CN101266024B - Distributed optical fibre oil gas conveying pipeline early early-warning system based on polarization detection - Google Patents

Abstract

The invention relates to a polarization-based early warning system of a distributed optical fiber oil transporting pipeline, which comprises a laser. A forward-propagating optical signal sent from a laser is input from a first port of a polarization beam splitter, and output from a second port to sensing optical fiber connected with a Faraday polariscope. The forward-propagating optical signal is reflected by the Faraday polariscope, and becomes a backward-propagating optical signal after the polarization state of the signal rotates 90 DEG. The backward-propagating optical signal is input from the second port of the polarization beam splitter, and output from a third port to a photoelectric detector. The changed electrical signal is transmitted to a digital signal processing subsystem. The early warning system can position a sensing line perturbing point according the time information of electric power change so as to output alarm and positioning information. The early warning system has the advantages of low cost, high safety and reliability. Furthermore, the early warning system can early position and warn against acts of sabotage to the oil transporting pipeline.

Description

Distributed optical fibre oil gas conveying pipeline early early-warning system based on Polarization Detection

[technical field]:

The invention belongs to long distance, distributing optical fiber sensing technical field, particularly a kind of distributed optical fibre oil gas conveying pipeline early early-warning system based on Polarization Detection.

[background technique]:

Pipeline has been widely used in the industrial departments such as oil, rock gas as a kind of safe, economic means of transprotation; Yet the oil transport pipeline stolen case that is perforated happens occasionally in recent years; Caused enormous economic loss, this makes the oil-gas pipeline automatic monitoring technical become and becomes more and more important.

At present, technological inner detection and the external detection two big classes of can being divided into substantially of the pipeline leakage testing of comparative maturity both at home and abroad comprise inner detection method: Magnetic leakage flux detection, ultrasound examination, eddy current testing, photograph and video recording detection method; External detection method: inspection along the line, high polymer cable, static test, quality analysis, stress wave, pressure difference, negative pressure wave method or the like.More domestic oil companies have also utilized more above-mentioned technology to realize the automatic detection and the warning of pipe leakage; And obtained certain achievement; For example: the method that Shengli Oil Field utilizes suction wave to combine with flow detection; Can find pipe leakage and position that its alert reaction time is 200s; Intelligent Acoustic detection and stress wave technology are adopted in the Zhongyuan Oil Field, have realized the real-time detection to oil transport pipeline.

But; Above-mentioned technology is difficult to satisfy simultaneously detect and leaks sensitivity (can only find a large amount of situation of leaking), positioning precision (500m-1000m), false alarm rate and the multinomial requirements such as (100s magnitudes) of in time reporting to the police owing to receive multiple effects limit such as detecting principle, sensor performance, sampled point closeness.In addition, these methods receive the influence of ambient noise bigger, and monitoring personnel's experience is had very strong dependence.

Optical fiber transducer is with its distinctive characteristics, as anti-electromagnetic interference, electrical insulation, corrosion-resistant, high temperature resistant, volume is little, in light weight, little and cost is low etc. to the measured medium influence, has obtained great development in recent years.Up to the present, optical fiber transducer has been applied to the measurement of physical quantitys such as magnetic field, electric current, sound, temperature and pressure.In various optical fiber sensing technologies; The collection of distributing optical fiber sensing technology collection information be transmitted in one; And can obtain measured sequential information, be particularly suitable for long distance monitoring, therefore have splendid application prospect in oil-gas pipeline automatic monitoring technical field along fiber distribution.

The main implementation method of distributing optical fiber sensing technology comprises: optical time domain reflection (OTDR) method, interferometry and length scanning method etc.Wherein, the OTDR method is utilized the backscattering of light, comprises Rayleigh scattering, Raman scattering and Brillouin scattering, through measuring its light intensity (Rayleigh scattering) or frequency displacement (Raman and Brillouin scattering), detects the stress and the variation of temperature of extraneous physical field.At present, the OTDR technology is comparative maturity, corresponding product is also arranged on the market, but also have certain deficiency for the long-distance pipe leakage monitoring: (1) Sensor Design trouble, and cost performance is low; (2) insensitive to little leakage; (3) monitoring distance is short.

The interfere type optical fiber transducer is to utilize optical fiber to receive institute's monitoring physical field induction, like temperature, rotation, pressure or vibration etc., the leaded light phase place is produced postpone, and causes output light intensity to change, and then learns the variation of physical field to be measured.The interfere type distribution optical fiber sensor advantage technological with respect to OTDR is that dynamic range is big, highly sensitive.Mainly can use in the interferometry Sagnac interferometer, Michelson interferometer, Mach-once interferometer and various interferometer mixed construction etc.But; Because photophase is very responsive for environmental change; Based on the optical fiber sensing system of interferometry for the later stage signal processing no matter at algorithm, still very high requirement is being proposed all aspect the hardware realization, also ripe without comparison in the market scheme or product.

