CN102162753A - Sensor structure for simultaneously measuring temperature and strain of long period fiber gratings (LPFGs) - Google Patents
Sensor structure for simultaneously measuring temperature and strain of long period fiber gratings (LPFGs) Download PDFInfo
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Abstract
The invention provides a sensor structure for simultaneously measuring the temperature and strain of long period fiber gratings (LPFGs). The sensor structure is characterized in that a pair of LPFGs which are written by high-frequency CO2 laser pulse in a fiber and have different periods are selected, namely an LPFG only sensitive to temperature variation and an LPFG sensitive to both temperature variation and strain variation; and the respective variation of the temperature and the strain can be accurately measured by cascading the two LPFGs. The sensor structure has the following prominent advantages: the temperature variation is measured by using the LPFG which has a specific period and is only sensitive to temperature variation, and the variation of the temperature and the strain is measured by using the other LPFG, thus realizing measurement of the two parameters (the temperature and the strain), and providing a scheme for solving the problem of cross sensitivity of the temperature and the strain; and meanwhile, the sensor has the capability of normally working at the high temperature of 750 DEG C and is unnecessary to be specially packaged.
Description
Technical field
The invention belongs to technical field of optical fiber sensing, be specifically related to utilize the long period fiber grating of a pair of different cycles to make the sensor construction that sensor is measured temperature and two parameters of strain simultaneously.
Background technology
Long period fiber grating (LPFG) be a kind of can be with the band resistance type optical fiber filter that couples light to covering of specific wavelength, its resonance wavelength can be along with the variation of parameters such as the temperature of external environment, strain, refractive index and is changed, according to this principle, the variation of resonance wavelength that can be by measuring LPFG realizes the measurement of environmental physics quantitative changeization to external world.Because LPFG compares and Fiber Bragg Grating FBG (FBG), and is more responsive to the variation of many external physical quantity, and the higher temperature of LPFG ability, so its great prospect aspect Fibre Optical Sensor.
In temperature and strain while fields of measurement, people such as H.J.Patrick issue paper (IEEE Photon.Tech.Lett., 1996, Vol.8, No.9 pp.1223-1225) has proposed strain and temperature simultaneously measuring scheme, but this scheme needs the combination of Fiber Bragg Grating FBG and long period fiber grating, so that the sensor cost is higher, and volume is bigger, is unfavorable for integrated.The river is built, publish thesis (optics journal, 2003,32 (9): measure when 1063～1066) proposing to have LPFG/EFPI integrating optical fiber sensor to realize temperature and strain such as Rao Yunjiang.Optical grating strain, temperature simultaneously measuring sensor that Li Aiqun etc. (ZL 200910026403) propose are that two fiber gratings are encapsulated in the special construction, cause the sensor cost higher, processing inconvenience.
In the fiber-optic grating sensor, the existence of temperature and strain cross sensitivity has had a strong impact on the precision of measurement, therefore studies only a certain physical quantity to be changed sensitivity and other physical quantitys are changed insensitive optical fiber optical grating sensors to have great significance.Utilize the accurate measurement that just can realize multiparameter that combines of this fiber-optic grating sensor and ordinary optic fibre grating sensor.
Summary of the invention
The purpose of this invention is to provide a pair of long-period fiber grating sensor, utilize one of them LPFG (long period fiber grating) insensitive and to responsive to temperature to strain, another LPFG measures when realizing temperature and strain temperature and all responsive characteristics of strain.And because this sensor is to be formed by two LPFG cascades, LPFG itself has resistant to elevated temperatures characteristic, has the ability of operate as normal under 750 ℃ of high temperature.
For achieving the above object, the present invention is achieved through the following technical solutions:
Measure the sensor construction of long period fiber grating temperature and strain simultaneously, select high frequency CO for use
2The a pair of long period fiber grating of the different cycles that laser pulse writes in optical fiber, be respectively one long period fiber grating to the temperature variation sensitivity, with a long period fiber grating to temperature and the equal sensitivity of strain variation, two long period fiber grating are carried out cascade use, can accurately measure temperature and strain variation separately.
Selected optical fiber is the bend resistant single moded fibers of band nano-rings structure.
The long period fiber grating that writes has following feature: the resonance wavelength of the long period fiber grating in the specific period scope is to responsive to temperature and insensitive to strain; The resonance wavelength of the long period fiber grating in the general periodic regime is responsive simultaneously to temperature and strain.
This sensor have still can operate as normal during up to 750 ℃ in environment temperature ability.
This sensor has the processing characteristic of simple, need not additional encapsulation processs such as isolated temperature, isolation stress except that general protection packaging.
