CN108036728A - A kind of phase difference solution mode fiber optics displacement measuring method and instrument - Google Patents
A kind of phase difference solution mode fiber optics displacement measuring method and instrument Download PDFInfo
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- CN108036728A CN108036728A CN201711337301.3A CN201711337301A CN108036728A CN 108036728 A CN108036728 A CN 108036728A CN 201711337301 A CN201711337301 A CN 201711337301A CN 108036728 A CN108036728 A CN 108036728A
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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
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Abstract
A kind of phase difference solution mode displacement surveying meter of optic fibre device and method, belong to technical field of optical fiber sensing.The system includes touch-screen, control and signal processing circuit, laser diode, fiber optic splitter, Measurement channel fiber coupler, measurement optical fiber, reference channel fiber coupler, reference optical fiber, Measurement channel photodiode and reference channel photodiode.Chosen on measurement optical fiber two fixed in treating geodesic structure, treat that the displacement of geodesic structure is converted to the variable quantity of measurement fiber lengths, reference optical fiber for temperature-compensating is laid on body structure surface to be measured at the same time, phase difference of the high frequency modulated laser between measurement optical fiber and the flashlight of reference optical fiber end face reflection is proportional to the length difference between two optical fiber, realizes that the high-resolution for treating geodesic structure absolute displacement and Larger Dynamic scope measure by high-precision phase position difference demodulation.Phase difference measurement of the present invention by high-precision optical fiber length measures conversion in displacement measurement for relatively simple two beams flashlight, only with photoelectron, electronic device and the general single mode fiber of low cost, a kind of technical solution of great competitiveness is provided for the displacement measurement in monitoring structural health conditions.
Description
Technical field
The invention belongs to technical field of optical fiber sensing, is related to a kind of phase difference solution mode fiber optics displacement measuring method and instrument
Device.
Background technology
Electromagnetism interference that optical fibre displacement sensor possesses with it, high sensitivity, be easy to series/parallel multiplexing and easily structure
The advantages that sensor network, in Slope Sliding, dam deformation, tunnel safety, settlement, steel bar corrosion and colliery microseism etc.
Important function has been played in monitoring structural health conditions application.
In current engineer application, optical fibre displacement sensor mainly has Fiber Optic Fabry-Perot Sensor, optical fiber mikey
That inferior white light interferometer, fiber-optic grating sensor and optical fiber Brillouin optical time-domain analyzer.Document Zhou X, Yu Q.Wide-
range displacement sensor based on fiber-optic Fabry–Perot interferometer for
subnanometer measurement[J].IEEE sensors journal,2011,11(7):Itd is proposed in 1602-1606
Fiber Optic Fabry-Perot Sensor carries out Fabry-Perot high-precision demodulation by spectrum demodulation method, and resolution ratio can reach
Nanometer scale, but measurement range only has millimeter magnitude, and spectrum demodulation instrument is expensive.Document Li T, Wang A, Murphy
K,et al.White-light scanning fiber Michelson interferometer for absolute
position–distance measurement[J].Optics letters,1995,20(7):The optical fiber that 785-787 is proposed
Michelson white light interferometer can compensate ambient temperature effect, with reference to white light interference demodulation techniques, it can be achieved that micron amount
The measurement accuracy of level.But the interferometric demodulation instrument volume in the program is larger, and the mechanical moving element such as motor has seriously affected and has been
The response speed of system, long-term measurement accuracy and reliability.Fiber-optic grating sensor is by measuring in optical fiber draw process in grating
The amount of movement of cardiac wave length, actual displacement amount is calculated, it can be achieved that single-point or quasi- distribution measuring, belong to one according to calibration relational expression
The indirect displacement-measurement procedure of kind, but fiber bragg grating center wavelength and measurement fiber lengths are all temperature sensitive, it is necessary to carry out more complicated
Temperature-compensating, and range of displacement measurement is small, and precision is not high.Optical fiber Brillouin optical time-domain analyzer is by measuring in optical fiber in cloth
The frequency displacement of deep pool scattering light, realizes the distribution measuring to dependent variable, according to the dependent variable and light measured in optical fiber draw process
Fine length gauge calculates displacement.But optical fiber Brillouin optical time-domain analyzer is temperature sensitive, it is necessary to carry out temperature-compensating at the same time, increase
System complexity is added, and high demodulation instrument price seriously hinders the popularization and application of the technology.Thus, design is a kind of
It is provided simultaneously with the fiber optics displacement measurement for the advantages such as of simple structure and low cost, temperature is unrelated, high certainty of measurement and dynamic range are big
Instrument, which has, is more widely applied value.
