CN104197206A - Distributed fiber-optic sensing based oil-gas pipeline safety monitoring system and method - Google Patents

Abstract

The invention discloses a distributed fiber-optic sensing based oil-gas pipeline safety monitoring system and method. The method includes the steps of 1, establishing a Michelson fiber-optic interferometer with a 3*3 fiber-optic coupler to obtain three interference signals of an oil-gas pipeline, with each two of the interference signals, having a fixed phase difference 2Pi/3; 2, demodulating the interference signals to obtain an interference optical phase Delta Phi(5t) caused by disturbance; 3, subjecting a formula of the interference optical phase Delta Phi(5t) to a sum-difference to product operation; 4, filtering a phase direct-current component and performing derivation by differentiation; 5, performing spectrum transformation; 6, calculating a disturbance position L2 of the oil-gas pipeline. The distributed fiber-optic sensing based oil-gas pipeline safety monitoring system and method has the advantages that complex and expensive hardware equipment is omitted, the diploma of sensitivity and trapped wave point aliasing in the white light interferometer positioning technology is also avoided, insertion loss is low, the system and the method are applicable to safety warning for long-distance wide-range oil and gas pipelines, an available monitoring range is up to 150km, and the system and the method have a promising application prospect.

Description

Oil/gas pipe line safety monitoring system and method based on distributing optical fiber sensing

Technical field

The present invention relates to a kind of oil/gas pipe line safety monitoring system and method based on distributing optical fiber sensing, belong to oil/gas pipe line safe early warning technical field.

Background technique

Growing along with China's economy, pipe safety especially oil/gas pipe line is segmentation field of significant concern that obtains for several years at this, if the rupture and leakage of oil/gas pipe line can cause resident living to suffer tremendous influence; If oil/gas pipe line wrecks, bring huge potential safety hazard, and cause immeasurable economic loss.

As everyone knows, the alarm monitoring system of prior art is supported by multiplexer channel mostly, and this system is to remove by the software of each different passage to control passage separately, too loaded down with trivial details from technological layer, implement also cumbersome, and set up and the cost safeguarded also all higher, be not suitable for applying under this long distance of oil/gas pipe line, inflammable and explosive occasion.

Be accompanied by the appearance of optical fiber sensing technology, numerous optical fiber sensing technologies such as Mach-Zehnder interference technique, white light interference technique start to be applied in this field of pipeline security protection, in addition, also have some technology that multiple interferometer is combined, as Sagnac and Mach-Zehnder, Sagnac and Sagnac, external at present also a lot of for the research of optical fiber security alarm technology, also be mainly based on Sagnac, MZ, to interfere the fiber fence alarm technique research of class, rarely have the application on monitoring pipeline safety.

Due to more inborn limitations of technical know-how separately, the trap wave point location technology of Mach-Zehnder New Interferometer Positioning Technique and Fiber White-light Interferometer of take is example, Mach-Zehnder New Interferometer Positioning Technique must adopt the synchronous acquisition device of two-forty, cost is higher, and along with monitoring distance be increased to certain distance after cost sharply increase; And Fiber White-light Interferometer trap wave point location technology postpones fibre optic ring owing to existing, and postpone fibre optic ring itself, also can produce trap wave point, in growing apart from position fixing process, easily cause trap wave point aliasing interference phenomenon, and postpone fibre optic ring length by minimizing, solve the sensitivity that Aliasing Problem can reduce system.

Various technology can not rise to pipeline security protection a good application height all the time above, on market, still lack a kind of effective pipeline security protection class technical products, in view of the above problems, develop a kind of oil/gas pipe line safety monitoring method simple, fiber orientation type that cost is low imperative.

Summary of the invention

The object of the invention is to overcome and on existing market, still lack a kind of effective pipeline security protection class technical products.Oil/gas pipe line safety monitoring system and method based on distributing optical fiber sensing of the present invention, avoided the hardware unit of loaded down with trivial details costliness, also evaded the double-barreled question of white light interferometer location technology simultaneously, insertion loss is less, be applicable to long distance, oil/gas pipe line safe early warning on a large scale, monitoring distance can reach 150km, has a good application prospect.

