CA2664010C - An optical fiber control system for safety early-warning - Google Patents
An optical fiber control system for safety early-warning Download PDFInfo
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- CA2664010C CA2664010C CA2664010A CA2664010A CA2664010C CA 2664010 C CA2664010 C CA 2664010C CA 2664010 A CA2664010 A CA 2664010A CA 2664010 A CA2664010 A CA 2664010A CA 2664010 C CA2664010 C CA 2664010C
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 178
- 230000010287 polarization Effects 0.000 claims abstract description 140
- 238000012545 processing Methods 0.000 claims abstract description 61
- 238000005562 fading Methods 0.000 claims abstract description 51
- 229940125730 polarisation modulator Drugs 0.000 claims abstract description 23
- 230000003287 optical effect Effects 0.000 claims description 25
- 238000000034 method Methods 0.000 description 22
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- 238000010586 diagram Methods 0.000 description 11
- 238000012544 monitoring process Methods 0.000 description 10
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- 239000003921 oil Substances 0.000 description 2
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35303—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using a reference fibre, e.g. interferometric devices
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- General Physics & Mathematics (AREA)
- Optical Communication System (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
An optical fiber control system for safety early-warning includes a phase fading control and/or a polarization fading control. A polarization modulator is serially connected between a laser and a first multiplex demultiplexer. The first multiplex demultiplexer is connected to a second multiplex demultiplexer by three strands of optical fibers. The first multiplex demultiplexer is connected to two photoelectric detectors, the outputs of which are connected to two A/Ds. Outputs of the two A/Ds are connected to a photoelectric signal processing circuit, one output of which is connected to a polarization controller. Outputs of polarization controller are connected to a polarization modulator and a phase modulator which is connected to the first strand optical fiber. The other output of the photoelectric signal processing circuit is connected to a phase controller, the output of which is connected to the phase modulator which is connected to the second strand optical fiber.
Description
An Optical Fiber Control System for Safety Early-warning Field of the invention The invention relates to an optical fiber control system for safety early-warning for buried conduits, architectures, or important facilities and regions. More particularly, the invention relates to an optical fiber control system for safety early-warning including a phase fading control and a polarization fading control or a phase fading control or a polarization fading control.
Background of the invention As for the substances such as crude oil, natural gas, oil, coal slurry, water etc, pipeline transportation is a safe, economical and efficient mode of conveying, especially important to the conveying of flammable and explosive and valuable energy substances, it can be said that pipeline is the artery of energy transportation. Crude oil, refined oil and natural gas transported through pipelines have not only commercial value, but also flammable and explosive features, once the pipelines leak, it is very likely that the leaking regions happen to burn and explode, which not only influences the production of the pipeline industry, resulting in tremendous economic loss, but also threatens the properties and life of the people nearby, and the damage to the surrounding ecological environment is unable to be estimated.
Along with the development of pipeline transportation industry, the monitoring technique for safety pipeline transportation is also continuously developing, currently, there are mainly two kinds of monitoring technique for safety pipeline transportation. The first is the monitoring technique after pipeline leakage, such as 'conduit hydrodynamics status detection technique and contributed optical fiber temperature and stress monitoring technique'. Conduit hydrodynamics status detection technique real-timely collects the signals such as the flux, temperature and stress of the fluid in the pipelines, so as to detect and locate the pipeline leakage, however, such technique is limited by the fluid features, transportation techniques and capability of the monitoring apparatus, which leads to the decrease of the sensitivity and location precision of pipeline leakage monitoring, such kind = ' CA 02664010 2014-09-04 , , of technique includes pressure gradient method, negative pressure wave method and flow equilibrium method. Contributed optical fiber temperature and stress monitoring technique real-timely collects the temperature influence and impact stress of the pipeline leakage medium on the optical fiber by using nonlinear features of optical fiber (Raman Effect and Brillouin Effect), so as to determine the location of leakage position, however, such kind of technique is limited by the structure of the optical cable and the distance between the optical cable and the leakage position, which influences the monitoring effect. The second is the preventive monitoring technique before the damage of pipeline, that is, the early-warning technique for pipeline damage, currently, such kind of technique is mainly 'acoustic wave testing techniques', that technique utilizes the principle of delivering the acoustic wave along the pipelines, fixing an active sensor every about 1 km, collecting the acoustic signals along the pipeline for analysis, determining the kind of the incidence, so as to find the pipeline damage in advance, however, each sensor must be equipped with a set of power supply device and communication device, which results in the increase of investment and maintenance cost of devices, moreover, these facilities themselves are easy to be destroyed, such that these devices are unable to operate normally.
In view of the problems of current monitoring techniques for pipeline safety, a Mach-Zehnder optical fiber interferometer is proposed in U.S. Patent No.
