CN205002877U - Long distance fiber optic distributed vibrates monitoring devices - Google Patents
Long distance fiber optic distributed vibrates monitoring devices Download PDFInfo
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- CN205002877U CN205002877U CN201520757193.5U CN201520757193U CN205002877U CN 205002877 U CN205002877 U CN 205002877U CN 201520757193 U CN201520757193 U CN 201520757193U CN 205002877 U CN205002877 U CN 205002877U
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Abstract
The utility model provides a long distance fiber optic distributed vibrates monitoring devices, including pulse coder, the coherent laser light source, the time coding light source, a fiber coupler, the 2nd fiber coupler, a wavelength division multiplexer, the 2nd wavelength division multiplexer, interfere the detector, code detector and signal processing unit, pulse coder is connected with coherent laser light source and time coding light source respectively, the time coding light source is connected with a wavelength division multiplexer, the coherent laser light source is connected with a fiber coupler, a fiber coupler divides two tunnel outputs, one of them sweetgum fruit is crossed optic fibre and is connected with the 2nd fiber coupler, another way is connected with a wavelength division multiplexer, a wavelength division multiplexer and the 2nd wavelength division multiplexer are through the fiber connection, the 2nd wavelength division multiplexer and the 2nd fiber coupler are connected, the 2nd fiber coupler is connected with interfering the detector, interfere the detector to be connected with signal processing unit, the 2nd wavelength division multiplexer is connected with the code detector, the code detector is connected with signal processing unit.
Description
Technical field
The utility model relates to detection technique, particularly the distributed vibration monitoring device of a kind of long-distance optical fiber.
Background technology
Optical fiber distribution type vibration sensing technology to have a wide range of applications demand at circumference security protection, pipeline monitoring and the optical cable sea monitoring arts such as cable.Technology in the past adopts bidirectional Mach Zehnder interferometer or optical time domain reflection technology usually, and detecting distance is shorter and can not be used in optical cable containing the environment of unidirectional optical amplifier.
Summary of the invention
The utility model is the problem that there is detecting distance finite sum poor anti jamming capability for optical fiber distribution type vibration sensing, propose the distributed vibration monitoring device of a kind of long-distance optical fiber, adopt optical pulse time coding method, detect and optical fiber technology in conjunction with laser interference, realize carrying out detection and positioning to the applied vibration signal that optical fiber cable is along the line, do not limit the constraint of detecting distance, adapt to various testing environment.
The technical solution of the utility model is: the distributed vibration monitoring device of a kind of long-distance optical fiber, comprise pulse encoder, coherent laser light source, time encoding light source, first fiber coupler, second fiber coupler, first wave division multiplexer, Second Wave division multiplexer, interference detection device, code detector and signal processing unit, described pulse encoder is connected with described coherent laser light source and time encoding light source respectively, time encoding light source is connected with first wave division multiplexer, coherent laser light source is connected with the first described fiber coupler, first fiber coupler divides two-way to export, optical fiber of wherein leading up to is connected with the second described fiber coupler, another road is connected with first wave division multiplexer, first wave division multiplexer and Second Wave division multiplexer pass through Fiber connection, Second Wave division multiplexer is connected with the second fiber coupler, second fiber coupler is connected with described interference detection device, interference detection device is connected with described signal processing unit, Second Wave division multiplexer is connected with described code detector, code detector is connected with signal processing unit.
Pulse encoder carries out the sequential coding by Gray code to coherent laser light source and time encoding light source, fibre system is entered into by the coherent laser light source output optical pulse of encoding, first divided two-way by the first fiber coupler, to lead up to after Optical Fiber Transmission and enter into the second fiber coupler through the first wave division multiplexer of series connection and Second Wave division multiplexer again, the second fiber coupler is entered after the direct onwards transmission in another road, second fiber coupler outputs signal interference detection device PD1, obtain interference light signal, between two fiber couplers, two-way cable length is equal; By the time encoding light source of encoding by entering into code detector through the wavelength division multiplexer of series connection after Optical Fiber Transmission, interference detection device and code detector carry out opto-electronic conversion by by the light signal obtained, electric signal after conversion enters into signal processing unit, signal processing unit processes signal, realizes the location to vibration signal.
Between described two fiber couplers, the length L of transmission cable satisfies condition following: T=Ln
eff/ c>M/f, wherein n
efffor the effective refractive index of optical fiber, c is the light light velocity in a vacuum, and T is the cycle of one group of Gray code, and M is Gray code code bit number, and f is AD sample frequency.
When transmission cable transmission range is long between described two fiber couplers, when the length L meeting transmission cable between two fiber couplers satisfies condition, increase one-way transmission amplification module in a fiber.
