CN113945542B - Optical fiber sensor, detection device based on optical fiber sensor and application of detection device - Google Patents
Optical fiber sensor, detection device based on optical fiber sensor and application of detection device Download PDFInfo
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 158
- 238000001514 detection method Methods 0.000 title claims abstract description 43
- 239000000835 fiber Substances 0.000 claims abstract description 98
- 239000010453 quartz Substances 0.000 claims abstract description 17
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 17
- 238000003466 welding Methods 0.000 claims description 14
- 239000007788 liquid Substances 0.000 claims description 11
- 230000003595 spectral effect Effects 0.000 claims description 10
- 230000003287 optical effect Effects 0.000 claims description 9
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- 230000005540 biological transmission Effects 0.000 claims description 6
- 230000005684 electric field Effects 0.000 claims description 4
- 238000007499 fusion processing Methods 0.000 claims 1
- 230000004927 fusion Effects 0.000 description 18
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 16
- 230000000694 effects Effects 0.000 description 9
- 230000035945 sensitivity Effects 0.000 description 9
- 239000011780 sodium chloride Substances 0.000 description 8
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- 238000007526 fusion splicing Methods 0.000 description 4
- 235000014820 Galium aparine Nutrition 0.000 description 3
- 240000005702 Galium aparine Species 0.000 description 3
- 230000008878 coupling Effects 0.000 description 3
- 238000010168 coupling process Methods 0.000 description 3
- 238000005859 coupling reaction Methods 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000006870 function Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 206010070834 Sensitisation Diseases 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
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- 238000012544 monitoring process Methods 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000001448 refractive index detection Methods 0.000 description 1
- 230000008313 sensitization Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods
- G01N2021/458—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods using interferential sensor, e.g. sensor fibre, possibly on optical waveguide
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Abstract
The application discloses an optical fiber sensor, a detection device based on the optical fiber sensor and application thereof, wherein the optical fiber sensor comprises: a single mode fiber jumper, a C-type fiber section and a single mode fiber section; the diameter of the inner cavity of the C-shaped optical fiber section is 10-80 mu m, the outer diameter of the C-shaped optical fiber section is 122-127 mu m, and the opening angle alpha of the inner cavity of the C-shaped optical fiber section is 30-120 DEG; the outer diameter of the C-shaped optical fiber section is the same as that of the single-mode optical fiber section; and two ends of the C-shaped optical fiber are respectively welded with the single-mode optical fiber to form a first light reflecting surface and a second light reflecting surface, and the tail end surface of the single-mode optical fiber section forms a third light reflecting surface. The first light reflecting surface and the second light reflecting surface form an inflatable Fabry-Perot resonant cavity; the second light reflecting surface and the third light reflecting surface form a quartz Fabry-Perot resonant cavity. Meanwhile, the detection device based on the optical fiber sensor and application thereof are also provided. The application is mainly used in the technical field of optical fiber sensing.
Description
Technical Field
The application relates to the technical field of optical fiber sensors, in particular to an optical fiber sensor, a detection device based on the optical fiber sensor and application thereof.
Background
Optical fiber-based gas and liquid refractive index sensing has received much attention due to its advantages of electromagnetic interference resistance, small size, light weight, corrosion resistance, etc. Representative sensors include fabry-perot interferometer type sensors, mach-zehnder interferometer type sensors, michelson interferometer type sensors, fiber grating sensors, and the like. Optical fiber sensing detects various parameters such as temperature, strain, humidity, gas by monitoring changes in optical power, phase and polarization state in the optical fiber. However, the sensitivity of these sensors is generally low, as in the air pressure sensor based on hollow-core photonic bandgap fiber side-open channel fabry-perot interferometer proposed by Jian Tan et al, the air pressure sensitivity is only 1462nm/RIU. Fangda Yu et al propose a core-shifted in-line Mach-Zehnder fiber temperature sensor with a temperature sensitivity of only 20nm/RIU. Furthermore Ruohui Wang et al propose an open cavity fabry-perot Luo Qiti refractive index sensor with a sensitivity of only 1042nm/RIU. Therefore, it is of great importance to explore new optical fiber sensing sensitization mechanisms.