6,621,947, which senses the vibration by using optical fiber. That invention is a breakthrough in early-warning the safety of linear target of long distance or large surface target, however, the disadvantage of the invention is that the optical path system is not stable, which leads to signal blanked due to phase fading and polarization fading and makes the system hard to work efficiently.
Summary of the invention The object of the invention is to provide an optical fiber system for safety early-warning, which utilizes the principle of Twin Mach-Zehnder optical fiber interferometer using phase fading control and polarization fading control technique or polarization fading control technique or phase fading control technique, the invention can eliminate the signal blanked due to phase fading and polarization fading or phase fading or
Background of the invention As for the substances such as crude oil, natural gas, oil, coal slurry, water etc, pipeline transportation is a safe, economical and efficient mode of conveying, especially important to the conveying of flammable and explosive and valuable energy substances, it can be said that pipeline is the artery of energy transportation. Crude oil, refined oil and natural gas transported through pipelines have not only commercial value, but also flammable and explosive features, once the pipelines leak, it is very likely that the leaking regions happen to burn and explode, which not only influences the production of the pipeline industry, resulting in tremendous economic loss, but also threatens the properties and life of the people nearby, and the damage to the surrounding ecological environment is unable to be estimated.
Along with the development of pipeline transportation industry, the monitoring technique for safety pipeline transportation is also continuously developing, currently, there are mainly two kinds of monitoring technique for safety pipeline transportation. The first is the monitoring technique after pipeline leakage, such as 'conduit hydrodynamics status detection technique and contributed optical fiber temperature and stress monitoring technique'. Conduit hydrodynamics status detection technique real-timely collects the signals such as the flux, temperature and stress of the fluid in the pipelines, so as to detect and locate the pipeline leakage, however, such technique is limited by the fluid features, transportation techniques and capability of the monitoring apparatus, which leads to the decrease of the sensitivity and location precision of pipeline leakage monitoring, such kind = ' CA 02664010 2014-09-04 , , of technique includes pressure gradient method, negative pressure wave method and flow equilibrium method. Contributed optical fiber temperature and stress monitoring technique real-timely collects the temperature influence and impact stress of the pipeline leakage medium on the optical fiber by using nonlinear features of optical fiber (Raman Effect and Brillouin Effect), so as to determine the location of leakage position, however, such kind of technique is limited by the structure of the optical cable and the distance between the optical cable and the leakage position, which influences the monitoring effect. The second is the preventive monitoring technique before the damage of pipeline, that is, the early-warning technique for pipeline damage, currently, such kind of technique is mainly 'acoustic wave testing techniques', that technique utilizes the principle of delivering the acoustic wave along the pipelines, fixing an active sensor every about 1 km, collecting the acoustic signals along the pipeline for analysis, determining the kind of the incidence, so as to find the pipeline damage in advance, however, each sensor must be equipped with a set of power supply device and communication device, which results in the increase of investment and maintenance cost of devices, moreover, these facilities themselves are easy to be destroyed, such that these devices are unable to operate normally.
In view of the problems of current monitoring techniques for pipeline safety, a Mach-Zehnder optical fiber interferometer is proposed in U.S. Patent No.
6,621,947, which senses the vibration by using optical fiber. That invention is a breakthrough in early-warning the safety of linear target of long distance or large surface target, however, the disadvantage of the invention is that the optical path system is not stable, which leads to signal blanked due to phase fading and polarization fading and makes the system hard to work efficiently.
Summary of the invention The object of the invention is to provide an optical fiber system for safety early-warning, which utilizes the principle of Twin Mach-Zehnder optical fiber interferometer using phase fading control and polarization fading control technique or polarization fading control technique or phase fading control technique, the invention can eliminate the signal blanked due to phase fading and polarization fading or phase fading or
2 = = CA 02664010 2014-09-04 , polarization, and form a optical path, at which two synchronized interference laser-modulated signals possessing stable phase and stable polarization state are transmitted oppositely in the interferometer and are picked up at the two ends of the interferometer.
