CN2819171Y - Wave frequency division duplexing system of platinum sensor by optical fiber method - Google Patents
Wave frequency division duplexing system of platinum sensor by optical fiber method Download PDFInfo
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- CN2819171Y CN2819171Y CN 200520034249 CN200520034249U CN2819171Y CN 2819171 Y CN2819171 Y CN 2819171Y CN 200520034249 CN200520034249 CN 200520034249 CN 200520034249 U CN200520034249 U CN 200520034249U CN 2819171 Y CN2819171 Y CN 2819171Y
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Abstract
It is a wave frequency division duplexing system of platinum sensor by optical fiber method. It includes a broadband luminaire, a thick wave-division multiplexing device, an optical fiber, a coupler (a beam splitter), a refractive index matching liquid, a sensor and an optical spectrometer, wherein the optical fiber adopts the common single-mode optical fiber and the sensor adopts the optical fiber method platinum sensor. The thick wave-division multiplexing device is used to divide the broadband light into a plurality of paths so as to realize the wave division multiplexing. The sensors with the different cavity length are connected into each path by the beam splitter to realize the frequency division multiplexing. The amount of the sensors which can be duplicated by the wave frequency division multiplexing system is the product of the multiplexing amount of the individual wave division and the multiplexing amount of the frequency division. Therefore, the system can greatly enhance the multiplexing efficiency of the sensor largely, and it still can get the rather accurate measured value. This feature can no doubt largely reduce the cost of the optical fiber method platinum sensor multiplexing system, and the system can lay the foundation for the large scale application of the optical fiber method platinum sensor.
Description
Technical field
The utility model belongs to the fiber optic sensor technology field, is specifically related to a kind of multiplex system of optical fiber Fabry-Perot sensor.
Technical background
In optical fiber intelligent structure, Fabry-perot optical fiber (Fabry-Perot) sensor is use success a kind of at present.The basic structure of optical fiber Fabry-Perot sensor mainly is made of capillary quartz glass tube and light importing/reflection single-mode fiber as shown in Figure 4, wherein, the placement that is parallel to each other of two fiber end faces, at the quartz ampoule two ends, optical fiber and quartz ampoule are glued together.Generally speaking, the reflectivity of two fiber end faces equates in the optical fiber Fabry-Perot sensor, and mirror based fiber optica plated film not, and its reflectivity is less; If two fiber end faces in the optical fiber Fabry-Perot sensor are plated one deck reflectance coating, make high reflectance and the unequal structure of reflectivity, we become optical fiber Fizeau sensor (temporarily also not having suitable Chinese translation at present) to the optical fiber Fabry-Perot sensor with such special construction.
Optical fiber Fabry-Perot sensor is following in working order, and incident light comes and goes the output that repeatedly forms multiple-beam interference between two reflection end faces; When the medium refractive index n in long d in chamber (distances between two fiber end faces that are parallel to each other) or the chamber changes with extraneous factor, it interferes output also to change thereupon, basic functional principle (the works such as Jin Wei of Here it is optical fiber Fabry-Perot sensor, Wave Guiding Optics sensor: philosophy and technique, Science Press, 1998, pp291).Generally be variation by external environment to the influence that the long d in chamber produces, carry out the measurement of strain, temperature, pressure etc.As for strain measurement, strain changes the long d in chamber, can obtain dependent variable ε=Δ d/L by obtaining the variation delta d of d under strain, and wherein L is the length of sensor.Here use fourier methods to carry out demodulation for the demodulation of transducing signal, because the approximate cosine distribution of sensor signal, can to obtain the chamber of sensor long by obtaining signal frequency.When external environment changes, thereby cause chamber changing of long hair transducing signal frequency to change, can obtain the variation of external environment like this by the calculating of transducing signal frequency.
