CN103389120A - Optical fiber ringdown cavity sensor array device based on wavelength division multiplexing - Google Patents
Optical fiber ringdown cavity sensor array device based on wavelength division multiplexing Download PDFInfo
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Abstract
The invention relates to an optical fiber ringdown cavity sensor array device based on wavelength division multiplexing, relates to a sensor networking system, and aims to solve problems of high cost and resource waste due to the fact that a plurality of optical fiber ringdown cavity sensors are required in the physical quantity measurement of a plurality of positions, and each optical fiber ringdown cavity sensor correspondingly requires a light source and a demodulation light path. The device comprises a tunable laser, an acoustic-optical modulator, an isolator, a photoelectric detector, M optical fiber ringdown cavity sensors and M fiber bragg gratings, wherein the tunable laser, the acoustic-optical modulator and the isolator are sequentially connected to a light path in series; couplers of the M optical fiber ringdown cavity sensors and the fiber bragg gratings are sequentially connected in a light path in series through optical fibers, and the isolator is communicated with an input end of the light path; and output couplers of the M optical fiber ringdown cavity sensors are sequentially connected in an output light path in series through optical fibers, a light signal in the output light path is received by the photoelectric detector, and the photoelectric detector outputs a sensing signal. The optical fiber ringdown cavity sensor array device is applicable to sensor networking.
Description
Technical field
The invention belongs to the Fibre Optical Sensor field of measuring technique, it relates to the sensor network system.
Background technology
Optical cavity ring-down (ringdown) technology after 20th century, be suggested the eighties, just studied widely and uses by people, particularly the application aspect micro-measure of the change.The fast development of photoelectron technology and optical communication technique, impel take the sensor of optical fiber as basis and obtain applying more widely, so in calendar year 2001, G.Stewart etc. propose first fiber annular and decline and swing the chamber system, and use it for the aspects such as stress, pressure and minimum gas.
Have the good characteristics such as cheap, light, acid and alkali-resistance, anticorrosive and anti-electromagnetic interference (EMI) due to Fibre Optical Sensor, based on the ring cavity of optical fiber structure, decline and swing (ringdown) sensor and therefore paid close attention to widely.This technology is also referred to as optical fiber and declines and swing (ringdown) chamber technology, and it is to utilize the light loss in optic fiber ring-shaped cavity relevant with extraneous related physical quantity variation, by match, can draw respective physical quantitative change information.
This technology is widely used on the physical quantities such as the concentration change, temperature variation of pressure, variations in refractive index, chemistry and biological solution.Owing to needing in actual applications the multiposition physical quantity, and require real-time, so need a plurality of optical fiber to decline to swing (ringdown) cavity sensor to measure simultaneously.And at present, each optical fiber declines and swings (ringdown) cavity sensor and need a light source and demodulation light path, when multiposition measuring, needs to arrange a plurality of sensors, therefore needs a plurality of light sources and demodulation light path, a large amount of wastes of the high and resource of cost.
Summary of the invention
The objective of the invention is to need each optical fiber to decline in measuring simultaneously to swing in order to solve existing real-time multiposition the problem of cavity sensor and the wasting of resources high to the cost that produces in requisition for a light source and demodulation light path, provide a kind of optical fiber based on wavelength-division multiplex to decline and swing chamber sensor array device.
decline and swing chamber sensor array device based on the optical fiber of wavelength-division multiplex, it comprises tunable laser, acousto-optic modulator, isolator, photodetector, detecting unit, M optical fiber declines and swings cavity sensor and M fiber grating, M is the integer greater than 1, tunable laser, acousto-optic modulator and isolator are serially connected in light path successively, optical fiber declines and swings cavity sensor and comprise input coupler, optical fiber and output coupler, utilize optical fiber to be connected to become an annular closed cavity structure between input coupler and output coupler, optical fiber declines, and the input coupler that swings cavity sensor is corresponding composes in series one group with a fiber grating by optical fiber, M group optical fiber input coupler and the fiber grating that swings cavity sensor that decline is serially connected in a road light path successively by optical fiber, the output terminal of isolator is communicated with the input end of described light path, M optical fiber output coupler that swings cavity sensor that declines is serially connected in output light path by optical fiber successively, in output light path, the optical signals photodetector receives, the output terminal of the detection signal of photodetector is communicated with the input end of the detection signal of detecting unit, and the output terminal of photodetector is the output terminal of transducing signal.