The content of the invention
It is an object of the invention to propose a kind of phase difference solution mode fiber optics displacement measuring method and instrument, it is intended to simplify light
The structure of fine displacement sensor demodulation instrument, is greatly reduced demodulation instrument cost, eliminates the influence of variation of ambient temperature, and possess
The advantage such as high measurement accuracy and Larger Dynamic scope, is expanded for optical fibre displacement sensor in the application in the fields such as monitoring structural health conditions
The space of bigger.
Technical scheme：
A kind of phase difference solution mode displacement surveying meter of optic fibre device, including touch-screen 1, control and signal processing circuit 2, laser
Diode 3, fiber optic splitter 4, Measurement channel fiber coupler 5, measurement optical fiber 6, reference channel fiber coupler 7, reference light
Fibre 8, Measurement channel photodiode 9 and reference channel photodiode 10；The control is received with signal processing circuit 2 and touched
After the control instruction for touching the input of screen 1, modulated signal driving laser diode 3 is produced；The laser that the laser diode 3 is launched
Two beams are divided into by fiber optic splitter 4, after inciding Measurement channel fiber coupler 5 and reference channel fiber coupler 7 respectively, point
Do not incide in measurement optical fiber 6 and reference optical fiber 8；From the part signal light difference of measurement 8 end face reflection of optical fiber 6 and reference optical fiber
After Measurement channel fiber coupler 5 and reference channel fiber coupler 7, then Measurement channel photodiode 9 is incided respectively
With reference channel photodiode 10；Control gathers Measurement channel photodiode 9 and reference channel light with signal processing circuit 2
Electric diode 10 change electric signal, carry out Digital Signal Processing after by the results show in touch-screen 1.
A kind of phase difference solution mode fiber optics displacement measuring method, high frequency modulated laser is in measurement optical fiber and reference optical fiber end face
Phase difference between the flashlight of reflection is proportional to the length difference between two optical fiber, and demodulating realization by phase difference treats geodesic structure
Absolute displacement measurement；Comprise the following steps that：
First, after control receives the control instruction that touch-screen 1 inputs with signal processing circuit 2, the high frequency sinusoidal letter of generation
Number to laser diode 3 carry out current-modulation；The intensity modulated laser that the laser diode 3 is launched is by fiber optic splitter 4
It is divided into two beams, after inciding Measurement channel fiber coupler 5 and reference channel fiber coupler 7, incides measurement optical fiber 6 respectively
In reference optical fiber 8；From the part signal light of 8 end face reflection of optical fiber 6 and reference optical fiber is measured respectively through Measurement channel optical fiber coupling
After clutch 5 and reference channel fiber coupler 7, then Measurement channel photodiode 9 and reference channel photoelectricity two are incided respectively
Pole pipe 10；The flashlight of two passages produces and the relevant phase shift of fiber link length after respective fiber link；Control
The electric signal that Measurement channel photodiode 9 and reference channel photodiode 10 are changed is gathered with signal processing circuit 2, is carried out
High-precision phase position detects, and respectively obtains the phase of two ways of optical signals；Control with signal processing circuit 2 by obtained two-way phase into
Row subtraction, calculates opposite between measurement optical fiber 6 and reference optical fiber 8 again according to phase difference, the light velocity and optical fibre refractivity
Length, i.e. absolute displacement amount；Finally, demodulation result is shown in touch-screen 1 by control with signal processing circuit 2.
The Sine Modulated frequency range of the laser diode 3 is 1MHz-1GHz.
The control and the core of signal processing circuit 2 are a kind of binary channels high-precision phase position detectors.
The measurement optical fiber 6 and the drift of the reference optical fiber 8 are of substantially equal.
The measurement optical fiber 6 and the length of the reference optical fiber 8 can reach 10km.
The principle of the present invention is as follows：Choose two fixed in treating geodesic structure on measurement optical fiber, treat the displacement of geodesic structure
The variable quantity of measurement fiber lengths is converted to, the reference optical fiber for temperature-compensating is laid on body structure surface to be measured, high frequency at the same time
Phase difference of the modulation laser between measurement optical fiber and the flashlight of reference optical fiber end face reflection is proportional between two optical fiber
Length difference, realizes that the high-resolution for treating geodesic structure absolute displacement and Larger Dynamic scope measure by high-precision phase position difference demodulation.
