CN201075010Y - Optical fiber grating digital demodulation system based on self-correlation principle - Google Patents
Optical fiber grating digital demodulation system based on self-correlation principle Download PDFInfo
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- CN201075010Y CN201075010Y CNU2007200276089U CN200720027608U CN201075010Y CN 201075010 Y CN201075010 Y CN 201075010Y CN U2007200276089 U CNU2007200276089 U CN U2007200276089U CN 200720027608 U CN200720027608 U CN 200720027608U CN 201075010 Y CN201075010 Y CN 201075010Y
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Abstract
The utility model discloses an optical fiber grating digital demodulation system which is based on the self-related principle. The utility model solves the problems of low measurement precision of demodulation technology, poor real-time property, inadequate reuse capability, high price, inability to meet the actual engineering needs and so on of the existing optical fiber grating sensing system, and the utility model has the advantages of high measurement precision, high scanning speed, good real-time property, strong reuse capability, high performance to cost ratio, strong universality, and so on. The system composition is that: the utility model includes a light source and at least one optical fiber grating sensor, the light source is connected with the optical fiber grating sensors which are sequentially connected in series by a coupling device, the coupling device is further connected with a tunable filter at the same time, the tunable filter is connected with a photodetector, the photodetector is connected with a preamplifier and a digital-analog converter sequentially, the digital-analog converter is connected with the input end of a digital controller; and the output end of the digital controller is connected with the control input end of the tunable filter by a mechatronic controller and a mechatronic demodulation system sequentially.
Description
Technical field
The utility model relates to a kind of optical fibre grating digital demodulation system based on autocorrelation principle.
Background technology
Fiber-optic grating sensor is a kind of wavelength-modulated type device, compact conformation, antijamming capability is strong, be convenient to utilize multiplexing (wavelength-division, time-division, the empty branch) technology to form optical fiber sensing network and carry out the large tracts of land multimetering, in many fields such as communication, building, machinery, medical treatment, space flight, navigation, mining industry wide application prospect is arranged all, obtain very big development in recent years.
At present, theoretical research about optical fiber grating sensing has obtained very big achievement, ripe fiber grating manufacturing process has also made fiber-optic grating sensor have the small serial production ability, and how to reduce cost, improve and separate the mediation multiplex technique, the requirement of satisfying high-precision applications on the engineering has become urgent problem.
Because the fiber grating demodulation technology is a kind of optic fiber grating wavelength drift high-resolution Detection Techniques, fundamental purpose is that the sensing grating reflectance spectrum is monitored in real time, analyze the coding wavelength change and be translated into electric signal output, its essence is the resolution of different coding light in a branch of light and the problem of measurement.Desirable detection method should satisfy following requirement:
(1) measurement range is big, the resolution height.In the practical application, usually require the investigative range of wavelength shift to reach nanoscale, Measurement Resolution is that inferior micromicron arrives several micromicrons, and promptly range of dynamic measurement is 1000: 1 ~ 100000: 1.
(2) reusability is good.Fiber grating sensing system mainly is made of light source, fiber-optic grating sensor and demodulating system three parts.By sharing light source and demodulating system, the cost of fiber grating sensing system will significantly reduce with the increase of multiplied sensor number, thereby reduce the cost of total system.
(3) real-time is good.For satisfying in the engineering, need demodulating system to have higher demodulation rate, so that in time follow the tracks of the variation of measured signal to the requirement of real time monitoring signals.
(4) highly versatile.For adapting to the needs of different scales fiber grating sensing system, require demodulating system can adapt to the measuring system of different wave length, varying number fiber-optic grating sensor formation, promptly have the versatility that does not rely on a certain particular fiber grating sensor.
At present, both at home and abroad this technology has been launched extensive and deep research, and proposed many demodulation schemes from different aspects, but commonly used mainly be filter method, interferometric method and tunable optical source scanning method, shown in subordinate list 1.Relatively get on very well, external research in this respect is comparatively ripe, and advanced technology and product are arranged; And the domestic development that still is in, the corresponding main dependence on import of product is so press for advanced technology with autonomous property right and product.
From subordinate list 1 as can be seen, existing demodulation method, or technical sophistication, cost performance is low, general field is difficult to accept; Real-time is poor, and resolution is low, is difficult to adapt to the needs of engineering survey, therefore all can not satisfy requirement of actual application fully.Particularly, the defective of prior art mainly shows the following aspects:
(1) high-resolution detection problem is difficult to solve under the strong noise background.In fiber grating sensing system, the spectrum width of sensing grating only is 0.07 ~ 0.6nm, and the reflected signal luminous energy is a part very small in the system source, therefore requires demodulating equipment higher signal to noise ratio (S/N ratio) to be arranged with the needed resolution of assurance system.And existing demodulation techniques adopt the light intensity detection method mostly, are difficult to solve the problem that high-resolution is surveyed under the strong noise background.