Disclosure of Invention
The present application is directed to an optical fiber sensor, a detection device based on the optical fiber sensor and application thereof, which solve one or more technical problems existing in the prior art, and at least provide a beneficial choice or creation condition.
The application solves the technical problems as follows: in a first aspect, there is provided a fiber optic sensor comprising: a single mode fiber jumper, a C-type fiber section and a single mode fiber section; the diameter of the inner cavity of the C-shaped optical fiber section is 10-80 mu m, the outer diameter of the C-shaped optical fiber section is 122-127 mu m, and the opening angle alpha of the inner cavity of the C-shaped optical fiber section is 30-120 DEG; the outer diameter of the C-shaped optical fiber section is the same as that of the single-mode optical fiber section; the head end face of the C-shaped optical fiber section is welded with one end face of a single-mode optical fiber jumper; the tail end face of the C-shaped optical fiber section is welded with the head end face of the single-mode optical fiber section;
the fiber core surface of one end surface of the single-mode fiber jumper wire forms a first light reflecting surface, the fiber core surface of the head end surface of the single-mode fiber section forms a second light reflecting surface, and the fiber core surface of the tail end surface of the single-mode fiber section forms a third light reflecting surface;
the first light reflecting surface and the second light reflecting surface form an inflatable Fabry-Perot resonant cavity; the second light reflecting surface and the third light reflecting surface form a quartz Fabry-Perot resonant cavity; the cavity length of the C-shaped optical fiber section is between 150 and 250 mu m, and the cavity length of the single-mode optical fiber section is between 150 and 250 mu m; the optical path difference between the two cavities is between 0 μm and 30 μm.
Further, the tail end face of the C-shaped optical fiber section is welded with the head end face of the single-mode optical fiber section, wherein the welding process comprises the following steps: welding with a 297bit discharge power by an optical fiber welding machine, wherein the discharge time is 300ms to 500ms.
In a second aspect, there is provided a detection device based on an optical fiber sensor, comprising: the device comprises a laser light source, an optical fiber circulator, a spectrometer and an optical fiber sensor;
the optical fiber sensor includes: a single mode fiber jumper, a C-type fiber section and a single mode fiber section; the diameter of the inner cavity of the C-shaped optical fiber section is 10-80 mu m, the outer diameter of the C-shaped optical fiber section is 122-127 mu m, and the opening angle alpha of the inner cavity of the C-shaped optical fiber section is 30-120 DEG; the outer diameter of the C-shaped optical fiber section is the same as that of the single-mode optical fiber section; the head end face of the C-shaped optical fiber section is welded with one end face of a single-mode optical fiber jumper; the tail end face of the C-shaped optical fiber section is welded with the head end face of the single-mode optical fiber section;
the fiber core surface of one end surface of the single-mode fiber jumper wire forms a first light reflecting surface, the fiber core surface of the head end surface of the single-mode fiber section forms a second light reflecting surface, and the fiber core surface of the tail end surface of the single-mode fiber section forms a third light reflecting surface;
the first light reflecting surface and the second light reflecting surface form an inflatable Fabry-Perot resonant cavity; the second light reflecting surface and the third light reflecting surface form a quartz Fabry-Perot resonant cavity; the cavity length of the C-shaped optical fiber section is between 150 and 250 mu m, and the cavity length of the single-mode optical fiber section is between 150 and 250 mu m; the optical path difference of the two cavities is between 0 and 30 mu m;
the second port of the optical fiber circulator is connected with the other end of the single-mode optical fiber jumper; the first port of the optical fiber circulator is connected with the output end of the laser light source; and a third port of the optical fiber circulator is connected with the input end of the spectrometer.
Further, the tail end face of the C-shaped optical fiber section is welded with the head end face of the single-mode optical fiber section, wherein the welding process comprises the following steps: welding with a 297bit discharge power by an optical fiber welding machine, wherein the discharge time is 300ms to 500ms.
Further, the laser light source emits laser light of a continuous wavelength, and the wavelength range of the continuous wavelength emitted by the laser light source is 480nm to 2200nm.
