CN203479323U - Optical fiber refractive index and temperature sensor - Google Patents
Optical fiber refractive index and temperature sensor Download PDFInfo
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- CN203479323U CN203479323U CN201320417892.6U CN201320417892U CN203479323U CN 203479323 U CN203479323 U CN 203479323U CN 201320417892 U CN201320417892 U CN 201320417892U CN 203479323 U CN203479323 U CN 203479323U
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- optical fiber
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Abstract
The invention discloses an optical fiber refractive index and temperature sensor. The optical fiber refractive index and temperature sensor comprises a broadband light source (1), an optical fiber sensing head (2), a spectrometer (3) and a computer (4), wherein the broadband light source (1) is connected to a first input port of the optical fiber sensing head (2) through an optical fiber. A first output port of the optical fiber sensing head (2) is connected with the spectrometer through an optical fiber. During measurement, two light beams split in a Mach-Zehnder interferometer interfere with each other, and the movements of the valley value wavelength and the Bragg wavelength of an interference fringe change with the refractive index or the temperature of a material to be measured where the optical fiber sensing head is positioned. The movement ranges of the valley value wavelength and the Bragg wavelength of the interference fringe are measured through the spectrometer, and the refractive index and the temperature of the material to be measured are obtained through calculation of the computer. The optical fiber refractive index and temperature sensor is capable of measuring the refractive index and the temperature in high-precision and real-time ways at the same time and is simple in structure and convenient to operate.
Description
Technical field
The utility model relates to a kind of refractive index and temperature sensor, relates in particular to a kind of optical fibre refractivity and temperature sensor based on Mach-Zehnder interferometer and Bragg grating.
Background technology
Refractive index and temperature are two very important parameters at ambits such as physics, biology, chemistry, and it is accurately measured in related industries departments such as chemical industry, medicine, food to significant and purposes.Therefore, many measurement refractive indexes and the method for temperature are arisen at the historic moment.Conventional measurement refractive index method has glancing incidence method, diffraction grating method, laser irradiation and CCD mensuration, and some new technologies such as optoacoustic, spr sensor and Raman spectrum.And the classic method of measuring temperature has high-precision thermometer method, SMS structured optical fiber method, Bragg grating method and Michelson interferometer method etc.The temperature of material has a great impact its refractive index, most in the situation that, the temperature of material can change along with the variation of its temperature of living in, and the precision that therefore above-mentioned various methodologies is separately carried out independent measurement by these two kinds of parameters just has deviation to a certain degree.In the day by day accurate scientific research of measuring technique, this deviation tends to result of study to cause larger impact.In two-parameter simultaneously-measured research for temperature and refractive index, a lot of new methods have been emerged, as Fabry pool sieve chamber mirror method, tapered fiber method, dual mode optical fiber method etc., although the design comparison of these methods is ingenious, when can realize temperature and refractive index under certain condition, measure, but these methods are expensive and not easy to operate, its stability is lower simultaneously, is of limited application.
Utility model content
The purpose of this utility model is to overcome prior art above shortcomings, and optical fibre refractivity and temperature sensor based on Mach-Zehnder interferometer and Bragg grating are provided, and concrete technical scheme is as follows.
Optical fibre refractivity based on Mach-Zehnder interferometer and Bragg grating and a temperature sensor, comprise wideband light source, optical fiber sensor head, spectrometer and computing machine; The first input end mouth of described optical fiber sensor head is connected by optical fiber with wideband light source, and the first output port is connected by optical fiber with spectrometer; During two beam Propagation in the Mach-Zehnder interferometer of optical fiber sensor head inside, interfere, be then transferred to spectrometer; Described optical fiber sensor head forms Mach-Zehnder interferometer structure by the ordinary optic fibre of three sections of dislocation, and wherein first paragraph ordinary optic fibre has Bragg grating, and the central shaft of the first paragraph ordinary optic fibre at second segment ordinary optic fibre two ends and the 3rd section of ordinary optic fibre overlaps.
In above-mentioned optical fibre refractivity and temperature sensor, also comprise for the output data of receiving spectrum instrument and calculate refractive index and the computing machine of temperature, spectrometer output terminal is connected with described compunication.
