CN103759804A - Method and device for optical fiber white light differential interference non-contact vibration measurement - Google Patents
Method and device for optical fiber white light differential interference non-contact vibration measurement Download PDFInfo
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- CN103759804A CN103759804A CN201410031369.9A CN201410031369A CN103759804A CN 103759804 A CN103759804 A CN 103759804A CN 201410031369 A CN201410031369 A CN 201410031369A CN 103759804 A CN103759804 A CN 103759804A
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Abstract
The invention relates to a method and device for optical fiber white light differential interference non-contact vibration measurement. The device comprises an ASE light source, an optical fiber circulator, a first optical fiber coupler, a delay optical fiber, a second optical fiber coupler, an optical fiber collimator and photoelectric detectors. One end of the first optical fiber coupler is connected with the three photoelectric detectors respectively, the optical path, connected with the first optical fiber coupler, of one photoelectric detector is connected with the optical fiber circulator, and the optical fiber circulator is connected with the ASE light source. The other end of the first optical fiber coupler is connected with one end of the second optical fiber coupler through two optical paths, wherein one optical path is connected with the delay optical fiber. The other end of the second optical fiber coupler is connected with the optical fiber collimator. According to the method and device for optical fiber white light differential interference non-contact vibration measurement, a low-coherence light source and a single-mode optical fiber device are adopted, the structure is simple, cost is low, the structure of each optical path in itself is not sensitive to low frequency disturbance such as noise, temperature and stress, and the measuring dynamic range is large.
Description
Technical field
The present invention relates to vibration measuring system, specifically a kind of method and device of optical fiber white light differential interference noncontact vibration measuring, belong to white light interferometric field.
Background technology
White light interference principle was suggested as far back as 1975, and nineteen eighty-three, white light interference principle is applied first in optical fiber sensing technology.During 1985 to 1989, white light interference principle is widely used in the research of pressure, temperature and strain measurement.After nineteen ninety, the sustainable development of optical fiber white light measuring technique, and be formed as gradually a research direction, the advantage that it has is disclosed and approves by numerous researchers.White light interference technique is widely used now, also showed increased of the physical quantity that can measure, for example: the absolute measurement of the physical parameters such as displacement, pressure, vibration, stress, strain, humidity, temperature and biochemical parameter.
White light interferometry method is sometimes also referred to as low-coherence measuring method, what in this interferometric method, use is low relevant, wideband light source, for example: ASE(amplified spontaneous emission) light source and LED(light emitting diode) light source, so we are commonly referred to " white light " interferometric method this interferometric method.Can carry out absolute measurement to physical quantity, measurement range is wide.Compared with coherent source, white light interference coherent length is short, is often micron dimension.
White light interferometric technology has advantages of: 1, white light interferometric technology provides displacement, temperature, the measuring method of the multiple absolute physical amount such as pressure; 2, due to what adopt, be low-coherence light source, so system rejection to disturbance is very capable, and the factor such as the resolution of system and the stability of optical source wavelength, the fluctuation of light source power, the disturbance of optical fiber all has nothing to do; 3, low-coherence light source low price, thus the cost of system reduced, and also white light interference system is simple in structure; 4, Fiber White-light Interferometer can be realized multiplexed.
When carrying out vibration survey, for measuring the vibration informations such as amplitude and frequency, need to carry out signal demodulation to opto-electronic conversion output.In some modulation and demodulation, as classical heterodyne demodulation method, pseudo-heterodyne demodulation method, synthetic process of heterodyning and PGC(phase generated carrier) demodulation techniques, need an additional modulator element, the dynamic range of measuring system is subject to the restriction of modulating frequency.Based on coupling mechanism demodulation method, do not need additional modulation, method simple and stable, and the measurement of optical fiber white light differential interference is subject to Environmental Noise Influence little.The passive demodulating algorithm that utilization is surveyed based on the fine differential interferometer He San of coupling mechanism low-coherent light road carries out noncontact vibration survey, and relevant patent and document have no report.
Summary of the invention
The present invention is directed to the problems referred to above, a kind of method and device of optical fiber white light differential interference noncontact vibration measuring is provided, the method and device simple and stable, be subject to Environmental Noise Influence little.