Development along with the modern surveying technology, optical fiber Fabry-Perot sensor more and more is subject to people's attention (Taylor's Henry works, Fibre Optical Sensor, New York: horse rope Deco publishing house, 2002, people's papers such as pp41 and Rao Yunjiang, the optics journal, 2002,22:85), it can carry out the measurement of strain, temperature and pressure etc.Now be widely applied to the monitoring structural health conditions of compound substance, heavy construction structure (as bridge etc.), aerospace vehicle, aircraft etc., (seen Eric Wood works, Fibre Optical Sensor, New York: horse rope Deco publishing house, 2002 to realize so-called intelligence structure; See and wear dimension Jackson paper, the physical engineering magazine: scientific instrument, 1985,18:981).Compare with traditional sensor, optical fiber Fabry-Perot sensor has remarkable advantages such as the electromagnetic interference (EMI) of not being subjected to, applied widely, good stability, good reliability, resolution height, precision height, volume be little, in light weight (to be seen and wears dimension Jackson works, optical fiber sensing technology, London: Cha Pumanhuo publishing house, 1998,2:167; Wear dimension Jackson paper, the physical engineering magazine: scientific instrument, 1985,18:981).
But it is exactly difficult multiplexing that still there is a shortcoming in optical fiber Fabry-Perot sensor, thereby causes system cost higher, has limited its practical ranges.
In order to improve its multiplexing capacity, since the eighties, people have proposed some multiplexing methods, (see papers such as Rao Yun river, SPIE 1995,2507:90) as space division multiplexing, it is that the reception optical fiber of each sensor is encoded according to the locus, by the addressing of scanning mechanism control photoswitch, this method complex structure, multiplexing limited amount; Time division multiplex (is seen papers such as Taylor Henry, applied optics, 1995,34:5861), it is multiplexing to utilize mistiming that light transmits in different length optical fiber to produce, thereby each sensor signal arrives photo-detector at different time order and functions, but this method is owing to be operated in single wavelength system, measurement range is little, and measuring accuracy is low; (see papers such as Davis, SPIE 1988, and 904:114), it needs reference interferometer, cause the system architecture complexity, and multiplexing quantity is also less, can not satisfy requirement of actual application for coherent multiplexing.
For this reason, we also study the multiplexing method of optical fiber Fabry-Perot sensor, the wavelength-division multiplex method that has proposed optical fiber Fabry-Perot sensor (is seen papers such as Zhou Changxue, Asian-Pacific optics meeting 2004, SPIE, 5634:41), its system architecture as shown in Figure 1, (CWDM) is divided into a plurality of passages with broadband light by Coarse Wave Division Multiplexer, as for a 1 * 4CWDM, the broadband light that can be 1521～1601nm with wavelength coverage is decomposed into 1521～1541nm, 1541～1561nm, 1561～1581nm, the passage of four different wavelength range of 1581～1601nm, connect the wavelength-division multiplex that a sensor has promptly been realized 4 sensors at each passage, it is simple in structure, and measuring accuracy is also high, but because sensor must occupy enough wide bandwidth (as 20nm), and, the multiplexing quantity of sensor is restricted, even the wideband light source of 200nm bandwidth also can only multiplexing 10 sensors owing to be subjected to the restriction of light source bandwidth and spectrometer work spectral range.