In order to achieve the above object, the technical solution adopted in the present invention is:

An oil/gas pipe line safety monitoring system based on distributing optical fiber sensing, is characterized in that: comprise

Laser, the first photodetector, the second photodetector, the 3rd photodetector, 3 * 3 Fiber Optic Coupler, the first sensor fibre terminal FRM and the second sensor fibre terminal FRM, described laser, the second photodetector is connected with the first via input end of 3 * 3 Fiber Optic Coupler by optical fiber circulator, described the first photodetector, the 3rd photodetector respectively with second of 3 * 3 Fiber Optic Coupler, three road input ends are connected, the first via output terminal of described 3 * 3 Fiber Optic Coupler is connected with the first sensor fibre terminal FRM by sensor fibre, the second road output terminal of described 3 * 3 Fiber Optic Coupler is connected with the second sensor fibre terminal FRM by optical fiber reference arm.

The aforesaid oil/gas pipe line safety monitoring system based on distributing optical fiber sensing, is characterized in that: described sensor fibre distributes along the transmission direction of oil/gas pipe line.

The aforesaid oil/gas pipe line safety monitoring system based on distributing optical fiber sensing, is characterized in that: described the first sensor fibre terminal FRM and the second sensor fibre terminal FRM are faraday rotator mirror.

The monitoring method of the oil/gas pipe line safety monitoring system based on distributing optical fiber sensing, is characterized in that: comprises the following steps,

Step (1), builds Michelson fibre optic interferometer by 3 * 3 Fiber Optic Coupler, obtains oil/gas pipe line Shang San road interference signal, has the fixed skew of 2 π/3 between adjacent two-way interference signal;

Step (2), utilizes three road interference signals, demodulates the interference light phase delta phi (t) that disturbance causes, process is,

(1) establishing disturbance φ (t) is single frequency sinusoidal function, as shown in formula (1),

φ(t)＝φ ₀sinω(t) (1)

Wherein, φ ₀refer to that the photophase that disturbance causes changes amplitude; ω refers to forcing frequency;

(2) according to formula (2), the interference light phase delta phi (t) that calculation perturbation causes,

Wherein, τ ₀first via light process L for fibre optic interferometer ₀the time of distance, τ ₁the second road light process L for fibre optic interferometer ₁the time of distance, τ ₂third Road light process L for fibre optic interferometer ₂the time of distance, during for undisturbed situation, the phase difference of optical fiber reference arm and sensor fibre; L ₀total length for the sensor fibre that is arranged in parallel with oil/gas pipe line; L1 is that disturbance point is to the distance at sensor fibre top; L2 is that disturbance point is to the distance of sensor fibre terminal FRM;

Step (3), carries out and differs from eliminate indigestion computing formula (2), obtains formula (3),

Step (4), to formula (3) elimination phase place flip-flop, and to formula (3) differential differentiate, obtains formula (4),

Δφ′(t)＝2φ ₀ωcosω(t+τ ₀)cosω(τ ₂) (4)；

Step (5), carries out Spectrum Conversion to formula (4), obtains formula (5),

Δφ′(ω)＝2φ ₀ωcosω(τ ₂) (5)；

Step (6), as cos ω (τ ₂)=0, according to formula (5), obtains formula (6),

2πfn(L ₂)/C＝kπ+π/2 (6)

, $L_2=(k+1/2)\·\frac{C}{2\mathrm{nf}}$

Wherein, n is that optical fibre refractivity, C are that the light velocity, K are natural number, and periodic depression points will appear in spectrogram, by determining the frequency values f of depression points, calculates L ₂, L ₂disturbance location for oil/gas pipe line.