Be transmitted to measurement optical fiber and reference optical fiber laser reflected by fiber end face after, be measured two pole of passage photoelectricity respectively
The time delays that pipe 9 and reference channel photodiode 10 receive generation are poor, and caused phase difference is：
In above formula, f is the modulating frequency of laser, and c is the light velocity in vacuum, and OPD is that above-mentioned two-beam produces in the optical path
Raw optical path difference：
OPD=2neqΔl (2)
In above formula, Δ l is the length difference for measuring optical fiber and reference optical fiber, neqIt is effective refractive index.
According to formula (1) and formula (2), displacement can be expressed as：
In above formula, Δ l0Be measure optical fiber and reference optical fiber initial length it is poor.By measuring phase differenceFurther according to
Formula (3), you can contraposition shifting is demodulated.
The effect and benefit of the present invention：It is relatively simple two beam by high-precision optical fiber length measures conversion in displacement measurement
The phase difference measurement of flashlight.Variation of ambient temperature, which can be eliminated, using the reference optical fiber isometric with measurement optical fiber causes measurement optical fiber
The displacement measurement errors that length change produces after thermal expansion.Only with photoelectron, electronic device and the general single mode light of low cost
The measurement to the high accuracy and Larger Dynamic scope of displacement structure can be achieved in fibre.The present invention is that the displacement in monitoring structural health conditions is surveyed
Amount provides a kind of technical solution of great competitiveness.
Brief description of the drawings
Fig. 1 is the structure diagram of the present invention.
Flashlight phase shift and phase difference vary with temperature figure when Fig. 2 is variation of ambient temperature.
Fig. 3 is that the phase difference of apparatus measures under change in displacement changes over time figure.
Fig. 4 is the phase difference and absolute displacement graph of a relation of apparatus measures.
Fig. 5 is the multiple stationary measurements under the conditions of shift invariant.
Fig. 6 is on-line displacement measurement result.
In figure：1 touch-screen；2 controls and signal processing circuit；3 laser diodes；
4 fiber optic splitters；5 Measurement channel fiber couplers；6 measurement optical fiber；
7 reference channel fiber couplers；8 reference optical fibers；
9 Measurement channel photodiodes；10 reference channel photodiodes；
The phase shift of 11 measurement fiber end face reflected signal light；
The phase shift of 12 reference optical fiber end face reflection flashlights；
The phase difference of 13 measurement optical fiber and reference optical fiber end face reflection flashlight.
Embodiment
Describe the embodiment of the present invention in detail below in conjunction with technical solution and attached drawing.
A kind of phase difference solution mode displacement surveying meter of optic fibre device, mainly include touch-screen 1, control with signal processing circuit 2,
Laser diode 3, fiber optic splitter 4, Measurement channel fiber coupler 5, measurement optical fiber 6, reference channel fiber coupler 7, ginseng
Examine optical fiber 8, Measurement channel photodiode 9 and reference channel photodiode 10.
After control receives the control instruction that touch-screen 1 inputs with signal processing circuit 2, modulated signal driving laser two is produced
Pole pipe 3；The laser that laser diode 3 is launched is divided into two beams by fiber optic splitter 4, incides 5 He of Measurement channel fiber coupler
After reference channel fiber coupler 7, incide respectively in measurement optical fiber 6 and reference optical fiber 8；From measurement optical fiber 6 and reference optical fiber 8
The part signal light of end face reflection is respectively after Measurement channel fiber coupler 5 and reference channel fiber coupler 7, then enter respectively
It is mapped to Measurement channel photodiode 9 and reference channel photodiode 10；Control gathers Measurement channel with signal processing circuit 2
The electric signal that photodiode 9 and reference channel photodiode 10 are changed, carry out after Digital Signal Processing by the results show in
Touch-screen 1.
Wherein, control and signal processing circuit 2 are binary channels high-frequency digital lock-in amplifiers, and sinusoidal modulation signal output is frequently
Rate is 50MHz.Laser diode 3 is two pole of optical fibre Fabry-perot laser with tail optical fiber output that centre wavelength is 1550nm
Pipe.The splitting ratio of fiber optic splitter 4 is 50:50.The coupling of Measurement channel fiber coupler 5 and reference channel fiber coupler 7
Than for 50:50.
Measurement optical fiber 6 and reference optical fiber 8 are the single mode optical fibers that length is 2km.Measurement channel photodiode 9 and reference are logical
Road photodiode 10 is tail fiber type InGaAs photodiodes.
