CN104568217A - High-pressure-resistant high-precision FBG (fiber Bragg grating) temperature sensing method - Google Patents
High-pressure-resistant high-precision FBG (fiber Bragg grating) temperature sensing method Download PDFInfo
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- CN104568217A CN104568217A CN201410828694.8A CN201410828694A CN104568217A CN 104568217 A CN104568217 A CN 104568217A CN 201410828694 A CN201410828694 A CN 201410828694A CN 104568217 A CN104568217 A CN 104568217A
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Abstract
The invention relates to a high-pressure-resistant high-precision FBG (fiber Bragg grating) temperature sensing method. The method comprises steps as follows: (1) an FBG is packaged to be produced into a sensor: packaging structural components comprise a pressure-resistant casing, an adaptor, a pigtail protection sleeve and an optical fiber protection sleeve, the FBG is fixed at a single end inside the pressure-resistant casing, a grid region is in a completely free state, and double-sealing treatment is performed at the tail of the pressure-resistant casing and between the pressure-resistant casing and the adaptor with laser welding and high-strength sealant application methods; (2) during calibration of the sensor, temperature calculation is performed by the aid of the measured wavelength with a temperature and FBG wavelength quadratic fitting method, and a temperature calculation equation of the sensor is T=a*lambda*lambda+b*lambda+C. The method has the benefit as follows: the pressure resistance is high. The FBG temperature sensor can withstand the pressure not less than 25 MPa, that is, the sensor can be applied to submarine temperature measurement at the depth exceeding 2000 m.
Description
Technical field
The invention belongs to fiber grating sensing technology field, be specifically related to a kind of high pressure resistant, high precision optical fiber grating temperature sensing method.
Background technology
Ocean temperature is the physical quantity reflecting that seawater situation is the most basic, and the measurement of ocean temperature is all of great significance aspects such as research thalassography, marine environmental monitoring, seasonal climate forecast, sea fishery, military affairs.Traditional sensors major part for marine temperature measurement is based on electricity structure, such as platinum resistance, thermistor.Platinum resistance temperature sensor has good stability, precision is high, but it is non-linear larger; Thermistor structure is simple, low price, measures than the low accurate temperature be more suitable in daily life.
Compared to traditional electricity temperature sensor, fiber-optical grating temperature sensor has outside the advantages such as electromagnetism interference, volume be little, lightweight, also have can bury, the life-span is long, reusability good, can form the characteristics such as quasi-distributed sensor network.Therefore, fiber-optical grating temperature sensor is widely used in the engineering fields such as dam, bridge, tunnel, mine.
In the ocean temperature for the degree of depth comparatively large (as the degree of depth is greater than the seabed of 2000m) is measured, temperature variation is very little, and this just requires that temperature sensor has very high compressive resistance and temperature measurement accuracy.
Summary of the invention
The object of the invention is to the deficiency overcoming prior art existence, and a kind of high pressure resistant, high precision optical fiber grating temperature sensing method is provided.
The object of the invention is to have come by following technical solution.This high pressure resistant, high precision optical fiber grating temperature sensing method, the method step is as follows:
(1), encapsulation is carried out to fiber grating and make sensor: the structural member of encapsulation comprises pressure casing, adaptor, tail optical fiber protective sleeve and optical fiber jacket, fiber grating is single-ended fixing in pressure casing, grid region is complete free state, at the afterbody of pressure casing, all adopts the additional mode of smearing high-intensity sealing glue of laser bonding to carry out double seal process between pressure casing and adaptor;
(2), carrying out in calibration process to sensor, adopting the method for temperature and optic fiber grating wavelength quadratic fit, utilize the wavelength recorded to carry out temperature and resolve, the temperature solution formula of sensor is:
T＝a*λ*λ+b*λ+C
In formula, a, b are respectively quadratic term coefficient and the Monomial coefficient of temperature and optic fiber grating wavelength quadratic fit, and λ is the real-time optical fiber grating wavelength that sensor records, and C is constant.
Described fiber grating is bragg grating, and reflectivity is not less than 80%, and side mode suppression ratio is not less than 15dB.
The internal diameter of described pressure casing is not more than 1mm, and wall thickness is not less than 1.5mm.
Beneficial effect of the present invention is:
(1) compressive resistance is high.The pressure that this fiber-optical grating temperature sensor can bear is not less than 25MPa, and namely this sensor can be applied to the degree of depth and measures more than the bottom-water temperature of 2000m.
(2) long-time stability are good.Because sensor internal fiber grating is in free state all the time, insensitive to environmental stress, therefore there are good long-time stability.