The device of a kind of optical fiber white light differential interference noncontact vibration measuring provided by the invention, comprises ASE light source, optical fiber circulator, the first fiber coupler, postpones optical fiber, the second fiber coupler, optical fiber collimator and photodetector; One end of described the first fiber coupler is connected with three described photodetectors respectively, in the light path that described in one of them, photodetector is connected with described the first fiber coupler, be connected with described optical fiber circulator, described optical fiber circulator is connected with described ASE light source; The other end of described the first fiber coupler is connected with one end of described the second fiber coupler by two light paths, wherein in a light path, is connected with described delay optical fiber; The other end of described the second fiber coupler is connected with described optical fiber collimator.
Wherein: described ASE light source is wideband light source.
Described the first fiber coupler is 3x3 fiber coupler, and described the second fiber coupler is 2x2 fiber coupler.
The splitting ratio of described the second fiber coupler is 50:50.
The method of a kind of optical fiber white light differential interference noncontact vibration measuring provided by the invention, comprises the following steps:
(a) Vibration Targets is arranged on to the exit end of described optical fiber collimator;
(b) light that described ASE light source sends is reflected back in described the first fiber coupler to described Vibration Targets through described the first fiber coupler and described the second fiber coupler, is then divided into three road light and enters respectively three described photodetectors; The vibration information that the output electrical signals of three described photodetectors has comprised described Vibration Targets;
(c) output electrical signals of three described photodetectors is realized A/D conversion by data collecting card, use three tunnels to survey demodulating algorithm disappears after direct current, differentiate, multiplication cross, integration, high-pass filtering on software, be divided by with interference signal quadratic sum, then integration obtains vibration signal to be measured.
Wherein: described data collecting card adopts the PCI-6251 data collecting card of NI company.
Described software adopts labview software.
Technique effect of the present invention is: the present invention adopts low-coherence light source and single-mode fiber device, cost simple in structure is low, the structure of light path itself is insensitive to low-frequency excitations such as noise, temperature, stress, the passive demodulation method that uses three tunnels to survey can be measured vibration information, the dynamic range of measuring is large, has realized the remote non-cpntact measurement of optical fiber white light interference.
Accompanying drawing explanation
Fig. 1 is the structural representation of apparatus of the present invention.
Fig. 2 is demodulation process flow diagram of the present invention.
Fig. 3 A and Fig. 3 B are respectively that Vibration Targets is piezoelectric ceramics (PZT), and driving signal is f=2KHz, during V=0.1V, and the oscillogram of demodulation result of the present invention and spectrogram.
Fig. 4 A and Fig. 4 B are respectively that Vibration Targets is piezoelectric ceramics (PZT), and driving signal is f=4KHz, during V=3V, and the oscillogram of demodulation result of the present invention and spectrogram.
Embodiment
Below in conjunction with accompanying drawing, the specific embodiment of the present invention is further described.
In Fig. 1, comprise ASE light source 1, optical fiber circulator 2, the first fiber coupler 3, postpone optical fiber 4, the second fiber coupler 5, photodetector 6, optical fiber collimator 7, Vibration Targets 8 etc.
As shown in Figure 1, be the device of a kind of optical fiber white light differential interference noncontact vibration measuring provided by the invention, its optical texture is Mach Zeng De and Sai Ge nanogram mixed type differential interferometer.The present invention includes ASE light source 1, optical fiber circulator 2, the first fiber coupler 3, postpone optical fiber 4, the second fiber coupler 5, optical fiber collimator 7 and photodetector 6; One end of the first fiber coupler 3 is connected with three photodetectors 6 respectively, in the light path that one of them photodetector 6 is connected with the first fiber coupler 3, is connected with optical fiber circulator 2, and optical fiber circulator 2 is connected with ASE light source 1; The other end of the first fiber coupler 3 is connected with one end of the second fiber coupler 5 by two light paths, wherein in a light path, is connected with and postpones optical fiber 4; The other end of the second fiber coupler 5 is connected with optical fiber collimator 7.
Wherein: ASE light source 1 is wideband light source.The first fiber coupler 3 is 3x3 fiber coupler, and the second fiber coupler 5 is 2x2 fiber coupler.The splitting ratio of the second fiber coupler 5 is 50:50.
The method of a kind of optical fiber white light differential interference noncontact vibration measuring provided by the invention, comprises the following steps:
(a) Vibration Targets 8 is arranged on to the exit end of optical fiber collimator 7;
(b) light that ASE light source 1 sends is reflected back in the first fiber coupler 3 to Vibration Targets 8 through the first fiber coupler 3 and the second fiber coupler 5, is then divided into three road light and enters respectively three photodetectors 6; The vibration information that the output electrical signals of three photodetectors 6 has comprised Vibration Targets 8;
(c) output electrical signals of three photodetectors 6 is realized A/D conversion by data collecting card, use three tunnels to survey demodulating algorithm disappears after direct current, differentiate, multiplication cross, integration, high-pass filtering on software, be divided by with interference signal quadratic sum, then integration obtains vibration signal to be measured.
