CN106705863A - Method for improving maximum test distance of optical frequency domain reflectometer - Google Patents
Method for improving maximum test distance of optical frequency domain reflectometer Download PDFInfo
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- CN106705863A CN106705863A CN201710030861.8A CN201710030861A CN106705863A CN 106705863 A CN106705863 A CN 106705863A CN 201710030861 A CN201710030861 A CN 201710030861A CN 106705863 A CN106705863 A CN 106705863A
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- coupler
- interferometer
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- phase difference
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
Abstract
The invention discloses a method for improving a maximum test distance of an optical frequency domain reflectometer. The system comprises a tunable scan laser, a first coupler, a trigger interferometer, a measuring interferometer, a data acquisition card and a computer. A light source of the tunable scan laser passes through the first coupler, one part of light sequentially enters a second coupler of the trigger interferometer, a third coupler, a device generating a phase difference and a first photoelectric detector, and the other part of light enters a fourth coupler of the measuring interferometer; one part of light exiting from the fourth coupler directly reaches the second photoelectric detector, and the other part of light enters an optical circulator and then reaches a to-be-measured device, and light reflected from the to-be-measured device passes through the optical circulator and then reaches the second photoelectric detector. The method disclosed by the invention has the advantages of no destructiveness, high precision rapid measurement and the like, the measurement result is accurate, and the measurement method is convenient.
Description
Technical field
The present invention relates to Fibre Optical Sensor and optical-fiber network device and system detectio instrument technical field, optical measuring technique neck
Domain, more particularly to a kind of method of the full test distance for improving probe beam deflation instrument.
Background technology
Optical frequency domain reflection technology (Optical Frequency Domain Reflectometry, OFDR) is distributed light
Fibre measurement and developing direction emerging in sensing technology.More traditional optical time domain reflection method (Optical Time Domain
Reflectometry, OTDR), OFDR has signal to noise ratio high, and spatial resolution is high, the features such as sensitivity is high.
In OFDR systems, all there is nonlinear characteristic in commodity laser in optical frequency sweep, and this will result in light frequency domain
The spatial resolution severe exacerbation of reflectometer.At present, it is used in same domain space sampled signal by additional triggers interferometer
The nonlinear effect of laser is solved, suppresses influence of the optical frequency nonlinear scanning of laser to probe beam deflation instrument.This side
Method uses the Additional interference instrument of fixed delay arm to produce the frequency intervals such as sample clock pulse, realization to adopt for main interferometer in real time
Sample, can suppress influence of the optical frequency nonlinear scanning of laser to probe beam deflation device.But according to sampling thheorem, optical frequency
The maximum measurement distance of domain reflectometer can be limited by the fixed delay arm lengths of Additional interference instrument, and the above method is not applied to simultaneously
The probe beam deflation instrument of long range.
The content of the invention
It is an object of the invention to propose a kind of method of the full test distance that can improve probe beam deflation instrument, with reality
The now measurement of long range.
The technical solution adopted by the present invention is as follows：
A kind of method of the full test distance for improving probe beam deflation instrument, the system that the method is realized includes：It is tunable
Scan laser, the first coupler, triggering interferometer, stellar interferometer, data collecting card and computer；The triggering interferometer
Including the second coupler, the 3rd coupler, the device and the first photodetector that produce phase difference；The stellar interferometer includes
4th coupler, optical circulator and the second photodetector；First photodetector and the second photodetector respectively with
Data collecting card is connected, and the data collecting card is connected to computer；The light source of the tunable scan laser passes through the first coupling
After clutch, a part of light sequentially enters triggering the second coupler of interferometer, the 3rd coupler, the device for producing phase difference and the
One photodetector, another part light enters the 4th coupler of stellar interferometer；A part for outgoing after the 4th coupler
Light directly reaches the second photodetector, and another part light reaches device under test again after entering optical circulator, anti-by device under test
The light for coming is emitted back towards by reaching the second photodetector after optical circulator.
The external clock that interferometer is triggered as stellar interferometer, trigger data acquisition card carries out data acquisition；It is logical
The device of the generation phase difference is overregulated, to produce different phase differences and then carry out multiple data acquisition, multiple is obtained and is adopted
With data, be then combined with these sampled datas, reach reduction the sampling period, improve maximum detection span from.
Preferably, the coupling ratio of first coupler is 90：10, second coupler, the 3rd coupler and the 4th
The coupling ratio of coupler is 50：50.
Preferably, the device of the generation phase difference is LC variable wave plate.
The principle of the inventive method is as follows；External clock of the interferometer as stellar interferometer is triggered, sample frequency isTrigger data acquisition card carries out data acquisition, in same frequency domain when meeting signal acquisition, solves Fourier transformation etc.
The sampling interval of the frequencies such as time.And there is optical path difference in the same two-arm of stellar interferometer, therefore according to sampling thheorem, triggering interference
The optical path difference of instrument two-arm is the twice of stellar interferometer, therefore maximum measurement distance is limited.The present invention is tunable sharp in solution
Light device nonlinear effect, while the sampling of frequency interval such as meeting, proposes to be applied additional using the device for producing phase difference
Produced on triggering interferometerPhase difference, carries out multiple repairing weld, in the adjacent double sampling phase difference of domain spaceSample it
Data afterwards merge, and are equal toAndTherefore triggering interferometer two-arm difference expands and is twice, stellar interferometer
Expansion is twice.One is sampled when being in time physically signal zero-crossing rising edge as sampling clock due to triggering interferometer
Secondary, the present invention increases a device for generation phase difference on triggering interferometer, it is possible to produce in timePhase difference, this
Sample has just reached the effect of domain space, increases full test distance, solves fixation of the measurement distance by Additional interference instrument
The limitation of time delay arm lengths improves the maximum measurement distance of probe beam deflation instrument.