Above-mentioned optical fibre refractivity and temperature sensor, the Mach of measuring optical fiber sensing head inside once moral structure and Bragg grating is the ordinary optic fibre tail optical fiber of removing covering.
Above-mentioned optical fibre refractivity and temperature sensor, Bragg grating reflectivity used is 70%, bragg wavelength is 1539.52nm.
In above-mentioned optical fibre refractivity and temperature sensor, described wideband light source is the fiber broadband light source of C-band (1520nm-1570nm), and described Transmission Fibers is general single mode fiber.
In above-mentioned optical fibre refractivity and temperature sensor, the rule that computing machine changes with test substance refractive index and temperature variation according to the valley wavelength of interference fringe and bragg wavelength, calculates test substance refractive index and temperature.
Utilize refractive index and the thermometry of above-mentioned optical fibre refractivity and temperature sensor, comprise: optical fiber sensor head is inserted in test substance, Mach once two light beams of moral internal transmission is interfered, the wavelength of interference fringe trough and bragg wavelength change with the variation of the residing test substance refractive index of optical fiber sensor head and temperature, by spectrometer and computing machine, record the moving range of interference fringe valley wavelength and bragg wavelength, then machine calculates refractive index and the temperature of test substance as calculated.
In above-mentioned measuring method, when the refractive index of test substance or temperature change, by spectrometer, detect the moving range of interference fringe valley wavelength and bragg wavelength, after computing machine calculates, obtain temperature to be measured and refractive index, compute matrix is:
K wherein
r1and K
t1that Mach-Zehnder interferometer is for the sensitivity of refractive index and temperature, K
r2and K
t2be Bragg grating for the sensitivity of refractive index and temperature, Δ n
xbe respectively the variation of refractive index and temperature, Δ λ with Δ T
mZIwith Δ λ
fBGbe respectively the movement of interference fringe valley wavelength in Mach-Zehnder interferometer and the movement of bragg wavelength.
The utility model compared with prior art, has following advantage and technique effect:
(1) sensor of the present utility model can be measured temperature and refractive index well simultaneously, eliminate measuring error that in inaccuracy that one-parameter measures and the inner light path of sensor-based system branch, different losses cause, reduced external environment and change the impact bringing measuring, improved measuring accuracy.
(2) sensor of the present utility model have measure solution concentration and temperature range large, the advantage that resolution is high.
(3) sensor construction of the present utility model is simple, and cost is low, easy to operate.
(4) sensor of the present utility model, except for general liquid detecting, also can be used for trace, dangerous liquid detection.In addition the industrial processes that, the utility model also can change for refractive index and temperature are monitored in real time.
This sensor can be realized high precision, refractive index and temperature survey on a large scale, simple in structure, easy to operate.
Accompanying drawing explanation
Optical fibre refractivity and the arrangement of temperature sensor schematic diagram of Fig. 1 based on Mach-Zehnder interferometer and Bragg grating.
Fig. 2 be measuring optical fiber transducing head structure and with the schematic diagram at solution material interface to be measured place.
Fig. 3 is the transmission spectrum in the sodium chloride solution that under room temperature, Fibre Optical Sensor is C=7.407% in concentration.
Fig. 4 a is the transmission spectrum of Mach-Zehnder interferometer when concentration of sodium chloride solution is respectively 7.407%, 16.667% and 24.242%.Fig. 4 b is the transmission spectrum of Bragg grating when concentration of sodium chloride solution is respectively 7.407%, 16.667% and 24.242%.Fig. 4 c changes at 1.3250 o'clock, the mobile matching rule of sensor interferometer striped valley wavelength in sodium chloride solution refractive index from 1.3232.
Fig. 5 a is concentration of sodium chloride solution while being 10%, and the interference fringe valley wavelength of sensor and bragg wavelength are with the variation of different temperatures; Fig. 5 b is concentration of sodium chloride solution while being 10%, interference fringe valley wavelength and bragg wavelength variation with temperature rule in the sensor of matching.