The aforesaid oil/gas pipe line safety monitoring method based on distributing optical fiber sensing, it is characterized in that: step (1), by 3 * 3 Fiber Optic Coupler, build Michelson fibre optic interferometer, the method that obtains oil/gas pipe line Shang San road interference signal is, each road interference signal comprises two-beam road, two-beam road forms interferes, and the path of a branch of light path is that laser to 3 * 3 Fiber Optic Coupler is to optical fiber reference arm to the first sensor fibre terminal FRM to optical fiber reference arm to 3 * 3 Fiber Optic Coupler to photodetector;

The path of another bundle light velocity is that laser to 3 * 3 Fiber Optic Coupler is to the second sensor fibre terminal FRM to 3 * 3 Fiber Optic Coupler to photodetector.

The invention has the beneficial effects as follows: oil/gas pipe line safety monitoring system and the method based on distributing optical fiber sensing of the present invention, avoided the hardware unit of loaded down with trivial details costliness, also evaded the double-barreled question of white light interferometer location technology simultaneously, insertion loss is less, be applicable to long distance, oil/gas pipe line safe early warning on a large scale, monitoring distance can reach 150km, has a good application prospect.

Accompanying drawing explanation

Fig. 1 is the system block diagram of the oil/gas pipe line safety monitoring method based on distributing optical fiber sensing of the present invention.

Fig. 2 is the flow chart of the oil/gas pipe line safety monitoring system based on distributing optical fiber sensing of the present invention.

Embodiment

Below in conjunction with Figure of description, the invention will be further described.Following examples are only for technological scheme of the present invention is more clearly described, and can not limit the scope of the invention with this.

As shown in Figure 1, oil/gas pipe line safety monitoring system based on distributing optical fiber sensing of the present invention, comprise laser, the first photodetector (photodetector 1), the second photodetector (photodetector 2), the 3rd photodetector (photodetector 3), 3 * 3 Fiber Optic Coupler (coupler), the first sensor fibre terminal FRM (FRM) and the second sensor fibre terminal FRM (the 2nd FRM), laser, the second photodetector is connected with the first via input end of 3 * 3 Fiber Optic Coupler by optical fiber circulator M, the first photodetector, the 3rd photodetector respectively with second of 3 * 3 Fiber Optic Coupler, three road input ends are connected, the first via output terminal of 3 * 3 Fiber Optic Coupler is connected with the first sensor fibre terminal FRM by sensor fibre, the second road output terminal of 3 * 3 Fiber Optic Coupler is connected with the second sensor fibre terminal FRM by optical fiber reference arm, wherein sensor fibre distributes along the transmission direction of oil/gas pipe line, the first sensor fibre terminal FRM and the second sensor fibre terminal FRM are faraday rotator mirror.

The monitoring method of the oil/gas pipe line safety monitoring system of the distributing optical fiber sensing based on above-mentioned, avoided the hardware unit of loaded down with trivial details costliness, also evaded the double-barreled question of white light interferometer location technology simultaneously, insertion loss is less, be applicable to long distance, oil/gas pipe line safe early warning on a large scale, monitoring distance can reach 150km, as shown in Figure 2, specifically comprise the following steps

Step (1), builds Michelson fibre optic interferometer by 3 * 3 Fiber Optic Coupler, obtains oil/gas pipe line Shang San road interference signal, has the fixed skew of 2 π/3 between adjacent two-way interference signal;

Step (2), utilizes three road interference signals, demodulates the interference light phase delta phi (t) that disturbance causes, process is,

(1) establishing disturbance φ (t) is single frequency sinusoidal function, as shown in formula (1),

φ(t)＝φ ₀sinω(t) (1)

Wherein, φ ₀refer to that the photophase that disturbance causes changes amplitude; ω refers to forcing frequency;

(2) according to formula (2), the interference light phase delta phi (t) that calculation perturbation causes,

