CN103217226A - Passive homodyne demodulation device and passive homodyne demodulation method for fai-OTDR (optical time domain reflectometer) - Google Patents
Passive homodyne demodulation device and passive homodyne demodulation method for fai-OTDR (optical time domain reflectometer) Download PDFInfo
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- CN103217226A CN103217226A CN2013100994277A CN201310099427A CN103217226A CN 103217226 A CN103217226 A CN 103217226A CN 2013100994277 A CN2013100994277 A CN 2013100994277A CN 201310099427 A CN201310099427 A CN 201310099427A CN 103217226 A CN103217226 A CN 103217226A
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Abstract
The invention discloses a passive homodyne demodulation device and a passive homodyne demodulation method for a fai-OTDR (optical time domain reflectometer). The device consists of piezoelectric ceramics, an optical fiber coupler, a photoelectric detector, an analysis control module and a piezoelectric ceramic driver module. The method belongs to a PGC (programmed gain control)algorithm with phase modulation degree measurement improvement, the passive homodyne detection of Rayleigh scattering light phases in sensing optical fibers of the fai-OTDR is realized, the phase external modulation is carried out through PZT (plumbum-based lanthanum-doped zirconate titanate), Rayleigh scattering light and local reference light interference signals are unfolded through a Bessel function, the amplitude value of each subharmonic items unfolded by the Bessel function is analyzed, further, the phase modulation degree is obtained through analysis, and the Rayleigh scattering light phase is further solved. The structure of the device is simple, the sensitivity is high, and the performance is stable. The method has the advantages that the passive homodyne detection of the Rayleigh scattering light in the sensing optical fibers of the fai-OTDR is realized, a detecting device is simplified, and the operation cost of a system is reduced. The device and the method are applicable to optical fiber hydrophones, public security, ground invasion detection, failure positioning and the like.
Description
Technical field
The present invention relates to a kind of distributing optical fiber sensing and a kind of Φ-OTDR; The method that also relates to a kind of passive homodyne demodulation, particularly a kind of utilization PZT piezoelectric ceramics are cheaply carried out in the fiber phase modulation detection distributed sensing pick-up unit and the detection method thereof of Rayleigh scattering light phase dorsad.
Background technology
The distributing optical fiber sensing technology is to utilize an optical fiber as the sensing element that extends, any one section on the optical fiber is sensing unit, be again the information transfer channel of other sensing unit, thereby can obtain the measured distributed intelligence that on room and time, changes along this optical fiber.It has eliminated the sensing " blind area " that traditional sensing unit exists, and has fundamentally broken through traditional spot measurement restriction.Wherein optical time domain reflection technology OTDR is the most ripe optical fiber distributed type sensing technology of development at present, is widely used in loss, breakpoint, little curved detection of optical link in the optical-fibre communications.But it is difficult to detect the destabilization sensing that carries out as temperature, strain and vibration because sensing sensitivity is not high.The optical time domain reflection technology (C-OTDR or phase-OTDR) of Polarization-Sensitive optical time domain reflection technology (P-OTDR) and phase sensitive optical time domain reflection technology development.The Juan C. Juarez of U.S. Texas A﹠M university utilizes C-OTDR and P-OTDR to realize the distributed perturbation sensing system of 10km, and in the disturbance testing engineering application of ground buried fiber optic cable.People such as the Yuelan Lu of Canada University of Ottawa and Xiaoyi Bao utilize the C-OTDR technology to realize measuring distance 1km, the vibration transducer of spatial resolution 5m.
H.F.Taylor has proposed the Φ-OTDR technology of phase sensitive in 1993, the appearance of this technology has improved the sensitivity of distributing optical fiber sensing technology greatly, also further develops and use technical support and the confidence that provides strong for this technology.Φ-OTDR mainly adopts pulsed light, and is very high with this requirement to the light source live width.Continuous maturation and development along with fiber amplifier and fiber laser technology make laser linewidth constantly reduce, and Φ-OTDR technology enters the through engineering approaches application stage.Φ-OTDR is a principle with Rayleigh scattering light in the detection fiber, reacting condition extraneous vibration by the Rayleigh scattering light phase and temperature variation etc., the detection method of Rayleigh scattering light is divided into heterodyne and detects and homodyne detection, heterodyne detects main acousto-optic or the electric light frequency shifter of adopting reference light is carried out frequency displacement, adopts acousto-optic frequency shifters, stable performance, but modulation band-width is limited, cost an arm and a leg, adopt integrated electro-optic frequency shifter modulating frequency height, but performance changes along with temperature and environmental change.
