CN106706111B - Acoustic emission sensor and acoustic emission signal detection method - Google Patents
Acoustic emission sensor and acoustic emission signal detection method Download PDFInfo
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- CN106706111B CN106706111B CN201710025119.8A CN201710025119A CN106706111B CN 106706111 B CN106706111 B CN 106706111B CN 201710025119 A CN201710025119 A CN 201710025119A CN 106706111 B CN106706111 B CN 106706111B
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- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
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Abstract
The invention discloses an acoustic emission sensor, comprising: the double-clad fiber, the single-mode input fiber and the single-mode output fiber are respectively connected with two ends of the double-clad fiber through light paths; the double-clad optical fiber is coated with a silicon rubber coating sensitive to acoustic emission vibration, the silicon rubber coating is deformed by external acoustic emission vibration, dynamic phase change is introduced into a cladding mode of the double-clad optical fiber, and acoustic emission parameters are sensed by detecting the resonance filtering characteristic. The invention is a full optical fiber structure, the double-clad optical fiber and the single-mode optical fiber can be directly welded by using conventional welding equipment, and the invention has the advantages of compact structure, simple manufacturing method and convenient use.
Description
Technical Field
The invention relates to the technical field of optical fiber sensing, in particular to a single-mode optical fiber-double-clad optical fiber-single-mode optical fiber acoustic emission sensor and an acoustic emission signal detection method.
Background
The optical fiber acoustic emission sensor is an important sensor and has been applied to the aspects of partial discharge acoustic emission, underwater acoustic detection, seismic wave detection and the like. The existing optical fiber acoustic emission sensor comprises an optical fiber interferometer, an optical fiber grating, a fused cone optical fiber coupler, an optical fiber Fabry-Perot cavity and the like, wherein the traditional optical fiber interferometer sensor usually has a larger size and is not suitable for being applied in a specific small-size environment; the fiber bragg grating, the fused taper fiber coupler, the fiber Fabry-Perot cavity and the like are suitable for small-size environment application, but a complex writing technology is needed for preparing the fiber bragg grating, and a special packaging technology is needed for improving the acoustic emission sensing sensitivity; the tapered area of the fused-tapered optical fiber coupler is small in size and is easy to cause sensing performance change due to environmental pollution; the optical fiber Fabry-Perot cavity is also fixed on a solid object to be measured by using a vibration film, so that the sensing performance is easy to change.
Disclosure of Invention
The invention provides an acoustic emission sensor and an acoustic emission signal detection method, which have the advantages of simple manufacturing process, single optical fiber integration, convenience in operation and use and high temperature stability.
In order to achieve the above object, the present invention discloses an acoustic emission sensor, which is characterized in that the sensor comprises: the double-clad fiber, the single-mode input fiber and the single-mode output fiber are respectively connected with two ends of the double-clad fiber through light paths;
the double-clad optical fiber is coated with a silicon rubber coating sensitive to acoustic emission vibration, the silicon rubber coating is deformed by external acoustic emission vibration, dynamic phase change is introduced into a cladding mode of the double-clad optical fiber, and acoustic emission parameters are sensed by detecting the resonance filtering characteristic.
The two ends of the double-clad optical fiber are respectively welded with the single-mode input optical fiber and the single-mode output optical fiber to form the filter with the cladding mode resonance coupling characteristic.
The refractive index of the silicon rubber coating is lower than that of the quartz cladding of the double-cladding optical fiber, and the phase change of the optical fiber caused by acoustic emission vibration is sensed.
The double-clad optical fiber comprises a fiber core and an inner cladding coated outside the fiber core, wherein the outer cladding is coated outside the inner cladding; the fiber core mold and the cladding mold of the double-cladding optical fiber interact through evanescent waves, and under the condition that the fiber core mold and the cladding mold meet phase matching, the light energy transmitted in the fiber core is transferred into the cladding layer for transmission, so that cladding mode resonance is realized.
The inner cladding of the double-clad optical fiber is prepared by fluorine-doped silicon oxide.
The refractive index of the core and the outer cladding of the double-clad optical fiber is higher than that of the inner cladding.
In the double-clad optical fiber, the diameter of a fiber core is 9 microns; the outer diameter of the inner cladding is 27 microns; the outer diameter of the outer cladding was 125 microns; the refractive index of the core and the outer cladding is 1.456; the refractive index of the inner cladding is 1.454.
The refractive index of the silicon rubber coating is 1.42; the thickness ranges from 0.1mm to 3 mm.
An acoustic emission signal detection method of the acoustic emission sensor is characterized by comprising the following steps:
the silicon rubber coating of the acoustic emission sensor receives an external acoustic emission signal to deform, so that the double-clad optical fiber is stretched, and the phase change of the clad mode causes the resonance filtering spectrum to move;
and judging and acquiring an external acoustic emission signal according to the change of the light intensity of a light source of the acoustic emission sensor.