Certain exemplary embodiments can provide an optical fiber system for safety early-warning for at least one of a phase fading control and a polarization fading control, comprising: three strands of optical fibers laid with a conduit in a same trench; a Mach-Zehnder optical fiber interferometer comprising two of the three strands of optical fibers, and two multiplex demultiplexers, wherein a first of the two multiplex demultiplexers is connected to a second of the two multiplex demultiplexers by means of the three strands of optical fibers; a laser; a polarization modulator connected in series via first and second optical fibers between the laser and the first multiplex demultiplexer, respectively; a first photoelectric detector and a second photoelectric detector connected to the first multiplex demultiplexer via third and fourth optical fibers, respectively; a first A/D
(analog to digital) converting circuit and a second A/D converting circuit electrically connected to outputs of the first photoelectric detector and the second photoelectric detector, respectively; a photoelectric signal processing circuit connected to outputs of the first and second A/D
converting circuits; a polarization controller connected to one output of the photoelectric signal processing circuit, a first output of the polarization controller being connected to the polarization modulator; a phase modulator connected in series to at least one of the two of the three strands of optical fibers, the phase modulator being connected to a second output of the polarization controller; and a phase controller connected to another output of the photoelectric signal processing circuit, an output of the phase controller being connected to the phase modulator, wherein the phase controller, the photoelectric signal processing circuit and the phase modulator realize a feedback control of phase fading, so a phase difference between two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired value, wherein the polarization controller, the polarization modulator, the phase modulator and the photoelectric signal processing circuit compose a polarization fading closed control loop, so a difference of polarization states between the two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired degree.
Certain exemplary embodiments can provide an optical fiber system for safety early-warning for at least one of a phase fading control and a polarization fading control, comprising: three strands of optical fibers laid with a conduit in a same trench; a Mach-Zehnder optical fiber interferometer comprising two of the three strands of optical fibers, and two multiplex demultiplexers, wherein a first of the two multiplex demultiplexers is connected to a second of the two multiplex demultiplexers by means of the three strands of optical fibers; a laser; a polarization modulator connected in series via first and second optical fibers between the laser and the first multiplex demultiplexer, respectively; a first photoelectric detector and a second photoelectric detector connected to the first multiplex demultiplexer via third and fourth optical fibers, respectively; a first A/D
(analog to digital) converting circuit and a second A/D converting circuit electrically connected to outputs of the first photoelectric detector and the second photoelectric detector, respectively; a photoelectric signal processing circuit connected to outputs of the first and second A/D
converting circuits; a polarization controller connected to one output of the photoelectric signal processing circuit, a first output of the polarization controller being connected to the polarization modulator; a phase modulator connected in series to at least one of the two of the three strands of optical fibers, the phase modulator being connected to a second output of the polarization controller; and a phase controller connected to another output of the photoelectric signal processing circuit, an output of the phase controller being connected to the phase modulator, wherein the phase controller, the photoelectric signal processing circuit and the phase modulator realize a feedback control of phase fading, so a phase difference between two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired value, wherein the polarization controller, the polarization modulator, the phase modulator and the photoelectric signal processing circuit compose a polarization fading closed control loop, so a difference of polarization states between the two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired degree.
3 = = CA 02664010 2014-09-04 , , Certain exemplary embodiments can provide an optical fiber system for safety early-warning for a polarization fading control, comprising: three strands of optical fibers laid with a conduit in a same trench; a Mach-Zehnder optical fiber interferometer comprising two of the three strands of optical fibers, and two multiplex demultiplexers, wherein a first of the two multiplex demultiplexers is connected to a second of the two multiplex demultiplexers by means of the three strands of optical fibers; a laser; a polarization scrambler connected in series via first and second optical fibers between the laser and the first multiplex demultiplexer, respectively; a first polaroid analyzer and a second polaroid analyzer connected to the first multiplex demultiplexer via third and fourth optical fibers, respectfully; a first polarization detector and a second polarization detector connected to outputs of the first polaroid analyzer and the second polaroid analyzer, respectively; a signal processing circuit connected via electrical signal wires to outputs of the first and second polarization detectors; a polarization controller connected to one output of the signal processing circuit, a first output of the polarization controller being electrically connected to the polarization scrambler; and a phase modulator connected in series to at least one of the two of the three strands of optical fibers, the phase modulator being connected via a fifth optical fiber to a second output of the polarization controller; wherein the polarization controller, the polarization scrambler, the phase modulator and the signal processing circuit compose a polarization fading closed control loop, so a difference of polarization states between the two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired degree.