The monitoring method of the distributed vibration monitoring device of described long-distance optical fiber, code detector obtains train pulse, and the time interval between two adjacent groups coded pulse is T, for transmission cable transmission range between two fiber couplers, has T=n
effl/c;
Interference detection device obtains interference pulse sequence S, first pulse S of each sequence
ncorresponding with time pulse N, last pulse S
n+1corresponding with time pulse N+1, between N and N+1, insert the pulse of M gray encoding, M is determined by the precision of Detection location, and the respective pulses cycle is Λ;
In time there is vibration event in position x a certain on optical cable, the pulse of usual N group coding transmits the τ time forward, in signal processing unit, often detection obtains a time encoding pulse N, just open corresponding high-speed counter, record time τ, and the analysis simultaneously started the signal that interference detection device detects, when determining that event occurs from interference pulse sequence S be, namely the timing to τ is stopped, utilize this time τ, in conjunction with the coded sequence Mx of interference pulse, the position that just can obtain vibrating generation is:
X＝(M×Λ-τ)C/n
eff。
The beneficial effects of the utility model are: the utility model optical fiber distribution type vibration monitoring device and monitoring method, are applicable to containing or do not guard apart from the external security of optical cable containing the long of light relay amplifier.
Accompanying drawing explanation
Fig. 1 is the distributed vibration monitoring device structural representation of the utility model long-distance optical fiber;
Fig. 2 is the light amplification link schematic diagram in communications optical cable;
Fig. 3 is the utility model embodiment schematic diagram;
Fig. 4 is the utility model coding and detection schematic diagram.
Embodiment
As shown in Figure 1, the distributed vibration monitoring device structural representation of long-distance optical fiber, pulse encoder M carries out the sequential coding by Gray code to coherent laser light source L1 and time encoding light source L2, fibre system is entered into by the light source output optical pulse of encoding, the coherent optical pulse that coherent laser light source L1 sends is divided into two-way by fiber coupler C1, enter into two optical fiber of transmission cable respectively, again through fiber coupler C2 after a direct onwards transmission of optical fiber, another root optical fiber is successively by wavelength division multiplexer W1, W2 enters fiber coupler C2, fiber coupler C2 output signal enters into interference detection device PD1, obtain interference light signal, pulse encoder M is by inner high precision clock, binary gray code mode is adopted to carry out precision encoding to time encoding light source L2, the sequence light pulse of the specific coding that time encoding light source L2 sends then enters into transmission cable through wavelength division multiplexer W1, then enters into code detector PD2 through wavelength division multiplexer W2.The pulse train of L1 and L2 is determined according to the figure place of the length of optical cable and coding, namely after sending first group of Gray code pulse, according to the precise length of optical cable, when determining that this group pulse has arrived PD1 and PD2 completely, then send next group Gray code pulse.The light signal obtained is carried out opto-electronic conversion by PD1 and PD2, electric signal after conversion enters into signal processing unit and carries out corresponding modulus AD conversion, and carry out high-speed digital video camera, first clock recovery techniques recovered clock source is adopted in the light pulse signal obtained from PD2, supply subsequent conditioning circuit is as time reference, simultaneously from interference pulse signal through signal analysis, extract the vibration information acted on optical cable, according to the energy feature of this information, binding time coded signal, determine the time encoding corresponding to point that energy is the most concentrated, obtain vibration signal thus and act on exact time on optical cable, obtain the particular location on optical cable that this vibration signal occurs again, realize the location to vibration signal.
Ensure to encode to the high precision of light pulse, the time, accuracy Δ T will reach ns magnitude, to ensure the accuracy requirement to location.When the length of optical fiber cable is too short, the transmission of light is too fast, the code rate requirement of system can exceed the processing power of AD conversion device and signal processor and system cannot be realized, and be assurance function, between two fiber couplers, the length L of transmission cable meets the following conditions: T=Ln
eff/ c>M/f, wherein n
efffor the effective refractive index of optical fiber, c is the light light velocity in a vacuum, and T is the cycle of one group of Gray code, and M is Gray code code bit number, and f is AD sample frequency.
In the large length communications optical cable of routine, in order to overcome the intrinsic loss of optical fiber, about 50km of being usually separated by just returns and adds a pair image intensifer, the light amplification link schematic diagram as shown in Figure 2 in communications optical cable.This image intensifer is in order to ensure the quality of optical communication information, and normally one-way transmission amplifying, therefore conventional distributed vibration detection technology is as just realized on optical texture based on two-way MZ interferometer technique with based on the measuring method of OTDR technology.Because these two kinds of technology all require light transmitted in both directions inside an optical fiber, corresponding distributed optical system could be formed.