The present invention has realized obtaining simultaneously M optical fiber by a light source and demodulation light path and has declined and swing the cavity sensor transducing signal, has realized that M is declined that to swing the chamber sensing probe multiplexing.Solved existing single optical fiber decline swing cavity sensor can't know a plurality of position simultaneously the time monitoring, measure in real time and a plurality of optical fiber declines and swings cavity sensor and need the problem of a plurality of light sources and demodulation light path.Reduced the cost of application sensors array, the application practicality more economically that making declines swings the chamber sensing technology.
Description of drawings
Fig. 1 is structural representation of the present invention in embodiment one, Fig. 2 is the composition structural representation of tunable laser in embodiment two, Fig. 3 is that in embodiment three, declining of single optic fiber ring-shaped cavity swung curve, Fig. 4 declines while changing without external environment in embodiment four to swing curve waveform, and Fig. 5 is that declining while having stress to apply in embodiment five swung curve waveform.
Embodiment
embodiment one: present embodiment is described in conjunction with Fig. 1, the described optical fiber based on wavelength-division multiplex of present embodiment declines and swings chamber sensor array device, it comprises tunable laser 1, acousto-optic modulator 2, isolator 3, photodetector 4, detecting unit 7, M optical fiber declines and swings cavity sensor 5 and M fiber grating 6, M is the integer greater than 1, tunable laser 1, acousto-optic modulator 2 and isolator 3 are serially connected in light path successively, optical fiber declines and swings cavity sensor 5 and comprise input coupler 5-1, optical fiber 5-2 and output coupler 5-3, utilize optical fiber 5-2 to be connected to become an annular closed cavity structure between input coupler 5-1 and output coupler 5-3, optical fiber declines, and the input coupler 5-1 that swings cavity sensor 5 is corresponding composes in series one group with a fiber grating 6 by optical fiber, the flashlight that fiber grating 6 reflects swings declining of cavity sensor as declining and swings signal.M group optical fiber input coupler 5-1 and the fiber grating 6 that swings cavity sensor 5 that decline is serially connected in a road light path successively by optical fiber, and the output terminal of isolator 3 is communicated with the input end of described light path; M optical fiber output coupler 5-3 that swings cavity sensor 5 that declines is serially connected in output light path by optical fiber successively, in output light path, optical signals photodetector 4 receives, the output terminal of the detection signal of photodetector 4 is communicated with the input end of the detection signal of detecting unit 7, and the output terminal of photodetector 4 is the output terminal of transducing signal.
Utilization of the present invention couples together M optic fiber ring-shaped cavity, and utilizes fiber grating to select ripple, and then being input to declines accordingly swings in chamber, has guaranteed that each optical fiber light that swings in chamber that declines is single wavelength.
A tunable light source produces the laser of wavelength continuous variable, this Shu Jiguang is modulated into pulse (obtaining higher extinction ratio) by acousto-optic modulator, then the splitting ratio that enters 2*2 via optoisolator is the coupling mechanism of 99:1, light after the input end input of first input coupler, is coupled away from 99% end of first input coupler.99% output terminal of first input coupler adds first bragg grating.
Constantly, the laser of tunable laser output is just in time gentle with the wavelength of first fiber grating for t1, and the light of specific wavelength is reflected back in the optic fiber ring-shaped cavity of two 99:1 coupling mechanisms formation.Light when the output coupler of the 99:1 that runs to 2*2, has 1% optically-coupled to go out in optic fiber ring-shaped cavity, the light that is coupled away is detected device and receives and be converted to electric signal.At this moment in optic fiber ring-shaped cavity, remaining most of light continues to propagate in optic fiber ring-shaped cavity, and intensity decays simultaneously, gets back to again on output coupler after light transmission one circle, again exports 1% light, and light forms to decline and swings in optic fiber ring-shaped cavity.So repeatedly, from t1 constantly, form the electric pulse string of a plurality of exponential dampinies.Swing in chamber when having physical quantity to be loaded into to decline, the ring-down time of optical fiber is changed.Electric signal is input to the variation of demodulating equipment according to ring-down time, can records the physical quantity change information.