(2) multiplied sensor limited amount, the sensing network scale is difficult to adapt to actual demand.By sharing light source and demodulating system, the cost of fiber grating sensing system will significantly reduce with the increase of multiplied sensor number, and then form the advantage with respect to the dynamo-electric sensor-based system of tradition.But existing demodulation techniques are only supported 20 ~ 40 multiplied sensor number, and the multiplexing capacity of optical fiber grating sensing network is very limited, can't satisfy the scale requirement of large-scale and complicated monitoring objective.
(3) detection problem in real time is difficult to solve.Detection in real time requires demodulating system to have signal demodulation rate faster, can also can both measure well stationary singnal and Dynamic Signal simultaneously, and prior art can't satisfy the requirement of this two aspect simultaneously.This also is that the restriction fiber grating sensing system enters the bottleneck place that engineering is used.
Summary of the invention
The purpose of this utility model is exactly that present fiber grating sensor system demodulation technology measuring accuracy is low, real-time is poor in order to solve, multiplexing capacity deficiency, price are high, can't satisfy problem such as actual demands of engineering, a kind of measuring accuracy height that has is provided, sweep velocity is fast, real-time good, multiplexing capacity is strong, cost performance is high, the optical fibre grating digital demodulation system based on autocorrelation principle of advantages such as highly versatile.
For achieving the above object, the utility model adopts following technical scheme:
A kind of optical fibre grating digital demodulation system based on autocorrelation principle, it comprises light source and at least one fiber-optic grating sensor, described light source is connected through the fiber-optic grating sensor of coupling device with series connection successively, this coupling device also is connected with tunable optic filter simultaneously, tunable optic filter then is connected with photodetector, photodetector is connected with prime amplifier, digital to analog converter successively, and digital to analog converter is connected with the digitial controller input end; The output terminal of digitial controller then is connected with the control input end of tunable optic filter through electromechanical controller, dynamo-electric modulating system successively.
Described system obtains the demodulation result of needs based on the autocorrelation analysis of measuring-signal by digital processing method; Described coupling device is 2 * 2 coupling mechanisms, and described light source is a wideband light source; The device that described tunable optic filter can be regulated for centre wavelength arbitrarily is as Bragg grating, long-period gratings, F-P chamber etc.; Described fiber-optic grating sensor is any wavelength modulation type grating sensor, and as Bragg grating sensor, long-period grating sensor etc., and the grating sensor spectral line shape of different measuring points can be identical or different, and its range can overlap, and also can not overlap; Described digitial controller is for being the controller that core constitutes with DSP or FPGA or ARM chip.
The beneficial effect of demodulation method of the present utility model is: fiber grating auto-correlation numeral demodulation method is a kind of general new digital demodulation method based on time series analysis, it is by the powerful signal handling capacity of modern digital disposal system, can realize high resolving power, the multiple spot fast demodulation of dynamic and static parameter, and cost is low, highly versatile.Specifically, mainly contain these points:
(1) Measurement Resolution height can be realized high-acruracy survey under strong noise background.Unlike the prior art, demodulation techniques described in the utility model are based on the auto-correlation computation of signal, and measuring accuracy depends on the arithmetic capability of signal processor fully, therefore can obtain the result of measuring accuracy far above existing demodulation techniques under the low signal-to-noise ratio situation.
(2) reusability is good.Unlike the prior art, demodulation techniques described in the utility model are to obtain the multiplied sensor wave length shift by the variation of comparing adjacent periods internal modulation signal waveform, therefore when multiplexing, allow the spectral line of different measuring points multiplied sensor to be of similar shape (having identical centre wavelength) as allowing the different measuring points sensor, also allow the different measuring points multiplied sensor to have identical wavelength variation range (as being 1550nm-1555nm), thereby promoted the multiplexing capacity of system significantly.In theory, the number of demodulation techniques multiplied sensor described in the utility model can be unlimited, then is subjected to the restriction of optical-fiber network building mode and digital signal processor arithmetic capability during practical application.
(3) real-time is good.The signal that only can follow the tracks of several hertz ~ tens hertz with prior art is different, and demodulation techniques described in the utility model adopt flexible measurement method, have very fast demodulation speed, can follow the tracks of the signal of KHz magnitude, can satisfy the needs of real-time monitoring fully.