(3) response time is relatively very fast.Sensor diameter is comparatively thin, and inner space is little, and heat conduction is fast, makes the temperature-responsive time of fiber grating pair environment very fast, is about 2s.
Accompanying drawing explanation
Fig. 1 is structural representation of the present invention;
Fig. 2 is cross-sectional view of the present invention;
Fig. 3 is the fluctuation schematic diagram of wavelength in continuous pressure process of sensor grating.
Description of reference numerals: pressure casing 1, adaptor 2, fiber grating 3, tail optical fiber protective sleeve 4, optical fiber jacket 5.
Embodiment
Below in conjunction with drawings and Examples, detailed introduction is done to the present invention:
This high pressure resistant, high precision optical fiber grating temperature sensing method of the present invention, be the optical fiber Bragg grating encapsulation of a kind of high pressure resistant (being not less than 25MPa water pressure) and the method for raising fiber grating temperature sensor precision, the method step is as follows:
(1), encapsulation is carried out to fiber grating 3 and make sensor: the structural member of encapsulation comprises pressure casing 1, adaptor 2, tail optical fiber protective sleeve 4 and optical fiber jacket 5; described fiber grating 3 is bragg grating; reflectivity is not less than 80%, and side mode suppression ratio is not less than 15dB.The internal diameter of described pressure casing 1 is not more than 1mm, and wall thickness is not less than 1.5mm.Fiber grating 3 is single-ended fixing in pressure casing 1, grid region is complete free state (fiber grating remains free state), at the afterbody of pressure casing 1, between pressure casing 1 and adaptor 2, all adopt the additional mode of smearing high-intensity sealing glue of laser bonding to carry out double seal process, thus ensure that this sensor can bear the pressure being not less than 25MPa.
(2), carrying out in calibration process to sensor, adopting the method for temperature and the matching of fiber grating 3 Wavelengths Twice, utilize the wavelength recorded to carry out temperature and resolve, the temperature solution formula of sensor is:
T＝a*λ*λ+b*λ+C
In formula, a, b are respectively quadratic term coefficient and the Monomial coefficient of temperature and the matching of fiber grating 3 Wavelengths Twice, and λ is real-time optical fiber grating 3 wavelength that sensor records, and C is constant.
Feature: 1, in demodulating algorithm, carries out quadratic fit to the wavelength of sensor and temperature, greatly promotes degree of fitting between the two, thus ensure that sensor there is higher temperature sensing precision.2, in the encapsulation process of fiber grating, fiber grating adopts single-ended fixing mode to be packaged in pressure casing, and grid region remains free state, unaffected to environmental stress, has good long-time stability.3, carrying out in calibration process to sensor, introducing the method for temperature and grating wavelength quadratic fit, utilizing the wavelength recorded to carry out temperature and resolve.Therefore, the degree of fitting very good (being not less than 0.99995) of temperature and grating wavelength, thus ensure that sensor has very high temperature measurement accuracy (being that under the condition of 0.3pm, temperature measurement accuracy reaches 0.02 DEG C in optic fiber grating wavelength demodulation accuracy).
1, the selection of encapsulating material and structural design
Corrosive properly is comparatively strong, in order to ensure the Long-Time Service of sensor, have selected the material of titanium alloy comparatively sensor pressure casing and adaptor.Because machining technique limit, not only dark but also thin aperture cannot be processed, so select the titanium alloy tube that ready-made external diameter is 4mm, internal diameter is 1mm to carry out secondary processing as pressure casing.
2, the encapsulation of fiber grating
Be fixed on by optical fibre raster single end in pressure casing, grid region is complete free state.The design of sensor is withstand voltage is not less than 25MPa, solely adopt the seam crossing of fluid sealant to the afterbody of pressure casing and it and adaptor to seal obviously can not meet the demands, therefore introducing laser welding technology, by moment, material first melts by localized hyperthermia, bonds together after cooling.Therefore, the sealing of sensor have employed laser bonding and adds the mode of smearing high-intensity sealing glue and carry out double seal process, ensure that the compressive resistance of sensor.
3, sensor voltage-withstand test
Withstand voltage checking is carried out in order to add the sealing means smearing fluid sealant to laser bonding, packaged sensor is put into head tank, continuous pressure is carried out to head tank, and the grating wavelength value of real-time read sensor, until be forced into design pressure, whether the grating wavelength value of observing sensor produces drift with the increase of pressure.As shown in Figure 3, at continuous pressure in 25MPa process, the grating wavelength value of sensor does not occur to the phenomenon of shortwave direction drift, then illustrating that the sealing means of sensor can bear design pressure.