We have also proposed the multiplexing method-optical fiber Fizeau sensor space frequency-division multiplexing method of another optical fiber Fabry-Perot sensor and (have seen papers such as Rao Yun river, Asian-Pacific optics meeting 2004, SPIE, 5634:304), its system architecture as shown in Figure 2, this method is utilized the frequency difference of the long sensor signal of different cavity, Fabry-Perot sensor is transformed, it is the same with common Fabry-Perot sensor wherein to import optical fiber, be the smooth general single mode fiber of end face, but the mirror based fiber optica end face has plated layer of metal silver, forms the reflecting surface with high reflectance (reflectivity about 95%).Because these sensing head two fiber end face reflectivity do not wait, for distinguishing mutually with the common Fa-Po cavity that the both ends of the surface reflectivity equates, with it be called the Fizeau chamber (see people's papers such as Rao Yun river, IEEE light wave science and technology magazine, 1994,12:1685).Because ordinary optic fibre Fabry-Perot sensor mirror based fiber optica is plated film not, its reflectivity is less, the signal that causes reflexing to incident optical from mirror based fiber optica too a little less than, the chamber length of common like this Fabry-Perot sensor can not be oversize, generally be no more than 1mm, otherwise since the mirror based fiber optica reflected light through after the long range attenuation too a little less than, can not interfere; But behind the mirror based fiber optica plated film, because the reflectivity of coated optical fibre is higher, make sensor cavity length can do longlyer like this, reach about 15mm, the sensor signal that the different cavity that mixes like this is long can be come out cavity length demodulating by the Fourier spectrum analytical approach.The optical fiber Fizeau sensor space Frequency Division Multiplexing system that adopts said method to make, simple in structure, the measuring accuracy height, but owing to the reason of crosstalking between each sensor, the long difference in two sensors chamber must be greater than certain value (about 600～800 microns) arbitrarily, because the chamber is long and the restriction of the long difference in chamber, the quantity of sensor that can be multiplexing still has only tens like this, can not satisfy the requirement of sensor large-scale application far away, need a kind of more efficient multiplex system.
As seen, common optical fiber Fabry-Perot sensor multiplex system all exists multiplexing quantity low, can not satisfy requirement of actual application; Also there is the shortcoming that measuring accuracy is low, equipment is complicated or cost is higher in the optical fiber Fabry-Perot sensor multiplex system that has.
Summary of the invention
At the common existing shortcoming of optical fiber Fabry-Perot sensor multiplex system, the purpose of this utility model is to provide a kind of wave-division frequency division multiplex system of optics fiber fabry-perot sensor of high multiplexing efficient.This system combines the Wave-division frequency division multiplex system of setting up optical fiber Fabry-Perot sensor with wavelength-division multiplex technique and spatial frequency multiplex technique, by Coarse Wave Division Multiplexer (CWDM) light source is divided into the wave band of a plurality of different wave lengths, inserts a plurality of Fabry-Perot sensors at each wave band by beam splitter and carry out frequency division multiplexing.Because this sensor-based system is while implementation space frequency division multiplexing on each CWDM wave band, so improved the multiplexing capacity of sensor greatly, in the health monitoring of large scale structure, can reduce the cost of system greatly, therefore good cost performance and big practical value are arranged.
The technical solution of the utility model is as follows:
A kind of wave-division frequency division multiplex system of optics fiber fabry-perot sensor, as shown in Figure 3, it comprises wideband light source, Coarse Wave Division Multiplexer (CWDM), optical fiber, beam splitter, index-matching fluid, sensor and spectrometer, and wherein optical fiber adopts general single mode fiber, and sensor adopts optical fiber Fabry-Perot sensor.With the beam splitter is the center, by optical fiber respectively with wideband light source, Coarse Wave Division Multiplexer, index-matching fluid, spectrometer links to each other, Coarse Wave Division Multiplexer passes sensor by beam splitter with optical fiber and Fabry-perot optical fiber and links to each other, spectrometer links to each other with computing machine by data line, the light that sends from wideband light source is behind 2 * 2 beam splitters, enter CWDM, broadband light by CWDM is broken down into the passage that a plurality of bandwidth are about 20nm (bandwidth too hour measuring accuracy is lower), noiseless between each passage, can insert sensor and promptly realize wavelength-division multiplex, the signal that reflects from sensor is gone into spectrometer through CWDM and beam splitter are laggard, by computer data acquisition, carry out data processing then; Because the approximate cosine waveform of sensor signal, and the sensor signal frequency difference that different cavity is long, the a plurality of sensor signals that mix can realize demodulation by the Fourier transform spectrum analysis, on each passage of CWDM, insert a plurality of long Fabry-Perot sensors of different cavity that have like this by beam splitter, multiplexing when promptly having realized wavelength-division and frequency division.Wave-division frequency division multiplex system can be multiplexing the quantity of sensor be the product of independent wavelength-division and frequency division multiplexing quantity, thereby can improve the multiplexing efficient of sensor greatly.Index-matching fluid in the system is used for preventing the interference that the fiber end face reflection brings.The structure of method amber sensing head is made of capillary quartz glass tube and light importing/reflection single-mode fiber as shown in Figure 4, and at the quartz ampoule two ends, optical fiber and quartz ampoule are glued together, and constitutes optical fiber Fabry-Perot sensor.
