WO2008003224A1

WO2008003224A1 - An optical fiber control system for safety early-warning

Info

Publication number: WO2008003224A1
Application number: PCT/CN2007/001866
Authority: WO
Inventors: Jinquan Zhang; Xiaojun Wang; Shuhao Jiao; Fei Wang; Dexue Fang; Ying Wang; Jingfeng Zhou
Original assignee: China National Petroleum Corporation; China Petroleum Pipeline Bureau
Priority date: 2006-06-30
Filing date: 2007-06-13
Publication date: 2008-01-10
Also published as: CA2664010C; CA2664010A1; WO2008003224A9

Abstract

An optical fiber control system for safety early-warning includes a phase fading control and a polarization fading control or a phase fading control or a polarization fading control. A polarization modulator [202] is connected between a laser [101] and a first multiplex demultiplexer [203] in series. The first multiplex demultiplexer [203] is connected to a second multiplex demultiplexer [204] by means of three strands of optical fibers [1, 2, 3] respectively, wherein the three strands of optical fibers [1, 2, 3] are laid with the conduit in a same trench. An optical fiber interferometer is consisted of the two multiplex demultiplexer [203, 204] and two strands of optical fibers [1, 2]. The first multiplex demultiplexer [203] is connected to two photoelectric detectors [309, 310], and the outputs of the two photoelectric detectors [309, 310] are connected to two A/D [312,313] respectively. The outputs of the two A/D [312,313] are connected to a photoelectric signal processing circuit [311] respectively, and one output of the photoelectric signal processing circuit [311] is connected to a polarization controller [201], and the output of polarization controller [201] is connected to a polarization modulator [202] and connected to a phase modulator [206] which is connected to the first strand optical fiber [1], and the other output of the photoelectric signal processing circuit [311] is connected to a phase controller [205], and the output of the phase controller [205] is connected to the phase modulator [206] which is connected to the second strand optical fiber [2].

Description

Optical fiber security early warning control system

Technical field

The present invention relates to a fiber optic safety early warning phase fading control and polarization fading control or phase fading control or polarization fading control system for buried pipelines or structures or for early warning of safety protection of important facilities and areas.

Background technique

For petroleum, natural gas, refined oil, coal slurry, water and other materials, pipeline transportation is a safe, economical and efficient means of transportation, especially in the transportation of energy materials with high flammability, explosiveness and high transaction value. Important location, it can be said that the pipeline is the main artery of energy transportation. Pipeline transportation of petroleum, refined oil and natural gas has both high transaction value and inflammable and explosive characteristics. Once the pipeline leaks, the leakage area is prone to combustion and explosion, which not only affects the safe production of the pipeline industry, but also causes huge economic losses. Moreover, it also seriously threatens the property and life safety of the people along the line, and the damage caused to the surrounding ecological environment is also incalculable.

With the development of the pipeline transportation industry, various pipeline transportation safety monitoring technologies are also constantly developing. At present, there are two main types of pipeline safety production monitoring technologies. One: The monitoring technology after the pipeline leakage event, this technology mainly includes "in-tube hydrodynamic state detection technology and distributed optical fiber temperature and stress monitoring technology". The in-tube hydrodynamic state detection technology is to collect the flow, temperature and pressure signals of the fluid in the pipeline in real time, and to detect and locate the pipeline leakage. This technology is limited by the fluid characteristics in the pipeline, the transportation process and the performance of the test instrument. Pipeline leak monitoring has low sensitivity and positioning accuracy. These technologies include: pressure gradient method, negative pressure wave method, and flow balance method. Distributed fiber temperature and stress monitoring technology utilizes the nonlinear characteristics of the fiber (Raman effect and Brillouin effect) to collect the temperature and impact stress of the fiber leaking from the pipeline in real time to determine the location of the leak point. The structure and the distance between the cable and the leak point limit the monitoring effect. Second, the preventive monitoring technology before the pipeline damage event, that is, the pipeline damage warning technology, the current technology is mainly "sonic technology monitoring", which uses the principle of sound wave transmission along the pipeline, every 1 km Install an active sensor on the left and right, pick up the sound signal along the pipeline and analyze it to determine the nature of the event, and then discover the event that destroyed the pipeline in advance, but It is necessary to equip each sensor device with a set of power supply devices and communication devices, which not only increases the investment and maintenance costs of the devices, but also the devices themselves are easily damaged, so that the devices cannot operate normally.

In response to the existing problems of pipeline safety monitoring technology, Australia has patented a technical solution based on the principle of Mach-Zehnder fiber optic interferometer, using fiber optic sensing vibration. The invention is a breakthrough for the long-distance line target or the large-area surface target security warning, but the invention is that the optical path system of the invention is unstable, and signal blanking due to phase fading and polarization fading is difficult to work effectively. .