One-way transmission amplification module is that to be placed on transmission range oversize, mainly used to overcome signal attenuation, is generally all one-way transmission in communication system.When in some system, the length of optical fiber cable is shorter, because the transmission of light is too fast, the coding of system just needs adjustment, the condition that the length L making it to meet above-mentioned transmission cable meets.
Two the unidirectional modules extracted in communications optical cable build, and the transmitting 11-reception 11 in such as Fig. 2 and transmitting 21-reception 22 these two optical fiber are as the transmission cable in Fig. 1 system.Provide embodiment schematic diagram as shown in Figure 3.
Pulse encoder M to coherent laser light source L1 and time encoding light source L2 temporally sequence carry out correlative coding, the coding of L2 carries out according to fiber lengths, makes the time interval between adjacent two codes be just in time that light pulse is transferred to the time of other end from one.L1 then carries out even decile and continuous programming code according to the time cycle of L2.Fibre system is entered into by the light source output optical pulse of encoding.The coherent optical pulse that L1 sends is divided into two-way by fiber coupler C1, enters into two optical fiber of transmission cable respectively, enters into interference detection device PD1 again, obtain interference light signal after onwards transmission through fiber coupler C2.The sequence light pulse of the specific coding that time encoding light source L2 sends then enters into transmission cable through wavelength division multiplexer W1, then enters into code detector PD2 through wavelength division multiplexer W2.The figure place of encoding due to the pulse train of L1 and L2 is determined according to the length of optical cable, only needs to know which coding vibration be corresponding is, and how long the previous coding of L2 accordingly has transmitted, and namely can determine the position that event occurs.Encode as shown in Figure 4 and detect schematic diagram.
PD2 obtains train pulse, the time interval between two adjacent groups coded pulse is T, for cable length L, (length of optical cable refers to the length in Fig. 1 between fiber coupler C1, C2, optical cable between C1 and C2 has two groups, one group is directly connected, one group comprises wavelength division multiplexer W1, W2, require that this total length of two groups is equal, PD2 and PD1 export into after opto-electronic conversion, delay compensation is carried out by circuit, it is synchronous that the clock reference gathered by AD keeps two paths of signals to gather), there is T=n
effl/c, wherein, n
efffor the effective refractive index of optical fiber, c is the light light velocity in a vacuum.
PD1 obtains interference pulse sequence S, first pulse S of each sequence
ncorresponding with time pulse N, last pulse S
n+1corresponding with time pulse N+1, between N and N+1, insert the pulse of M gray encoding, M is determined by the precision of Detection location, and the respective pulses cycle is Λ.
In time there is vibration event in a certain position position x on optical cable, the pulse of usual N group coding transmits the τ time forward, and therefore in signal processing unit, often detection obtains a time encoding pulse N, just open corresponding high-speed counter, record time τ.And the analysis simultaneously started the signal that PD1 detects, be namely stop the timing to τ when determining that event occurs from interference pulse sequence S.Utilize this time τ, in conjunction with the coded sequence Mx of interference pulse, just can obtain vibrating the position occurred:
X＝(M×Λ-τ)C/n
eff
In sum, by real-time analysis in interference pulse sequence, obtain the characteristic information of external event, may be used for the generation judging that class event.In conjunction with coded message and the calculating to the corresponding time, the positional information that event occurs can be obtained, thus realize the distributed monitoring to the external aggression event acted on optical cable.
Claims (1)
1. the distributed vibration monitoring device of long-distance optical fiber, comprise pulse encoder, coherent laser light source, time encoding light source, first fiber coupler, second fiber coupler, first wave division multiplexer, Second Wave division multiplexer, interference detection device, code detector and signal processing unit, it is characterized in that: described pulse encoder is connected with described coherent laser light source and time encoding light source respectively, time encoding light source is connected with first wave division multiplexer, coherent laser light source is connected with the first described fiber coupler, first fiber coupler divides two-way to export, optical fiber of wherein leading up to is connected with the second described fiber coupler, another road is connected with first wave division multiplexer, first wave division multiplexer and Second Wave division multiplexer pass through Fiber connection, Second Wave division multiplexer is connected with the second fiber coupler, second fiber coupler is connected with described interference detection device, interference detection device is connected with described signal processing unit, Second Wave division multiplexer is connected with described code detector, code detector is connected with signal processing unit.
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| CN107782346A (en) * | 2017-10-27 | 2018-03-09 | 武汉理工大学 | Large-scale optical fiber grating sensing network demodulation system and method based on Gray code |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107782346A (en) * | 2017-10-27 | 2018-03-09 | 武汉理工大学 | Large-scale optical fiber grating sensing network demodulation system and method based on Gray code |
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