Because the long 1mm that generally is no more than in ordinary optic fibre Fabry-Perot sensor chamber, and because will there be certain difference in the chamber between long, thereby quantity that can frequency division multiplexing has only 2～3.Use the forms of modification of optical fiber Fabry-Perot sensor: optical fiber Fizeau sensor (wherein imports optical fiber for end face being cut into the general single mode fiber on plane for this reason, the mirror based fiber optica end face has plated layer of metal silver, forms the reflecting surface with high reflectance (reflectivity about 95%).Because these sensing head two fiber end face reflectivity do not wait,, it is called the Fizeau chamber) for distinguishing mutually with the common Fa-Po cavity that the both ends of the surface reflectivity equates.Because optical fiber Fizeau sensor cavity length can reach 15mm, if the long difference in chamber between the sensor is made as 1mm (actual can be littler), the Fizeau sensor that frequency division multiplexing can be multiplexing 15 like this.That use in the system is 1 * N CWDM, when utilizing can be on each CWDM passage multiplexing 15 sensor of optical fiber Fizeau sensor Wave-division frequency division multiplex method like this, i.e. and sensor that altogether can multiplexing 15 * N; If use 1 * 10CWDM, number of sensors that can be multiplexing will reach about 150.
The beneficial effect of this system is:
1, in this system, because the interference of light beam can Approximate Equivalent be two-beam interference in the optical fiber Fabry-Perot sensor, its spectrum is approximately cosine distribution (as Fig. 5), and the frequency difference of the Fabry-Perot sensor of different cavity length.The frequency difference of each Fabry-Perot sensor signal of ought mixing like this is that the chamber of Fa-Po cavity is long not simultaneously, can the cavity length demodulating of each Fabry-Perot sensor be come out by FFT.And, because the chamber length in Fizeau chamber can be very long, reach the above and contrast of 10mm descend little, so can carry out frequency division multiplexing very easily.
2, in this system, used CWDM, each road transducing signal lays respectively at different wave bands, and each road signal is carried out the wavelength-division multiplex that same signal demodulation has promptly realized the multichannel transducing signal respectively.For CWDM, its adjacent channel isolation is greater than 35dB, can think not have between the adjacency channel and crosstalk, its return loss is especially greater than 45dB, can not consider, promptly compare with common optical fiber Fabry-Perot sensor system (no CWDM), the components and parts CWDM that this system adds is very little to the signal to noise ratio (S/N ratio) influence of system, still can obtain more accurate measured value.
3, wavelength-division and frequency multiplexing technique combine the multiplexing quantity that has improved Fabry-Perot sensor greatly, its multiplexing quantity is the product of independent wavelength-division and frequency division multiplexing quantity, solved the multiplexing inefficient problem of optical fiber Fabry-Perot sensor, this will reduce the cost of sensing system undoubtedly greatly, for the large-scale application of optical fiber Fabry-Perot sensor is laid a good foundation.In order to check the measuring accuracy of this system, carried out the strain measurement experiment, experiment shows that this sensor multiplexing system strain measurement precision can reach ± 5 μ ε, can satisfy requirement of actual application.Therefore, this sensor-based system has that multiplexing capacity is strong, and signal processing method is simple, and the result is accurate, and measuring accuracy is higher, and the characteristics that cost is low have higher utility.