Method compared to existing technology, the method for the present invention has the advantages that lossless, high accuracy, quickly measures, and obtains
Measurement result is more accurate, and the measuring method is more facilitated.
Brief description of the drawings
Fig. 1 is present system structural representation；
Fig. 2 is signal graph of the embodiment of the present invention in domain space；
Fig. 3 is signal graph of the embodiment of the present invention in time domain space.
Specific embodiment
The present invention is further described below in conjunction with the accompanying drawings.
If Fig. 1 is the system structure diagram for realizing the inventive method, system includes tunable laser 1,90：10 couplings
Device 2, triggering interferometer, stellar interferometer, data collecting card 10, computer 11.Wherein, triggering interferometer includes 50:50 couplers
3、50:50 couplers 4, LC variable wave plate 5, photodetector 6；Stellar interferometer includes 50:50 couplers 7, optical circulator
8th, photodetector 9.
Laser 1 carries out frequency sweep, and light passes through 90:10 couplers 2, wherein 10% light enters triggers interferometer, 90%
Light enters stellar interferometer.10% light splitting enters the coupler 3 of triggering interferometer, and two-arm has optical path difference, is arrived after forming interference
Up to photodetector 6；90% light enters stellar interferometer, and photodetector 9 is directly reached by the rear portion light of coupler 7,
After another part light enters optical circulator 8, then device under test 12 is reached, the light that device under test 12 is reflected is again introduced into the ring of light
Shape device 8, with another beam light modulation, photodetector 9 is reached after forming interference.
The modulation rate of tunable laser 1 is γ, and when two-arm has optical path difference, differential group delay is τ0, meet low modulation rate
ApproximatelyInterference is formed, the electric signal after photodetector 6 is changed is U (v)=U0[1+cos(2πvτ0+ ξ)], U is
Voltage, τ0It is triggering interferometer two-arm delay inequality, ν is frequency, and ξ is phase constant.Triggering interferometer is used as stellar interferometer
External clock sample frequency isTrigger data acquisition card 10 carries out data acquisition.And the same two-arm of stellar interferometer is deposited
In optical path difference, therefore according to sampling thheorem, the optical path difference for triggering interferometer two-arm is the twice of stellar interferometer, therefore maximum survey
Span is from limited.
The present embodiment method is divided into double sampling, and sample frequency isAs shown in Fig. 2 in domain space for the first time
It is poor with second sampling phaseTwo secondary datas are respectively N1 (n1, n2, n3, n4 ...), N2 (e1, e2, e3, e4 ...)
Data after sampling merge into N3 (n1, e1, n2, e2, n3, e3), are equal toAndTriggering interferometer two
Arm difference expands and is twice, and stellar interferometer also expands and is twice.
As shown in figure 3, in time, because triggering interferometer is physically signal zero-crossing rising edge as sampling clock
When sampling once, by triggering interferometer on increase a LC variable wave plate 10, produce in timePhase difference, so
The effect of domain space is just reached, has increased full test distance.
Claims (4)
1. it is a kind of improve probe beam deflation instrument full test distance method, it is characterised in that the method realize system bag
Include：Tunable scan laser, the first coupler, triggering interferometer, stellar interferometer, data collecting card and computer；It is described
Device and the first photodetector that triggering interferometer includes the second coupler, the 3rd coupler, produces phase difference；The measurement
Interferometer includes the 4th coupler, optical circulator and the second photodetector；First photodetector and the second smooth electrical resistivity survey
Survey device to be connected with data collecting card respectively, the data collecting card is connected to computer；
By after the first coupler, a part of light sequentially enters the of triggering interferometer to the light source of the tunable scan laser
Two couplers, the 3rd coupler, the device and the first photodetector for producing phase difference, another part light enter stellar interferometer
The 4th coupler；A part of light of outgoing directly reaches the second photodetector after the 4th coupler, and another part light enters
Device under test is reached again after entering optical circulator, and the light reflected by device under test is by reaching the second smooth electrical resistivity survey after optical circulator
Survey device.
2. it is according to claim 1 it is a kind of improve probe beam deflation instrument full test distance method, it is characterised in that
The external clock that interferometer is triggered as stellar interferometer, trigger data acquisition card carries out data acquisition；By adjusting
The device for producing phase difference is stated, to produce different phase differences and then carry out multiple data acquisition, multiple is obtained and is used data, so
After merge these sampled datas, reach reduction the sampling period, improve maximum detection span from.
3. it is according to claim 1 it is a kind of improve probe beam deflation instrument full test distance method, it is characterised in that
The coupling ratio of first coupler is 90：10, the coupling ratio of second coupler, the 3rd coupler and the 4th coupler is equal
It is 50：50.
4. it is according to claim 1 it is a kind of improve probe beam deflation instrument full test distance method, it is characterised in that
The device of the generation phase difference is LC variable wave plate.
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| CN110749420A (en) * | 2019-09-12 | 2020-02-04 | 芯华创(武汉)光电科技有限公司 | OFDR detection device |
| CN111928972A (en) * | 2020-08-06 | 2020-11-13 | 中国人民解放军海军工程大学 | Method and system for improving spatial resolution of distributed optical fiber temperature measurement system |
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| CN106705863B (en) | 2019-03-22 |
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