Summary of the invention

It is an object of the present invention to provide a dual Mach-Zehnder fiber interferometer using phase fading control and polarization fading control techniques or polarization fading control techniques or phase fading control techniques to eliminate phase fading and polarization. Signal blanking caused by fading or phase fading or polarization fading, forming a two-way synchronous interfering laser modulated signal with stable phase and stable polarization state, which is relatively transmitted on the interferometer, and optical fiber security warning of the optical path structure picked up at the double end of the interferometer system.

The phase fading and polarization fading control system of the present invention comprises Mach-Zehnder consisting of three optical fibers 1, 2, 3, multiplexer 203, and splitter 204, which are laid in the same trench as the pipeline or applied to the ground around the structure.

(Mach-Zehnder) fiber interferometer and laser 101, which is characterized in that, as shown in FIG. 1, the polarization modulator 202 is connected in series between the laser 101 and the multiplexer 203 connected by the optical fiber, and the multiplexer 203 is connected to three optical fibers respectively. 1, 2, 3 to the combined demultiplexer 204, the combined demultiplexer 203, the combined demultiplexer 204 and the optical fiber 1, the optical fiber 2 constitutes a Mach-Zehnder fiber interferometer, and the combined demultiplexer 203 The two optical fibers are connected to the photodetector 309, the photodetector 310, the photodetector 309, and the photodetector 310. The output of the photoelectric signal is connected to each of the A/D 312, A/D 313, A/D 312, and A/D 313 outputs. The signal processing circuit 311, an output of the photoelectric signal processing circuit 311 is connected to the polarization controller 201, and is connected to the polarization modulator 202 and the phase modulator 206 connected in the optical fiber 1 or 2 by the output of the polarization controller 201, and photoelectric signal processing The other output of the circuit 311 is connected to the phase controller 205, and is connected to the phase modulator 206 connected in series in the optical fiber 2 or 1 by the output of the phase controller 205; the phase controller 205 and the photoelectric signal processing circuit 311, phase modulation 206 fading closed control loop and the phase composition, so that the Mach - Zehnder

(Mach-Zehnder) Phase difference of two interfering light waves propagating on a fiber optic interferometer to form interference Stabilizing the phase values required by the system; polarization controller 201, polarization modulator 202 and phase modulator 206 and optoelectronic signal processing circuit 311 form a polarization fading closed-loop control loop, enabling interference in Mach-Zehnder fiber The polarization state difference of the two interfering light waves propagating on the instrument and forming the interference is stabilized at the angle value required by the system.

The electrical principle of the combined control of phase fading and polarization fading according to the present invention is shown in FIG. 2. The polarization modulator 202 is connected in series between the laser 101 and the multiplexer 203 connected by the optical fiber, and the multiplexer 203 is connected to the optical fiber by two fibers. There are two input and output photoelectric signal processing circuits 309-1 two optical input ports, and the two electrical output ports of the photoelectric signal processing circuit 309-1 are connected to the polarization control host 201-1 and the phase control host 205-1 I/O. Port, the polarization control host 201-1 output port is connected to the input port of the polarization controller 201-2, the output port of the polarization controller 201-2 is connected to the input port of the polarization modulator 202, and the other is connected to the input port of the phase modulator 206. The output port of the phase control host 205-1 is connected to the input port of the phase controller 205-2, and the output port of the phase controller 205-2 is connected to the input port of the other phase modulator 206. In the electrical schematic diagram, the functions of the two photodetectors 309, the photodetectors 310, the A/D 312, the A/D 313, and the photoelectric signal processing circuit 311 are completed by a photoelectric signal processing circuit 309-1, and the polarization control host 201 is controlled by the polarization control unit 201. The function of the polarization controller 201 is completed by -1 and the polarization controller 201-2, and the functions of the phase controller 205 are completed by the phase control host 205-1 and the phase controller 205-2.

The polarization fading control of the present invention can also be realized by the following scheme: as shown in FIG. 3, the laser 101 is connected to the snubber 410 through the optical fiber, and then connected to the multiplexer 204 and the three optical fibers 1, 2, 3 by the optical fiber to form Mach-Zengde ( Mach-Zehnder) The multiplexer 203 of the fiber interferometer, and the multiplexer 203 is connected to the analyzer 412 and the analyzer 413 by the optical fiber, respectively, and the analyzer 412 and the analyzer 413 are respectively connected to the polarization detector

Both the 407 and the polarization detector 408 are connected to the signal processing circuit 411 by an electrical signal line, and the signal processing circuit

[411] The output is connected to the polarization controller [201], and the polarization controller [201] is connected to the polarization modulator [202] by an electrical signal line and the phase modulation in the fiber [1] or [2] by the optical fiber connection. [206].