Certain exemplary embodiments can provide an optical fiber system for safety early-warning for phase fading control comprising: three strands of optical fibers laid with a conduit in a same trench; a Mach-Zehnder optical fiber interferometer comprising two of the three strands of optical fibers, and two multiplex demultiplexers, wherein a first of the two multiplex demultiplexers is connected to a second of the two multiplex demultiplexers by means of the three strands of optical fibers, a laser, a first output of which is connected via a first optical fiber to the first multiplex demultiplexer ; a first photoelectric detector and a second photoelectric detector connected to the first multiplex demultiplexer via second and third optical fibers, respectively; a first A/D (analog to digital) collecting card and a second
Certain exemplary embodiments can provide an optical fiber system for safety early-warning for phase fading control comprising: three strands of optical fibers laid with a conduit in a same trench; a Mach-Zehnder optical fiber interferometer comprising two of the three strands of optical fibers, and two multiplex demultiplexers, wherein a first of the two multiplex demultiplexers is connected to a second of the two multiplex demultiplexers by means of the three strands of optical fibers, a laser, a first output of which is connected via a first optical fiber to the first multiplex demultiplexer ; a first photoelectric detector and a second photoelectric detector connected to the first multiplex demultiplexer via second and third optical fibers, respectively; a first A/D (analog to digital) collecting card and a second
4 =
AID collecting card connected via electric wires to outputs of the first photoelectric detector and the second photo electric detector, respectively; a signal demodulating host including:
a frequency mixer connected to outputs of the first and second A/D collecting cards; and a signal generator to which an output is connected to the frequency mixer, a first filter connected to an output of the frequency mixer, a signal processor connected to an output of the first filter, a second filter connected to an output of the signal processor, and a signal demodulator connected to an output of the second filter; a signal generator connected to a second output of the laser; a phase modulator connected to at least one of the two of the three strands of optical fibers, the phase modulator being connected an output of the signal generator; and a phase controller connected to an output of the signal generator, an output of the phase controller being connected to the phase modulator, wherein the phase controller, the signal demodulating host and the phase modulator realize a feedback control of phase fading, so a phase difference between two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired value.
Brief description of the drawings Figure 1 is the schematic diagram of associated polarization and phase control of the optical fiber system for safety early-warning according to the invention.
Figure 2 is the electrical schematic diagram of associated polarization and phase control of the optical fiber system for safety early-warning according to the invention.
Wherein, 101-laser, 201-polarization controller, 202-polarization modulator, multiplex demultiplexer, 204-multiplex demultiplexer, 205-phase controller, 206-phase modulator, 309-photoelectic detector, 310-photoelectric detector, 311-pheotoelectic signal processing circuit, 312-A/D, 313-A/D
Figure 3 is the schematic diagram of polarization control of optical fiber for safety early-warning according to the invention.
Figure 4 is the electric schematic diagram of polarization control of optical fiber for safety early-warning according to the invention.
Wherein, 407-polarization detector, 408-polarization detector, 409-signal processing circuit, 410-polarization scrambler, 412-polaroid analyzer, 413-polaroid analyzers
AID collecting card connected via electric wires to outputs of the first photoelectric detector and the second photo electric detector, respectively; a signal demodulating host including:
a frequency mixer connected to outputs of the first and second A/D collecting cards; and a signal generator to which an output is connected to the frequency mixer, a first filter connected to an output of the frequency mixer, a signal processor connected to an output of the first filter, a second filter connected to an output of the signal processor, and a signal demodulator connected to an output of the second filter; a signal generator connected to a second output of the laser; a phase modulator connected to at least one of the two of the three strands of optical fibers, the phase modulator being connected an output of the signal generator; and a phase controller connected to an output of the signal generator, an output of the phase controller being connected to the phase modulator, wherein the phase controller, the signal demodulating host and the phase modulator realize a feedback control of phase fading, so a phase difference between two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired value.
Brief description of the drawings Figure 1 is the schematic diagram of associated polarization and phase control of the optical fiber system for safety early-warning according to the invention.
Figure 2 is the electrical schematic diagram of associated polarization and phase control of the optical fiber system for safety early-warning according to the invention.
Wherein, 101-laser, 201-polarization controller, 202-polarization modulator, multiplex demultiplexer, 204-multiplex demultiplexer, 205-phase controller, 206-phase modulator, 309-photoelectic detector, 310-photoelectric detector, 311-pheotoelectic signal processing circuit, 312-A/D, 313-A/D
Figure 3 is the schematic diagram of polarization control of optical fiber for safety early-warning according to the invention.
Figure 4 is the electric schematic diagram of polarization control of optical fiber for safety early-warning according to the invention.
Wherein, 407-polarization detector, 408-polarization detector, 409-signal processing circuit, 410-polarization scrambler, 412-polaroid analyzer, 413-polaroid analyzers
5 = = CA 02664010 2014-09-04 Figure 5 is the schematic diagram of phase control of optical fiber for safety early-warning according to the invention.
Figure 6 is the electric schematic diagram of phase control of optical fiber for safety early-warning according to the invention.