Constantly, the light of laser instrument output and second fiber grating coincide t2, and this flashlight will pass through first input coupler, first fiber grating successively., through second input coupler, enter second fiber grating.Just in time equal the reflection wavelength of second fiber grating due to wavelength, so this flashlight will reflect, and enter second and decline and swing chamber.The operational process of light is identical with the first order, and light is decayed in the optic fiber ring-shaped cavity of the second level, and often transmits and export light intensity one time once enclosing in optic fiber ring-shaped cavity, and so repeatedly, decline and swing string in the formation second level.Read corresponding light intensity variable quantity by demodulating equipment equally, draw declining of the second level and swing die-away time, determine that second physical quantity of swinging chamber that declines changes.
The method of operation of M level optic fiber ring-shaped cavity is consistent with above-mentioned front two-stage.Utilize the tunable laser cycle of carrying out to sweep ripple, with regard to passable to periodicity, exporting.Because the wavelength of each optic fiber ring-shaped cavity is different, therefore which optic fiber ring-shaped cavity can distinguish easily the variation of ringdown time comes from, and namely can determine to come from the sensor information of which position.
Because the wavelength of tunable laser is continuously adjustable, wavelength spacing by two gratings rationally are set and the wavelength of tunable laser be rate over time, and we can distinguish declining of different wave length and swing the heat transfer agent of cavity sensor by the decline sequential difference of swinging spectrum of M the difference of swinging chamber of declining.
Utilize the sensor of this technology or principle all should belong to the scope of its claim.
Embodiment two: in conjunction with Fig. 2, present embodiment is described, present embodiment is that the described optical fiber based on wavelength-division multiplex of embodiment one is declined and swings the tunable laser 1 of chamber sensor array device.Can use following structure, it comprises wavelength division multiplexer 1-1,80:20 coupling mechanism 1-2, isolator 1-3, erbium-doped fiber 1-4, F-P wave filter 1-5 and semiconductor laser 1-6, wavelength division multiplexer 1-1, erbium-doped fiber 1-4, isolator 1-3, F-P wave filter 1-5 and 80:20 coupling mechanism 1-2 are serially connected in the closed loop light path successively by optical fiber, the light output end of semiconductor laser 1-6 is communicated with the light input end of wavelength division multiplexer 1-1, and 20% signal output part of 80:20 coupling mechanism 1-2 is the output terminal of tunable laser 1.
Tunable laser 1, in wavelength-division multiplex formula ringdown cavity sensor, an effect of sweeping ripple is provided, namely in pulse of acousto-optic modulator 2 outputs, can complete the ripple of sweeping of one-period, do the multiplexing of M fiber optic loop, need during this period of time can export the continuous laser that covers M wavelength, and that variable wavelength wherein is provided is F-P wave filter 1-5, due to the seeing through wavelength and control voltage and meet linear relationship of this wave filter, the optical wavelength that can utilize continuous regulation voltage to need is utilized the output of F-P wave filter 1-5 continuous tuning.
Light source 1-6 by 980nm carries out pumping, utilizes erbium-doped fiber to produce the broad band laser of 1550nm, uses F-P wave filter selectivity to see through the wavelength that needs, and realizes the tunable optical source design.
This programme utilizes the tunable laser of autonomous Design to realize wavelength control, but is not restricted to this tunable optical Source Type, meets and can realize that the continuously adjustable light source of the multiplexing condition of Fibre Optical Sensor all can.
Embodiment three: the principle of utilizing optical fiber to decline to swing ring, four of our design are declined and swing the multiplexing sensor array structure in chamber.Selection optical fiber declines while swinging the long 60m of being in chamber, and the ringdown time meets such formula:
Wherein the loss of optic fiber ring-shaped cavity one circle should meet: A=α L+E+ γ, consider that the scattering loss generalized case is very little, scattering loss γ=0, namely have such formula: A=α L+E, L=60m wherein, α=0.34dB/km simultaneously, the insertion loss supposition one of coupling mechanism is 0.09dB, optical fiber tie point loss 0.02dB, draw: E=2 * 0.09+3 * 0.02dB=0.24dB finally.Draw like this
=0.0599, (4.343 introducing is dB to be converted to 1 be the data procedures amount dB=10/ln10 of unit).That is:
In draw t
0=4.88 μ s.Wherein commonly use single-mode fiber refractive index n=1.464.Can obtain simultaneously bright dipping and transmit the time of a circle in optical fiber:
Fig. 3 has provided single declining and has swung declining of chamber and swing figure.