Wherein, τ ₀first via light process L for fibre optic interferometer ₀the time of distance, τ ₁the second road light process L for fibre optic interferometer ₁the time of distance, τ ₂third Road light process L for fibre optic interferometer ₂the time of distance, during for undisturbed situation, the phase difference of optical fiber reference arm and sensor fibre; L ₀total length for the sensor fibre that is arranged in parallel with oil/gas pipe line; L1 is that disturbance point is to the distance at sensor fibre top; L2 is that disturbance point is to the distance of sensor fibre terminal FRM;

Step (3), carries out and differs from eliminate indigestion computing formula (2), obtains formula (3),

Step (4), to formula (3) elimination phase place flip-flop, and to formula (3) differential differentiate, obtains formula (4),

Δφ′(t)＝2φ ₀ωcosω(t+τ ₀)cosω(τ ₂) (4)；

Step (5), carries out Spectrum Conversion to formula (4), obtains formula (5),

Δφ′(ω)＝2φ ₀ωcosω(τ ₂) (5)；

Step (6), as cos ω (τ ₂)=0, according to formula (5), obtains formula (6),

2πfn(L ₂)/C＝kπ+π/2 (6)

, $L_2=(k+1/2)\·\frac{C}{2\mathrm{nf}}$

Wherein, n is that optical fibre refractivity, C are that the light velocity, K are natural number, and periodic depression points will appear in spectrogram, by determining the frequency values f of depression points, calculates L2, and L2, for the extraneous disturbance location that puts on oil/gas pipe line, facilitates detection failure.

Step (1), by 3 * 3 Fiber Optic Coupler, build Michelson fibre optic interferometer, the method that obtains oil/gas pipe line Shang San road interference signal is, each road interference signal comprises two-beam road, two-beam road forms interferes, and the path of a branch of light path is that laser to 3 * 3 Fiber Optic Coupler is to optical fiber reference arm to the first sensor fibre terminal FRM to optical fiber reference arm to 3 * 3 Fiber Optic Coupler to photodetector;

Path of another bundle light velocity is, laser to 3 * 3 Fiber Optic Coupler is to the second sensor fibre terminal FRM to 3 * 3 Fiber Optic Coupler to photodetector,

As shown in Figure 1, A road interference signal comprises that a branch of light path is laser-3 * 3coupler (3 * 3 Fiber Optic Coupler)-optical fiber reference arm-one FRM (faraday rotator mirror)-optical fiber reference arm-3 * 3coupler-photodetector 1; Another beam optical path is laser-3 * 3coupler-sensor fibre-two FRM-sensor fibre-3 * 3coupler-photodetector 1;

B road interference signal comprises that a branch of light path is laser-3 * 3coupler-optical fiber reference arm-one FRM-optical fiber reference arm-3 * 3coupler-photodetector 2; Laser-3 * 3coupler-sensor fibre-two FRM-sensor fibre-3 * 3coupler-photodetector 2;

C road interference signal comprises that a branch of light path is laser-3 * 3coupler-optical fiber reference arm-one FRM-optical fiber reference arm-3 * 3coupler-photodetector 3; Laser-3 * 3coupler-sensor fibre-two FRM-sensor fibre-3 * 3coupler-photodetector 3.

, between adjacent two-way interference signal, there is the fixed skew of 2 π/3 in above-mentioned A, B, C tri-road interference signals.

More than show and described basic principle of the present invention, major character and advantage.The technician of the industry should understand; the present invention is not restricted to the described embodiments; that in above-described embodiment and specification, describes just illustrates principle of the present invention; without departing from the spirit and scope of the present invention; the present invention also has various changes and modifications, and these changes and improvements all fall in the claimed scope of the invention.The claimed scope of the present invention is defined by appending claims and equivalent thereof.

Claims (5)

1. the oil/gas pipe line safety monitoring system based on distributing optical fiber sensing, is characterized in that: comprise

Laser, the first photodetector, the second photodetector, the 3rd photodetector, 3 * 3 Fiber Optic Coupler, the first sensor fibre terminal FRM and the second sensor fibre terminal FRM, described laser, the second photodetector is connected with the first via input end of 3 * 3 Fiber Optic Coupler by optical fiber circulator, described the first photodetector, the 3rd photodetector respectively with second of 3 * 3 Fiber Optic Coupler, three road input ends are connected, the first via output terminal of described 3 * 3 Fiber Optic Coupler is connected with the first sensor fibre terminal FRM by sensor fibre, the second road output terminal of described 3 * 3 Fiber Optic Coupler is connected with the second sensor fibre terminal FRM by optical fiber reference arm.