Wherein, 513-single generator, 514-signal generator, 517-frequency mixer, 518-filter, 519-signal processor, 520-filter, 521-singal demodulator Detailed description of the drawings The phase fading and polarization fading control system of the invention comprises a laser 101 and a Mach-Zehnder optical fiber interferometer consisted of three strands of optical fibers 1,2,3 laid with the conduit in a same trench or laid underground about the architectures, a multiplex demultiplexer 203 and a multiplex demutiplexer 204, characterized in that, as shown in figure 1, a polarization modulator 202 is connected in series between the laser 101 and the multiplex demultiplexer 203 via optical fibers, the multiplex demultiplexer 203 is connected to the multiplex demutiplexer 204 by means of three strands of optical fibers 1,2,3 respectively, the Mach-Zehnder optical fiber interferometer comprises the multiplex demutiplexer 203, the multiplex demutiplexer 204 and optical fiber 1 and optical fiber 2, the multiplex demutiplexer 203 is connected to a photoelectric detector 309 and a photoelectric detector 310 via two strands of optical fibers respectively, the outputs of the photoelectric detector 309 and the photoelectric detector 310 are connected electrically to A/D 312 and A/D 313 respectively, the outputs of A/D 312 and A/D 313 are connected to a photoelectric signal processing circuit 311, one output of the photoelectric signal processing circuit 311 is connected to a polarization controller 201, and the outputs of the polarization controller 201 are connected to a polarization modulator 202 and a phase modulator 206 which is connected in series to optical fiber 1 or optical fiber 2, another 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 a phase modulator 206 which is connected in series to optical fiber 2 or optical fiber 1; the phase controller 205, the photoelectric signal processing circuit 311 and the phase modulator 206 compose a feedback control of phase fading, such that the phase difference between the two
Figure 6 is the electric schematic diagram of phase control of optical fiber for safety early-warning according to the invention.
Wherein, 513-single generator, 514-signal generator, 517-frequency mixer, 518-filter, 519-signal processor, 520-filter, 521-singal demodulator Detailed description of the drawings The phase fading and polarization fading control system of the invention comprises a laser 101 and a Mach-Zehnder optical fiber interferometer consisted of three strands of optical fibers 1,2,3 laid with the conduit in a same trench or laid underground about the architectures, a multiplex demultiplexer 203 and a multiplex demutiplexer 204, characterized in that, as shown in figure 1, a polarization modulator 202 is connected in series between the laser 101 and the multiplex demultiplexer 203 via optical fibers, the multiplex demultiplexer 203 is connected to the multiplex demutiplexer 204 by means of three strands of optical fibers 1,2,3 respectively, the Mach-Zehnder optical fiber interferometer comprises the multiplex demutiplexer 203, the multiplex demutiplexer 204 and optical fiber 1 and optical fiber 2, the multiplex demutiplexer 203 is connected to a photoelectric detector 309 and a photoelectric detector 310 via two strands of optical fibers respectively, the outputs of the photoelectric detector 309 and the photoelectric detector 310 are connected electrically to A/D 312 and A/D 313 respectively, the outputs of A/D 312 and A/D 313 are connected to a photoelectric signal processing circuit 311, one output of the photoelectric signal processing circuit 311 is connected to a polarization controller 201, and the outputs of the polarization controller 201 are connected to a polarization modulator 202 and a phase modulator 206 which is connected in series to optical fiber 1 or optical fiber 2, another 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 a phase modulator 206 which is connected in series to optical fiber 2 or optical fiber 1; the phase controller 205, the photoelectric signal processing circuit 311 and the phase modulator 206 compose a feedback control of phase fading, such that the phase difference between the two
6 ' = CA 02664010 2014-09-04 , , interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at the desired phase value; the polarization controller 201, the polarization modulator 202, the phase modulator 206 and the photoelectric signal processing circuit 311 compose a polarization fading closed control loop, such that the difference of polarization states between the two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at the desired degree value.
Figure 2 shows the electric schematic diagram of associated control on phase fading and polarization fading, a polarization modulator 202 is connected in series between a laser 101 and a multiplex demutiplexer 203 via optical fibers, the multiplex demutiplexer 203 is connected via optical fiber to two optical inputs of a photoelectric signal processing circuit 309-1 having two inputs/outputs, the two electric outputs of the photoelectric signal processing circuit 309-1 are connected to the input of a polarization control host 201-1 and the I/O of a phase controller 205-1 respectively, the output of the polarization control host 201-1 is connected to the input of a polarization controller 201-2, the output of the polarization controller 201-2 is connected to the input of a polarization modulator 202 and the input of a phase modulator 206, the output of the phase control host 205-1 is connected to the input of a phase controller 205-2, the output of the phase controller 205-2 is connected to the input of another phase modulator 206. In this electric schematic diagram, the photoelectric signal processing circuit 309-1 performs the function of two photoelectric detectors 309 and 310, A/D 312, A/D 313 and the photoelectric signal processing circuit 311, the polarization control host 201-1 and the polarization controller 201-2 perform the function of the polarization controller 201, the phase control host 205-1 and the phase controller 205-2 perform the function of phase controller 205.