The single-mode input optical fiber of the acoustic emission sensor receives an external light source and transmits the external light source to the double-clad optical fiber, and the light source passes through the double-clad optical fiber and then is output to the photoelectric detector through the single-mode output optical fiber.
Compared with the prior art, the acoustic emission sensor and the acoustic emission signal detection method have the advantages that the acoustic emission sensor disclosed by the invention is of an all-fiber structure, and the double-clad fiber and the single-mode fiber can be directly welded by conventional welding equipment, so that the acoustic emission sensor has the advantages of compact structure, simple manufacturing method, convenience in use and the like;
the inner cladding of the double-clad optical fiber can be prepared by fluorine-doped silicon oxide, and has good temperature stability, so that the double-clad optical fiber has the advantage of avoiding temperature cross interference.
Drawings
FIG. 1 is a schematic structural diagram of an acoustic emission sensor according to the present invention;
fig. 2 is a flowchart of a method of an acoustic emission detection method of an acoustic emission sensor according to the present invention.
Detailed Description
The following further describes specific embodiments of the present invention with reference to the drawings.
As shown in fig. 1, the present invention discloses a single mode fiber-double clad fiber-single mode fiber acoustic emission sensor, which comprises: single mode input optical fiber 1, double-clad optical fiber 2, single mode output optical fiber 3 and silicon rubber coating 4.
The double-clad optical fiber 2 includes a core 5, an inner cladding 6 covering the core 5, and an outer cladding 7 covering the inner cladding 6. The inner cladding 6 of the double-clad fiber 2 is prepared from fluorine-doped silica, and has good temperature stability, so that the double-clad fiber has the advantage of avoiding temperature cross interference. And the refractive index of the core 5 and the outer cladding 7 of the double-clad optical fiber 2 is higher than that of the inner cladding 6.
The diameter of the fiber core 5 is 9 microns, the outer diameter of the inner cladding 6 is 27 microns, the outer diameter of the outer cladding 7 is 125 microns, the refractive indexes of the fiber core 5 and the outer cladding 7 are 1.456, and the refractive index of the inner cladding 6 is 1.454.
According to the coupled-mode theory, light is transmitted in two adjacent optical waveguides, and when the transmitted mode meets the phase matching condition, the optical waveguides can realize energy exchange between the two waveguides through evanescent wave mode coupling. The core fiber and the cladding mode of the double-cladding optical fiber 2 disclosed by the invention interact through evanescent waves, and under the condition that the core fiber and the cladding mode meet phase matching, the light energy transmitted in the fiber core is transferred into the cladding layer for transmission, so that cladding mode resonance is realized. Since the phase matching condition of the modal dispersion characteristic is related to the wavelength, i.e., the resonance wavelength, at which the core-mode transmission spectrum exhibits the stop-band filtering characteristic.
The single-mode input optical fiber 1 and the single-mode output optical fiber 3 are welded at two ends of the double-clad optical fiber 2 through an optical fiber welding machine and are communicated with the optical path of the double-clad optical fiber 2 to form the filter with the cladding mode resonance coupling characteristic. Here, the fusion may be performed in a standard single mode fiber fusion mode.
The double-clad optical fiber 2 is coated with a silicone rubber coating 4 sensitive to acoustic emission vibration, the typical value of the refractive index of silicone rubber adopted by the silicone rubber coating 4 is 1.42, the silicone rubber coating 4 completely covers the double-clad optical fiber 2, no special requirement is required for the covering distance between the single-mode input optical fiber 1 and the single-mode output optical fiber 3 at two ends, the double-clad optical fiber can be covered on the single-mode input optical fiber 1 and the single-mode output optical fiber 3, and the coating thickness of the silicone rubber coating 4 is 0.1-3 mm. In this embodiment, the silicone rubber coating 4 may be coated by a pulling method, and after the coating is completed, the silicone rubber coating 4 is naturally cured in the air to complete the preparation of the silicone rubber coating 4. The structure of the silicon rubber coating 4 coated outside the double-clad optical fiber 2 has the characteristic of stop band filtering spectrum, a narrow-band spectrum laser is used as a light source, the output light intensity is modulated by an external acoustic emission vibration signal, and the acoustic emission signal can be detected through the change of the output light intensity.
Therefore, when external acoustic emission vibration acts on the structure, the external acoustic emission vibration enables the silicon rubber coating 4 to deform, and as the refractive index of the silicon rubber coating 4 is lower than that of the quartz cladding of the double-cladding optical fiber 2, dynamic phase change is introduced into the cladding mode of the double-cladding optical fiber 2, the fiber phase change caused by the acoustic emission vibration is sensed, and the acoustic emission parameters are sensed through detection of the resonance filtering characteristic.
As shown in fig. 2, the method for detecting an acoustic emission signal of an acoustic emission sensor according to the present invention specifically includes the following steps:
s1, and outside acoustic emission signals.
