, the Li-Fi transmitting unit is connected with the third port through a matching grating, and the Li-Fi receiving unit is connected with the photoelectric detector so as to establish a wireless transmission network between the photoelectric detector and the magnetic field sensor.
Further, the Li-Fi emission unit comprises a first LED lamp and a signal modulator, and the signal modulator is used for modulating the central wavelength signal transmitted through the matched grating into a high-frequency light wave signal and emitting the high-frequency light wave signal through the first LED lamp.
Further, the Li-Fi receiving unit includes a second LED lamp and a signal demodulator, and the center wavelength signal loaded in the lightwave signal is demodulated by the signal demodulator.
Further, the magnetic field sensor comprises a temperature compensation probe and a magnetic field detection probe, wherein the temperature compensation probe is used for detecting the ambient temperature in the magnetic field to be used as the temperature compensation basis of the magnetic field detection probe.
Further, the temperature compensation probe is directly constructed at the first end part of the Y-shaped optical fiber body, and the temperature compensation probe is of a first D-shaped optical fiber grating cantilever beam structure.
Further, the magnetic field detection probe includes:
a second D-shaped fiber grating cantilever beam directly constructed at the second end of the Y-shaped fiber body;
the metal film is plated on the upper surface of the second D-shaped fiber grating cantilever beam;
a giant magnetostrictive film disposed at a surface of the metal film to induce a strength of a magnetic field;
and the F-P resonant cavity consists of the second D-type fiber grating cantilever beam and a fiber end face, and the giant magnetostrictive film is arranged on the outer side of the fiber end face.
Furthermore, the magnetic field detection probe and the Y-shaped optical fiber body are of an integrated structure.
Further, the thickness of the giant magnetostrictive film is 0.5-2 μm.
Further, the metal film is gold or chromium.
The magnetic field detection system comprises an optical fiber directional coupler, an LD light source, a magnetic field sensor, matching fluid and a Li-Fi module, wherein the magnetic field sensor comprises a temperature compensation probe and a magnetic field detection probe. The strength of the magnetic field is detected in real time through the magnetic field detection probe, the magnetic field is returned to the matched grating through the optical fiber loop, and finally the information collected by the magnetic field sensor is transmitted to the photoelectric detector for processing through the Li-Fi module.
Furthermore, a metal film and a giant magnetostrictive film are sequentially arranged on the outer surface of the second D-type fiber grating cantilever beam to form a double-layer sensitive resonance structure. The giant magnetostrictive film has a larger magnetostrictive coefficient and can generate larger magnetostriction, thereby effectively improving the detection precision of a magnetic field.
Furthermore, the magnetic field detection probe can detect the magnetic field intensity through the center wavelength information returned by the second D-type fiber bragg grating cantilever beam, and can also calculate the magnetic field intensity through the frequency change of a reverse signal returned by the F-P resonant cavity.
The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.
Drawings
Some specific embodiments of the invention will be described in detail hereinafter, by way of illustration and not limitation, with reference to the accompanying drawings. The same reference numbers in the drawings identify the same or similar elements or components. Those skilled in the art will appreciate that the drawings are not necessarily drawn to scale. In the drawings:
fig. 1 is a schematic structural diagram of a Li-Fi-based all-optical transmission magnetic field detection system according to an embodiment of the present invention.
Detailed Description
Fig. 1 is a schematic structural diagram of a Li-Fi-based all-optical transmission magnetic field detection system according to an embodiment of the present invention. As shown in fig. 1, the present invention provides a Li-Fi-based all-optical transmission magnetic field detection system, which includes an optical fiber directional coupler 2, an LD light source 1, a magnetic field sensor, a matching fluid 5, and a Li-Fi module 11. The fiber optic directional coupler 2, which is configured as a 2 x 2 fiber optic directional coupler, has a first port 21 to a fourth port 24. The LD light source 1 is configured to emit modulated laser with a preset frequency to the magnetic field detection system, and an output end of the LD light source is connected to the first port 21. The magnetic field sensor is connected to the second port 22 via a Y-shaped optical fiber body for detecting the intensity of the magnetic field. And a matching fluid 5 connected to the fourth port 24 to prevent fresnel reflection. The Li-Fi module 11 includes a Li-Fi transmitting unit 110 and a Li-Fi receiving unit 111, the Li-Fi transmitting unit 110 is connected to the third port 23 through the matching grating 4, and the Li-Fi receiving unit 111 is connected to the photodetector to establish a wireless transmission network between the photodetector 3 and the magnetic field sensor.
The magnetic field detection system comprises an optical fiber directional coupler 2, an LD light source 1, a magnetic field sensor, matching fluid 5 and a Li-Fi module 11, wherein the magnetic field sensor comprises a temperature compensation probe and a magnetic field detection probe. The strength of the magnetic field is detected in real time by the magnetic field detection probe, the magnetic field returns to the matched grating 4 through the optical fiber loop, and finally the information collected by the magnetic field sensor is transmitted to the photoelectric detector 3 through the Li-Fi module 11 for processing.