The electrical principle of this scheme is shown in FIG. 4, the laser 101 is connected to the input of the scrambler 410 through the optical fiber, and the output of the scrambler 410 is connected to the multiplexer 203 of the optical fiber interferometer by the optical fiber, and the combiner and the splitter 203, the input of the analyzer 412, the analyzer 413, the output of the analyzer 412, and the analyzer 413 are respectively connected by the optical fibers. The inputs of polarization detector 407 and polarization detector 408 are respectively coupled, and the outputs of polarization detector 407 and polarization detector 408 are coupled to the input of signal processing unit 411.

The phase fading control of the present invention can also be realized by the following scheme as shown in FIG. 5. The laser 101 is connected to the multiplexer/demultiplexer 203 by an optical fiber, and the multiplexer 203 is connected to the photodetector 309 and the photodetector 310 by two optical fibers respectively. The two photodetectors 309 and the photodetector 310 are respectively connected to the A/D capture card 312 and the A/D capture card 313 by wires, and then connected to the mixer 517 input by the signal generator 514, and the mixer 517. The output is sub-series filter 518, signal processor 519, filter 520, and signal demodulator 521 to demodulate the phase signal generated by the vibration of the soil; at the same time, the laser 101 is connected to the signal generator 513 by the optical fiber, and then the signal is generated. The 513 outputs a phase modulator 206 connected in series in the optical fiber 1 or 2; after the interference signal is converted by the photodetectors 309 and 310, it is quantized by the A/D capture cards 312 and 313, and the signal generator 514 generates an amplitude A. a modulation signal of frequency F, modulating the laser 101 or modulating the phase modulator 206 on an interference arm of the interferometer to produce a periodically varying phase difference in the interferometer, The photodetectors 309 and 310 detect the two output lights of the interferometer and convert them into electrical signals, which are sent to the A/D circuits 312 and 313 for conversion, and then sent to the mixer 517 and the signal generator 514 to generate a signal of frequency F. And the frequency multiplication signal is mixed, after filtering by the filter 518, the signal processor 519 undergoes calculus, addition and subtraction, and then passes through the filter 520, and finally the signal demodulator 521 demodulates the phase generated by the soil vibration. signal. '

The electrical schematic diagram of the present scheme is shown in FIG. 6. The multiplexer 203 is connected to the optical signal processing circuit 309-1 having two functions of a photodetector 309, a photodetector 310, a signal conditioning circuit 312 and a signal conditioning circuit 313. The two optical input ports, the two optical input ports of the photoelectric signal processing circuit 309-1, and the two electrical output ports are respectively connected to an A/D capture card 312 and an A/D capture card 313, and the A/D capture card 312 The output of the A/D capture card 313 is coupled to a signal demodulation host 521-1 having the functions of a mixer 517, a signal generator 514, a filter 518, a signal processor 519, an over filter 520, and a signal demodulator 521. The signal generator 513 outputs an output phase controller 205-2, and the phase controller 205-2 outputs a phase modulator 206 connected in series with the optical fiber 1 or 2. Here, the functions of the two photodetectors 309, the photodetector 310, the signal conditioning circuit 312 and the signal conditioning circuit 313 are realized by the photoelectric signal conditioning circuit 301-1, and the mixer 517 is implemented by the signal demodulation host 521-1. Signal generator 513, filter 518, signal processor 519, The function of filter 520 and signal demodulator 521 is passed.

The laser 101 is a continuous monochromatic laser.

The photodetector 309, the photodetector 310, the photoelectric signal processing circuit 309.1, the photoelectric signal processing circuit 311, the polarization controller 201, the polarization control host 201-1, the polarization controller 201-2, the polarization modulator 202, The phase controller 205, the phase control host 205-1, the phase controller 205-2, and the phase modulator 206 are all commercially available products.

In Fig. 1, 1, 2 and 3 are three optical fibers, wherein the optical fibers 1 and 2 are interference fibers, the optical fibers 3 are transmission fibers, and the splitter 203, 204 and the optical fibers 1, 2 are composed of Mach-Zehnder. ) Fiber optic interferometer. The monochromatic laser emitted by the continuous monochromatic laser 101 and the monochromatic laser transmitted from the optical fiber to the multiplexer 203 are divided into two paths: one of the lasers is terminated by a Mach-Zehnder fiber optic combiner and splitter 203. At the entrance, the multiplexer 204 combines the waves to form an interference light wave, and the interference light wave is transmitted back to the multiplexer/demultiplexer 203 through the optical fiber 3, and the other laser light is transmitted through the optical fiber 3 to the multiplexer/demultiplexer 204, by Mach-Zehnder ( The Mach-Zehnder) is incident on the end of the interferometer and the demultiplexer 204, and combines at the end of the multiplexer/demultiplexer 203 to form an interference light wave.

