CN101290245A - All-sensing interference -type light time domain reflectometer - Google Patents

Abstract

The invention discloses a full sensing interference-type optical time domain reflectometer. The full sensing interference-type optical time domain reflectometer comprises an optical signal emitting and receiving processing module [100] and a sensing fiber [101] and a sensing fiber [102]; the optical signal emitting and receiving processing module [100] comprises a computer [1], a light source driver [2], a light source [3], a detector [4], a circuit processing board [5] with the detector and a fiber coupler [6]; and two circuits of the sensing fiber [101] and the sensing fiber[102] form a cable and realize the long-distance distributed vibration, impact detection and positioning. A single full sensing interference-type optical time domain reflectometer is additionally provided with an optical switch for carrying out multichannel periodic check and measurement and monitoring to the phenomena of large-area vibration and impact. A plurality of reflectometers are connected to the Internet to realize remote intelligent monitoring.

Description

All-sensing interference-type light time domain reflectometer

Technical field

The present invention discloses a kind of all-sensing interference-type light time domain reflectometer, and the distributed measurement that relate to vibration, impacts belongs to the safety precautions technical field.

Background technology

The safety of maintain infrastructure is a basic demand of social stability, rapid economic development.Infrastructure such as communications optical cable, high-voltage fence, oil pipeline, gas pipe line, bridge, dam, buildings are carried out safety monitoring, to determine health, maintenance needs, life-span and other characteristic, be not only these facilities and realize the guarantee of technical function, the effective means of avoiding causing heavy economic losses especially, maintaining social stability and develop.

The being perfectly safe property of optical fiber information transmission is broken in recent years, eavesdropping incident at the land lightguide cable link has report repeatly, and Central Intelligence Agency's submarine optical fiber cable eavesdropping plan that related media discloses more causes the abundant attention of people to the submarine optical fiber cable information transmission safety.How in time to find and accurately a kind of especially challenge of these accidents of location.

Along with the development of pipeline transportation industry, various pipeline transportation safety monitoring technologies are also in continuous development, and present existing pipe safety production monitoring technology mainly contains two classes.One: the monitoring technology after the pipe leakage incident takes place, this technology mainly contains " tube fluid mechanical state detection technique ".Tube fluid mechanical state detection technique is to gather signals such as the flow of fluid in the pipeline, temperature and pressure in real time, carry out pipeline leakage testing and location, this technology is subjected to the effects limit such as performance of fluid behaviour, delivery technology and testing tool in the pipeline, sensitivity and bearing accuracy to line leakage are lower, and this class technology comprises: pressure gradient method, negative pressure wave method, flow equilibrium method.They are two years old, prevention monitoring technology before the pipeline damage incident takes place, pipeline damage early warning technology just, existing such technology mainly is " technology of acoustic wave monitoring " at present, this technology is to utilize sound wave along the pipeline transmission principle, an active sensor is being installed every about 1km, picking up pipeline voice signal along the line is analyzed, determine event property, and then the incident of destroying pipeline found in advance, but each senser element must be equipped with a cover electric supply installation and a communicator, not only increases the investment and the maintenance cost of equipment, and these facilities are also destroyed easily itself, and device can not normally be moved.

Along with the development of optical fiber sensing technology, the long-distance distributed optical fiber sensing technology also begins to be applied to pipeline leakage testing and communications optical cable safety monitoring, mainly contains scattering method and optical interferometry behind the light.Scattering method utilizes the influence of external event to optical fiber transmission property based on Rayleigh, Raman, Brillouin, polarization theory behind the light, judges local external force, temperature variation by astigmatism strong variation the in back in the detection and localization optical fiber, and then can assess the safety case of pipeline.For pipeline, distribution type fiber-optic temperature and stress monitoring technology are the positions that the medium that utilizes the nonlinear characteristic of optical fiber (Ramam effect and brillouin effect) to gather pipe leakage is in real time determined leakage point to the temperature effect and the shock stress of optical fiber, the light signal that this technology has only brillouin effect to return is the strongest, can realize single acquisition and calculate Monitoring Data that all the other need just to reach the signal to noise ratio (S/N ratio) of calculating Monitoring Data after average thousands of times.

That optical interferometry has is highly sensitive, dynamic range big, response is fast, transmission range is long, can satisfy long distance, microvibration detection requirement.Chinese invention patent application 200410020046.6,200410040282.4,200610113044.0,200510023104.5,200610090594.5,200710051004.2 Deng certain closed-loop path of formation, realize that interference condition detects microvibration, but these interferometric methods can only be implemented in and detect a point on the whole sensing path, occur more than 2 and 2 just powerless on the sensing path simultaneously.

Summary of the invention

Scattering method constitutes safety monitoring system cheaply after the objective of the invention is to adopt all-sensing interference-type light Rayleigh, realizes long-distance distributed vibration, impulse detection and location.In order to achieve the above object, the following technical scheme that the present invention adopts: comprise transmitting and receiving light signal processing module [100] that sensor fibre [101] and sensor fibre [102] constitute all-sensing interference-type light time domain reflectometer (as shown in Figure 1); Transmit and receive processing of circuit plate [5] and fiber coupler [6] that light signal processing module [100] comprises computing machine [1], light source drive [2], light source [3], detector [4], band detector; Two-way sensor fibre [101], [102] stranding.