Analysis through to above-mentioned existing technology can find that all technology can only be reported to the police, located after leakage, belong to antitheft afterwards, can't commit a crime the lawless person and carry out early warning in early days.

[summary of the invention]:

The present invention seeks to overcome the above-mentioned deficiency that existing technology exists,, a kind of distributed optical fibre oil gas conveying pipeline early early-warning system based on Polarization Detection is provided to the requirement of oil-gas pipeline early warning.

This system architecture is very simple, and cost performance is high, accurate positioning; Monitoring distance is long, have very high sensitivity, and optical fibre installation is around oil-gas pipeline; Enable to position, report to the police, thereby reach the purpose of early warning in early stage (the shoveling stage) of lawless person's crime.

Distributed optical fibre oil gas conveying pipeline early early-warning system based on Polarization Detection provided by the invention; Comprise laser; Laser sends the first port input of the optical signal of forward-propagating from polarizing splitter, and exports sensor fibre to from second port, and the end of sensor fibre connects the faraday polariscope; The optical signal of forward-propagating becomes the optical signal of reverse transmission after via Faraday mirror reflection, its polarization state half-twist; This reverse optical signal is imported from second port of polarizing splitter, and exports photodetector to from its 3rd port, and photodetector changes reverse light intensity information into electrical signal and is sent to the digital signal processing sub system;

Wherein said sensor fibre is attached on the oil/gas pipe line; Both used as sensor; Also use simultaneously, and the polarization state that can the sense line disturbance be caused changes and be sent to the digital signal processing sub system via photodetector, and this is disturbed the variation that changes electric power into as signal transmission link; The temporal information that changes according to its electric power positions disturbance point, final output alarm, locating information.

Polarization Controller also is installed between laser and the polarizing splitter, and this Polarization Controller is an electric-controlled type, or manually operated type, when being used for system initialization laser is exported polarization state of light and aims at polarizing splitter first port.

The only polarization state of said laser output and the continuous light of power stability, or photoderm.

The tail optical fiber of said polarizing splitter second port is an ordinary optic fibre, and the tail optical fiber of first port, the 3rd port is a deflection fibre-optical, and light transmission shaft is vertical each other.

Described digital signal processing sub system comprises high speed A and signal processing two-part.

In this system, Active Device only comprises laser, photodetector and digital signal processing sub system, and other is passive device, and this makes this system have high stability, almost Maintenance free.

Said laser, Polarization Controller, polarizing splitter, photodetector and digital signal processing sub system are positioned at the control room, are convenient to protection.

Said optical fiber is responsive to variation in pressure and oscillating signal; Optical fiber both used as sensor, also used as signal transmission link simultaneously.

Said Faraday mirror is positioned at the end of sensor fibre, lays with the sense light line locking, imbeds underground, safe, good concealment.

Working principle of the present invention (as shown in Figure 2):

The first, when sense line does not have disturbance,

The evolution process of each port polarization state:

The adjustment Polarization Controller makes: ${\stackrel{\→}{S}}_{1P}={\stackrel{\→}{S}}_{2P}---\left(1\right)$

If when sense line does not have disturbance, its forward polarization transmission matrix is G ₀, then: ${\stackrel{\→}{S}}_{\mathrm{FP}}=G_0\·{\stackrel{\→}{S}}_{2P}---\left(2\right)$

If the polariscopic polarization transmission matrix of faraday is G _F, then: ${\stackrel{\→}{S}}_{\mathrm{FC}}=G_F\·{\stackrel{\→}{S}}_{\mathrm{FP}}---\left(3\right)$

When this reverse light arrives polarizing splitter two ports via sensor fibre, ${\stackrel{\→}{S}}_{2C}=G_0^{-1}\·{\stackrel{\→}{S}}_{\mathrm{FC}}---\left(4\right)$

Simultaneous formula (1)-(4) can get: ${\stackrel{\→}{S}}_{2C}=G_F\·{\stackrel{\→}{S}}_{1P}---\left(5\right)$

According to the characteristic of polarizing splitter, ${\stackrel{\→}{S}}_{3C}={\stackrel{\→}{S}}_{2C}---\left(6\right)$

So, ${\stackrel{\→}{S}}_{3C}=G_F\·{\stackrel{\→}{S}}_{1P}---\left(7\right)$

Above-mentioned analysis explanation is not when sense line has disturbance, by the forward polarization state S of polarizing splitter port one input _IP, via " sensor fibre-Faraday mirror-sensor fibre " afterwards, arrive the reverse polarization state S of polarizing splitter port two _2CWith half-twist.Characteristic based on polarization beam apparatus can know that reverse light will be all from three outputs of polarization beam apparatus port, and at this moment, the electric signal power of photodetector output will reach maximum.