After the interference signal is converted by the photodetector 309 and the photodetector 310, the photoelectric signal processing circuit 311 performs processing and analysis, and through signal processing and calculation, and averages the phase generated by the external interference amount over a period of time, The phase modulator 206 is controlled based on the calculated phase average to generate a compensation phase that counteracts the effects of external disturbances such that the interferometer operates at a determined operating point.

The photoelectric signal processing circuit 311 analyzes and calculates the amount of change of the polarization state of the interferometer while ensuring that the phase of the interferometer is controlled at a certain working point, and controls the polarization controller 201 to emit a modulation signal of frequency F, which is polarized. The modulator 202 modulates the interferometer such that the interferometer produces a modulated interference wave of frequency F. The photodetectors 309 and 310 detect the polarization state of the two output beams of the interferometer, and send it to the signal processing circuit 311 to calculate the polarization of the interferometer. In the case of the state, the polarization controller 201 changes the polarization state of the input light of the interferometer, so that the polarization controller 201, the polarization modulator 202 and the photoelectric signal processing circuit 311 form a closed-loop control circuit of the polarization state, so that in Mach-Zehnder The polarization state difference of the two interfering light waves propagating on the fiber interferometer is stabilized at the angle value required by the system; in addition, when the polarization state of the interferometer is controlled, two interferometers are caused. The phase difference between the two interfering signals detected by the terminal is irregularly changed, which will affect the positioning accuracy of the optical fiber security early warning system. For this reason, the present invention proposes to add a phase modulator 206 to any interference arm of the interferometer. The signal processing circuit 311 calculates and analyzes the change of the phase difference of the two signals, and modulates and corrects the phase difference between the two output signals of the interferometer, so as to ensure that the phase difference reaches the angle required by the system while adjusting the polarization state.

The invention adopts a Mach-Zehnder fiber interferometer. The length of the interferometer can be up to 80 kilometers. The soil vibration signal along the pipeline causes the phase of the interfering light wave on the interferometer to form a belt. There is vibration information interference signal. The theoretical basis of the interferometric Mach-Zehnder fiber interferometer is the interference of two beams. When the two monochromatic waves vibrate in the same direction, they are completely coherent, and the vibration directions are perpendicular to each other. Without interference at all, it is not difficult to speculate that in other cases, the two beams should be partially coherent. Interference of the interferometer requires that the polarization states of the two beams be in the same direction. Theoretically speaking, when the optical fiber is an ideal cylinder, the two modes in which the polarization states are orthogonal to each other are transmitted independently and do not interfere with each other, but in reality, the manufactured single-mode optical fiber is not a symmetric cylinder, and the optical fiber security early warning system is adopted. The interferometer is the longest interferometer currently in use. It is about 80 kilometers long. The environmental changes along the pipeline of about 80 kilometers are very complicated, which makes the phase and polarization changes of the beam on the interferometer extremely complicated during the transmission process. The bending, deformation, manufacturing defects, etc. of the pressure, temperature, etc. cause the optical propagation constants of the two orthogonal directions to differ, and the so-called birefringence phenomenon occurs, that is, the random coupling between the two polarization states. The polarization state of the light outputted from the fiber is randomized, and the interference effect of the two beams is not guaranteed. The final output signal is in a random blanking state. This phenomenon becomes a polarization fading phenomenon; while making the polarization state change randomly. It also causes the phase of the interference light output from the fiber to randomly change, eventually leading to the system's letter. Than random fluctuation, or even completely blanking signal, the phase of the fading phenomenon becomes a phenomenon.

However, the laser active and passive laser devices used in the fiber security early warning system have polarization and phase correlation characteristics at the same time. The polarization control of the interferometer will cause phase changes, and the phase control will also cause polarization changes. Therefore, how to ensure that the two polarized lights of the interferometer are stably interfered, and that the phase fading is controlled under the conditions required by the system, the joint coordinated control of the two is one of the most critical technologies for the optical fiber security early warning system. The implementation principle of the present invention is:

According to the invention, the two polarized lights propagating on the fiber optic interferometer optical fiber interferometer have arbitrary polarization states and random phase changes, and the optical fiber interferometer output light intensity signal can be written by photoelectric conversion:

V = V _X +V ₂ + 2^VJ ₂ cos(^ +φ„+φ ₀ ) + V _n (1)

(1) can be written as

V = V ₀ +V _g cos(^ +φ _η +φ ₀ ) + ν _η (2)

Among them, is the output voltage signal, is the visibility of the interferometer, is the circuit additional noise, is the phase difference signal caused by the soil vibration sound wave, that is, the soil vibration sound wave signal to be detected, ^. The initial phase of the interferometer is a constant, which is a low-frequency drift indicating the phase difference between various disturbances and noise, where , and is an uncertainty, which varies with temperature and external environment.