The above description of this invention does not have restricted, if those of ordinary skill in the art enlightens by it, not departing from the situation of protection of the claims in the present invention, making other malformation of the present invention and embodiment, all belonging to protection scope of the present invention.
Claims (3)
1. high pressure resistant, a high precision optical fiber grating temperature sensing method, is characterized in that: the method step is as follows:
(1), encapsulation is carried out to fiber grating (3) and make sensor: the structural member of encapsulation comprises pressure casing (1), adaptor (2), tail optical fiber protective sleeve (4) and optical fiber jacket (5), fiber grating (3) is single-ended fixing in pressure casing (1), grid region is complete free state, the afterbody in pressure casing (1), all adopts the additional mode of smearing high-intensity sealing glue of laser bonding to carry out double seal process between pressure casing (1) and adaptor (2);
(2), carrying out in calibration process to sensor, adopting the method for temperature and fiber grating (3) Wavelengths Twice matching, utilize the wavelength recorded to carry out temperature and resolve, the temperature solution formula of sensor is:
T＝a*λ*λ+b*λ+C
In formula, a, b are respectively quadratic term coefficient and the Monomial coefficient of temperature and fiber grating (3) Wavelengths Twice matching, and λ is real-time optical fiber grating (3) wavelength that sensor records, and C is constant.
2. high pressure resistant, high precision optical fiber grating temperature sensing method according to claim 1, is characterized in that: described fiber grating (3) is bragg grating, and reflectivity is not less than 80%, and side mode suppression ratio is not less than 15dB.
3. high pressure resistant, high precision optical fiber grating temperature sensing method according to claim 1, is characterized in that: the internal diameter of described pressure casing (1) is not more than 1mm, and wall thickness is not less than 1.5mm.
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| CN201410828694.8A CN104568217A (en) | 2014-12-26 | 2014-12-26 | High-pressure-resistant high-precision FBG (fiber Bragg grating) temperature sensing method |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105444922A (en) * | 2015-11-13 | 2016-03-30 | 济南大学 | Optical fiber grating temperature sensor wavelength shift correction method and temperature measuring device |
| US20210396602A1 (en) * | 2020-06-22 | 2021-12-23 | Heraeus Electro-Nite International N.V. | Device and Method for Measuring a Temperature of a Molten Metal |
| CN114184301A (en) * | 2021-11-16 | 2022-03-15 | 西安交通大学 | Ultra-high temperature resistant fiber bragg grating temperature sensor and signal demodulation method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101858796A (en) * | 2010-05-18 | 2010-10-13 | 华北电力大学（保定） | Seawater temperature profile measurement method based on fiber grating principle |
| CN202562651U (en) * | 2012-01-19 | 2012-11-28 | 厦门出入境检验检疫局检验检疫技术中心 | High-response FBG temperature sensor |
| CN103033308A (en) * | 2012-12-17 | 2013-04-10 | 中国船舶重工集团公司第七一五研究所 | Fiber grating pressure sensor with temperature real-time fine compensation |
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2014
- 2014-12-26 CN CN201410828694.8A patent/CN104568217A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101858796A (en) * | 2010-05-18 | 2010-10-13 | 华北电力大学（保定） | Seawater temperature profile measurement method based on fiber grating principle |
| CN202562651U (en) * | 2012-01-19 | 2012-11-28 | 厦门出入境检验检疫局检验检疫技术中心 | High-response FBG temperature sensor |
| CN103033308A (en) * | 2012-12-17 | 2013-04-10 | 中国船舶重工集团公司第七一五研究所 | Fiber grating pressure sensor with temperature real-time fine compensation |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105444922A (en) * | 2015-11-13 | 2016-03-30 | 济南大学 | Optical fiber grating temperature sensor wavelength shift correction method and temperature measuring device |
| US20210396602A1 (en) * | 2020-06-22 | 2021-12-23 | Heraeus Electro-Nite International N.V. | Device and Method for Measuring a Temperature of a Molten Metal |
| US11959813B2 (en) * | 2020-06-22 | 2024-04-16 | Heraeus Electro-Nite International N.V. | Device and method for measuring a temperature of a molten metal |
| CN114184301A (en) * | 2021-11-16 | 2022-03-15 | 西安交通大学 | Ultra-high temperature resistant fiber bragg grating temperature sensor and signal demodulation method |
| CN114184301B (en) * | 2021-11-16 | 2022-12-09 | 西安交通大学 | Ultra-high temperature resistant fiber bragg grating temperature sensor and signal demodulation method |
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