Summary of the invention
The concrete technical matters that the present invention will solve is to measure the passive homodyne detection of improved PGC algorithm realization to Rayleigh scattering light phase place in Φ-OTDR sensor fibre by band phase modulation (PM) degree, and provide a kind of cheap, highly sensitive, a kind of passive homodyne demodulation devices and methods therefor that is used for Φ-OTDR of stable performance.
A kind of passive homodyne demodulation device that is used for Φ-OTDR provided by the present invention comprises piezoelectric ceramics, fiber coupler, photodetector, analysis and Control module and piezoelectric ceramic actuator module; It is characterized in that:
Carry out phase modulation (PM) by piezoelectric ceramic actuator module drive PZT stretching optical fiber, make the local reference light phase place generation sinusoidal variations of transmitting in the optical fiber, back in local reference light and the Φ-OTDR optical fiber sensing system sensor fibre interferes in fiber coupler to Rayleigh scattering light, interference signal is transferred to the analysis and Control module after receiving by photodetector, when the analysis and Control module is measured control optical fiber piezoelectric ceramic actuator phase modulation (PM) degree back in distributed Φ-OTDR optical fiber sensing system sensor fibre carried out demodulation to the Rayleigh scattering light phase, constitute a kind of passive homodyne demodulation device that is used for Φ-OTDR.
A kind of demodulation method that is used for a kind of passive homodyne demodulation device of Φ-OTDR of the present invention, its described demodulation method are to measure improved PGC algorithm by band phase modulation (PM) degree, realize the passive homodyne detection to Rayleigh scattering light phase place in Φ-OTDR sensor fibre; Carry out the phase place external modulation by PZT, Rayleigh scattering light and local reference light interference signal launch by Bessel's function, by analyzing the size of the each harmonic item amplitude after Bessel's function launches, and then analyze and obtain the phase modulation (PM) degree, further find the solution the Rayleigh scattering light phase.
Realize the above-mentioned a kind of passive homodyne demodulation devices and methods therefor that is used for Φ-OTDR of the present invention, compared with prior art, demodulating equipment of the present invention is simple in structure, and is highly sensitive, stable performance; The inventive method is measured improved phase carrier by band phase modulation (PM) degree and is generated the PGC algorithm, realized passive homodyne detection to Rayleigh scattering light in Φ-OTDR sensor fibre, carry out external modulation by piezoelectric ceramics PZT, simplified detection method, greatly reduce the operating cost of distributed Φ-OTDR optical fiber sensing system, can be widely used in fields such as fibre optic hydrophone, public safety, ground intrusion detection and localization of fault.
Description of drawings
Fig. 1 is a kind of passive homodyne demodulation structure drawing of device that the present invention is used for Φ-OTDR.
Embodiment
Below the specific embodiment of the present invention is made further instruction.
A kind of passive homodyne demodulation device and the demodulation method thereof that is used for ф-OTDR provided by the present invention, thereby be to make full use of the characteristics that piezoelectric ceramics PZT stretching optical fiber makes that fiber phase changes, phase modulation (PM) in addition, make the local reference light phase place generation sinusoidal variations of transmitting in the optical fiber, thereby interfere to Rayleigh scattering light by back in local reference light and the distributed Φ-OTDR optical fiber sensing system sensor fibre, interference signal launches by Bessel's function, by analyzing the size of the each harmonic item amplitude after Bessel's function launches, back in distributed Φ-OTDR optical fiber sensing system sensor fibre carried out demodulation to Rayleigh scattering light.
Because back in local reference light and the distributed Φ-OTDR optical fiber sensing system sensor fibre changes during in the sensor fibre change in location to the Rayleigh scattering light optical path difference, make that local reference light changed with respect to the back phase modulation (PM) degree to Rayleigh scattering light in distributed Φ-OTDR optical fiber sensing system sensor fibre when local reference light carried out phase modulation (PM).When the characteristics of the each harmonic item amplitude after launching by Bessel's function also solve phase modulation (PM) degree big or small simultaneously, the solving precision of phase modulation (PM) degree since with distributed Φ-OTDR optical fiber sensing system sensor fibre in back relevant to the Rayleigh scattering light phase change.By measuring the each harmonic item amplitude size after Bessel's function launches, thereby judge back in distributed Φ-OTDR optical fiber sensing system sensor fibre to Rayleigh scattering light phase change direction, find the solution back phase modulation (PM) degree size in the local relatively reference light of local reference light and the distributed Φ-OTDR optical fiber sensing system sensor fibre by different expression formulas, and then the back phase place to Rayleigh scattering light in distributed Φ-OTDR optical fiber sensing system sensor fibre is carried out accurate demodulation by improved phase generated carrier PGC to Rayleigh scattering light.