Description of drawings
Fig. 1 is an optical fiber Fabry-Perot sensor wavelength-division multiplex sensor-based system structural drawing, wherein, and 1. wideband light source, 2. spectrometer, 3. beam splitter, 4. index-matching fluid, 5. Coarse Wave Division Multiplexer, 6. sensor, 7.PC machine;
Fig. 2 is an optical fiber Fizeau sensor space Frequency Division Multiplexing system structural drawing, wherein, and 1. wideband light source, 2. spectrometer, 3. beam splitter, 4. index-matching fluid, 6. sensor, 7.PC;
Fig. 3 is the wave-division frequency division multiplex system of optics fiber fabry-perot sensor structural drawing, wherein, and 1. wideband light source, 2. spectrometer, 3. beam splitter, 4. index-matching fluid, 5. Coarse Wave Division Multiplexer, 6. sensor, 7.PC;
Fig. 4 is the optical fiber Fabry-Perot sensor structural drawing, wherein, 8. imports single-mode fiber, 9. capillary quartz glass tube, 10. glue, 11. mirror based fiber opticas (to optical fiber Fizeau sensor, being plating high reflection film mirror based fiber optica));
Fig. 5 is the typical reflectance spectrum of optical fiber Fabry-Perot sensor;
Fig. 6 is a kind of embodiment structural drawing of wave-division frequency division multiplex system of optics fiber fabry-perot sensor, wherein, and 1. wideband light source, 2. spectrometer, 3. beam splitter, 4. index-matching fluid, 5. Coarse Wave Division Multiplexer, 6. sensor, 7.PC;
Fig. 7 is the mixed signal of 4 Fizeau sensors;
Fig. 8 has the long four-sensor signal FFT spectrum of different cavity;
Fig. 9 Wave-division frequency division multiplex strain experimental system, wherein, 1. wideband light source, 2. spectrometer, 3. beam splitter, 4. index-matching fluid, 5. Coarse Wave Division Multiplexer, 6. sensor, 7.PC);
The reflectance spectrum (system shown in Figure 9) of Figure 10 CWDM two passages;
Figure 11 is the strain experimental result picture;
Specific embodiments
Earlier system is created as structure shown in Figure 6, four have different cavity length (is 0.5mm, 1.5mm, 2.5mm Fizeau sensor 3.5mm) is connected in the system, its signal that reflects is the mixed signal of four sensors, with its go behind the direct current the result as shown in Figure 7, can't tell this mixed signal fully contain those frequency contents this moment, and it is long to use traditional crest value algorithm to obtain the chamber of Fizeau sensor, so need handle it.After signal carried out filtering and FFT, obtain waveform as shown in Figure 8, wherein horizontal ordinate is counting of FFT conversion, and it is long to obtain sensor cavity according to the horizontal ordinate of each peak value.As can be seen from Figure 8, signal can be separated in transform domain fully, in a CWDM passage, realized the multiplexing of four sensors thus, four long differences of sensor cavity are 1mm among Fig. 8, because Fizeau chamber length can reach about 15mm, in fact the quantity of sensor that can be multiplexing is about 15, the wavelength-division multiplex of adding four road CWDM passages just can multiplexing nearly 60 sensors, like this, wavelength-division multiplex and frequency division multiplexing combine the multiplexing capacity that has improved optical fiber Fizeau sensor greatly.
To propose the feasibility of principle and method in order verifying, to carry out the strain measurement experiment with system.The implementation structure of native system is seen Fig. 9, forms whole Wave-division frequency division multiplex system by wideband light source 1, spectrometer 2, beam splitter 3, index-matching fluid 4,1 * 2CWDM 5, a plurality of optical fiber Fizeau sensor 6 and computing machine 7 arranged side by side.S1 in four Fizeau strain transducers shown in Fig. 8 and S2 are connected on CWDM wavelength 1521nm～1541nm passage by beam splitter, and S3 and S4 are connected on wavelength 1541nm～1561nm passage, and its waveform as shown in figure 10.Wherein S1 and S3 stick on the metal cantilever, and the metal cantilevered distal end is installed stepper motor and cantilevered distal end is subjected to displacement and is produced strain, and S2 and S4 are then not strained, be used for measuring between the CWDM passage crosstalk and passage in crosstalking between the two Fizeau sensors.With the step-length decline 10mm of metal cantilevered distal end with every 1mm, the strain result of four sensor measurements as shown in figure 11.As can be seen from the figure this sensor accuracy is higher, between the CWDM passage crosstalk and passage in crosstalk all very little (± 3 μ ε) between the two Fizeau sensors, experimental results show that its measuring accuracy is ± 5 μ ε.For the health monitoring of most heavy construction structures (as bridge), this precision is all enough in engineering is used.