Due to the microbend, distortion, and ambient temperature changes of the fiber, the output polarization state of the fiber changes randomly, which is reflected in the random variation between 0 and 1 when the visibility is 0, and the signal is completely blanked when _g is 0. This phenomenon is called fiber. The polarization of the interferometer induces signal fading.

In addition, in order to analyze the convenience of the problem, (2) can be written as:

Where = _{1 + 2 +} „, V _g = 2^V ₂ ~, incorporation. The general external interference signal is a low frequency large signal, ^ is a high frequency small signal, when the signal has a small variation ^^ - AV « V _g sin ,, · (4)

Since the low-frequency interference varies randomly and the amplitude is large, it is not difficult to conclude that the signal-to-noise ratio of the system output is changing by (4), and when ^{sin = ()} , the signal is completely blanked. The random fluctuation of the signal appearing in the interferometer output signal as the external environment changes is called the phase fading phenomenon of the interferometer.

When the polarization state of the interferometer is controlled separately, the phase of the interferometer changes. When the phase control of the interferometer is performed separately, the polarization state of the interferometer changes. In addition, when the phase or polarization state of the interferometer is controlled, the phase difference between the two interfering signals detected at both ends of the interferometer will change irregularly, which will affect the positioning accuracy of the optical fiber security early warning system.

In response to these phenomena, the present invention proposes an active phase in an interferometer for a fiber optic security early warning system. At the same time of bit compensation, the phase difference between the polarization state of the interferometer and the two interfering signals detected at both ends of the interferometer is monitored in real time, and the phase and polarization states of the interferometer are compensated and adjusted according to the amount of change. The phase difference of the road signal reaches the optimum value required by the system.

The signal output by the fiber optic security warning system is quantified by the A/D capture card after photoelectric conversion, and can be written as: = ^ + J^ cosC^ + ^) (3)

The general signal is high frequency, the interference of the outer boundary is ^ low frequency, and the average of (3) is averaged over a certain period of time, and the average value of the external interference amount ^ of the time period can be obtained. A phase modulator is added to one arm of the interferometer, and then a feedback control voltage VF is applied to the phase modulator to generate a control phase difference, which cancels the influence of external interference, so that the interferometer operates at a certain working point, as follows:

φ _α + φ _η = ηπ + π/2 (" = 0,1,2· · · ·) ( ₅ ) When changing, ^ also changes. We adjust it, through this continuous loop, hydrophone The working point can be stabilized nearby, and we can obtain a reliable and stable signal output. This makes the system operating point stable at the most sensitive point, overcoming the phase fading of the fiber security warning system.

DRAWINGS

Figure 1 is a block diagram of the fiber security early warning polarization and phase joint control system.

Figure 2 Electrical schematic diagram of the fiber security early warning polarization and phase joint control system.

Among them: 101—laser, 201—polarization controller, 202—polarization modulator,

203-demultiplexer, 204-demultiplexer, 205-phase controller, 206-phase modulator, 309-photodetector, 310-photodetector, 311-photoelectric signal processing circuit,

312—A/D, 313—A/D

Figure 3 Block diagram of the fiber security early warning polarization control.

Figure 4 is a schematic diagram of the fiber security early warning polarization control.

Wherein: 407—polarization detector, 408—polarization detector, 409—signal processing circuit, 410—scrambler, 412—analyzer, 413—analyzer

Figure 5 is a block diagram of the principle of fiber security early warning phase control. Figure 6 is a schematic diagram of the fiber safety warning phase control circuit.

Where: 513 - signal generator, 514 - signal generation, 517 - mixer, 518 - filter, 519 - signal processor, 520 - filter, 521 - signal demodulator

detailed description

Example 1.