Fig. 6 a represent bragg wavelength in distilled water over time.The valley wavelength that Fig. 6 b represents interference fringe in distilled water over time.
Embodiment
Below in conjunction with accompanying drawing, concrete enforcement of the present utility model is described in further detail, but enforcement of the present utility model and protection domain are not limited to this, the utility model are done to the replacement that is equal to that essence is identical and all belong to protection domain of the present utility model.
Referring to Fig. 1, the optical fibre refractivity based on Mach-Zehnder interferometer and Bragg grating and temperature sensor comprise wideband light source 1, optical fiber sensor head 2, spectrometer 3 and computing machine 4.Wherein, wideband light source 1 is connected to the input port of optical fiber sensor head 2, and the output port of optical fiber sensor head 2 connects spectrometer 3, and computing machine 4 and spectrometer 3 communication connections, carry out data processing.Concrete measurement is the transmission spectrum when being gone out optical fiber sensor head and inserted solution material to be measured by spectrometer measurement, its corresponding data is input to computing machine, by calculating, obtain the moving range of interference fringe valley wavelength and bragg wavelength, according to matched curve, obtain refractive index and the temperature of detected solution.
Fig. 2 be measuring optical fiber transducing head structure and with the schematic diagram at solution material interface to be measured place, integral body is the optical fiber sensor head 2 in Fig. 1.Described optical fiber sensor head 2 forms Mach-Zehnder interferometer structure by the ordinary optic fibre of three sections of dislocation, wherein first paragraph ordinary optic fibre (202) has Bragg grating 201, and the central shaft of the first paragraph ordinary optic fibre 202 at second segment ordinary optic fibre 204 two ends and the 3rd section of ordinary optic fibre 203 overlaps.Wherein 5 is containers, and inside is full of solution material to be measured.
In utility model, described wideband light source 1 is C-band (1520nm～1570nm) wideband light source.The splitting ratio of Mach-Zehnder interferometer is 50%～50%.Transmission Fibers is single-mode fiber.
While measuring, optical fiber sensor head is inserted in test substance in (as solution).The principle that interference fringe valley wavelength and bragg wavelength change with the measurement residing test substance refractive index of sensing head and temperature variation is as follows:
Due to optical fiber dislocation, form Mach-Zehnder interferometer, make the light beam transmitting in single-mode fiber be divided into two beam propagations, a branch of in fibre core, a branch of in covering.The path of two beam Propagation is different, can produce each other the phase differential 2 π Δ nL of accumulation
1/ λ, wherein Δ n is the refringence of the light beam that transmits between fibre core and covering, L
1be the length of optical fiber dislocation, λ is the wavelength of input.When the temperature of the test substance of surveying when Fibre Optical Sensor or variations in refractive index, can make the path of the beam Propagation in covering change, phase differential between two light beams also can change, and makes the valley wavelength of the interference fringe between them occur corresponding mobile.
The chief component material of Bragg grating is silicon, its be fiber core refractive index by the single-mode fiber of periodic modulation, its bragg wavelength is λ
b=2n
effΛ, wherein Λ is the index modulation cycle, n
efffor effective refractive index.Bragg wavelength derives from thermal expansion effects and the thermo-optical phenomenon of silicon to the sensitivity of temperature, its mutual relationship as shown in the formula
Δλ
B=(α
th+ξ)·λ
B·ΔT （1）
α wherein
thbe the thermal expansivity of silicon, ξ is thermo-optical coeffecient, Δ λ
bthe movement value of bragg wavelength, the changing value that Δ T is temperature.
For silicon, α
thbe respectively 0.55 * 10 with ξ
-6/ ° C and 8.0 * 10
-6/ ° C, so Bragg grating Changing Pattern along with temperature when 1550nm is 0.01nm/ ° of C, this is mainly because heat-dependent causes.So when extraneous variations in refractive index, bragg wavelength is not moved.