We make 4 and decline and swing chamber, choose optic fiber grating wavelength 1530nm, 1535nm, and 1540nm, 1545nm, corresponding each declines and swing the ring ring-down time is 4.88 μ s.Therefore what need is that continuous tuning scan period of F-P wave filter 1530-1545nm is greater than 20 μ s.Both the F-P wave filter will cover 4 ringdown times of declining and swinging chamber modulation period.Fig. 4 has provided four optical fiber and has declined and swing multiplexing the declining of cavity sensor and swing figure.
Embodiment four: present embodiment is described in conjunction with Fig. 1 and Fig. 3, present embodiment is that the described optical fiber based on wavelength-division multiplex of embodiment one is declined and swings the further restriction of chamber sensor array device, and acousto-optic modulator 2 adopts AMM-55-8-70-1550-2FP.
This acousto-optic modulator is only as illustration, and other acousto-optic modulators that meet arbitrarily service condition all can.
The model of acousto-optic modulator is the AMM-55-8-70-1550-2FP of BRIMROSE, S/N:0611-SY-7400.Use simultaneously the ACOUSTO-OPTIC DRIVER of BRIMROSE as driving, that signal controlling is used is the AFG320 of Tektronix.Know by calculating, if want to realize that M is individual multiplexing or more, the signal source cycle must meet the ringdown time doubly greater than M, and the acousto-optic modulator signal source frequency is 30KHz, and dutycycle is set to 1%.Signal amplitude is set as 3V, and offset is set to 1.5V.
Embodiment five: in conjunction with Fig. 1, present embodiment is described, present embodiment is that the described optical fiber based on wavelength-division multiplex of embodiment one is declined and swings the further restriction of chamber sensor array device, and fiber grating 6 adopts bragg grating.
Embodiment six: present embodiment is described in conjunction with Fig. 1, Fig. 4 and Fig. 5, present embodiment is that the described optical fiber based on wavelength-division multiplex of embodiment one is declined and swings the further restriction of chamber sensor array device, and it is the detector of DC-125MHZ that photodetector 4 adopts Low Noise Photoreceiver model.
This photodetector is only as illustration, and other photodetectors that meet arbitrarily service condition all can.
The major part of sensor is optic fiber ring-shaped cavity, and the setting length of ring cavity is L=60m, use be coupling mechanism and the optical fiber of 99:1, form optical fiber ringdown chamber.
The photo-detector of realizing photoelectric converting function is Low Noise Photoreceiver (DC-125MHZ), uses 0901 shape Current-Limited Power Supply to provide power supply for it.So just convert electrical signals to light signal, then can utilize oscillograph analysis.
Stress is applied on optic fiber ring-shaped cavity, the variation that the output light intensity waveform occurs.Due to each fiber optic loop perception is the STRESS VARIATION of diverse location, the change of ring-down time is different separately, for example, in Fig. 5 in the ringdown time of the 4th fiber optic loop and Fig. 4 the corresponding ringdown time that does not add stress contrast, the ringdown time becomes 2 μ s., by linear fit, draw the numerical value that concerns parameter k of ring-down time and ambient pressure.
Certainly, this multiplex technique is applicable to stress measurement incessantly, if can make optic fiber ring-shaped cavity to responsive to temperature, this sensor also can be made temperature monitor.Because this sensor can realize that therefore this sensor, can rely on its multiposition physical quantity measuring ability to the different physical quantities sensitivity, the Real-Time Monitoring ability waits by force good characteristic to be widely used.
Solved the ability that can't know simultaneously a plurality of positions physical quantity of existing single optical fiber ringdown cavity sensor, do not use a large amount of time delay optical fiber, just can realize that more sensing probes are multiplexing, improve resource utilization, and use optical fiber as material, be convenient to into net laying and establish, low to the arrangement environment conditional request, have higher practicality., because this wavelength-division multiplex formula of above advantage ringdown cavity sensor array has prospect widely in practical engineering application, be the structure monitoring sensor array of future ideality.