Principle of work of the present invention: as shown in Figure 1, computing machine [1] control light source drive [2] makes light source [3] by certain frequency emission light pulse, pulsewidth is less than 10ns (avoiding stimulated Brillouin scattering), and light pulse power makes light pulse power on every optical fiber cable smaller or equal to the excited Raman threshold value of loosing.Light pulse input 2 * 2 fiber couplers [6], preferred coupled device [6] merit proportion by subtraction is 1: 1, the light pulse that is divided into two bundle equivalent is propagated in two-way sensor fibre [101], [102] respectively, the light pulse power magnitude diminished variation factor S after last some point of sensor fibre [101] was subjected to extraneous vibration, percussive action _1i≤ 1, and phase change φ _1i, the light pulse power magnitude diminished variation factor S after sensor fibre [102] was subjected to same extraneous vibration, percussive action with the last identical point of sensor fibre [101] _2i≤ 1, and phase change φ _2iLight in sensor fibre [101] and the sensor fibre [102] carries out Rayleigh scattering simultaneously, wherein back scattered light turns back to coupling mechanism [6] along the former road of optical fiber and carries out coherent interference, they continue to propagate the back and are converted to electric signal by photo-detector [4], be converted to digital signal by processing of circuit plate [5] again, handle, calculate these vibrations, impact position on the sensor fibre circuit by computing machine [1].

Advantageously improve the incident beam quality, light source [3] preferred pulse fiber laser.

Advantageously on the sensor fibre [102] polarization controller [7] is set, guarantees that coherent interference is than maximum.

Advantageously equal optical pulse width the switching time of the analog to digital converter on the processing of circuit plate [5].

Advantageously the light pulse Transmission Time Interval is greater than light travel-time back and forth in optical fiber.

If sensor fibre [101] and sensor fibre [102] length are L rice, there are m vibration, shock point in sensor fibre [101], [102] on processing module [100] length l rice, and back light power is so:

$P\left(\frac{2\mathrm{nl}}{c}\right)=\frac{1}{4}{\mathrm{Pe}}^{-2\mathrm{\αl}}{r}_1{r}_2(\underset{i=1}{\overset{m}{\mathrm{\Π}}}{S}_{1i}^2+\underset{i=1}{\overset{m}{\mathrm{\Π}}}{S}_{2i}^2+2\underset{i=1}{\overset{m}{\mathrm{\Π}}}{S}_{1i}{S}_{2i}\cos \left(2\underset{i=1}{\overset{m}{\mathrm{\Σ}}}({\mathrm{\φ}}_{1i}-{\mathrm{\φ}}_{2i})\right))---\left(1\right)$

P is an incident power in the formula (1), r ₁Be scattering coefficient, r ₂Be the back dispersion factor, n is an optical fibre refractivity, and c is a light speed in a vacuum.If remove sensor fibre [101], back light power is:

$P_1\left(\frac{2\mathrm{nl}}{c}\right)=\frac{1}{4}{\mathrm{Pe}}^{-2\mathrm{\αl}}{r}_1{r}_2\underset{i=1}{\overset{m}{\mathrm{\Π}}}{S}_{1i}^2---\left(2\right)$

Formula (1) gets divided by formula (2):

$P\left(\frac{2\mathrm{nl}}{c}\right)\backslash P_1\left(\frac{2\mathrm{nl}}{c}\right)=1+\underset{i=1}{\overset{m}{\mathrm{\Π}}}{\left(\frac{S_{2i}}{S_{1i}}\right)}^2+2\underset{i=1}{\overset{m}{\mathrm{\Π}}}\frac{S_{2i}}{S_{1i}}\cos \left(2\underset{i=1}{\overset{m}{\mathrm{\Σ}}}({\mathrm{\φ}}_{1i}-{\mathrm{\φ}}_{2i})\right)---\left(3\right)$

Because S _1i≈ S _2i≤ 1 reaches $\left|\underset{i=1}{\overset{m}{\mathrm{\Σ}}}({\mathrm{\φ}}_{1i}-{\mathrm{\φ}}_{2i})\right|\→0,$ Obviously interfere type formula (1) improves 6dB than the Optical Signal To Noise Ratio of direct type formula (2), and electric signal to noise ratio (S/N ratio) improves 12dB.

When the light pulse power of propagating on every sensor fibre all looses threshold value near excited Raman, advantageously improve back light power, sensor fibre is parallel to be laid more than two, only need digital averaging just can detect vibration, impact position and relative intensity tens times, so each reflectometer working time significantly reduces, and has improved the reflectometer life-span.All sensor fibre bar numbers are preferably 2 integral multiple, and several 2 * 2 fiber couplers easy to use connect these optical fiber.