When the refractive index of test substance or temperature change, by spectrometer, can detect the moving range of interference fringe valley wavelength and bragg wavelength, after computing machine calculates, can obtain temperature to be measured and refractive index.Its compute matrix is as follows:
K wherein
r1and K
t1that Mach-Zehnder interferometer is for the sensitivity of refractive index and temperature, K
r2and K
t2be Bragg grating for the sensitivity of refractive index and temperature, Δ n
xbe respectively the variation of refractive index and temperature, Δ λ with Δ T
mZIwith Δ λ
fBGbe respectively the movement of interference fringe valley wavelength in Mach-Zehnder interferometer and the movement of bragg wavelength, the two can be surveyed and be obtained by spectrometer.Spectrometer, by the data input computing machine of surveying, after over-fitting, obtains the numerical value of 4 above-mentioned sensitivity, and corresponding calculating can obtain the final refractive index n measuring
xwith temperature Δ T.
Fig. 3 is the transmission spectrum in the sodium chloride solution that under room temperature, Fibre Optical Sensor is C=7.407% in concentration.From the graph, we can clearly see the conoscope image of striped and the local dent that Bragg grating forms.
For further checking feasibility of the present utility model, spy carries out following experiment:
Experiment 1:
In experiment, apply the transmission light spectrogram of fiber sensor measuring different refractivity solution of the present utility model, as shown in Fig. 4 a, in figure three curves respectively corresponding optical fiber sensor head be positioned over the transmission spectrum in 7.407%, 16.667% and 24.242% mass percent sodium chloride solution.Wherein, the optical fiber longitudinal length of Mach-Zehnder interferometer dislocation is about 3.6cm, and lateral length is 8.1 μ m.Bragg grating is 7.1cm apart from longitudinal fiber lengths of Mach-Zehnder interferometer.From Fig. 4 a and b, can find out, the increase that the interference fringe valley wavelength in Mach-Zehnder interferometer is put solution refractive index with optical fiber sensor head increases; And bragg wavelength is not moved.
Table 1 moves the variation relation with same liquid (sodium chloride solution) refractive index of different quality percent concentration for interference fringe valley wavelength.
Table 1
Fig. 4 c is data result and the fitting result of application Fibre Optical Sensor of the present utility model to the refractometry of variable concentrations sodium chloride solution.In figure, curve A and B are respectively measurement result and fitting result.From Fig. 4 c, can find out, solution refractive index to be measured by 1.3232 to 1.3520 variation ranges in, matched curve is Matched measurement result accurately, the linearity is 0.99.From matched curve, can obtain Mach-Zehnder interferometer and Bragg grating for the detection sensitivity K of refractive index
r1and K
r2be respectively 13.7592nm/RI and 0.In general scientific research scope, this sensitivity can reach corresponding requirement.
Experiment 2:
In order to verify that this sensor is for the feasibility of detecting temperature, we by transformation temperature, have tested the sensitivity of this sensor for temperature in the situation that concentration of sodium chloride solution is 10%.Fig. 5 a is the transmission spectrum of the sensor recording.Wherein, the valley wavelength of bragg wavelength and interference fringe is along with red shift all occurs in the increase of temperature.The fringe contrast of Bragg grating is along with being increased in of temperature reduces, and the contrast of the interference fringe of Mach-Zehnder interferometer first increases and reduces.
Table 2 moves the variation relation with the same liquid (concentration of sodium chloride solution is 10%) of different temperatures for interference fringe valley wavelength moves with bragg wavelength.
Table 2
Fig. 5 b is concentration of sodium chloride solution while being 10%, interference fringe valley wavelength and bragg wavelength variation with temperature rule in the sensor of matching.The detection data that wherein A is bragg wavelength, B is the detection data of interference fringe valley wavelength, C is matched curve.We find that the linearity of match value and measured value is 0.99, and degree of fitting is very high.In addition by matched curve, obtain Mach-Zehnder interferometer and Bragg grating and be respectively K for the sensitivity of temperature
t1=0.0440nm/ ° of C and K
t2=0.0106nm/ ° of C, has verified the detected with high accuracy ability of the utility model sensor again.
Experiment 3:
In order further to verify the feasibility of this sensor, we have carried out the stability experiment of this sensor.In this experiment, Fibre Optical Sensor of the present utility model is placed in distilled water, measures the side-play amount of its wavelength of different time, as shown in table 3.