Wherein: data collecting card adopts the PCI-6251 data collecting card of NI company; Software adopts labview software.
Principle of work of the present invention is: light that ASE light source 1 sends enters the first fiber coupler 3 through optical fiber circulator 2 and is divided into three-beam, and wherein two light paths are connected with the second fiber coupler 5, and delay optical fiber 4 is connected to wherein in a light path.One end output light of the second fiber coupler 5 connects optical fiber collimator 7 as sensing probe.From the irradiation of optical fiber collimator 7 outgoing, Vibration Targets 8 surfaces, recycling optical fiber collimator 7 receives the scattered light of Vibration Targets 8, is back to the second fiber coupler 5.Back light is finally divided into three road light by the first fiber coupler 3 and enters respectively three photodetectors 6.Light is from 1 outgoing of ASE light source, and through Vibration Targets 8 surfaces, scattering reaches photodetector 6 after receiving, and the path of passing through has four: (a) D L1 D; (b) D L1 F; (c) F L1 D; (d) F L1 F.Four road light a and d two-way light path in fiber coupler too very much not meet interference condition, can not interfere, only have b, c two-beam just to pass through the sequencing difference of vibration source by identical light path, this two-way light meets interference condition, can interfere, the mistiming of utilizing time delay optical fiber 4 to bring, after interference signal is received by three photodetectors 6, the vibration information that photodetector 6 output electrical signals have comprised Vibration Targets 8, is used three tunnels to survey demodulating algorithm and carries out the demodulation of signal.
Demodulation principle of the present invention: No. three photodetector 6 output electrical signals are realized A/D conversion by the PCI-6521 data collecting card of NI, in input PC.By labview software, do computing, obtain the vibration information of demodulation result and Vibration Targets 8.
The photogenerated current of three photodetectors 6 of incident is respectively:
In above formula,
it is light source intensity
,
for the angular frequency of modulation signal.For simplifying expression formula, definition D=4E
0 2, E=2E
0 2,
, by above formula after photoelectric diode and prime amplifier, can be reduced to:
V
1, V
2, V
3for the magnitude of voltage of output,
be signal to be demodulated.
The algorithm of demodulation as shown in Figure 2, comprises the following steps:
1, calculate the mean value of the DC quantity D of three road signals:
2, after three road signal cancellation DC terms D, obtain:
3, for obtaining the orthogonal signal of two-way,
with
after differentiate, multiplication cross is subtracted each other integration again:
These two-way orthogonal signal, by differential multiplication cross integration again, demodulate measured signal.
Wherein
4, in order to calculate coefficient E
2, ask a, b, tri-squares of summations of c
5, remove
cancellation E
2after obtain the speed amount of restituted signal.Integration once obtains the displacement of restituted signal again:
Cause
with
all very little, can approximate treatment be
with
Above formula can be reduced to:
Below by the feasibility of experimental verification optical fiber white light differential interference noncontact vibration measuring:
(1) utilize function generator to drive piezoelectric ceramics (PZT) to produce vibration signal, load signal frequency f=2KHz, during driving voltage V=0.1V, pass through the result of Labview algorithm routine observation signal demodulation, Fig. 3 A is the oscillogram of restituted signal, Fig. 3 B is corresponding spectrogram, can find out thus signal to noise ratio snr=55dB, amplitude is 0.033rad.
(2) utilize function generator to drive piezoelectric ceramics (PZT) to produce vibration signal, load signal frequency f=4KHz, during driving voltage V=3V, pass through the result of Labview algorithm routine observation signal demodulation, Fig. 4 A is the oscillogram of restituted signal, Fig. 4 B is corresponding spectrogram, can find out that thus signal to noise ratio (snr) is 70dB, side mode suppression ratio (SMSR) is 45dB, and amplitude is 1.3rad.
Above lab diagram has all obtained stable demodulation result, has measured the absolute amplitude of vibration, has verified the method for optical fiber white light differential interference noncontact vibration measuring and the validity of device.