S2, transmitting the external acoustic emission signal to the acoustic emission sensor to cause the silicon rubber of the silicon rubber coating 4 of the acoustic emission sensor to deform.
S3, the deformation of the silicone rubber coating 4 causes the double-clad optical fiber 2 to expand and contract.
S4, the double-clad fiber 2 stretches and contracts to cause the phase of the cladding mode of the double-clad fiber 2 to change.
S5, the phase of the cladding mode of the double-clad fiber 2 changes, causing the resonance filtering spectrum to shift.
S6, a single-mode input optical fiber 1 of the acoustic emission sensor receives the light source in real time, the light wave passes through the double-clad optical fiber 2 and is output by a single-mode output optical fiber 3, and the light source passes through the acoustic emission sensor and then is received and detected by a photoelectric detector. The resonant filtering spectral shift causes the intensity of the light wave output through double-clad fiber 2 to change.
And S7, detecting the light intensity change by the photoelectric detector, and acquiring the external acoustic emission signal.
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.
Claims (9)
1. An acoustic emission sensor, comprising: the double-clad fiber, the single-mode input fiber and the single-mode output fiber are respectively connected with two ends of the double-clad fiber through light paths;
the double-clad optical fiber is coated with a silicon rubber coating sensitive to acoustic emission vibration, the silicon rubber coating is deformed by external acoustic emission vibration, dynamic phase change is introduced into a cladding mode of the double-clad optical fiber, and acoustic emission parameters are sensed by detecting the resonance filtering characteristic;
the double-clad optical fiber comprises a fiber core and an inner cladding coated outside the fiber core, wherein the outer cladding is coated outside the inner cladding; the fiber core mold and the cladding mold of the double-cladding optical fiber interact through evanescent waves, and under the condition that the fiber core mold and the cladding mold meet phase matching, the light energy transmitted in the fiber core is transferred into the cladding layer for transmission, so that cladding mode resonance is realized.
2. The acoustic emission sensor of claim 1, wherein the double-clad fiber is fused at each end to a single-mode input fiber and a single-mode output fiber, respectively, to form a filter having a cladding-mode resonant coupling characteristic.
3. The acoustic emission sensor of claim 1, wherein the silicone rubber coating has a refractive index lower than the refractive index of the silica cladding of the double-clad fiber, and sensing acoustic emission vibrations causes a phase change in the fiber.
4. The acoustic emission sensor of claim 1, wherein the inner cladding of the double-clad fiber is made of fluorine-doped silica.
5. The acoustic emission sensor of claim 1, wherein the core and outer cladding of the double-clad fiber have a refractive index higher than the refractive index of the inner cladding.
6. The acoustic emission sensor of claim 1, wherein in the double-clad fiber, the core diameter is 9 microns; the outer diameter of the inner cladding is 27 microns; the outer diameter of the outer cladding was 125 microns; the refractive index of the core and the outer cladding is 1.456; the refractive index of the inner cladding is 1.454.
7. The acoustic emission sensor of claim 1, wherein the silicone rubber coating has a refractive index of 1.42; the thickness ranges from 0.1mm to 3 mm.
8. A method of detecting an acoustic emission signal of an acoustic emission sensor according to any one of claims 1 to 7, the method comprising:
the silicon rubber coating of the acoustic emission sensor receives an external acoustic emission signal to deform, so that the double-clad optical fiber is stretched, and the phase change of the clad mode causes the resonance filtering spectrum to move;
and judging and acquiring an external acoustic emission signal according to the change of the light intensity of a light source of the acoustic emission sensor.
9. The method of claim 8, wherein the single-mode input fiber of the acoustic emission sensor receives an external light source and transmits the external light source to the double-clad fiber, and the light source passes through the double-clad fiber and is output to the photodetector by the single-mode output fiber.
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| CN109827676B (en) * | 2017-11-23 | 2021-06-08 | 桂林电子科技大学 | Single-mode heterogeneous optical fiber cascaded strain array sensor |
| CN109708675B (en) * | 2018-12-13 | 2021-02-26 | 云南电网有限责任公司电力科学研究院 | Optical fiber sensor based on Helmholtz resonator |
| CN110208668B (en) * | 2019-07-10 | 2021-07-20 | 国网上海市电力公司 | Optical fiber acoustic emission vibration sensor and partial discharge sensing system |
| CN112665658B (en) * | 2021-01-20 | 2023-06-09 | 哈尔滨工程大学 | Optical fiber sensor for simultaneously measuring refractive index and temperature and preparation method |
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| CN103234620A (en) * | 2013-04-28 | 2013-08-07 | 哈尔滨理工大学 | Extrinsic optical-fiber F-B (fabry-perot) acoustic-emission sensor, ultrasonic detector containing sensor and use method of detector |
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| CN101236272A (en) * | 2008-02-29 | 2008-08-06 | 上海大学 | Pure quartz core cladding mode resonant special type optical fibre and method for making same |
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