Table 2
The bragg wavelength that Fig. 6 a and b are this fiber sensor measuring of application and interference fringe valley wavelength be relation over time.Wherein we can observe Mach once the valley wavelength of the moral interference fringe maximum offset in 55min be 0.04nm, and bragg wavelength is stabilized in 1539.51nm always.Because Mach-Zehnder interferometer is higher than bragg wavelength for the sensitivity of temperature, so the former is vulnerable to the impact of external environment.Cause the factor of this impact a lot, as the stability of light source, the shake of sensing head in measuring process, variation of temperature etc.In addition the bending of sensing head also can affect greatly the skew of valley wavelength.
From experiment above, although transmission spectrum interference fringe valley wavelength and bragg wavelength are in time and random variation, because its temporal evolution is very little, illustrates that this sensor stability is feasible.
Claims (4)
1. optical fibre refractivity and a temperature sensor, is characterized in that comprising wideband light source (1), optical fiber sensor head (2) and spectrometer (3); The input port of described optical fiber sensor head (2) is connected by optical fiber with wideband light source (1), the output port of optical fiber sensor head (2) is connected by optical fiber with spectrometer (3), in optical fiber sensor head, interfere during two beam Propagation of Mach-Zehnder interferometer inside, be then transferred to spectrometer (3); Described optical fiber sensor head (2) forms Mach-Zehnder interferometer structure by the ordinary optic fibre of three sections of dislocation, wherein first paragraph ordinary optic fibre (202) has Bragg grating (201), and the first paragraph ordinary optic fibre (202) at second segment ordinary optic fibre (204) two ends and the central shaft of the 3rd section of ordinary optic fibre (203) overlap.
2. optical fibre refractivity according to claim 1 and temperature sensor, is characterized in that Mach-Zehnder interferometer structure and Bragg grating that described optical fiber sensor head (2) is inner are the ordinary optic fibre tail optical fiber of removing covering.
3. optical fibre refractivity as claimed in claim 1 and temperature sensor, is characterized in that the wideband light source that described wideband light source is C-band.
4. optical fibre refractivity and the temperature sensor as described in claim 1～3 any one, is characterized in that used optical fiber is general single mode fiber.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104297209A (en) * | 2014-10-23 | 2015-01-21 | 中国计量学院 | Mach-Zehnder refractive index sensor based on peanut-taper-peanut structure |
| CN104776872A (en) * | 2015-04-27 | 2015-07-15 | 宁波工程学院 | Fiber bragg grating sensor based on olive type and grating wet etching manufacturing method |
| CN104914055A (en) * | 2015-06-09 | 2015-09-16 | 华中科技大学 | Microscale fibre-optical probe as well as method and device for detecting content of glucose |
| CN107179047A (en) * | 2017-04-28 | 2017-09-19 | 华中科技大学 | A kind of dual interferometer based on Fiber Bragg Grating FBG |
| CN108534979A (en) * | 2016-10-08 | 2018-09-14 | 哈尔滨理工大学 | Vertical turbulence effect simulator |
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2013
- 2013-07-12 CN CN201320417892.6U patent/CN203479323U/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104297209A (en) * | 2014-10-23 | 2015-01-21 | 中国计量学院 | Mach-Zehnder refractive index sensor based on peanut-taper-peanut structure |
| CN104776872A (en) * | 2015-04-27 | 2015-07-15 | 宁波工程学院 | Fiber bragg grating sensor based on olive type and grating wet etching manufacturing method |
| CN104914055A (en) * | 2015-06-09 | 2015-09-16 | 华中科技大学 | Microscale fibre-optical probe as well as method and device for detecting content of glucose |
| CN108534979A (en) * | 2016-10-08 | 2018-09-14 | 哈尔滨理工大学 | Vertical turbulence effect simulator |
| CN107179047A (en) * | 2017-04-28 | 2017-09-19 | 华中科技大学 | A kind of dual interferometer based on Fiber Bragg Grating FBG |
| CN107179047B (en) * | 2017-04-28 | 2019-10-25 | 华中科技大学 | A kind of dual interferometer based on fiber bragg grating |
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