Claims (7)
1. a device for optical fiber white light differential interference noncontact vibration measuring, is characterized in that: comprise ASE light source (1), optical fiber circulator (2), the first fiber coupler (3), postpone optical fiber (4), the second fiber coupler (5), optical fiber collimator (7) and photodetector (6); One end of described the first fiber coupler (3) is connected with three described photodetectors (6) respectively, in the light path that photodetector described in one of them (6) is connected with described the first fiber coupler (3), be connected with described optical fiber circulator (2), described optical fiber circulator (2) is connected with described ASE light source (1); The other end of described the first fiber coupler (3) is connected with one end of described the second fiber coupler (5) by two light paths, wherein in a light path, is connected with described delay optical fiber (4); The other end of described the second fiber coupler (5) is connected with described optical fiber collimator (7).
2. according to the device of optical fiber white light differential interference noncontact vibration measuring claimed in claim 1, it is characterized in that: described ASE light source (1) is wideband light source.
3. according to the device of optical fiber white light differential interference noncontact vibration measuring claimed in claim 1, it is characterized in that: described the first fiber coupler (3) is 3x3 fiber coupler, and described the second fiber coupler (5) is 2x2 fiber coupler.
4. according to the device of optical fiber white light differential interference noncontact vibration measuring claimed in claim 1, it is characterized in that: the splitting ratio of described the second fiber coupler (5) is 50:50.
5. right to use requires the method that in 1 to 4, described in any one, device carries out optical fiber white light differential interference noncontact vibration measuring, it is characterized in that, comprises the following steps:
(a) Vibration Targets (8) is arranged on to the exit end of described optical fiber collimator (7);
(b) light that described ASE light source (1) sends is reflected back in described the first fiber coupler (3) to described Vibration Targets (8) through described the first fiber coupler (3) and described the second fiber coupler (5), is then divided into three road light and enters respectively three described photodetectors (6); The vibration information that the output electrical signals of three described photodetectors (6) has comprised described Vibration Targets (8);
(c) output electrical signals of three described photodetectors (6) is realized A/D conversion by data collecting card, use three tunnels to survey demodulating algorithm disappears after direct current, differentiate, multiplication cross, integration, high-pass filtering on software, be divided by with interference signal quadratic sum, then integration obtains vibration signal to be measured.
6. according to the method for optical fiber white light differential interference noncontact vibration measuring claimed in claim 5, it is characterized in that: described data collecting card adopts the PCI-6251 data collecting card of NI company.
7. according to the method for optical fiber white light differential interference noncontact vibration measuring claimed in claim 5, it is characterized in that: described software adopts labview software.
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| CN105424605A (en) * | 2015-11-18 | 2016-03-23 | 安徽大学 | Photoacoustic spectrometry measuring device and method based on low-coherence optical fiber differential interference non-contact vibration measurement |
| CN106289669A (en) * | 2016-08-04 | 2017-01-04 | 安徽大学 | Gas leakage detection device based on Low coherence optical fiber microphone and method |
| CN104215319B (en) * | 2014-09-01 | 2017-01-11 | 安徽大学 | Dynamic range adjustable differential interferometer and measuring method |
| CN106839972A (en) * | 2017-01-11 | 2017-06-13 | 天津大学 | A kind of interference signal processing method of full light fiber white light interference instrument |
| CN113237570A (en) * | 2021-04-28 | 2021-08-10 | 安徽大学 | Low-coherence distributed optical fiber sensor based on wavelength light splitting |
| CN113776644A (en) * | 2021-09-24 | 2021-12-10 | 中国电子科技集团公司第三十四研究所 | Optical fiber fence intrusion signal simulation device based on Mach-Zehnder interferometer |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104215319B (en) * | 2014-09-01 | 2017-01-11 | 安徽大学 | Dynamic range adjustable differential interferometer and measuring method |
| CN105424605A (en) * | 2015-11-18 | 2016-03-23 | 安徽大学 | Photoacoustic spectrometry measuring device and method based on low-coherence optical fiber differential interference non-contact vibration measurement |
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| CN106839972B (en) * | 2017-01-11 | 2019-05-10 | 天津大学 | A kind of interference signal processing method of full light fiber white light interference instrument |
| CN113237570A (en) * | 2021-04-28 | 2021-08-10 | 安徽大学 | Low-coherence distributed optical fiber sensor based on wavelength light splitting |
| CN113776644A (en) * | 2021-09-24 | 2021-12-10 | 中国电子科技集团公司第三十四研究所 | Optical fiber fence intrusion signal simulation device based on Mach-Zehnder interferometer |
| CN113776644B (en) * | 2021-09-24 | 2023-08-01 | 中国电子科技集团公司第三十四研究所 | Optical fiber fence intrusion signal simulation equipment based on Mach-Zehnder interferometer |
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Application publication date: 20140430 |