Flashlight phase shift and phase difference vary with temperature figure when Fig. 2 is variation of ambient temperature.Measure optical fiber and reference optical fiber
The phase difference 13 of end face reflection flashlight is that the phase shift 11 for measuring fiber end face reflected signal light is believed with reference optical fiber end face reflection
The difference of the phase shift 12 of number light.When variation of ambient temperature, phase shift 11 and the reference optical fiber of fiber end face reflected signal light are measured
The phase shift 12 of end face reflection flashlight changes therewith, this is because the thermal expansion effects of optical fiber cause optical fiber during temperature change
Length varies widely, and isometric reference optical fiber 8 has almost equal length change with measurement optical fiber 6.Light is measured in Fig. 2
The fine result of calculation with the phase difference 13 of reference optical fiber end face reflection flashlight shows that phase difference demodulation method can eliminate environment temperature
Change the influence to displacement measurement.
Fig. 3 is that the phase difference of apparatus measures under change in displacement changes over time figure.By adjusting fixing point in measurement optical fiber
Between stress, change the length of measurement optical fiber, measure the phase difference between optical fiber and reference optical fiber.
Fig. 4 is the phase difference and absolute displacement graph of a relation of apparatus measures.
Fig. 5 is the multiple stationary measurements under the conditions of shift invariant.By calculating standard deviation δ, the position of instrument is estimated
Shift measurement resolution ratio (1 δ) reaches 3.1 μm.
Fig. 6 is on-line displacement measurement result.It will be arranged to 10ms the times of integration, system can be to the dynamic of 50Hz frequencies below
Displacement is measured in real time.
The foregoing is merely the preferred embodiment of the present invention, is not intended to limit the invention, for those skilled in the art
For member, the invention may be variously modified and varied.Any modification within the spirit and principles of the invention, being made,
Equivalent substitution, improvement etc., should all be included in the protection scope of the present invention.
Claims (10)
1. a kind of phase difference solution mode fiber optics displacement measuring method, high frequency modulated laser is anti-in measurement optical fiber and reference optical fiber end face
Phase difference between the flashlight penetrated is proportional to the length difference between two optical fiber, is realized by phase difference demodulation and treats geodesic structure
Absolute displacement measures；It is characterized in that, step is as follows：
First, after control receives the control instruction of touch-screen (1) input with signal processing circuit (2), the high frequency sinusoidal letter of generation
Number to laser diode (3) carry out current-modulation；The intensity modulated laser of laser diode (3) transmitting is by fiber beam splitting
Device (4) is divided into two beams, after inciding Measurement channel fiber coupler (5) and reference channel fiber coupler (7), incides respectively
Measure in optical fiber (6) and reference optical fiber (8)；From the part signal light difference of measurement optical fiber (6) and reference optical fiber (8) end face reflection
After Measurement channel fiber coupler (5) and reference channel fiber coupler (7), then two pole of Measurement channel photoelectricity is incided respectively
Manage (9) and reference channel photodiode (10)；The flashlight of two passages is after respective fiber link, generation and optical fiber
The relevant phase shift of linkage length；Control and signal processing circuit (2) collection Measurement channel photodiode (9) and reference channel light
The electric signal of electric diode (10) conversion, carries out high-precision phase position detection, respectively obtains the phase of two ways of optical signals；Control and letter
Obtained two-way phase is carried out subtraction by number process circuit (2), is calculated again according to phase difference, the light velocity and optical fibre refractivity
Measure the relative length between optical fiber (6) and reference optical fiber (8), i.e. absolute displacement amount；Finally, control and signal processing circuit
(2) demodulation result is shown in touch-screen (1).
2. a kind of phase difference solution mode fiber optics displacement measuring method according to claim 1, it is characterised in that described swashs
The Sine Modulated frequency range of optical diode (3) is 1MHz-1GHz.
3. a kind of phase difference solution mode fiber optics displacement measuring method according to claim 1 or 2, it is characterised in that described
The core of control and signal processing circuit (2) be a kind of binary channels high-precision phase position detector.
4. a kind of phase difference solution mode fiber optics displacement measuring method according to claim 1 or 2, it is characterised in that described
Measurement optical fiber (6) and reference optical fiber (8) drift it is equal.
A kind of 5. phase difference solution mode fiber optics displacement measuring method according to claim 3, it is characterised in that the survey
The drift for measuring optical fiber (6) and reference optical fiber (8) is equal.
A kind of 6. phase difference solution mode fiber optics displacement measuring method according to claim 4, it is characterised in that the survey
The length of amount optical fiber (6) and reference optical fiber (8) reaches 10km.