The present invention adopts the long period fiber grating of the different cycles of two cascades to come the variation of perception ambient temperature and strain, and wherein LPFG1 is only to responsive to temperature, i.e. the variation of its resonance wavelength (Δ λ
Res) only relevant with temperature variation (Δ T), can be represented by the formula:
Δλ
res-LPFG1＝A*ΔT (1)
LPFG2 is then all responsive to temperature and strain variation (Δ μ ε microstrain), and the variation of resonance wavelength can be expressed as:
Δλ
res-LPFG2＝B*ΔT+C*Δμε (2)
In equation (1) and (2), coefficient A, B, C are the coefficient of Resonant Wavelengths of Long Period Fiber Gratings with temperature and strain variation, and simultaneous equations (1) and (2) just can solve the variable quantity of temperature and strain.
Long period fiber grating described in the present invention is to utilize high frequency CO
2Laser instrument is the bend resistant single moded fibers in a kind of novel band nano-rings structure of release in 2009 in Corning Incorporated
On write, these two long period fiber grating have the different cycles, and their cycle be positioned at same interval, to be in same its resonance wavelength of length of an interval period optical fiber grating identical with the character of temperature and strain variation.
Outstanding advantage of the present invention is: with a long period fiber grating feature measurement temperature variation to the temperature variation sensitivity of a specific period, measure the variation of temperature and strain with another long period fiber grating, thereby realize the measurement of temperature and strain biparametric, provided a kind of scheme that solves the temperature strain cross sensitivity.This type sensor has the ability of operate as normal under 750 ℃ of high temperature simultaneously, and does not need special package.
Description of drawings
Fig. 1 is the sensor construction synoptic diagram that the present invention adopts;
Fig. 2 is a long period fiber grating wiring method among the present invention;
Fig. 3 is the emergent property of the grating of periods lambda=470 μ m;
Fig. 4 is the temperature characteristics of the grating of periods lambda=470 μ m;
Fig. 5 is the emergent property curve of the grating of periods lambda=295 μ m;
Fig. 6 is the temperature characteristics of the grating of periods lambda=295 μ m;
Fig. 7 is the hot properties curve of the grating of periods lambda=468 μ m;
Fig. 8 is temperature and the simultaneously-measured proving installation figure of strain among the present invention.
Embodiment
According to embodiment and accompanying drawing the present invention is described in further detail below.
Shown in Fig. 1-8, the long period fiber grating that we select for use is two long period fiber grating of the different cycles that writes on healthy and free from worry bend insensitive optical fiber with high frequency CO 2 laser pulses.This to the long period fiber grating structure as shown in Figure 1.Among the figure, long period fiber grating 1 and long period fiber grating 2 are two different long period fiber grating of cycle.
1 cycle of long period fiber grating is 470 μ m, and periodicity N=60, harmonic peak wavelength be at 1536.5nm, the grating strain characteristic in this cycle as shown in Figure 3, its harmonic peak is basic not skew under 1500 microstrains; Temperature characteristics as shown in Figure 4, its temperature control is about 0.098nm/ ℃, the linearity is R
2=0.998.
2 cycles of long period fiber grating are 295 μ m, periodicity N=80, the harmonic peak wavelength is at 1514.7nm, the grating strain characteristic in this cycle as shown in Figure 5, its strain sensitivity is about 2.8pm/ μ ε, strain increases and is heavy and property is relatively good when reducing, and resonance wavelength presents the good linearity with strain variation, its linearity R
2=0.999; Temperature characteristics as shown in Figure 6, its temperature control is about 0.1448nm/ ℃, the linearity is R
2=0.996.Simultaneously to temperature and strain variation sensitivity.
The device of making long period fiber grating comprises: wideband light source 3, high frequency CO as shown in Figure 2
2 Laser instrument 4, healthy and free from worry bend insensitive optical fiber 5, spectroanalysis instrument 6.When writing long period fiber grating, high frequency CO
2The pulsewidth of laser instrument is 90 μ s, and frequency is 5kHz, CO
2Laser is focused the small spot that diameter is 50 μ m, and average power is 0.45W.
The hot properties of the long period fiber grating that this type sensor is used as shown in Figure 7.Long period fiber grating cycles 468 μ m, periodicity N=60, the harmonic peak wavelength is at 1509.05nm.Among Fig. 7, its temperature control in 100-250 ℃ of interval is about 0.1194nm/ ℃, and the linearity is R
2=0.9998.Its temperature control at 300-750 ℃ is about 0.2084nm/ ℃, and the linearity is R
2=0.9991.High temperature section sensitivity is higher, is keeping good linearty in all temps interval.