The polarization fading control of the invention can also be complemented through the following solution, as shown in figure 3. The polarization fading control shown in Figs.
3 and 4 may be implemented with components of the system of Fig. 1 that are not shown in Figs. 3 and 4; however, for consistency, where the same components in Figs. 3 and 4 and Fig.
I may be used, the reference numerals for the component shown in Fig. 1 may be used.
The laser 101 is connected to a polarization scrambler 410 via optical fiber, and then to connect to the multiplex demutiplexer 203 via optical fiber, the multiplex demutiplexer 203
Figure 2 shows the electric schematic diagram of associated control on phase fading and polarization fading, a polarization modulator 202 is connected in series between a laser 101 and a multiplex demutiplexer 203 via optical fibers, the multiplex demutiplexer 203 is connected via optical fiber to two optical inputs of a photoelectric signal processing circuit 309-1 having two inputs/outputs, the two electric outputs of the photoelectric signal processing circuit 309-1 are connected to the input of a polarization control host 201-1 and the I/O of a phase controller 205-1 respectively, the output of the polarization control host 201-1 is connected to the input of a polarization controller 201-2, the output of the polarization controller 201-2 is connected to the input of a polarization modulator 202 and the input of a phase modulator 206, the output of the phase control host 205-1 is connected to the input of a phase controller 205-2, the output of the phase controller 205-2 is connected to the input of another phase modulator 206. In this electric schematic diagram, the photoelectric signal processing circuit 309-1 performs the function of two photoelectric detectors 309 and 310, A/D 312, A/D 313 and the photoelectric signal processing circuit 311, the polarization control host 201-1 and the polarization controller 201-2 perform the function of the polarization controller 201, the phase control host 205-1 and the phase controller 205-2 perform the function of phase controller 205.
The polarization fading control of the invention can also be complemented through the following solution, as shown in figure 3. The polarization fading control shown in Figs.
3 and 4 may be implemented with components of the system of Fig. 1 that are not shown in Figs. 3 and 4; however, for consistency, where the same components in Figs. 3 and 4 and Fig.
I may be used, the reference numerals for the component shown in Fig. 1 may be used.
The laser 101 is connected to a polarization scrambler 410 via optical fiber, and then to connect to the multiplex demutiplexer 203 via optical fiber, the multiplex demutiplexer 203
7 = = CA 02664010 2014-09-04 , , associated with the multiplex demutiplexer 204 and three strands of optical fibers 1,2,3 compose a Mach-Zehnder optical fiber interferometer, the multiplex demutiplexer 203 is connected to the polaroid analyzers 412 and 413 via optical fibers respectively, the polaroid analyzers 412 and 413 are connected to the polarization detectors 407 and 408 respectively, and then to connect to a signal processing circuit 411 via electric signal wires, the output of the signal processing circuit 411 is connected to the polarization controller 201, the polarization controller 201 is electrically connected to the polarization modulator 202, and is connected via optical fiber to the phase modulator 206 connected in series between optical fiber lor optical fiber 2.
Figure 4 shows the electric schematic diagram of this solution, the laser 101 is connected to the input of the polarization scrambler 410 via optical fiber, the output of the polarization scrambler 410 is then connected to the multiplex demutiplexer 203 of the optical fiber interferometer via optical fiber, and the multiplex demutiplexer 203 is connected to the inputs of the polaroid analyzers 412 and 413 respectively via optical fibers, the outputs of the polaroid analyzers 412 and 413 are connected to the inputs of the polarization detectors 407 and 408 respectively, the outputs of the polarization detectors 407 and 408 are connected to the inputs of the signal processing unit 411.
The phase fading control of the invention can also be implemented through the following solution, as shown in figure 5. The phase fading control shown in Figs. 5 and 6 may be implemented with components of Fig. 1 that are not shown in Figs. 5 and 6; however, for consistency, where the same components in Figs. 5 and 6 and Fig. 1 may be used, the reference numerals for the component in Fig. 1 may be used. The laser 101 is connected to the multiplex demutiplexer 203 via optical fiber, the multiplex demutiplexer 203 is connected to the photoelectric detectors 309 and 310 respectively via two optical fibers, and then the photoelectric detectors 309 and 310 are connected to A/D collecting cards 312 and 313 via electric wires, the A/D collecting cards 312 and 313 are connected to a frequency mixer 517 which is input by a signal generator 514, the output of the frequency mixer 517 is sequentially connected in series a filter 518, a signal processor 519, a filter 520 and a signal demodulator 521 to demodulate the phase signal produced by the vibration of soil; meantime, the laser 101 is connected to a signal generator 513 via optical fiber, the signal generator 513
Figure 4 shows the electric schematic diagram of this solution, the laser 101 is connected to the input of the polarization scrambler 410 via optical fiber, the output of the polarization scrambler 410 is then connected to the multiplex demutiplexer 203 of the optical fiber interferometer via optical fiber, and the multiplex demutiplexer 203 is connected to the inputs of the polaroid analyzers 412 and 413 respectively via optical fibers, the outputs of the polaroid analyzers 412 and 413 are connected to the inputs of the polarization detectors 407 and 408 respectively, the outputs of the polarization detectors 407 and 408 are connected to the inputs of the signal processing unit 411.