The second, suppose at t ₁Constantly, disturbance takes place in a point place,

At this moment, the reverse light in a point place is Y, and forward light is X.The moment that defines reverse smooth Y arrival polarizing splitter second port is t ₂, the moment that forward light X arrives polarizing splitter second port is t ₃, then: t ₂=t ₁+ L ₂/ c, t ₃=t ₁+ (L ₀+ L ₁)/c, wherein c is the light velocity,

If t ₁Constantly, the forward polarization transmission matrix of sensor fibre will become G ₁, so at t ₂The time be carved into t ₃Constantly, the reverse polarization state of polarizing splitter second port is: ${{\stackrel{\→}{S}}^{\′}}_{2C}=G_1^{-1}\·G_F\·G_0\·{\stackrel{\→}{S}}_{1P}\≠{\stackrel{\→}{S}}_{2C}---\left(8\right)$

So, at t ₂To t ₃In time period, understand some light behind reverse light process polarizing splitter second port and export, and can reduce from the power of the 3rd port output via first port.

At t ₃Constantly, the reverse polarization state of second port is: ${{\stackrel{\→}{S}}^{\′\′}}_{2C}=G_1^{-1}\·G_F\·G_0\·{\stackrel{\→}{S}}_{1P}={\stackrel{\→}{S}}_{2C}---\left(9\right)$

So at t ₃Constantly, the electric signal power of photodetector output will return to maximum value.

when disturbance was arranged, the electric signal power of photodetector output changed as shown in Figure 3.In the digital signal processing sub system, warning algorithm only needs the variable power according to electrical signal, and then extrapolates L ₁, just can realize location, warning function.

Advantage of the present invention and beneficial effect: the present invention adopts the method for Polarization Detection to realize the distribution type fiber-optic early warning system; This system has kept the advantage of all optical fiber transducers; Have following some advantage especially: one, accurate positioning, warning are rapid, can realize early warning.Based on working principle of the present invention; The polarization scrambling information that is arranged in the sensor fibre any point will be sent to the photodetector in control room along optical fiber with the light velocity; Digital information processing system will be confirmed the disturbance location according to the temporal information of this polarization scrambling signal; Therefore, the accurate positioning property of native system and time of fire alarming are only determined by the processing rate upper limit of digital signal processing chip; Two, stability, reliability is high.Because the device that native system adopted is commercial devices ripe already on the market, so its reliability is high.The Active Device quantity that adopts of native system is few in addition, and all is positioned at indoorly, makes it not receive Effect of Environmental, therefore has high stability, once using hardly with safeguarding; Three, safe, good concealment.Most constituent elements of native system all are positioned at the control room, and Faraday mirror and sensor fibre then can be imbedded underground along monitored circuit, so native system Security, disguised high is difficult for being found or destroying by other people.Based on above-mentioned advantage, the present invention is fit to long distance monitoring very much, has splendid application prospect in oil-gas pipeline automatic monitoring technical field.

[description of drawings]:

Fig. 1 forms schematic representation based on the distribution type fiber-optic early warning system of Polarization Detection.Among the figure, 1 laser, 2 Polarization Controllers, 3 polarizing splitter (comprising three ports), 4 sensor fibres, 5 Faraday mirrors, 6 photodetectors, 7 digital signal processing sub systems.

Fig. 2 is the distribution type fiber-optic early warning system working principle schematic representation based on Polarization Detection.Among the figure, S _1PForward polarization state, S for polarizing splitter port one _2PForward polarization state, S for polarizing splitter port two _2CReverse polarization state, S for polarizing splitter port two _3CForward polarization state, S for polarizing splitter port three _FPBe Faraday mirror forward polarization state, S _FCBe the reverse polarization state of Faraday mirror, L ₀For sensor fibre total length, a are polarization scrambling point, L ₁Be disturbance point and Faraday distance between mirrors, L ₂Be distance between disturbance point and polarizing splitter.

Fig. 3 is when having disturbance, and the electric signal power of photodetector output changes.