The device of testing this sensor comprises: wideband light source 7 as shown in Figure 8; High precision micropositioner 8; Be used for sensor is applied strain; High-accuracy and constant incubator 9 is used for the simulated environment temperature variation; Long period fiber grating 10, spectroanalysis instrument 11 with the present invention's making.
Claims (3)
1. measure the sensor construction of long period fiber grating temperature and strain simultaneously, it is characterized in that, select high frequency CO for use
2The a pair of long period fiber grating of the different cycles that laser pulse writes in optical fiber, be respectively one long period fiber grating to the temperature variation sensitivity, with a long period fiber grating, two long period fiber grating are carried out cascade use temperature and the equal sensitivity of strain variation.
2. the sensor construction of measuring long period fiber grating temperature and strain simultaneously according to claim 1 is characterized in that, selected optical fiber is the bend resistant single moded fibers of band nano-rings structure.
3. the sensor construction of measuring long period fiber grating temperature and strain simultaneously according to claim 1 is characterized in that, two long period fiber grating have the different cycles, and their cycle is positioned at same interval.
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Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102620858A (en) * | 2012-03-29 | 2012-08-01 | 西北大学 | Double long period fiber grating (LPFG) temperature and humidity sensor |
| CN103323143A (en) * | 2013-06-13 | 2013-09-25 | 重庆大学 | Quasi-distributed fiber sensor capable of measuring temperature and vibration simultaneously and manufacturing method |
| CN103364102A (en) * | 2012-04-05 | 2013-10-23 | 电子科技大学 | Bending-resistant single-LPFG (Long Period Fiber Grating) sensor simultaneously measuring temperature and strain |
| CN103411550A (en) * | 2013-06-28 | 2013-11-27 | 武汉理工大学 | Inner surface stress and temperature monitoring method of internal combustion engine main bearing based on fiber bragg grating |
| CN103674085A (en) * | 2013-12-16 | 2014-03-26 | 西安电子科技大学 | U-shaped structure sapphire fiber grating temperature and stress sensor and manufacturing method thereof |
| CN103940360A (en) * | 2014-04-23 | 2014-07-23 | 鲁东大学 | Strain monitoring device based on cascade chirped fiber gratings |
| CN103955019A (en) * | 2014-04-25 | 2014-07-30 | 深圳大学 | Expanding type long-period fiber bragg grating based on photonic crystal fiber and manufacturing method of expanding type long-period fiber bragg grating |
| CN104185779A (en) * | 2012-01-23 | 2014-12-03 | 株式会社丰田自动织机 | Optical fiber for temperature sensor and power device monitoring system |
| CN104864895A (en) * | 2015-04-30 | 2015-08-26 | 天津大学 | Method for measuring little-mode long-period fiber grating based on carbon nanomaterial and sensor thereof |
| CN105866041A (en) * | 2016-04-02 | 2016-08-17 | 上海大学 | SiC material oxidation state monitoring method and sensor system based on LPFG sensing properties |
| CN106524935A (en) * | 2016-10-11 | 2017-03-22 | 北京信息科技大学 | Method for measuring strain of double-pass MZ structure fused with long period fiber grating |
| CN108827374A (en) * | 2018-04-16 | 2018-11-16 | 北京工业大学 | A kind of tandem hydrogen and oxygen concentration and temperature and humidity measuring system simultaneously |
| CN113686460A (en) * | 2021-03-17 | 2021-11-23 | 广东工业大学 | Fiber grating temperature sensor and sensing device based on vernier effect |
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| US5945666A (en) * | 1996-05-20 | 1999-08-31 | The United States Of America As Represented By The Secretary Of The Navy | Hybrid fiber bragg grating/long period fiber grating sensor for strain/temperature discrimination |
| CN2733328Y (en) * | 2004-09-15 | 2005-10-12 | 中国科学院上海光学精密机械研究所 | Temperature sensing device of long-period fiber grating |
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2010
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| US5945666A (en) * | 1996-05-20 | 1999-08-31 | The United States Of America As Represented By The Secretary Of The Navy | Hybrid fiber bragg grating/long period fiber grating sensor for strain/temperature discrimination |
