CN213902467U - Temperature and humidity sensor based on fiber bragg grating - Google Patents
Temperature and humidity sensor based on fiber bragg grating Download PDFInfo
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- CN213902467U CN213902467U CN202023340085.8U CN202023340085U CN213902467U CN 213902467 U CN213902467 U CN 213902467U CN 202023340085 U CN202023340085 U CN 202023340085U CN 213902467 U CN213902467 U CN 213902467U
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Abstract
The utility model discloses a temperature and humidity sensor based on fiber bragg grating, which comprises a fiber core, a first fiber cladding and a second fiber cladding which are arranged at intervals and sleeved on the fiber core; the first optical fiber cladding comprises a first section, a second section and a third section which are sequentially connected in the length extending direction of the optical fiber core; the diameter of the first section is equal to that of the third section and is larger than that of the second section; the temperature and humidity sensor further comprises a long-period fiber grating engraved in the fiber core of the second section of the package, a temperature sensitive film wrapped outside the second section, a Bragg fiber grating engraved in the fiber core between the first fiber cladding and the second fiber cladding, and a humidity sensitive film wrapped outside the fiber core between the first fiber cladding and the second fiber cladding. The utility model relates to a temperature and humidity sensor based on fiber grating cascades long period fiber grating and bragg fiber grating, can realize the accurate measurement to the small change of external environment temperature, humidity.
Description
Technical Field
The utility model relates to a sensor field, in particular to temperature and humidity sensor based on fiber grating.
Background
The fiber grating sensor has the advantages of light and small structure, electromagnetic interference resistance, long service life, high response speed, long-distance transmission, high sensitivity, low cost and the like, is concerned by researchers in the sensing technical field in recent years, and becomes a research hotspot. The external environment comprises a plurality of environment parameters such as temperature, humidity and the like, and the specific state of the measured parameters cannot be reflected by directly measuring the drift of the coupling wavelength, so the application and development of the fiber grating in the sensing field are severely restricted. In order to better solve the problem of cross sensitivity, a fiber grating cascade mode is often adopted, and the positions of resonance peaks generated by different environmental parameters can be distinguished, so that specific environmental parameter values are distinguished and restored.
The existing cascade grating structure at present comprises:
the double-Bragg fiber grating (FBG) structure has the advantages of capability of realizing long-distance distributed sensing and relatively low manufacturing cost. The disadvantage is that it is necessary to ensure that the central wavelengths of the two FBGs are sufficiently different, so that two side light emitting diodes (ELEDs) and a spectrometer are required, which is difficult to be put into practical use.
The dual Long Period Fiber Grating (LPFG) structure has an advantage of higher sensitivity to temperature and refractive index than FBG. The disadvantage is that the transmission band is wide, resulting in difficult multiplexing and unfavorable for distributed sensing.
Disclosure of Invention
The utility model aims at providing a temperature and humidity sensor based on fiber grating cascades long period fiber grating and bragg fiber grating, can realize the accurate measurement to the small change of external environment temperature, humidity.
In order to achieve the above purpose, the utility model adopts the technical scheme that:
a temperature and humidity sensor based on fiber bragg grating comprises a fiber core, a first fiber cladding and a second fiber cladding, wherein the first fiber cladding and the second fiber cladding are arranged at intervals and sleeved on the fiber core;
the first optical fiber cladding comprises a first section, a second section and a third section which are sequentially connected in the length extending direction of the optical fiber core; the diameter of the first section is equal to that of the third section and is larger than that of the second section;
the temperature and humidity sensor further comprises a long-period fiber grating engraved in the fiber core of the second section of the package, a temperature-sensitive film wrapped on the outer side of the second section, a Bragg fiber grating engraved in the fiber core between the first fiber cladding and the second fiber cladding, and a humidity-sensitive film wrapped on the outer side of the fiber core between the first fiber cladding and the second fiber cladding.
Preferably, the first section, the second section and the third section are integrally formed, and the second section is a stretching section arranged between the first section and the third section.
More preferably, the diameter of the second section gradually decreases in a direction from both ends toward the center.
Even more preferably, said second section has a length of 1-3cm and a minimum diameter of 60-80 μm.
Preferably, the thickness of the temperature-sensitive film is 50-300 nm.
Preferably, the length of the optical fiber core used for writing the bragg fiber grating is 1-3 cm.