[embodiment]:

Embodiment

Embodiment below in conjunction with accompanying drawing and inventor accomplish according to technological scheme does further to describe in detail to principle of the present invention, the invention is not restricted to this embodiment.

Fig. 1 is the system block diagram of the embodiment of the invention; The wherein forward light of each device different port, the definition of reverse polarization state, and the working principle of system is as shown in Figure 2.The evolution process of each port polarization state at first, is described when sense line does not have disturbance:

The adjustment Polarization Controller makes: ${\stackrel{\→}{S}}_{1P}={\stackrel{\→}{S}}_{2P}---\left(1\right)$

If when sense line does not have disturbance, its forward polarization transmission matrix is G ₀, then: ${\stackrel{\→}{S}}_{\mathrm{FP}}=G_0\·{\stackrel{\→}{S}}_{2P}---\left(2\right)$

If the polariscopic polarization transmission matrix of faraday is G _F, then: ${\stackrel{\→}{S}}_{\mathrm{FC}}=G_F\·{\stackrel{\→}{S}}_{\mathrm{FP}}---\left(3\right)$

When this reverse light arrives polarizing splitter two ports via sensor fibre, ${\stackrel{\→}{S}}_{2C}=G_0^{-1}\·{\stackrel{\→}{S}}_{\mathrm{FC}}---\left(4\right)$

Simultaneous formula (1)-(4) can get: ${\stackrel{\→}{S}}_{2C}=G_F\·{\stackrel{\→}{S}}_{1P}---\left(5\right)$

According to the characteristic of polarizing splitter, ${\stackrel{\→}{S}}_{3C}={\stackrel{\→}{S}}_{2C}---\left(6\right)$

So, ${\stackrel{\→}{S}}_{3C}=G_F\·{\stackrel{\→}{S}}_{1P}---\left(7\right)$

Above-mentioned analysis explanation is not when sense line has disturbance, by the forward polarization state S of polarizing splitter port one input _1P, via " sensor fibre-Faraday mirror-sensor fibre " afterwards, arrive the reverse polarization state S of polarizing splitter port two _2CWith half-twist.Characteristic based on polarization beam apparatus can know that reverse light will be all from three outputs of polarization beam apparatus port, and at this moment, the electric signal power of photodetector output will reach maximum.

Be located at t ₁Constantly, disturbance takes place in a point place, and at this moment, the reverse light in a point place is Y, and forward light is X.The moment that defines reverse smooth Y arrival polarizing splitter port two is t ₂, the moment that forward light X arrives polarizing splitter port two is t ₃, then: t ₂=t ₁+ L ₂/ c, t ₃=t ₁+ (L ₀+ L ₁)/c, wherein c is the light velocity,

If t ₁Constantly, the forward polarization transmission matrix of sensor fibre will become G ₁, so at t ₂The time be carved into t ₃Constantly, the reverse polarization state of polarizing splitter port two is: ${{\stackrel{\→}{S}}^{\′}}_{2C}=G_1^{-1}\·G_F\·G_0\·{\stackrel{\→}{S}}_{1P}\≠{\stackrel{\→}{S}}_{2C}---\left(8\right)$

So, at t ₂To t ₃In time period, understand some light via port one output behind the reverse light process polarizing splitter port two, and can reduce from the power of port three outputs.

At t ₃Constantly, the reverse polarization state of port two is: ${{\stackrel{\→}{S}}^{\′\′}}_{2C}=G_1^{-1}\·G_F\·G_0\·{\stackrel{\→}{S}}_{1P}={\stackrel{\→}{S}}_{2C}---\left(9\right)$

So at t ₃Constantly, the electric signal power of photodetector output will return to maximum value.

when disturbance was arranged, the electric signal power of photodetector output changed as shown in Figure 3.In the digital signal processing sub system, warning algorithm only needs the variable power according to electrical signal, and then extrapolates L ₁, just can realize location, warning function.

The present invention utilizes above-mentioned principle, has designed the distribution type fiber-optic early warning system based on Polarization Detection, mainly comprises laser, Polarization Controller, polarizing splitter, sensor fibre, Faraday mirror, photodetector and digital signal processing sub system.It is characterized in that laser sends the optical signal of forward-propagating, utilize its polarization state of Polarization Controller adjustment to make it first port input, and export sensor fibre to from second port from polarizing splitter.The optical signal of forward-propagating becomes the light of reverse transmission via the Faraday mirror reflection, and its polarization state is with half-twist.This reverse light is imported from second port of polarizing splitter, and exports photodetector to from its 3rd port.Photodetector changes reverse light intensity information into electrical signal and is sent to the digital signal processing sub system.Utilize said apparatus, the present invention can be the variation of electric power with the polarization state change transitions that is caused by the sense line disturbance, and the temporal information that changes according to its electric power positions final output alarm, locating information to disturbance point.