The present invention program embodiment utilizes piezoelectric ceramics PZT by the piezoelectric ceramic actuator module local reference light to be carried out sinusoidal phase modulation, obtains phase place random fluctuation coherence continuous laser signal preferably.Back after Rayleigh scattering light interferes in the 2*1 fiber coupler in local reference light and the distributed Φ-OTDR optical fiber sensing system sensor fibre, carry out preposition amplification and filtering by back the reception afterwards of the output arm output of 2*1 fiber coupler behind the signals by photodetector 5, filtered signal is by data acquisition and analysis and Control module 6 collection analysises, by calculating local reference light back to the phase modulation (PM) degree value of Rayleigh scattering light and the back phase value to Rayleigh scattering light in distributed Φ-OTDR optical fiber sensing system sensor fibre with respect in distributed Φ-OTDR optical fiber sensing system sensor fibre.
Owing to local reference light changes to the Rayleigh scattering light sensing location along with back in distributed Φ-OTDR optical fiber sensing system sensor fibre with respect to the back phase modulation (PM) degree to Rayleigh scattering light in distributed Φ-OTDR optical fiber sensing system sensor fibre, in order to obtain suitable phase modulation (PM) degree value, this just requires the local reference light phase modulation (PM) degree that transmits in the optical fiber is controlled, the present invention is by data acquisition and analysis and Control module real-time analysis phase modulation (PM) degree size, and then by control piezoelectric ceramic actuator module, make the input piezoelectric ceramics change for the amplitude of the sinusoidal signal of PZT, and then regulate local reference light with respect to the back phase modulation (PM) degree in distributed Φ-OTDR optical fiber sensing system sensor fibre to Rayleigh scattering light, make when back in distributed Φ-OTDR optical fiber sensing system sensor fibre to the Rayleigh scattering light optical path difference during in the Fibre Optical Sensor change in location, the signal to noise ratio (S/N ratio) of raising transducing signal.
Implement a kind of passive homodyne demodulation device that the present invention is used for Φ-OTDR, comprise piezoelectric ceramics, fiber coupler, photodetector, analysis and Control module and piezoelectric ceramic actuator module; Its architectural feature is:
Carry out phase modulation (PM) by piezoelectric ceramic actuator module drive PZT stretching optical fiber, make the local reference light phase place generation sinusoidal variations of transmitting in the optical fiber, back in local reference light and the Φ-OTDR optical fiber sensing system sensor fibre interferes in fiber coupler to Rayleigh scattering light, interference signal is transferred to the analysis and Control module after receiving by photodetector, when the analysis and Control module is measured control optical fiber piezoelectric ceramic actuator phase modulation (PM) degree back in distributed Φ-OTDR optical fiber sensing system sensor fibre is carried out demodulation to the Rayleigh scattering light phase.
Implement the demodulation method that the present invention is used for a kind of passive homodyne demodulation device of Φ-OTDR, this method is to generate the passive homodyne detection of PGC algorithm realization to Rayleigh scattering light phase place in Φ-OTDR sensor fibre by the improved phase carrier that band phase modulation (PM) degree is measured, and carries out the phase place external modulation by piezoelectric ceramics PZT.
The reference light of Rayleigh scattering light and process piezoelectric ceramics PZT external modulation is interfered, and its output intensity is:
In the formula
Be the Rayleigh scattering light intensity,
Be local reference light intensity,
Be the phase differential of two interference lights,
The light intensity that receives for photodetector.
Wherein
Consist of the following components:
1) to the phase modulation (PM) item of PZT:
,
Be the phase modulation (PM) degree,
Be the modulation angular frequency
2) Rayleigh scattering light phase:
3) local reference light phase place:
Order
, then have
(1) formula is carried out Bezier launch, order
,
:
Then:
Wherein
Be the Bessel's function expansion coefficient.