Claims (4)
1, a kind of wave-division frequency division multiplex system of optics fiber fabry-perot sensor, comprise wideband light source, Coarse Wave Division Multiplexer, optical fiber, beam splitter, index-matching fluid, Fabry-perot optical fiber passes sensor and spectrometer, with the beam splitter is the center, by optical fiber respectively with wideband light source, Coarse Wave Division Multiplexer, index-matching fluid, spectrometer links to each other, Coarse Wave Division Multiplexer passes sensor by beam splitter with optical fiber and Fabry-perot optical fiber and links to each other, spectrometer links to each other with computing machine by data line, it is characterized in that, the light that sends from wideband light source is behind beam splitter, enter Coarse Wave Division Multiplexer, be broken down into a plurality of bandwidth channel by Coarse Wave Division Multiplexer, on each passage of Coarse Wave Division Multiplexer, insert a plurality of long Fabry-Perot sensors of different cavity that have by beam splitter, the signal that reflects from sensor is gone into spectrometer through Coarse Wave Division Multiplexer and beam splitter are laggard, by computer data acquisition, carry out data processing then.
2, a kind of wave-division frequency division multiplex system of optics fiber fabry-perot sensor according to claim 1 is characterized in that, described Coarse Wave Division Multiplexer is divided into the passage that a plurality of bandwidth are about 20nm with wideband light source.
3, a kind of wave-division frequency division multiplex system of optics fiber fabry-perot sensor according to claim 1 is characterized in that, described Fabry-Perot sensor can be common Fabry-Perot sensor, also can be optical fiber Fizeau sensor.
According to claim 1,3 described a kind of wave-division frequency division multiplex system of optics fiber fabry-perot sensor, it is characterized in that 4, the long difference in the chamber of described Fabry-Perot sensor or optical fiber Fizeau sensor is greater than 600 to 800 microns.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1694389B (en) * | 2005-05-23 | 2010-04-28 | 电子科技大学 | Wave-division frequency division multiplex system of optics fiber fabry-perot sensor |
| CN101868688B (en) * | 2007-11-21 | 2013-03-06 | 约翰尼斯海登海恩博士股份有限公司 | Interferometer arrangement and method for the operation thereof |
| CN106092394A (en) * | 2016-06-23 | 2016-11-09 | 重庆大学 | High temperature strain measurement system and method based on optical fiber Fabry-Perot sensor |
| CN106197496A (en) * | 2013-11-21 | 2016-12-07 | 充梦霞 | A kind of laser sensor frequency division multiplexing device using photodetector |
| CN111289851A (en) * | 2020-02-24 | 2020-06-16 | 华北电力大学 | Frequency division multiplexing-based distributed GIS partial discharge ultrasonic optical sensing system |
-
2005
- 2005-05-23 CN CN 200520034249 patent/CN2819171Y/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1694389B (en) * | 2005-05-23 | 2010-04-28 | 电子科技大学 | Wave-division frequency division multiplex system of optics fiber fabry-perot sensor |
| CN101868688B (en) * | 2007-11-21 | 2013-03-06 | 约翰尼斯海登海恩博士股份有限公司 | Interferometer arrangement and method for the operation thereof |
| CN106197496A (en) * | 2013-11-21 | 2016-12-07 | 充梦霞 | A kind of laser sensor frequency division multiplexing device using photodetector |
| CN106092394A (en) * | 2016-06-23 | 2016-11-09 | 重庆大学 | High temperature strain measurement system and method based on optical fiber Fabry-Perot sensor |
| CN111289851A (en) * | 2020-02-24 | 2020-06-16 | 华北电力大学 | Frequency division multiplexing-based distributed GIS partial discharge ultrasonic optical sensing system |
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