The phase fading control of the invention can also be implemented through the following solution, as shown in figure 5. The phase fading control shown in Figs. 5 and 6 may be implemented with components of Fig. 1 that are not shown in Figs. 5 and 6; however, for consistency, where the same components in Figs. 5 and 6 and Fig. 1 may be used, the reference numerals for the component in Fig. 1 may be used. The laser 101 is connected to the multiplex demutiplexer 203 via optical fiber, the multiplex demutiplexer 203 is connected to the photoelectric detectors 309 and 310 respectively via two optical fibers, and then the photoelectric detectors 309 and 310 are connected to A/D collecting cards 312 and 313 via electric wires, the A/D collecting cards 312 and 313 are connected to a frequency mixer 517 which is input by a signal generator 514, the output of the frequency mixer 517 is sequentially connected in series a filter 518, a signal processor 519, a filter 520 and a signal demodulator 521 to demodulate the phase signal produced by the vibration of soil; meantime, the laser 101 is connected to a signal generator 513 via optical fiber, the signal generator 513
8 = CA 02664010 2014-09-04 =
is connected to the phase modulator 206 which is connected in series between optical fiber 1 or optical fiber 2; the interference signals are converted by the photoelectric detectors 309 and 310, and then are quantified by the A/D collecting cards 312 and 313, the signal generator 514 generates a modulated signal having amplitude A and frequency F, the modulated signal modulates the laser 101 or the phase modulator 206 on one of the interference arms of the modulation interferometer, producing a phase difference periodically changed in the interferometer, the two outputs of the interferometer are detected and converted to electric signals by the photoelectric detectors 309 and 310, and then are sent to A/D circuits 312 and 313, after that, the signals are sent to the frequency mixer 517 to be frequency-mixed with the signal and multiple frequency signal thereof produced by the signal generator 514, after being filtered by the filter 518, the signals undergo the differential and integral calculation and the addition and subtraction calculation of the signal processor 519, after being filtered by the filter 520, the signals are demodulated by the signal demodulator 521 to the phase signal produced by the vibration of soil.
Figure 6 shows the electric schematic diagram of that solution, the multiplex demutiplexer 203 is connected to the two optical inputs of the photoelectric signal processing circuit 309-1 which possess the function of two photoelectric detectors 309 and 310 and the signal conditioning circuits 312 and 313, the two electric outputs of the photoelectric signal processing circuit 309-1 are connected to the A/D
collecting cards 312 and 313 respectively, the outputs of the A/D collecting cards 312 and 313 are connected to the inputs of the signal demodulating host which possess the function of the frequency mixer 517, the signal generator 514, the filter 518, the signal processor 519, the filter 520 and the signal demodulator 521, the output of the signal generator 513 is connected to the phase controller 205-2, the output of the phase controller 205-2 is connected to the phase modulator 206 which is connected in series between optical fiber 1 or optical fiber 2. Here, the photoelectric signal conditioning circuit 309-1 carries out the function of the two photoelectric detectors 309 and 310 and the signal conditioning circuits 312 and 313, the signal demodulating host carries out the function of the frequency mixer 517, the signal generator 513, the filter 518, the signal processor 519, the filter 520 and the signal demodulator 521.
is connected to the phase modulator 206 which is connected in series between optical fiber 1 or optical fiber 2; the interference signals are converted by the photoelectric detectors 309 and 310, and then are quantified by the A/D collecting cards 312 and 313, the signal generator 514 generates a modulated signal having amplitude A and frequency F, the modulated signal modulates the laser 101 or the phase modulator 206 on one of the interference arms of the modulation interferometer, producing a phase difference periodically changed in the interferometer, the two outputs of the interferometer are detected and converted to electric signals by the photoelectric detectors 309 and 310, and then are sent to A/D circuits 312 and 313, after that, the signals are sent to the frequency mixer 517 to be frequency-mixed with the signal and multiple frequency signal thereof produced by the signal generator 514, after being filtered by the filter 518, the signals undergo the differential and integral calculation and the addition and subtraction calculation of the signal processor 519, after being filtered by the filter 520, the signals are demodulated by the signal demodulator 521 to the phase signal produced by the vibration of soil.