A kind of 7. phase difference solution mode fiber optics displacement measuring method according to claim 5, it is characterised in that the survey
The length of amount optical fiber (6) and reference optical fiber (8) reaches 10km.
A kind of 8. phase difference solution mode displacement surveying meter of optic fibre device, it is characterised in that the phase difference solution mode fiber optics displacement
Measuring instrument includes touch-screen (1), control and signal processing circuit (2), laser diode (3), fiber optic splitter (4), measurement
Channel fiber coupler (5), measurement optical fiber (6), reference channel fiber coupler (7), reference optical fiber (8), Measurement channel photoelectricity
Diode (9) and reference channel photodiode (10)；The control and signal processing circuit (2) reception touch-screen (1) are defeated
After the control instruction entered, modulated signal driving laser diode (3) is produced；The laser quilt of laser diode (3) transmitting
Fiber optic splitter (4) is divided into two beams, after inciding Measurement channel fiber coupler (5) and reference channel fiber coupler (7), point
Measurement optical fiber (6) and reference optical fiber are not incided (in 8；From the part letter of measurement optical fiber (6) and reference optical fiber (8) end face reflection
Number light is respectively after Measurement channel fiber coupler (5) and reference channel fiber coupler (7), then incide Measurement channel respectively
Photodiode (9) and reference channel photodiode (10)；Control and signal processing circuit (2) collection Measurement channel photoelectricity two
Pole pipe (9) and reference channel photodiode (10) conversion electric signal, carry out Digital Signal Processing after by the results show in touch
Touch screen (1).
9. phase difference solution mode displacement surveying meter of optic fibre device according to claim 8, it is characterised in that the control with
Signal processing circuit (2) is binary channels high-frequency digital lock-in amplifier, and sinusoidal modulation signal output frequency is 50MHz；Laser two
Pole pipe (3) is the optical fibre Fabry-perot laser diode with tail optical fiber output that centre wavelength is 1550nm；Fiber optic splitter
(4) splitting ratio is 50:50；The coupling ratio of Measurement channel fiber coupler (5) and reference channel fiber coupler (7) is 50:
50。
10. phase difference solution mode displacement surveying meter of optic fibre device according to claim 8 or claim 9, it is characterised in that the survey
It is tail fiber type InGaAs photodiodes to measure passage photodiode (9) and reference channel photodiode (10).
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109253698A (en) * | 2018-09-21 | 2019-01-22 | 湖北工业大学 | A kind of displacement sensor |
| CN111692972A (en) * | 2020-06-16 | 2020-09-22 | 中国科学院国家授时中心 | Single-fiber unidirectional optical fiber length measuring method and system |
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| CN102853920A (en) * | 2012-09-29 | 2013-01-02 | 华中科技大学 | High-sensitivity Mach-Zahnder interference system |
| CN105737753A (en) * | 2016-02-03 | 2016-07-06 | 西安交通大学 | Light intensity modulation type signal demodulation system and signal demodulation method |
| CN105823757A (en) * | 2016-03-10 | 2016-08-03 | 哈尔滨工程大学 | High-precision liquid refractive index measurer realized by using fiber white-light interferometry, and measurement method thereof |
| CN107063431A (en) * | 2017-01-24 | 2017-08-18 | 电子科技大学 | A kind of optical fiber vibration sensing system and method based on double light path |
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Patent Citations (6)
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| JPS5357056A (en) * | 1976-11-02 | 1978-05-24 | Nippon Telegr & Teleph Corp <Ntt> | Method and device for measuring length of optical fiber |
| CN101013025A (en) * | 2007-02-09 | 2007-08-08 | 北京交通大学 | Optical fiber interference type on-line micro-displacement measuring system using fibre grating |
| CN102853920A (en) * | 2012-09-29 | 2013-01-02 | 华中科技大学 | High-sensitivity Mach-Zahnder interference system |
| CN105737753A (en) * | 2016-02-03 | 2016-07-06 | 西安交通大学 | Light intensity modulation type signal demodulation system and signal demodulation method |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109253698A (en) * | 2018-09-21 | 2019-01-22 | 湖北工业大学 | A kind of displacement sensor |
| CN109253698B (en) * | 2018-09-21 | 2021-07-13 | 湖北工业大学 | Displacement sensor |
| CN111692972A (en) * | 2020-06-16 | 2020-09-22 | 中国科学院国家授时中心 | Single-fiber unidirectional optical fiber length measuring method and system |
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