Claims (5)
1. decline and swing chamber sensor array device based on the optical fiber of wavelength-division multiplex, it is characterized in that, it comprises tunable laser (1), acousto-optic modulator (2), isolator (3), photodetector (4), detecting unit (7), M optical fiber declines and swings cavity sensor (5) and M fiber grating (6), M is the integer greater than 1, tunable laser (1), acousto-optic modulator (2) and isolator (3) are serially connected in light path successively, optical fiber declines and swings cavity sensor (5) and comprise input coupler (5-1), optical fiber (5-2) and output coupler (5-3), utilize optical fiber (5-2) to be connected to become an annular closed cavity structure between input coupler (5-1) and output coupler (5-3), optical fiber declines, and the input coupler (5-1) that swings cavity sensor (5) is corresponding composes in series one group with a fiber grating (6) by optical fiber, M group optical fiber input coupler (5-1) and the fiber grating (6) that swings cavity sensor (5) that decline is serially connected in a road light path successively by optical fiber, the output terminal of isolator (3) is communicated with the input end of described light path, M optical fiber output coupler (5-3) that swings cavity sensor (5) that declines is serially connected in output light path by optical fiber successively, in output light path, optical signals photodetector (4) receives, the output terminal of the detection signal of photodetector (4) is communicated with the input end of the detection signal of detecting unit (7), and the output terminal of photodetector (4) is the output terminal of transducing signal.
2. decline and swing chamber sensor array device based on the optical fiber of wavelength-division multiplex according to claim 1, it is characterized in that, tunable laser (1) comprises wavelength division multiplexer (1-1), 80:20 coupling mechanism (1-2), isolator (1-3), erbium-doped fiber (1-4), F-P wave filter (1-5) and semiconductor laser (1-6), wavelength division multiplexer (1-1), erbium-doped fiber (1-4), isolator (1-3), F-P wave filter (1-5) and 80:20 coupling mechanism (1-2) are serially connected in the closed loop light path successively by optical fiber, the light output end of semiconductor laser (1-6) is communicated with the light input end of wavelength division multiplexer (1-1), 20% signal output part of 80:20 coupling mechanism (1-2) is the output terminal of tunable laser (1).
3. decline and swing chamber sensor array device based on the optical fiber of wavelength-division multiplex according to claim 1, it is characterized in that, acousto-optic modulator (2) adopts AMM-55-8-70-1550-2FP.
4. decline and swing chamber sensor array device based on the optical fiber of wavelength-division multiplex according to claim 1, it is characterized in that, fiber grating (6) adopts bragg grating.
5. decline and swing chamber sensor array device based on the optical fiber of wavelength-division multiplex according to claim 1, it is characterized in that, it is the detector of DC-125MHZ that photodetector (4) adopts Low Noise Photoreceiver model.
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Cited By (4)
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| CN104811241A (en) * | 2015-04-29 | 2015-07-29 | 中国科学院半导体研究所 | Wavelength-tunable optical time domain reflectometer and fiber ring-down cavity sensor array integrated system |
| CN106091973A (en) * | 2016-07-05 | 2016-11-09 | 哈尔滨理工大学 | Based on annular Research on Cavity Ring Down Spectroscopy strain transducer and strain detecting method |
| CN108801500A (en) * | 2018-08-22 | 2018-11-13 | 太原理工大学 | Fiber-optical grating temperature sensor based on chaos associated fiber ring attenuation and vibration technique |
| CN114646340A (en) * | 2022-03-16 | 2022-06-21 | 华中科技大学 | Multiplexing FLRD sensor based on wide-spectrum continuous light and multi-parameter detection method |
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Cited By (4)
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| CN104811241A (en) * | 2015-04-29 | 2015-07-29 | 中国科学院半导体研究所 | Wavelength-tunable optical time domain reflectometer and fiber ring-down cavity sensor array integrated system |
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| CN108801500A (en) * | 2018-08-22 | 2018-11-13 | 太原理工大学 | Fiber-optical grating temperature sensor based on chaos associated fiber ring attenuation and vibration technique |
| CN114646340A (en) * | 2022-03-16 | 2022-06-21 | 华中科技大学 | Multiplexing FLRD sensor based on wide-spectrum continuous light and multi-parameter detection method |
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