(4) cost performance height.Prior art has very strong dependence to the particular optical device, and this device mainly relies on import, so cost is very high.Demodulation techniques described in the utility model adopt numerical approach, have reduced the dependence to optical device to a certain extent, therefore can reduce system cost effectively, improve the cost performance of system.
(5) highly versatile.Unlike the prior art, demodulation techniques described in the utility model only require that in use reflected signal can be accepted by photodetector, and do not need system itself that measuring basis is provided, therefore to not having specific (special) requirements such as parameters such as grating sensor centre wavelength, adjacent sensors wavelength intervals, have stronger versatility, be easy to engineering and use.
Description of drawings
Fig. 1 is the fiber-optic grating sensor transmission demodulation synoptic diagram of the utility model demodulating system;
Fig. 2 is the fiber-optic grating sensor reflection demodulation synoptic diagram of the utility model demodulating system;
The interior signal waveforms of K scan period that Fig. 3 accepts for photodetector;
The interior signal waveforms of K+1 scan period that Fig. 4 accepts for photodetector;
K the signal waveforms that Fig. 5 accepts for photodetector;
K+1 the signal waveforms that Fig. 6 accepts for photodetector.
Wherein, 1. light source, 2. fiber-optic grating sensor, 3.2 * 2 coupling mechanisms, 4. tunable optic filter, 5. photodetector, 6. prime amplifier, 7. digital to analog converter, 8. digitial controller, 9. electromechanical controller, 10. dynamo-electric modulating system.
Embodiment
The utility model is described in further detail below in conjunction with accompanying drawing and embodiment.
Among Fig. 1, Fig. 2, fiber grating auto-correlation numeral demodulating system, comprise the fiber-optic grating sensor 2 that wideband light source 1 and several are connected successively, light source 1 is connected with fiber-optic grating sensor 2 through 2 * 2 coupling mechanisms 3, this coupling device also is connected with tunable optic filter 4 simultaneously, 4 of tunable optic filters are connected with photodetector 5, and photodetector 5 is connected with prime amplifier 6, digital to analog converter 7 successively, and digital to analog converter 7 is connected with digitial controller 8 input ends that adopt dsp chip; The output terminal of digitial controller 8 then is connected with the control input end of tunable optic filter 4 through electromechanical controller 9, dynamo-electric modulating system 10 successively.Tunable optic filter 4 can be Bragg grating, long-period gratings, F-P chamber etc.; Fiber-optic grating sensor 2 can be Bragg grating sensor, long-period grating sensor etc.System of the present utility model can adopt the projection demodulation also can adopt the system of reflection demodulation.
Demodulation method of the present utility model is,
The light that wideband light source sends enters fiber grating (FBG) sensor array through 2 * 2 coupling mechanisms, enters tunable optic filter after being reflected.Under the effect of dynamo-electric modulating system, the sensing grating reflected light that tunable optic filter will comprise metrical information is modulated into the signal of cycle variation in time, sends into photodetector again and carries out opto-electronic conversion, obtains the timing signal sequence that the cycle changes.This sequence signal is sent in the digital signal processor (DSP) after preposition amplification, digital-to-analog conversion (ADC) and is carried out computing, needing to obtain the optic fiber grating wavelength drift value of measurement, reaches the purpose of demodulation.
The demodulation example
In system shown in Figure 1, the wavelength tuning range of supposing tunable optic filter is 1550-1560nm, and half high bandwidth is 0.1nm, and the scan period is 1s, and sweep speed is 10nm/s.Simultaneously for the sake of simplicity, have only two multiplied sensor FBG1 and FBG2 in the supposing the system.
(1) situation one: multiplied sensor centre wavelength is inequality
Ignoring under the situation of noise, the initial center wavelength of supposing FBG1 is 1552nm, and half high bandwidth is 0.2nm; The initial center wavelength of FBG2 is 1553nm, and half high bandwidth is 0.3nm.In k scan period, suppose that external parameter does not change, the signal that this moment, photodetector was accepted is as shown in Figure 3; K+1 scan period, suppose that external parameter changes, cause the centre wavelength of FBG1 to become 1552.001nm, the centre wavelength of FBG2 becomes 1552.999nm, and then the signal accepted at this moment of photodetector is as shown in Figure 4.