In a third aspect, an application of the optical fiber sensor-based detection device is provided, where the optical fiber sensor-based detection device described in the above technical solution is applied to detection of a refractive index of a liquid, detection of an air pressure, and detection of a refractive index of air.
The beneficial effects of the application are as follows: in the first aspect, the optical fiber sensor uses a serial double-resonant cavity structure, simplifies the structure of the Fabry-Perot interferometer sensor based on vernier effect on the basis of improving sensitivity, simplifies the preparation process and reduces the production cost. The large opening open cavity formed by the structure of the C-shaped optical fiber section can enable some transparent liquid and even liquid with larger viscosity to flow rapidly so as to realize rapid and real-time sensing. The function which can not be realized by the small fluid channel cavity opening structure is realized. In a second aspect and a third aspect, a detection device based on an optical fiber sensor is provided, which improves the detection sensitivity of the refractive index of the liquid and the detection sensitivity of the air pressure and the refractive index.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings that are required to be used in the description of the embodiments will be briefly described below. It is evident that the drawings described are only some embodiments of the application, but not all embodiments, and that other designs and drawings can be obtained from these drawings by a person skilled in the art without inventive effort.
FIG. 1 is a schematic diagram of a fiber optic sensor;
FIG. 2 is a schematic cross-sectional view of a segment of a C-type optical fiber;
FIG. 3 is a schematic diagram of the structure of the optical fiber sensor-based detection device when applied to NaCl solution detection;
FIG. 4 is a schematic diagram of the structure of an optical fiber sensor-based detection device applied to an air pressure detection device;
FIG. 5 shows a spectral drift curve obtained by NaCl solution concentration detection;
fig. 6 is a spectral drift curve obtained by air pressure detection.
Detailed Description
The conception, specific structure, and technical effects produced by the present application will be clearly and completely described below with reference to the embodiments and the drawings to fully understand the objects, features, and effects of the present application. It is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments, and that other embodiments obtained by those skilled in the art without inventive effort are within the scope of the present application based on the embodiments of the present application. In addition, all coupling/connection relationships mentioned herein do not refer to direct connection of the components, but rather, refer to the fact that a more optimal coupling structure may be formed by adding or subtracting coupling aids depending on the particular implementation. The technical features in the application can be interactively combined on the premise of no contradiction and conflict.
Embodiment 1, referring to fig. 1 and 2, an optical fiber sensor includes: a single mode fiber jumper 200, a C-type fiber segment 100, and a single mode fiber segment 300; the diameter of the inner cavity 110 of the C-shaped optical fiber section 100 is 10-80 μm, the outer diameter of the C-shaped optical fiber section 100 is 122-127 μm, and the opening angle alpha of the inner cavity 110 of the C-shaped optical fiber section 100 is 30-120 degrees; the outer diameter of the C-shaped optical fiber section 100 is the same as the outer diameter of the single-mode optical fiber section 300; the head end surface of the C-shaped optical fiber section 100 is welded with one end surface of a single-mode optical fiber jumper 200; the tail end surface of the C-shaped optical fiber segment 100 is welded with the head end surface of the single-mode optical fiber segment 300;
a first light reflecting surface 101 is formed on a core surface of one end surface of the single-mode fiber jumper 200, a second light reflecting surface 102 is formed on a core surface of the head end surface of the single-mode fiber section 300, and a third light reflecting surface 103 is formed on a core surface of the tail end surface of the single-mode fiber section 300;
the first light reflecting surface 101 and the second light reflecting surface 102 form an aerated fabry-perot resonator; the second light reflecting surface 102 and the third light reflecting surface 103 form a quartz Fabry-Perot resonant cavity; the cavity length of the C-shaped optical fiber section is between 150 and 250 mu m, and the cavity length of the single-mode optical fiber section is between 150 and 250 mu m; the optical path difference between the two cavities is between 0 μm and 30 μm. Where the optical path is the product of the geometrical path of light propagation in the medium and the refractive index of light in the medium.