2. the oil/gas pipe line safety monitoring system based on distributing optical fiber sensing according to claim 1, is characterized in that: described sensor fibre distributes along the transmission direction of oil/gas pipe line.

3. the oil/gas pipe line safety monitoring system based on distributing optical fiber sensing according to claim 1, is characterized in that: described the first sensor fibre terminal FRM and the second sensor fibre terminal FRM are faraday rotator mirror.

4. the monitoring method based on the oil/gas pipe line safety monitoring system based on distributing optical fiber sensing claimed in claim 1, is characterized in that: comprises the following steps,

Step (1), builds Michelson fibre optic interferometer by 3 * 3 Fiber Optic Coupler, obtains oil/gas pipe line Shang San road interference signal, has the fixed skew of 2 π/3 between adjacent two-way interference signal;

Step (2), utilizes three road interference signals, demodulates the interference light phase delta phi (t) that disturbance causes, process is,

(1) establishing disturbance φ (t) is single frequency sinusoidal function, as shown in formula (1),

φ(t)＝φ ₀sinω(t) (1)

Wherein, φ ₀refer to that the photophase that disturbance causes changes amplitude; ω refers to forcing frequency;

(2) according to formula (2), the interference light phase delta phi (t) that calculation perturbation causes,

Wherein, τ ₀first via light process L for fibre optic interferometer ₀the time of distance, τ ₁the second road light process L for fibre optic interferometer ₁the time of distance, τ ₂third Road light process L for fibre optic interferometer ₂the time of distance, during for undisturbed situation, the phase difference of optical fiber reference arm and sensor fibre; L ₀total length for the sensor fibre that is arranged in parallel with oil/gas pipe line; L1 is that disturbance point is to the distance at sensor fibre top; L2 is that disturbance point is to the distance of sensor fibre terminal FRM;

Step (3), carries out and differs from eliminate indigestion computing formula (2), obtains formula (3),

Step (4), to formula (3) elimination phase place flip-flop, and to formula (3) differential differentiate, obtains formula (4),

Δφ′(t)＝2φ ₀ωcosω(t+τ ₀)cosω(τ ₂) (4)；

Step (5), carries out Spectrum Conversion to formula (4), obtains formula (5),

Δφ′(ω)＝2φ ₀ωcosω(τ ₂) (5)；

Step (6), as cos ω (τ ₂)=0, according to formula (5), obtains formula (6),

2πfn(L ₂)/C＝kπ+π/2 (6)

, $L_2=(k+1/2)\·\frac{C}{2\mathrm{nf}}$

Wherein, n is that optical fibre refractivity, C are that the light velocity, K are natural number, and periodic depression points will appear in spectrogram, by determining the frequency values f of depression points, calculates L ₂, L ₂disturbance location for oil/gas pipe line.

5. the oil/gas pipe line safety monitoring method based on distributing optical fiber sensing according to claim 4, it is characterized in that: step (1), by 3 * 3 Fiber Optic Coupler, build Michelson fibre optic interferometer, the method that obtains oil/gas pipe line Shang San road interference signal is, each road interference signal comprises two-beam road, two-beam road forms interferes, and the path of a branch of light path is that laser to 3 * 3 Fiber Optic Coupler is to optical fiber reference arm to the first sensor fibre terminal FRM to optical fiber reference arm to 3 * 3 Fiber Optic Coupler to photodetector;

The path of another bundle light velocity is that laser to 3 * 3 Fiber Optic Coupler is to the second sensor fibre terminal FRM to 3 * 3 Fiber Optic Coupler to photodetector.