Single all-sensing interference-type light time domain reflectometer installs photoswitch additional, carries out the hyperchannel cycle and patrols and examines measurement, monitor large-area vibration, impact phenomenon.A plurality of reflectometer networkings realize the long-distance intelligent monitoring.

Advantage of the present invention:

1., be widely used: promptly can be applicable to the safety monitoring of pipeline, can be applied to large-area safety monitoring again.

2., detection sensitivity height, monitoring distance be far away: light source [3] Transmission Time Interval is set greater than light travel-time back and forth in optical fiber, returning coherent optical pulse can not mix, and the reflectometer signal to noise ratio (S/N ratio) is guaranteed; Equaling the light pulse duration switching time of the analog to digital converter on the processing of circuit plate [5] makes the undistorted phenomenon of electric signal.Along with the increase of sensor fibre bar number, total incident optical power increase, next light coherence stack is returned in back scattering simultaneously, its detection sensitivity and the corresponding increase of detection distance.

3., bearing accuracy height: adopt short-pulse laser, can obtain positioning error in theory less than 2m less than 10ns.

4., locate multiple spot vibration, impact position simultaneously: adopt optical time domain reflectometer to have and detect multiple spot unique point function simultaneously.

5., digital averaging number of times of the present invention significantly reduces,, each reflectometer working time is just less, the serviceable life of improving instrument.

Accompanying drawing and description of drawings

Fig. 1 principle of the invention structural drawing;

Four sensor fibre structural drawing of Fig. 2 the present invention;

Scatter diagram behind the photosignal that Fig. 3 Fig. 2 embodiment of the present invention gathers;

The repeated use of reference number is intended to represent identical or similar feature of the present invention or element in instructions of the present invention and the accompanying drawing.

Embodiment

For the purpose of summarizing the present invention, this paper has described some aspect of the present invention, advantage and novel feature.Should be appreciated that, need not realize all these advantages according to a particular embodiment of the invention.Therefore, the invention is not restricted to disclosed any specific embodiment.

Embodiments of the invention are as follows:

Embodiment be safety monitoring length apart from buildings corridor 5000m, this example is an experimental prototype, it constitutes as shown in Figure 2.Thick connecting line is an optical fiber among the figure, is provided by optical cable company of Chengdu Zhongzhu, and thin connecting line is an electric wire.Computing machine [1] is the PC104 system, the processing of circuit plate [5] of light source drive [2], band detector is that 1 100MHz10bitA/D chip, 1 PIN detector, driving circuit, treatment circuit, buffer zone are integrated in the integrated circuit board, finish by our making in laboratory, light source [3] also is homemade fiber laser, 980nm pump erbium-doped optical fiber output 1550nm light pulse, live width 2nm, pulsewidth 10ns, peak power 6W, repetition frequency 20kHz, be coiled in the integrated circuit board upper strata, integrated circuit board inserts in the slot of PC104 system.Coupling mechanism [6] is provided by Shanghai writing brush space company; System software is worked out by our laboratory, comprises system drive, collection, analysis, demonstration storage.Computing machine [1] control light source drive [2] makes light source [3] press 20kHz repetition frequency emission light pulse.The coupler array that 42 * 2 fiber couplers of light pulse input are formed, the light pulses that are divided into four bundle equivalent are propagated in four sensor fibres respectively and the back scattering is returned by photodetector [4] and is converted to electric signal, be converted to digital signal by processing of circuit plate [5] again, digital averaging number of times 400, each monitoring time is 250ms, handles, calculates vibration position on the sense line by computing machine [1].Scatter diagram behind the photosignal of the collection among the embodiment (as shown in Figure 3), finding has the position of three vibrations, shock point and actual vibration to meet on the sensor fibre.

Claims (5)

1, a kind of all-sensing interference-type light time domain reflectometer comprises transmitting and receiving light signal processing module [100], and sensor fibre [101] and sensor fibre [102] constitute all-sensing interference-type light time domain reflectometer; Transmit and receive processing of circuit plate [5] and fiber coupler [6] that light signal processing module [100] comprises computing machine [1], light source drive [2], light source [3], detector [4], band detector; Two-way sensor fibre [101], [102] stranding are realized long-distance distributed vibration, impulse detection and location.

2, by the described reflectometer of claim 1, it is characterized in that: polarization controller [7] is set on the sensor fibre [102].

3, by the described reflectometer of claim 1, it is characterized in that: the coupling mechanism of use [6] is preferably fused-tapered fiber coupler, and the merit proportion by subtraction is preferably divided equally.

4, according to the described reflectometer of claim 1, it is characterized in that: sensor fibre is more than two and two, and the optical fiber of use is single-mode fiber, or multimode optical fiber, perhaps polarization maintaining optical fibre.

5, according to the described reflectometer of claim 1, it is characterized in that: single all-sensing interference-type light time domain reflectometer installs photoswitch additional, and carry out the hyperchannel cycle and patrol and examine measurement, monitor large-area vibration, impact phenomenon, a plurality of reflectometer networkings realize the long-distance intelligent monitoring.

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