Interference signal
By centre frequency be
Bandpass filter after, with signal
Multiply each other,, obtain through low-pass filtering:
（3）
Interference signal
By centre frequency be
Bandpass filter after, with signal
Multiply each other,, obtain through low-pass filtering:
Interference signal
By centre frequency be
Bandpass filter after, with signal
Multiply each other,, obtain through low-pass filtering:
Interference signal
By centre frequency be
Bandpass filter after, with signal
Multiply each other,, obtain through low-pass filtering:
Because:
（8）
By (7) formula and the optimizing of (8) formula iteration, ask for the phase modulation (PM) degree
When
Be partial to
(
Be integer) time, (7) formula of utilization is found the solution the phase modulation (PM) degree
When
Be partial to
(
Be integer) time, (8) formula of utilization is found the solution the phase modulation (PM) degree
Find the solution the phase modulation (PM) degree by (7) formula and (8) iteration optimizing
After, substitution (9) formula can be asked for by the arc tangent algorithm
Thereby, solve the Rayleigh scattering light signal phase
Claims (2)
1. be used for a kind of passive homodyne demodulation device of Φ-OTDR, comprise piezoelectric ceramics, fiber coupler, photodetector, analysis and Control module and piezoelectric ceramic actuator module; It is characterized in that:
Carry out phase modulation (PM) by piezoelectric ceramic actuator module drive PZT stretching optical fiber, make the local reference light phase place generation sinusoidal variations of transmitting in the optical fiber, back in local reference light and the Φ-OTDR optical fiber sensing system sensor fibre interferes in fiber coupler to Rayleigh scattering light, interference signal is transferred to the analysis and Control module after receiving by photodetector, when the analysis and Control module is measured control optical fiber piezoelectric ceramic actuator phase modulation (PM) degree back in distributed Φ-OTDR optical fiber sensing system sensor fibre carried out demodulation to the Rayleigh scattering light phase, constitute a kind of passive homodyne demodulation device that is used for Φ-OTDR.
2. demodulation method that is used for a kind of passive homodyne demodulation device of Φ-OTDR, its described demodulation method is to measure improved PGC algorithm by band phase modulation (PM) degree, realization is to the passive homodyne detection of Rayleigh scattering light phase place in Φ-OTDR sensor fibre, carry out the phase place external modulation by PZT, Rayleigh scattering light and local reference light interference signal launch by Bessel's function, by analyzing the size of the each harmonic item amplitude after Bessel's function launches, and then analyze and to obtain the phase modulation (PM) degree, further find the solution the Rayleigh scattering light phase.
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| CN107014289A (en) * | 2017-03-23 | 2017-08-04 | 天津大学 | Modulation degree and initial phase measuring method for sinusoidal phase modulation interferometry |
| CN107063433A (en) * | 2017-04-28 | 2017-08-18 | 电子科技大学 | Phase-sensitive optical time domain reflectometer and its implementation based on Golay complementary series |
| CN108180978A (en) * | 2018-01-30 | 2018-06-19 | 广州天长通信技术有限公司 | A kind of combination PGC technologies and the method and device of Φ-OTDR technique detection optical fiber vibration |
| CN108802756A (en) * | 2018-08-09 | 2018-11-13 | 常州信息职业技术学院 | A kind of full optical fiber laser Doppler range rate measuring system based on acousto-optic null coupler |
| CN109272017A (en) * | 2018-08-08 | 2019-01-25 | 太原理工大学 | The vibration signal mode identification method and system of distributed fiberoptic sensor |
| CN110044401A (en) * | 2019-05-07 | 2019-07-23 | 电子科技大学 | A kind of signal demodulating method and system of fibre optical sensor |
| CN111025306A (en) * | 2019-11-15 | 2020-04-17 | 浙江浙能天然气运行有限公司 | Vibration positioning method and system based on phase-sensitive OTDR |
| CN113517922A (en) * | 2020-04-09 | 2021-10-19 | 华为技术有限公司 | Signal detection method and optical time domain reflectometer |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111025306A (en) * | 2019-11-15 | 2020-04-17 | 浙江浙能天然气运行有限公司 | Vibration positioning method and system based on phase-sensitive OTDR |
| CN113517922A (en) * | 2020-04-09 | 2021-10-19 | 华为技术有限公司 | Signal detection method and optical time domain reflectometer |
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