Preferably, the thickness of the moisture-sensitive membrane is 50 to 500 nm.
Because of above-mentioned technical scheme's application, compared with the prior art, the utility model have the following advantage: the utility model relates to a temperature and humidity sensor based on fiber grating, which can realize the accurate measurement of the tiny change of the temperature by reducing the diameter of the fiber cladding (the second section) and wrapping the temperature sensitive film on the second section; the humidity micro-change accurate measurement can be realized by arranging the bare section of the fiber core of the optical fiber and wrapping the humidity sensitive film on the bare section; the positions of the sensing resonance peaks of the long-period fiber grating and the Bragg fiber grating can be respectively changed by changing the lengths of the fiber gratings in the second section and the exposed section, so that the resonance peaks of the two sensing structures are respectively positioned at different positions, and the temperature change and the humidity change of the external environment can be conveniently distinguished by the drift of the resonance peaks. The temperature and humidity sensor has the advantages of high sensitivity, small volume, simple manufacture and electromagnetic interference resistance.
Drawings
Fig. 1 is a schematic structural diagram of the device of the present invention.
Wherein: 1. a fiber core; 2. a second optical fiber cladding; 3. a first stage; 4. a second stage; 5. a third stage; 6. a long-period fiber grating; 7. a temperature sensitive membrane; 8. a Bragg fiber grating; 9. a moisture sensitive membrane.
Detailed Description
The technical solution of the present invention will be further explained with reference to the accompanying drawings.
Referring to fig. 1, the temperature and humidity sensor based on the fiber bragg grating includes a fiber core 1, and a first fiber cladding and a second fiber cladding 2 which are arranged at intervals and sleeved on the fiber core 1. And a bare section of the optical fiber core 1 is arranged between the first optical fiber cladding and the second optical fiber cladding 2. The bare section may be obtained by local etching of the fibre cladding.
The first optical fiber cladding comprises a first section 3, a second section 4 and a third section 5 which are sequentially connected in the length extending direction of the optical fiber core 1; the diameter of the first section 3 is equal to the diameter of the third section 5 and greater than the diameter of the second section 4.
In the present embodiment, referring to fig. 1, there are a first segment 3, a second segment 4 and a third segment 5 from left to right, and the diameter of the first segment 3 is the same as that of the second fiber cladding 2. The first section 3, the second section 4 and the third section 5 are integrally formed, and the second section 4 is a stretching section arranged between the first section 3 and the third section 5. The drawn section may be obtained by fusion tapering the cladding of the optical fiber.
In the present embodiment, the diameter of the second segment 4 is gradually tapered in the direction from both ends toward the center. The second section 4 has a length of 1-3cm and a minimum diameter of 60-80 μm.
The temperature and humidity sensor based on the fiber bragg grating further comprises a long-period fiber bragg grating 6 and a temperature-sensitive film 7, wherein the long-period fiber bragg grating 6 is engraved in the fiber core 1 wrapped by the second section 4, and the temperature-sensitive film 7 is wrapped on the outer side of the second section 4. In this embodiment, the thickness of the temperature-sensitive film 7 is 50-300 nm.
By the tapered long-period fiber bragg grating 6 (LPFG) sensing structure, the energy of the fiber core 1 can be maximally coupled into the fiber cladding (the second section 4) by utilizing the coupling of the fiber core 1 and the fiber cladding (the second section 4) when the phase matching condition is met, and the tapered structure of the fiber cladding (the second section 4) and the surface of the tapered structure are coated with the temperature-sensitive film 7, so that the influence of the change of the external environment on the drift of the resonance peak is more severe, and the sensitivity is higher.
The temperature and humidity sensor based on the fiber bragg grating further comprises a fiber bragg grating 8 and a humidity sensitive film 9, wherein the fiber bragg grating 8 is engraved in the bare fiber core 1 between the first fiber cladding and the second fiber cladding 2, and the humidity sensitive film 9 is wrapped on the outer side of the bare fiber core 1. In the present embodiment, the length of the bare optical fiber core 1 is 1-3 cm; the thickness of the moisture-sensitive membrane 9 is 50 to 500 nm.
Through this bare bragg fiber grating 8 (FBG) sensing structure, utilize the coupling of preceding fiber core 1 and backward fiber core 1, when satisfying the phase matching condition, the energy of bare fiber core 1 can reflect back to the maximize, through coating moisture sensitive membrane 9 for external environment's change is more violent to its influence that the resonance peak drifted, and sensitivity is higher.