In one embodiment, the Li-Fi transmitting unit 110 of the present invention includes a first LED lamp and a signal modulator, by which a central wavelength signal transmitted through the matching grating 4 is modulated into a high frequency lightwave signal and transmitted through the first LED lamp. The Li-Fi receiving unit 111 includes a second LED lamp and a signal demodulator, by which the center wavelength signal loaded in the lightwave signal is demodulated.
The invention adopts full optical transmission, does not generate interference to a magnetic field to be measured, has small volume and is suitable for narrow space.
As shown in fig. 1, the magnetic field sensor includes a temperature compensation probe 8 and a magnetic field detection probe 9, and the temperature compensation probe 8 is used for detecting the ambient temperature in the magnetic field to serve as the basis for temperature compensation of the magnetic field detection probe 9. The temperature compensation probe 8 is directly constructed at the first end part 6 of the Y-shaped optical fiber body and has a first D-shaped optical fiber grating cantilever beam structure. The magnetic field detection probe 9 includes: a second D-type fiber grating cantilever beam, a metal film 102, a giant magnetostrictive film 103 and an F-P resonant cavity. A second D-shaped fiber grating cantilever beam constructed directly at the second end 7 of the Y-shaped fiber body. And the metal film 102 is plated on the upper surface of the second D-shaped fiber grating cantilever beam. A giant magnetostrictive film 103 disposed at a surface of the metal film 102 to induce the intensity of a magnetic field. And the F-P resonant cavity is composed of the second D-type fiber grating cantilever beam and a fiber end face, and the giant magnetostrictive film 103 is arranged on the outer side of the fiber end face.
The outer surface of the second D-type fiber grating cantilever beam is sequentially provided with a metal film 102 and a giant magnetostrictive film 103 to form a double-layer sensitive resonance structure. The giant magnetostrictive film 103 has a large magnetostrictive coefficient, and can generate large magnetostriction, thereby effectively improving the detection accuracy of a magnetic field. Further, the magnetic field detection probe 9 of the present invention can detect the magnetic field strength through the center wavelength information returned by the second D-type fiber grating cantilever beam, and can also calculate the magnetic field strength through the frequency change of the reverse signal returned by the F-P resonant cavity.
The magnetic field detection probe 9 and the Y-shaped optical fiber body are of an integrated structure. The thickness of the giant magnetostrictive film 103 is 0.5 μm to 2 μm. The metal film 102 is gold or chromium.
The working principle of the magnetic field detection system is as follows: the infrared laser with modulated frequency enters from the first port 21 of the optical fiber directional coupler 2, is coupled and transmitted into the Y-shaped optical fiber body from the second port of the optical fiber directional coupler 2, the magnetic field detection probe 9 is coated with a metal film 102 on the second D-type fiber bragg grating cantilever, because the second D-shaped fiber grating cantilever beam has photo-thermal excitation resonance due to the double-membrane thermal effect and the second D-shaped fiber grating cantilever beam has resonance, the central wavelength of the fiber grating changes due to the periodic change of the fiber grating, namely, the grating structure vibrates downwards to be stressed, vibrates upwards to be pulled to be periodically changed, a reflection signal modulated by the fiber grating returns along a fiber optical path, and the reflection signal light is received by the photoelectric detector 3 through the matching grating 4 and the Li-Fi module 11 through the third port of the fiber directional coupler 2. The D-type fiber grating cantilever beam is also provided with a giant magnetostrictive film 101, under the action of a magnetic field, the giant magnetostrictive film 101 can extend or shorten along different directions of the magnetic field, the different external magnetic field causes different extension degrees of the giant magnetostrictive film 101, so that the second D-type fiber grating cantilever beam is driven to flex, the amplitude of the second D-type fiber grating cantilever beam changes along with the extension degrees, the extension and extrusion ranges of grating pitches on the second D-type fiber grating cantilever beam also change, and finally the change range of the central wavelength of a reflected signal also changes. The higher the magnetic field intensity is, the larger the deflection and amplitude of the second D-type fiber grating cantilever beam is, and the wider the change range of the central wavelength of the reflected signal of the grating is. The reflected signal with the changed central wavelength enters the matched grating 4, the transmitted light intensity of the matched grating 4 is received by the photoelectric detector 3, and the matched filter matched grating 4 converts the variable quantity of the central wavelength of the second D-type fiber grating cantilever beam into the change of the light intensity signal so as to measure the intensity of the magnetic field.