In some preferred embodiments, the trailing end face of the C-shaped fiber segment 100 is fusion spliced to the leading end face of the single-mode fiber segment 300, wherein the fusion splicing process comprises: the C-type optical fiber segment 100 and the single-mode optical fiber segment 300 are first fusion-spliced by an optical fiber fusion splicer, and then fusion-spliced by the optical fiber fusion splicer at a discharge power of 297bit for 300ms to 500ms. To ensure adequate fusion. The welding power and the discharging time are required to be well controlled, and if the welding time is too long or the power is too high, the ideal effect cannot be achieved. After the fusion splice is completed, the spliced C-type fiber segment 100 and single-mode fiber segment 300 are then cut to the desired lengths using a fiber cutter.
In practice, the fusion splicer is of the type (fujikura, FSM-100M), the single mode fiber segment 300 is of the type (G652D), and the fiber cleaver is of the type (SUMITOMO ELECTRIC INDUSTRIES, LTD, FC-6S).
The working principle of the optical fiber sensor is as follows:
wherein, the cavity length of the inflatable Fabry-Perot resonant cavity is L 1 The cavity length of the quartz Fabry-Perot resonant cavity is L 2 The refractive index of the object to be measured in the cavity of the C-shaped optical fiber segment 100 is n 1 The core refractive index of the single mode fiber segment 300 is n 2 Since the C-shaped fiber segment 100 is a structure having an open cavity 110, the refractive index of the C-shaped fiber segment 100 is based on the effective refractive index of the measurement object.
The sensing principle of the optical fiber sensor probe is the working principle of a high-sensitivity Fabry-Perot interferometer based on vernier effect.
The method comprises the following steps: calculating the whole reflected electric field:
wherein:
φ 1 ＝2πn 1 L 1 /λ，
φ 2 ＝2πn 2 L 2 /λ，
Ei n is the electric field input into the optical fiber sensing probe, k 1 Transmission loss, k of an aerated fabry-perot resonator 2 Is the transmission loss of the quartz Fabry-Perot resonant cavity, R 1 Is the reflection coefficient of the first light reflection surface 101, R 2 Is the reflection coefficient of the second light reflecting surface 102, R 3 Is the reflection coefficient of the third light reflection surface 103. Phi (phi) 1 Is the phase of transmission in the aerated fabry-perot resonator, phi 2 Is the phase of light transmitted in a quartz fabry-perot resonator. n1 is the refractive index of the object to be measured in the cavity of the C-type optical fiber segment 100, n 2 Is the refractive index of the 300 fiber core of the single mode fiber segment, L 1 Is the cavity length, L, of an inflatable Fabry-Perot resonant cavity 2 Is the cavity length of the quartz Fabry-Perot resonant cavity, and lambda is the wavelength of the input light.
Since the C-shaped fiber segment 100 is a structure having an open cavity 110, the effective refractive index of the C-shaped fiber segment 100 is based on the refractive index of the measurement object.
The function of the reflection spectrum received from spectrometer 430 can be derived from equation (1):
the refractive index n can be known by the formula (2) 1 The variation of (a) results in a phase phi 1 Changes occur, resulting in spectral shifts. In order to generate vernier effect, the optical paths of the gas filled Fabry-Perot resonant cavity and the quartz Fabry-Perot resonant cavity are very close but not equal.
The experimental spectrum is the superposition of the spectrums of two independent Fabry-Perot cavities of the gas-filled Fabry-Perot resonant cavity and the quartz Fabry-Perot resonant cavity. Because the FSR (distance between two wave troughs of interference fringes) of each spectrum of the gas filled Fabry-Perot resonant cavity and the quartz Fabry-Perot resonant cavity has small phase difference, a large envelope appears in the superimposed spectrums, which is a vernier effect. The so-called envelope is obtained by connecting the valleys of the high frequency fringes.
On the other hand, referring to fig. 3, fig. 3 is a schematic diagram of a structure of a detection device based on an optical fiber sensor when applied to NaCl solution detection.