The embodiments of the present invention are described by way of examples and the invention is further described. This example is an experimental prototype, and its composition is shown in Figure 1 and Figure 2. In the figure, the thick connecting line is the optical fiber, and the thin connecting line is the electric wire. The specific configuration is as follows: The polarization modulator 202 is connected in series between the laser 101 and the multiplexer/demultiplexer 203 connected by the optical fiber, and the multiplexer 203 is connected by two optical fibers to an optical signal processing circuit having two input and output 'circuit 309-1 The two optical input ports, the two electrical output ports of the photoelectric signal processing circuit 309.1 are connected to the I/O port of the polarization control host 201-1 and the phase control host 205-1, and the polarization control host 201-1 output port is connected to the polarization control. The input port of the device 201-2, the output port of the polarization controller 201-2 is connected to the input port of the polarization modulator 202, and the other channel is connected to the input port of the phase modulator 206 connected in series in the fiber 1 or 2, the phase control host The output of port 205-1 is connected to the input of phase controller 205-2, and the output of phase controller 205-2 is connected to the input of another phase modulator 206 connected in series in fiber 2 or 1. In the electrical schematic diagram, the functions of two photodetectors 309, photodetectors 310, A/D 312, A/D 313, and photoelectric signal processing circuits 311 are completed by a photoelectric signal processing circuit 309.1 having two input and output signals. The function of the polarization controller 201 is completed by the polarization control host 201-1 and the polarization controller 201-2, and the functions of the phase controller 205 are completed by the phase control host 205-1 and the phase controller 205-2.

Among them, single-frequency laser model: KOHERAS ADJUSTIK HP E15; combined splitter 203 and splitter 204 model: Langguang's WDM-A-2 X 2- 1550-1- FC/UPC-3*54; polarization control host Model 201-1: NI PXI-1042 8-Slot 3U CPU: PXI-8186 P4 2. 2 I/O: NI PXI-5112, 2 channel, 100 MHz, 32 MB/Channel, 8-bit; PXI-6111 A /D 2channel 12bit , D/A 2channel 12bit ; Phase Control Host 205-1 Model: NI PXI-1050, PXI/SCXI CPU: PXI-8187 P4M 2. 5G PXI-6120 A/D 4 channel 16bit, D/A2 channel 16-bi ; Polarization Controller 201-2 and Polarization Modulator 202 Model: 0Z OPTICS EPC- 400 EPC DRIVER-04-RS232 ; Phase Controller 205-2 and Phase Modulator 206: 0Z OPTICS FICE PZ-STD-FC/PC; Photoelectric signal processing circuit 309-1: Universal two-way symmetrical photoelectric conversion amplifier circuit, optical input range: -20~- 45dBm, output range: - 3V~+3V.

Here, the photoelectric signal processing circuit 309-1 is a photoelectric conversion output circuit, and the A/D 312, the photoelectric signal processing circuit 311, and the polarization controller 201 are realized by the polarization control host 201-1 of FIG. 2, and the polarization control host 201-1 is integrated. The A/D 312 conversion circuit; the A/D 313, the photoelectric signal processing circuit 311, and the phase controller 205 are implemented by the phase control host 205-1.

The monochromatic laser emitted by the continuous monochromatic laser 101 is transmitted through an optical fiber to a Mach-Zehnder fiber interferometer, which is used as a continuous distributed vibration sensor to pick up the vibration signal of the soil along the pipeline, and is transmitted through the optical fiber. Photoelectric signal processing circuit 309-1. The phase control host 205-1, the phase controller 205-2 and the photoelectric signal processing circuit 309-1 and the phase modulator 206 form a phase fading closed loop control loop for propagation on a Mach-Zehnder fiber interferometer. The phase difference of the two interfering light waves forming the interference is stabilized at the phase value required by the system. The polarization control host 201-1, the polarization controller 201-2 and the photoelectric signal processing circuit 309-1 and the phase modulator 206 form a polarization fading closed-loop control loop, so that the Mach-Zehnder fiber interferometer propagates on the Mach-Zehnder fiber interferometer. The polarization state difference of the two interfering light waves forming the interference is stabilized at the angle value required by the system.

Example 2.

This example is a prototype experiment of polarization fading control, and its composition is shown in Figure 3. The circuit is shown in Figure 4. After the laser 101 is connected to the scrambler 410 through the optical fiber, the optical fiber is connected to the multiplexer 204 and the three optical fibers 1, 2, 3 to form a Mach-Zehnder fiber interferometer multiplexer 203. The multiplexer/demultiplexer 203 is respectively connected to the input of the analyzer 412 and the analyzer 413 by the optical fiber, and the output of the analyzer 412 and the analyzer 413 is connected to the input of the polarization detector 407 and the polarization detector 408, and the polarization detector The output of 407 and polarization detector 408 are both connected to signal processing unit 411 by an electrical signal line, the output processing circuit [411] is connected to a polarization controller [201], and the polarization controller [201] is connected to the polarization modulation by an electrical signal line. [202] and a phase modulator [206] connected in series with fiber [1] or [2].