The other working principle of the magnetic field detection system is as follows: in a magnetic field, the giant magnetostrictive film 103 expands and contracts, which causes the cavity length of the F-P resonant cavity to change correspondingly. Modulated light emitted by a laser light source enters an optical fiber through combination, enters an F-P resonant cavity, is reflected in the F-P resonant cavity, returns along the original path, meets to generate interference, and is received by a photoelectric detector 3 through a Li-Fi module 11. The larger the magnetic field intensity is, the larger the contraction degree of the giant magnetostrictive material is, and the longer the cavity length of the F-P resonant cavity is, so that the interference output signal received by the photoelectric detector 3 also changes correspondingly. The magnitude of the external magnetic field can be obtained by signal conditioning of the interference output signal received by the photodetector 3.
Thus, it should be appreciated by those skilled in the art that while a number of exemplary embodiments of the invention have been illustrated and described in detail herein, many other variations or modifications consistent with the principles of the invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be understood and interpreted to cover all such other variations or modifications.
Claims (3)
1. A Li-Fi-based all-optical transmission magnetic field detection system comprises:
a fiber optic directional coupler configured as a 2 x 2 fiber optic directional coupler having a first port to a fourth port;
the LD light source is used for emitting modulated laser with preset frequency to the magnetic field detection system, and the output end of the LD light source is connected with the first port;
the magnetic field sensor is connected with the second port through the Y-shaped optical fiber body and used for detecting the strength of a magnetic field;
the matching fluid is connected with the fourth port to prevent Fresnel reflection;
the Li-Fi module comprises a Li-Fi transmitting unit and a Li-Fi receiving unit, the Li-Fi transmitting unit is connected with the third port through a matching grating, and the Li-Fi receiving unit is connected with the photoelectric detector so as to establish a wireless transmission network between the photoelectric detector and the magnetic field sensor;
the Li-Fi emission unit comprises a first LED lamp and a signal modulator, and central wavelength signals transmitted through the matching grating are modulated into high-frequency light wave signals through the signal modulator and emitted through the first LED lamp;
the Li-Fi receiving unit comprises a second LED lamp and a signal demodulator, and the central wavelength signal loaded in the lightwave signal is demodulated through the signal demodulator;
the magnetic field sensor comprises a temperature compensation probe and a magnetic field detection probe, wherein the temperature compensation probe is used for detecting the ambient temperature in the magnetic field to be used as the temperature compensation basis of the magnetic field detection probe;
the temperature compensation probe is directly constructed at the first end part of the Y-shaped optical fiber body and is of a first D-shaped optical fiber grating cantilever beam structure;
the magnetic field detection probe includes: a second D-shaped fiber grating cantilever beam directly constructed at the second end of the Y-shaped fiber body; the metal film is plated on the upper surface of the second D-shaped fiber grating cantilever beam; a giant magnetostrictive film disposed at a surface of the metal film to induce a strength of a magnetic field; the F-P resonant cavity consists of the second D-type fiber grating cantilever beam and a fiber end face, and the giant magnetostrictive film is arranged on the outer side of the fiber end face;
the magnetic field detection probe and the Y-shaped optical fiber body are of an integrated structure.
2. The Li-Fi based all-optical transmission magnetic field detection system according to claim 1, wherein the giant magnetostrictive film has a thickness of 0.5 μm to 2 μm.
3. The Li-Fi based all-optical transmission magnetic field detection system according to claim 1, wherein the metal thin film is gold or chromium.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH06230091A (en) * | 1993-02-03 | 1994-08-19 | Nippon Telegr & Teleph Corp <Ntt> | Distributed magneto-optical fiber sensor |
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| CN101598773B (en) * | 2009-07-02 | 2011-09-14 | 西北工业大学 | Magnetic induction intensity sensing head and magnetic induction intensity measurement method and device thereof |
| CN104776954B (en) * | 2014-01-09 | 2018-06-22 | 中国计量学院 | A kind of light stimulus fiber grating cantilever beam harmonic oscillator vacuum sensor |
| CN107085130B (en) * | 2016-02-16 | 2020-05-19 | 姚晓天 | Polarization insensitive current and magnetic field sensor with active temperature compensation |
| CN107131896A (en) * | 2016-02-26 | 2017-09-05 | 上海淇岸生物科技有限公司 | A kind of fiber grating resonant biosensor |
| CN205656289U (en) * | 2016-03-25 | 2016-10-19 | 中国计量学院 | Optic fibre cantilever beam magnetic field sensing probe based on giant magnetostrictive film |
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| JPH06230091A (en) * | 1993-02-03 | 1994-08-19 | Nippon Telegr & Teleph Corp <Ntt> | Distributed magneto-optical fiber sensor |
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Effective date of registration: 20200331 Address after: 233000 Youyi Road 925, hi tech Development Zone, Anhui, Bengbu Applicant after: BENGBU GAOLING SENSING SYSTEM PROJECT Co.,Ltd. Address before: 528100 Guangdong, Foshan, Sanshui District, southwest Street, Dexing five street, 11, 401 Applicant before: Yu Mengmeng |
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