The embodiment also provides a detection device based on the optical fiber sensor, which comprises: the laser light source 420, the fiber optic circulator 410, the spectrometer 430 and the fiber optic sensor, which is referred to herein as the liquid refractive index detection fiber optic sensor probe 501 for convenience in distinguishing between different media to be detected;
the liquid refractive index fiber optic sensor probe 501 includes: a single mode fiber jumper 200, a C-type fiber segment 100, and a single mode fiber segment 300; the diameter of the inner cavity 110 of the C-shaped optical fiber section 100 is 10-80 μm, the outer diameter of the C-shaped optical fiber section 100 is 122-127 μm, and the opening angle alpha of the inner cavity 110 of the C-shaped optical fiber section 100 is 30-120 degrees; the outer diameter of the C-shaped optical fiber section 100 is the same as the outer diameter of the single-mode optical fiber section 300; the head end surface of the C-shaped optical fiber section 100 is welded with one end surface of a single-mode optical fiber jumper 200; the tail end surface of the C-shaped optical fiber segment 100 is welded with the head end surface of the single-mode optical fiber segment 300;
a first light reflecting surface 101 is formed on a core surface of one end surface of the single-mode fiber jumper 200, a second light reflecting surface 102 is formed on a core surface of the head end surface of the single-mode fiber section 300, and a third light reflecting surface 103 is formed on a core surface of the tail end surface of the single-mode fiber section 300;
the first light reflecting surface 101 and the second light reflecting surface 102 form an aerated fabry-perot resonator; the second light reflecting surface 102 and the third light reflecting surface 103 form a quartz Fabry-Perot resonant cavity; the cavity length of the C-shaped optical fiber section is between 150 and 250 mu m, and the cavity length of the single-mode optical fiber section is between 150 and 250 mu m; the optical path difference between the two cavities is between 0 μm and 30 μm.
The second port of the optical fiber circulator 410 is connected with the other end of the single-mode optical fiber jumper 200; the first port of the fiber optic circulator 410 is connected to the output end of the laser source 420; the third port of the fiber optic circulator 410 is connected to an input port of a spectrometer 430.
Wherein the laser light source 420 emits laser light with continuous wavelength, and the wavelength range of the continuous wavelength emitted by the laser light source 420 is 480nm to 2200nm.
In some preferred embodiments, the trailing end face of the C-shaped fiber segment 100 is fusion spliced to the leading end face of the single-mode fiber segment 300, wherein the fusion splicing process comprises: the C-type optical fiber segment 100 and the single-mode optical fiber segment 300 are fused by an optical fiber fusion splicer, and the fusion splicing time is 300ms to 500ms by the optical fiber fusion splicer with the discharge power of 297 bit. To ensure adequate fusion. The welding power and the discharging time are required to be well controlled, and if the welding time is too long or the power is too high, the ideal effect cannot be achieved. After the fusion splice is completed, the spliced C-type fiber segment 100 and single-mode fiber segment 300 are then cut to the desired lengths using a fiber cutter.
In practice, the fusion splicer is of the type (fujikura, FSM-100M), the single mode fiber segment 300 is of the type (G652D), and the fiber cleaver is of the type (SUMITOMO ELECTRIC INDUSTRIES, LTD, FC-6S).
When the optical fiber sensor-based detection device is applied to the detection of NaCl solution, the liquid refractive index optical fiber sensor probe 501 is firstly placed in a container 440 for containing NaCl solution, and the container 440 for containing NaCl solution is placed in a NaCl solution with a certain concentration.
The NaCl solution concentration (mass fraction) was then increased from 0% to 0.1% with a gradient of 0.01% and the spectral shift was recorded by spectrometer 430 and fitted linearly to the spectral shift to give a spectral shift curve as shown in fig. 5. From FIG. 5, it is understood that the sensitivity of the liquid concentration experiment reached 44000nm/RIU. Wherein the abscissa of the spectral drift curve is the wavelength and the ordinate is the light intensity.
On the other hand, referring to fig. 4, fig. 4 is a schematic structural view of an application of the optical fiber sensor-based detecting device to an air pressure detecting device.