Among them, single-frequency laser 101 is selected as: OHERAS ADJUSTIK HP E15; Scrambler 410: Scrambler model: IQS-5100B from EXF0; analyzer 412, 413: Phoenix Photonics Division POL-20 - 15- PP-1-0; Polarization Detector 407 and Polarization Detector 408: Polarization Component Detector PDD-001-13-SM-NC; Signal Processing Unit 409: Processed by the polarization control host.

Example 3

This example is a phase fading control industrial experimental prototype, and its composition is shown in Fig. 5 and Fig. 6. In the figure, the thick connection is the fiber, and the thin connection is the wire. The specific configuration is as follows: The laser 101 is connected to the multiplexer/demultiplexer 203 by an optical fiber, and the multiplexer 203 is connected to the two optical input ports of the photoelectric signal processing circuit 309-1 by two optical fibers, and two optical signal processing circuits 3Q9-1 The electrical output ports are respectively connected to the input ports of the A/D capture card 312 and the A/D capture card 313 by wires, and the output ports of the A/D capture card 312 and the A/D capture card 313 are connected to the signal demodulation host 521-1. The signal demodulation host 521-1 has the functions of a mixer 517, a filter 518, a signal processor 519, a filter 520, and a signal demodulator 521 input by the signal generator 514; at the same time, the laser 101 is connected to the signal generator by an optical fiber. 513, the signal generator 513 is further connected to the input of the phase controller 205-2, and the output of the phase controller 205-2 is connected to the phase modulator 205 of the series fiber 1 or 2.

Among them, photoelectric signal conditioning circuit 309-1: two-fiber input port of general-purpose circuit; input range: -20~ -45dBm, output range: _3V~+3V; A/D capture card 312 and A/D capture card 313 Model: PXI- 5112, 2 channel, 100 MHz, 32 MB/Channel, 8-bit; Signal Demodulation Host 521-1 Model: NI PXI-Wrist 8-Slot 3U CPU: PXI-8186 P4 2. 2 I/O: NI ; Signal Generator 513 Model: Agilent33250A; Phase Controller 205-2: 0Z OPTICS F ICE PZ-STD-FC/PC ; Phase Modulator: 0Z' OPTICS FICE PZ-STD-FC/PC ₀

After the interference signal is converted by the photoelectric signal processing circuit 309.1, it is quantized by the A/D acquisition cards 312 and 313, and the signal generator 513 generates a modulation signal having an amplitude of A frequency F, modulating the laser 101 or modulating the interference of the interferometer. The phase modulation ^ 206 on the arm generates a periodically varying phase difference in the interferometer, and the photoelectric signal processing circuit 309-1 detects the two output lights of the interferometer and converts them into electrical signals, and sends them to the A/D circuits 312 and 313. After the conversion, the signal of the frequency F generated by the signal demodulation host 521-1 and the frequency-multiplied signal are mixed, and after filtering, calculus, addition and subtraction, filtering, and finally demodulating the soil vibration to generate Phase signal.

Industrial applicability The invention utilizes the common communication fiber in the cable laying in the same trench with the pipeline, the structure or the important facility and the underground area as the interference arm and the transmission fiber of the interferometer, thereby forming a continuous distributed soil vibration detecting sensor, and stably and reliably picking up The vibration signal of the soil along the monitored target is connected to the positioning system. According to the analysis of the transmission time difference of the two laser signals, the location of the soil vibration event along the vicinity of the monitored target is calculated, and then the signal identification system can be determined. The nature and type of soil vibration events can be detected on ground ground excavation, striking pipelines, welding on pipelines, drilling, high positioning accuracy, accurate event nature judgment, no missed inspection, and pipeline safety monitoring and early warning. Role, to avoid the occurrence of pipeline safety accidents. It can effectively detect any soil vibration signal within 3 meters near the cable, and has high sensitivity; the positioning accuracy can reach ± 10 meters, which fully meets the pipeline maintenance and repair requirements. The monitoring distance of a single system can reach about 120 kilometers. With the communication system, multiple devices can be connected together to form a complete seamless monitoring network. Therefore, the monitoring distance of the present invention can be determined according to needs.

This system is applicable not only to pipeline safety precautions and early warning systems, but also to other important facilities and safety precautions and warnings in important areas, such as: communication optical cables, transportation facilities, cultural relics protection areas, armory, key institutions and important industrial plants. Safety and protection early warning systems for facilities and areas.