Above-mentioned distribution type fiber-optic early warning system based on Polarization Detection is characterized in that, the light of said laser output can be continuous light, can be photoderm also, requires its output polarization state and power stability.

Above-mentioned distribution type fiber-optic early warning system based on Polarization Detection; It is characterized in that said Polarization Controller can be automatically controlled, also can be manual; It is only regulated when system initialization and once gets final product, and its effect is laser to be exported polarization state of light aim at polarizing splitter port one.

Above-mentioned distribution type fiber-optic early warning system based on Polarization Detection is characterized in that the tail optical fiber of said polarizing splitter port two is an ordinary optic fibre, and the tail optical fiber of port one, port three is a deflection fibre-optical, and light transmission shaft is vertical each other.

Above-mentioned distribution type fiber-optic early warning system based on Polarization Detection is characterized in that, said sensor fibre is responsive to variation in pressure and oscillating signal; Optical fiber both used as sensor, also used as signal transmission link simultaneously.

Above-mentioned distribution type fiber-optic early warning system based on Polarization Detection is characterized in that said Faraday mirror is positioned at the end of sensor fibre, lays with the sense light line locking, imbeds underground, safe, good concealment.

Above-mentioned distribution type fiber-optic early warning system based on Polarization Detection is characterized in that, said digital signal processing sub system comprises high speed mould/number (A/D) conversion and signal processing two-part.

Above-mentioned distribution type fiber-optic early warning system based on Polarization Detection is characterized in that said laser, Polarization Controller, polarizing splitter, photodetector and digital signal processing sub system are positioned at the control room, is convenient to protection.

Above-mentioned distribution type fiber-optic early warning system based on Polarization Detection; It is characterized in that said Active Device only comprises laser, photodetector and digital signal processing sub system, other is passive device; Therefore this system has high stability, almost Maintenance free.

Above-mentioned distribution type fiber-optic early warning system based on Polarization Detection is characterized in that the Location accuracy of system and time of fire alarming are only determined by the processing rate upper limit of digital signal processing chip.

The above is a most preferred embodiment of the present invention, and its cost is minimum, reliability is high.But be not that the present invention is done any pro forma restriction, every foundation technical spirit of the present invention is done any simple modification, equivalent variations and modification to the foregoing description, all belongs in the scope of technological scheme of the present invention.

Claims (5)

1. distributed optical fibre oil gas conveying pipeline early early-warning system based on Polarization Detection; It is characterized in that this early warning system comprises laser; Laser sends the first port input of the optical signal of forward-propagating from polarizing splitter; And export sensor fibre to from second port; The end of sensor fibre connects the faraday polariscope, and the optical signal of forward-propagating becomes the optical signal of reverse transmission after via Faraday mirror reflection, its polarization state half-twist, and this reverse optical signal is from second port input of polarizing splitter; And exporting photodetector to from its 3rd port, photodetector changes the strength information of reverse optical signal into electrical signal and is sent to the digital signal processing sub system;

Wherein said sensor fibre is attached on the oil/gas pipe line; Both used as sensor; Also use simultaneously, and can sense line be sent to the digital signal processing sub system because of the polarization state variation that disturbance causes via photodetector, and change this disturbance the variation of electric power into as signal transmission link; The temporal information that changes according to its electric power positions disturbance point, final output alarm, locating information.

2. the distributed optical fibre oil gas conveying pipeline early early-warning system based on Polarization Detection according to claim 1 is characterized in that the only polarization state of said laser output and the continuous light of power stability, or photoderm.

3. the distributed optical fibre oil gas conveying pipeline early early-warning system based on Polarization Detection according to claim 1; The tail optical fiber that it is characterized in that said polarizing splitter second port is an ordinary optic fibre; The tail optical fiber of first port, the 3rd port is a deflection fibre-optical, and light transmission shaft is vertical each other.

4. the distributed optical fibre oil gas conveying pipeline early early-warning system based on Polarization Detection according to claim 1 is characterized in that described digital signal processing sub system comprises high speed A and signal processing two-part.

5. the distributed optical fibre oil gas conveying pipeline early early-warning system based on Polarization Detection according to claim 1; It is characterized in that also being equipped with between laser and the polarizing splitter Polarization Controller; This Polarization Controller is an electric-controlled type; Or manually operated type, when being used for system initialization laser is exported polarization state of light and aim at polarizing splitter first port.

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