(2) situation two: multiplied sensor centre wavelength is identical
Ignoring under the situation of noise, the initial center wavelength of supposing FBG1 is 1552nm, and half high bandwidth is 0.2nm; The initial center wavelength of FBG2 is 1552nm, and half high bandwidth is 0.3nm.In k scan period, suppose that external parameter does not change, the signal that this moment, photodetector was accepted is as shown in Figure 5; K+1 scan period, suppose that external parameter changes, cause the centre wavelength of FBG1 to become 1552.001nm, the centre wavelength of FBG2 becomes 1551.998nm, and then the signal accepted at this moment of photodetector is as shown in Figure 6.
(3) situation three: multiplied sensor center wavelength variation scope has coincidence
Ignoring under the situation of noise, the initial center wavelength of supposing FBG1 is 1552nm, and half high bandwidth is 0.2nm; The initial center wavelength of FBG2 is 1552nm, and half high bandwidth is 0.3nm.Since k scan period, suppose that external parameter changes the center sensor wavelength variations that causes and is:
| |
1# |
2# center sensor wavelength |
| K | 1552.000 | 1552.000 |
| K+1 | 1552.001 | 1551.998 |
| K+2 | 1552.002 | 1552.001 |
| K+3 | 1552.003 | 1552.000 |
| K+4 | 1552.001 | 1551.999 |
| K+5 | 1551.999 | 1552.000 |
| K+6 | 1551.997 | 1551.998 |
The center sensor wavelength variations that adopts the utility model demodulation to obtain is followed successively by:
| |
1# |
2# center sensor wavelength |
| K | 1552.000 | 1552.000 |
| K+1 | 1552.001 | 1551.984 |
| K+2 | 1552.002 | 1551.983 |
| K+3 | 1552.002 | 1552.000 |
| K+4 | 1552.001 | 1551.982 |
| K+5 | 1552.988 | 1551.998 |
| K+6 | 1551.979 | 1551.989 |
Claims (2)
1. optical fibre grating digital demodulation system based on autocorrelation principle, it comprises light source (1) and at least one fiber-optic grating sensor (2), it is characterized in that: described light source (1) is connected through the fiber-optic grating sensor (2) of coupling device with series connection successively, this coupling device also is connected with tunable optic filter (4) simultaneously, tunable optic filter (4) then is connected with photodetector (5), photodetector (5) is connected with prime amplifier (6), digital to analog converter (7) successively, and digital to analog converter (7) is connected with digitial controller (8) input end; The output terminal of digitial controller (8) then is connected with the control input end of tunable optic filter (4) through electromechanical controller (9), dynamo-electric modulating system (10) successively.
2. the optical fibre grating digital demodulation system based on autocorrelation principle according to claim 1 is characterized in that: described system obtains the demodulation result of needs based on the autocorrelation analysis of measuring-signal by digital processing method; Described coupling device is 2 * 2 coupling mechanisms (3), and described light source (1) is a wideband light source; The device that described tunable optic filter (4) can be regulated for centre wavelength arbitrarily; Described fiber-optic grating sensor (2) is any wavelength modulation type grating sensor, and the grating sensor spectral line shape of different measuring points can be identical or different, and its range can overlap, and also can not overlap; Described digitial controller (8) is for being the controller that core constitutes with DSP or FPGA or ARM chip.
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| Application Number | Priority Date | Filing Date | Title |
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| CNU2007200276089U CN201075010Y (en) | 2007-09-07 | 2007-09-07 | Optical fiber grating digital demodulation system based on self-correlation principle |
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| CNU2007200276089U CN201075010Y (en) | 2007-09-07 | 2007-09-07 | Optical fiber grating digital demodulation system based on self-correlation principle |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100541138C (en) * | 2007-09-07 | 2009-09-16 | 李东升 | Optical fibre grating digital demodulation method and system thereof based on autocorrelation principle |
| CN105823497A (en) * | 2016-05-24 | 2016-08-03 | 北京信息科技大学 | Fiber grating reflection spectrum demodulation algorithm based on signal autocorrelation matching |
-
2007
- 2007-09-07 CN CNU2007200276089U patent/CN201075010Y/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100541138C (en) * | 2007-09-07 | 2009-09-16 | 李东升 | Optical fibre grating digital demodulation method and system thereof based on autocorrelation principle |
| CN105823497A (en) * | 2016-05-24 | 2016-08-03 | 北京信息科技大学 | Fiber grating reflection spectrum demodulation algorithm based on signal autocorrelation matching |
| CN105823497B (en) * | 2016-05-24 | 2017-12-19 | 北京信息科技大学 | A kind of fiber grating reflection spectrum demodulating algorithm based on signal autocorrelation matching |
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Granted publication date: 20080618 |