In the industrial test, a two-month on-site experiment was carried out in the East Bridge of Suzhou City in the West-East Gas Pipeline in the Jiangsu-Zhejiang-Shanghai area. The length of the pipeline being monitored was 33. 6 kilometers, the diameter of the pipeline was 01016, and it was located along the Jiangnan Water Network. 5米左右。 The soil is a black soft silt, the cable is a silicon tube cable in the same trench, buried in the upper right direction of the pipe airflow, the silicon tube buried depth of about 1. 5 meters. The test section passes through the Suzhou Industrial Park. There are many construction sites in the park, such as factories, bridges, highways and buildings. The pipelines cross the roads and rivers many times. There are many disturbance vibration sources along the line, and the test site environment is complex. During the field test, the fiber-optic pipeline safety early warning system accurately warned 5 damage events, including 4 optical cable construction personnel performing optical cable line rectification; 1 construction machinery destruction event: The optical fiber pipeline early warning system was monitored to Dongqiao Station. 5km had serious damage events, and the test and maintenance personnel arrived at the scene. The excavator at the construction site about 25km away from the East Bridge substation was found to be constructing above the pipeline. The communication silicon tube was cut off and the behavior of destroying the safety of the fiber optic pipeline was stopped in time.

Claims

Claim

1. A fiber optic security early warning control system comprising phase fading control and polarization fading control or phase fading control or polarization fading control, three fibers of the pipeline laid in the same trench or applied to the ground around the structure [1], [2], [ 3], Mach-Zehnder fiber interferometer composed of fiber [1], [2] and multiplexer [203], multiplexer [204], laser [101], characterized in that : A polarization modulator [202] is connected in series between the laser [101] and the multiplexer [203] by a fiber, and the multiplexer [203] is connected to three fibers [1], [2], [3], respectively. The splitter [204], the combiner/demultiplexer [203], the combiner/demultiplexer [204] and the optical fiber [1], the optical fiber [2] form a Mach-Zehnder fiber optic chi-meter, multiplexed wave The device [203] is connected to the photodetector [309] and the photodetector [310], the photodetector [309] and the photodetector [310] are connected by an electrical signal line to each of the A/D [312], A. /D [313], A/D [312], A/D [313] output each photoelectric signal processing circuit [311], an output signal of the photoelectric signal processing circuit [311] is connected to the polarization controller [201], And the output of the polarization controller [201] is connected to the polarization modulator [202], and is connected by fiber to the phase modulation ^ [206] connected in series [1] or [2], the photoelectric signal processing circuit [311] An output is connected to the phase controller [205] and is connected by the output of the phase controller [205] to the phase modulator [206] connected to the fiber [2] or [1]; the phase controller [205] and the photoelectric signal The processing circuit [311] and the phase modulator [206] constitute a phase fading closed-loop control loop, so that the phase difference of the two interfering optical waves propagating on the Mach-Zehnder fiber interferometer is stabilized in the system. The required phase value; the polarization controller [201], the polarization modulator [202] and the phase modulator [206], and the photoelectric signal processing circuit [311] form a polarization fading closed-loop control loop, making it in Mach-Zehnder (Mach - Zehnder) The polarization state difference of the two interfering light waves propagating on the fiber interferometer to form an interference is stabilized at the angle value required by the system.

2. The optical fiber security early warning control system according to claim 1, wherein: the polarization fading control is further connected to the polarizer [410] by the laser [101], and then connected to the combiner and the splitter by the optical fiber. [204] and three optical fibers [1], [2], [3] constitute a Mach-Zehnder fiber optic interferometer multiplexer [203], and the multiplexer [203] is connected by optical fibers respectively. The analyzer [412] and the analyzer [413], the analyzer [412] and the analyzer [413] are connected to the polarization detector [407] and the polarization detection, respectively. After [408], the electrical signal line is connected to the signal processing circuit [411], the signal processing circuit [411] is connected to the polarization controller [201], and the polarization controller [201] is connected to the polarization modulator by the electrical signal line. [202] and a phase modulator [206] connected in series with fiber [1] or [2].

3. The optical fiber security early warning control system according to claim 1, wherein: the phase fading control is further connected to the multiplexer/demultiplexer by a laser [101], and the multiplexer [203] The two optical fibers are respectively connected to the photodetector [309] and the photodetector [310], the photodetector [309] and the photodetector [310] are respectively connected by the wire to the A/D capture card [312] and the A/D. After the card [313], the mixer [517] with the input of the signal generator [514] is commonly connected, and the mixer [517] outputs the sub-series filter [518], the signal processor [519], and the filter [ 520], the signal demodulator [521], while the laser [101] is connected to the signal generator [513] by the optical fiber, and then the phase of the signal generator [513] is connected in series with the fiber [1] or [2]. Modulator [206].