The embodiment also provides a detection device based on the optical fiber sensor, which comprises: the laser light source 420, the fiber optic circulator 410, the spectrometer 430 and the fiber optic sensor, which is referred to herein as the air pressure fiber optic sensor probe 502 for convenience in distinguishing between different media to be detected;
the air pressure fiber optic sensor probe 502 includes: a single mode fiber jumper 200, a C-type fiber segment 100, and a single mode fiber segment 300; the diameter of the inner cavity 110 of the C-shaped optical fiber section 100 is 10-80 μm, the outer diameter of the C-shaped optical fiber section 100 is 122-127 μm, and the opening angle alpha of the inner cavity 110 of the C-shaped optical fiber section 100 is 30-120 degrees; the outer diameter of the C-shaped optical fiber section 100 is the same as the outer diameter of the single-mode optical fiber section 300; the head end surface of the C-shaped optical fiber section 100 is welded with one end surface of a single-mode optical fiber jumper 200; the tail end surface of the C-shaped optical fiber segment 100 is welded with the head end surface of the single-mode optical fiber segment 300;
a first light reflecting surface 101 is formed on a core surface of one end surface of the single-mode fiber jumper 200, a second light reflecting surface 102 is formed on a core surface of the head end surface of the single-mode fiber section 300, and a third light reflecting surface 103 is formed on a core surface of the tail end surface of the single-mode fiber section 300;
the first light reflecting surface 101 and the second light reflecting surface 102 form an aerated fabry-perot resonator; the second light reflecting surface 102 and the third light reflecting surface 103 form a quartz Fabry-Perot resonant cavity; the cavity length of the C-shaped optical fiber section is between 150 and 250 mu m, and the cavity length of the single-mode optical fiber section is between 150 and 250 mu m; the optical path difference between the two cavities is between 0 μm and 30 μm.
The second port of the optical fiber circulator 410 is connected with the other end of the single-mode optical fiber jumper 200; the first port of the fiber optic circulator 410 is connected to the output end of the laser source 420; the third port of the fiber optic circulator 410 is connected to an input port of a spectrometer 430.
Wherein the laser light source 420 emits laser light with continuous wavelength, and the wavelength range of the continuous wavelength emitted by the laser light source 420 is 480nm to 2200nm.
In some preferred embodiments, the trailing end face of the C-shaped fiber segment 100 is fusion spliced to the leading end face of the single-mode fiber segment 300, wherein the fusion splicing process comprises: the C-type optical fiber segment 100 and the single-mode optical fiber segment 300 are first fusion-spliced by an optical fiber fusion splicer, and then fusion-spliced by the optical fiber fusion splicer at a discharge power of 297bit for 300ms to 500ms. To ensure adequate fusion. The welding power and the discharging time are required to be well controlled, and if the welding time is too long or the power is too high, the ideal effect cannot be achieved. After the fusion splice is completed, the spliced C-type fiber segment 100 and single-mode fiber segment 300 are then cut to the desired lengths using a fiber cutter.
In practice, the fusion splicer is of the type (fujikura, FSM-100M), the single mode fiber segment 300 is of the type (G652D), and the fiber cleaver is of the type (SUMITOMO ELECTRIC INDUSTRIES, LTD, FC-6S).
When the optical fiber sensor-based detection device is applied to the air pressure detection device, firstly, the air pressure optical fiber sensor probe 502 is placed in the air chamber 450 and sealed, the air pressure in the air chamber 450 is controlled to be reduced from 0.8Mpa to 0Mpa by the air pump 460, and the spectrum drift is recorded by the spectrometer 430 with 0.08Mpa as a gradient, so that a spectrum drift curve is obtained, as shown in fig. 6. As can be seen from fig. 6, the envelope profile moves uniformly in the long wave direction when the pressure gradually decreases from 0.8Mpa to 0 Mpa. To evaluate the linearity of the proposed detection device, a linear fit to the spectral shift is made by tracking the movement of the envelope trough with pressure. The result shows that the pressure linearity of the detection device is good, and the sensitivity is 43000nm/RIU. Wherein the abscissa of the spectral drift curve is the wavelength and the ordinate is the light intensity.
Through the conversion relation between the air pressure and the air refractive index, the air refractive index can be obtained from the obtained air pressure, so that the air refractive index is detected.