Through this LPFG and FBG cascade structure, can make two narrow band waves appear in the reflectance spectrum, the narrow band wave center wavelength of the great department of wavelength receives FBG to influence, and the narrow band wave center wavelength of the less department of wavelength receives FBG and LPFG to influence jointly, and the light intensity of two ripples receives FBG and LPFG simultaneously influences. Therefore, for the LPFG and FBG cascaded structure, the dual-parameter measurement can be carried out at the same time only by observing the reflection spectrum.
This temperature and humidity sensor's advantage lies in:
the optimized cascade structure of the LPFG and the FBG, the tapered structure adopted by the LPFG and the temperature-sensitive film 7 coated on the optical fiber cladding (the second section 4) can greatly improve the detection sensitivity to temperature; the FBG sensing structure with the bare optical fiber core 1 and the humidity sensitive film 9 coated on the bare optical fiber core 1 can improve the detection sensitivity to humidity; the two structures are cascaded, can simultaneously detect the transformation of temperature and humidity and are not interfered with each other.
The temperature and humidity sensor is a fiber grating sensor, has the characteristics of electromagnetic interference resistance and chemical corrosion resistance, can be applied to severe environments such as the power field and the oil gas detection field, is safe and reliable, and has small size and wide application.
When measuring, one end of the temperature and humidity sensor is connected with the broadband light source, and the other end of the temperature and humidity sensor is connected with the spectrometer. Light is emitted from the broadband light source and is transmitted to the sensor with the LPFG and FBG cascade structure, finally, a light signal is input into the spectrometer, and changes of resonant wavelengths respectively corresponding to the LPFG and the FBG are analyzed through a spectrum so as to obtain changes of external environment temperature and humidity, and finally, the purpose of simultaneously measuring the external environment temperature and the external environment humidity is achieved.
The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose of the embodiments is to enable people skilled in the art to understand the contents of the present invention and to implement the present invention, which cannot limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered by the protection scope of the present invention.
Claims (7)
1. The utility model provides a temperature and humidity sensor based on fiber grating which characterized in that: the optical fiber comprises an optical fiber core, a first optical fiber cladding and a second optical fiber cladding which are arranged at intervals and sleeved on the optical fiber core;
the first optical fiber cladding comprises a first section, a second section and a third section which are sequentially connected in the length extending direction of the optical fiber core; the diameter of the first section is equal to that of the third section and is larger than that of the second section;
the temperature and humidity sensor further comprises a long-period fiber grating engraved in the fiber core of the second section of the package, a temperature-sensitive film wrapped on the outer side of the second section, a Bragg fiber grating engraved in the fiber core between the first fiber cladding and the second fiber cladding, and a humidity-sensitive film wrapped on the outer side of the fiber core between the first fiber cladding and the second fiber cladding.
2. The temperature and humidity sensor based on the fiber bragg grating as claimed in claim 1, wherein: the first section, the second section and the third section are integrally formed, and the second section is a stretching section arranged between the first section and the third section.
3. The temperature and humidity sensor based on the fiber bragg grating as claimed in claim 2, wherein: the diameter of the second section is gradually reduced along the direction from the two ends to the center.
4. The temperature and humidity sensor based on the fiber bragg grating as claimed in claim 3, wherein: the length of the second section is 1-3cm, and the minimum diameter is 60-80 μm.
5. The temperature and humidity sensor based on the fiber bragg grating as claimed in claim 1, wherein: the thickness of the temperature-sensitive film is 50-300 nm.
6. The temperature and humidity sensor based on the fiber bragg grating as claimed in claim 1, wherein: the length of the optical fiber core for writing the Bragg fiber grating is 1-3 cm.
7. The temperature and humidity sensor based on the fiber bragg grating as claimed in claim 1, wherein: the thickness of the humidity sensitive membrane is 50-500 nm.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202023340085.8U CN213902467U (en) | 2020-12-31 | 2020-12-31 | Temperature and humidity sensor based on fiber bragg grating |
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| CN202023340085.8U CN213902467U (en) | 2020-12-31 | 2020-12-31 | Temperature and humidity sensor based on fiber bragg grating |
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| CN213902467U true CN213902467U (en) | 2021-08-06 |
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