| CN2733328Y (en) * | 2004-09-15 | 2005-10-12 | 中国科学院上海光学精密机械研究所 | Temperature sensing device of long-period fiber grating |
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| 《中国优秀硕士学位论文全文数据库 信息科技辑》 20081115 李占平 双长周期光纤光栅对温度与应变的同时测量 第8-9,48-60页 1-3 , 第11期 * |
Cited By (24)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104185779A (en) * | 2012-01-23 | 2014-12-03 | 株式会社丰田自动织机 | Optical fiber for temperature sensor and power device monitoring system |
| CN104185779B (en) * | 2012-01-23 | 2016-08-31 | 株式会社丰田自动织机 | Temperature sensor optical fiber and electric device monitoring system |
| CN102620858B (en) * | 2012-03-29 | 2013-12-25 | 西北大学 | Double long period fiber grating (LPFG) temperature and humidity sensor |
| CN102620858A (en) * | 2012-03-29 | 2012-08-01 | 西北大学 | Double long period fiber grating (LPFG) temperature and humidity sensor |
| CN103364102A (en) * | 2012-04-05 | 2013-10-23 | 电子科技大学 | Bending-resistant single-LPFG (Long Period Fiber Grating) sensor simultaneously measuring temperature and strain |
| CN103323143A (en) * | 2013-06-13 | 2013-09-25 | 重庆大学 | Quasi-distributed fiber sensor capable of measuring temperature and vibration simultaneously and manufacturing method |
| CN103323143B (en) * | 2013-06-13 | 2015-02-25 | 重庆大学 | Quasi-distributed fiber sensor capable of measuring temperature and vibration simultaneously and manufacturing method |
| CN103411550A (en) * | 2013-06-28 | 2013-11-27 | 武汉理工大学 | Inner surface stress and temperature monitoring method of internal combustion engine main bearing based on fiber bragg grating |
| CN103411550B (en) * | 2013-06-28 | 2016-07-06 | 武汉理工大学 | Internal combustion engine main bearing inner surface stress and temperature monitoring method based on fiber grating |
| CN103674085A (en) * | 2013-12-16 | 2014-03-26 | 西安电子科技大学 | U-shaped structure sapphire fiber grating temperature and stress sensor and manufacturing method thereof |
| CN103674085B (en) * | 2013-12-16 | 2016-08-17 | 西安电子科技大学 | The sapphire fiber grating temperature of a kind of U-shape structure and the preparation method of strain gauge |
| CN103940360A (en) * | 2014-04-23 | 2014-07-23 | 鲁东大学 | Strain monitoring device based on cascade chirped fiber gratings |
| CN103940360B (en) * | 2014-04-23 | 2016-10-05 | 鲁东大学 | A kind of strain monitoring device based on cascade chirped fiber grating |
| CN103955019A (en) * | 2014-04-25 | 2014-07-30 | 深圳大学 | Expanding type long-period fiber bragg grating based on photonic crystal fiber and manufacturing method of expanding type long-period fiber bragg grating |
| CN103955019B (en) * | 2014-04-25 | 2017-02-01 | 深圳大学 | Expanding type long-period fiber bragg grating based on photonic crystal fiber and manufacturing method of expanding type long-period fiber bragg grating |
| CN104864895B (en) * | 2015-04-30 | 2017-04-05 | 天津大学 | Measuring method and sensor based on the few mould LPFG of carbon nanomaterial |
| CN104864895A (en) * | 2015-04-30 | 2015-08-26 | 天津大学 | Method for measuring little-mode long-period fiber grating based on carbon nanomaterial and sensor thereof |
| CN105866041A (en) * | 2016-04-02 | 2016-08-17 | 上海大学 | SiC material oxidation state monitoring method and sensor system based on LPFG sensing properties |
| CN105866041B (en) * | 2016-04-02 | 2019-10-11 | 上海大学 | SiC substance state of oxidation monitoring sensor-based system and monitoring method based on LPFG sensing characteristics |
| CN106524935A (en) * | 2016-10-11 | 2017-03-22 | 北京信息科技大学 | Method for measuring strain of double-pass MZ structure fused with long period fiber grating |
| CN106524935B (en) * | 2016-10-11 | 2019-01-18 | 北京信息科技大学 | A kind of method of the round trip MZ structure measurement strain of welding long-period fiber grating |
| CN108827374A (en) * | 2018-04-16 | 2018-11-16 | 北京工业大学 | A kind of tandem hydrogen and oxygen concentration and temperature and humidity measuring system simultaneously |
| CN113686460A (en) * | 2021-03-17 | 2021-11-23 | 广东工业大学 | Fiber grating temperature sensor and sensing device based on vernier effect |
| CN113686460B (en) * | 2021-03-17 | 2024-01-23 | 广东工业大学 | Fiber bragg grating temperature sensor and sensing device based on vernier effect |
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