While the preferred embodiment of the present application has been described in detail, the application is not limited to the embodiments, and various equivalent modifications and substitutions can be made by those skilled in the art without departing from the spirit of the application, and these modifications and substitutions are intended to be included in the scope of the present application as defined in the appended claims.
Claims (3)
1. The application of a detection device based on an optical fiber sensor comprises a laser light source, an optical fiber circulator, a spectrometer and the optical fiber sensor; the optical fiber sensor includes: a single mode fiber jumper, a C-type fiber section and a single mode fiber section; the diameter of the inner cavity of the C-shaped optical fiber section is 10-80 mu m, the outer diameter of the C-shaped optical fiber section is 122-127 mu m, and the opening angle alpha of the inner cavity of the C-shaped optical fiber section is 30-120 DEG; the outer diameter of the C-shaped optical fiber section is the same as that of the single-mode optical fiber section; the head end face of the C-shaped optical fiber section is welded with one end face of a single-mode optical fiber jumper; the tail end face of the C-shaped optical fiber section is welded with the head end face of the single-mode optical fiber section; the fiber core surface of one end surface of the single-mode fiber jumper wire forms a first light reflecting surface, the fiber core surface of the head end surface of the single-mode fiber section forms a second light reflecting surface, and the fiber core surface of the tail end surface of the single-mode fiber section forms a third light reflecting surface; the first light reflecting surface and the second light reflecting surface form an inflatable Fabry-Perot resonant cavity; the second light reflecting surface and the third light reflecting surface form a quartz Fabry-Perot resonant cavity; the cavity length of the C-shaped optical fiber section is between 150 and 250 mu m, and the cavity length of the single-mode optical fiber section is between 150 and 250 mu m; the optical path difference of the two cavities is between 0 and 30 mu m; the second port of the optical fiber circulator is connected with the other end of the single-mode optical fiber jumper; the first port of the optical fiber circulator is connected with the output end of the laser light source; the third port of the optical fiber circulator is connected with the input end of the spectrometer;
the method is characterized in that a detection device based on an optical fiber sensor is applied to detection of liquid refractive index, detection of air pressure and detection of air refractive index, the refractive index of the C-shaped optical fiber section is the effective refractive index based on a measured object, and the whole reflected electric field is calculated:
wherein:
φ 1 ＝2πn 1 L 1 /λ，
φ 2 ＝2πn 2 L 2 /λ，
wherein E is in Is the electric field input into the optical fiber sensing probe, k 1 Transmission loss, k of an aerated fabry-perot resonator 2 Is the transmission loss of the quartz Fabry-Perot resonant cavity, R 1 Is the reflection coefficient of the first light reflection surface 101, R 2 Is the reflection coefficient of the second light reflecting surface 102, R 3 Is the reflection coefficient of the third light reflection surface 103, phi 1 Is the phase of transmission in the aerated fabry-perot resonator, phi 2 Is the phase of light transmitted in the quartz Fabry-Perot resonant cavity, n1 is the refractive index of the object to be measured in the cavity of the C-type optical fiber segment 100, n 2 Is the refractive index of the 300 fiber core of the single mode fiber segment, L 1 Is the cavity length, L, of an inflatable Fabry-Perot resonant cavity 2 Is the cavity length of the quartz Fabry-Perot resonant cavity, and lambda is the wavelength of input light;
calculating a function of the reflection spectrum received from the spectrometer:
the detection of the refractive index of the liquid, the detection of the air pressure and the detection of the refractive index of the air are performed based on the spectral drift curve.
2. The use of a fiber optic sensor based detection apparatus according to claim 1, wherein the trailing end face of the C-shaped fiber section is fused to the leading end face of the single-mode fiber section, wherein the fusion process comprises: welding with a 297bit discharge power by an optical fiber welding machine, wherein the discharge time is 300ms to 500ms.
3. Use of a detection device based on an optical fiber sensor according to claim 1, characterized in that: the laser light source emits laser light with continuous wavelength, and the wavelength range of the continuous wavelength emitted by the laser light source is 480nm to 2200nm.
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