Figure 6 shows the electric schematic diagram of that solution, the multiplex demutiplexer 203 is connected to the two optical inputs of the photoelectric signal processing circuit 309-1 which possess the function of two photoelectric detectors 309 and 310 and the signal conditioning circuits 312 and 313, the two electric outputs of the photoelectric signal processing circuit 309-1 are connected to the A/D
collecting cards 312 and 313 respectively, the outputs of the A/D collecting cards 312 and 313 are connected to the inputs of the signal demodulating host which possess the function of the frequency mixer 517, the signal generator 514, the filter 518, the signal processor 519, the filter 520 and the signal demodulator 521, the output of the signal generator 513 is connected to the phase controller 205-2, the output of the phase controller 205-2 is connected to the phase modulator 206 which is connected in series between optical fiber 1 or optical fiber 2. Here, the photoelectric signal conditioning circuit 309-1 carries out the function of the two photoelectric detectors 309 and 310 and the signal conditioning circuits 312 and 313, the signal demodulating host carries out the function of the frequency mixer 517, the signal generator 513, the filter 518, the signal processor 519, the filter 520 and the signal demodulator 521.
9 = CA 02664010 2014-09-04 , Wherein, said laser 101 is a continuous monochromatic laser.
Said photoelectric detectors 309 and 310, photoelectric signal processing circuit 309-1, photoelectric signal processing circuit 311, polarization controller 201, polarization control host 201-1, polarization controller 201-2, polarization modulator 202, phase controller 205, phase control host 205-1, phase controller 205-2 and the phase modulator 206 are all products on sale.
In figure 1, regarding three strands of optical fibers 1, 2 and 3, wherein optical fibers 1 and 2 are interference optical fibers, optical fiber 3 is transmission optical fiber, the multiplex demutiplexers 203 and 204 and optical fibers 1 and 2 compose the Mach-Zehnder optical fiber interferometer. The monochromatic laser 101 emits monochromatic laser beam, the monochromatic laser beam is transmitted to the multiplex demutiplexers 203 via optical fiber and then divided into two beams: One beam of the laser is incident at the multiplex demutiplexers 203 of the Mach-Zehnder optical fiber interferometer, and combined at the multiplex demutiplexers 204 to form interference light wave, the interference light wave is sent back to the multiplex demutiplexers 203 via optical fiber 3;
the other beam of the laser is transmitted to the multiplex demutiplexers 204 via optical fiber 3, and incident at the multiplex demutiplexers 204 of the Mach-Zehnder optical fiber interferometer, and combined at the multiplex demutiplexers 203 to form interference light waves.
After converted by the photoelectric detectors 309 and 310, the interference signal is analyzed by the photoelectric signal processing circuit 311. The average of the phase due to the disturbance of outside over a period of time is calculated through signal processing and calculation, the phase average is used to control the phase modulator 206 to compensate the phase, so as to counteract the influence of outside and make the interferometer working at a certain working point.
When ensuring the phase of the interferometer maintained at a certain working point, The photoelectric signal processing circuit 311 analyzes and calculates the variable amount of the polarization state of the interferometer to control the polarization controller 201 to send a modulated signal having a frequency F. The interferometer is modulated by the polarization modulator 202, so as to produce a modulated interference wave having a =
frequency F. The photoelectric detectors 309 and 310 detect the polarization state of the two strands of output light of the interferometer, and send them to the signal processing circuit 311 to calculate the polarization state of the interferometer. The polarization state of input light of the interferometer is modified by the polarization controller 201, therefore, the polarization controller 201, the polarization modulator 202 and the photoelectric signal processing circuit 311 form a polarization state closed control loop, such that the difference of polarization states between the two strands of interference light waves produced due to the transmission in the Mach-Zehnder optical fiber interferometer is maintained at the desired degree value of the system. In addition, when the polarization state of the interferometer is controlled, the phase difference between the two strands of interference signals detected at the interferometer will change irregularly, which will influence the location precision of the optical fiber system for safety early-warning. For this, the invention proposes to add a phase modulator 206 at any one of the interference arms of the interferometer, thus the photoelectric signal processing circuit 311 analyzes and calculates the change of the phase difference between the two strands of signals, then modifies the phase difference between the two strands of output signals of the interferometer, such that ensures the phase difference reach to the desired degree while the polarization state is adjusted.
The invention applies Twin Mach-Zehnder optical fiber interferometer, the longest length of the interferometer is up to about 80 km, the vibration signals of the soil long pipelines makes the phase of the interference light wave on the interferometer changed, so as to form a interference signal with vibration information. The principle base of the interferometric Mach-Zehnder optical fiber interferometer is that the interference of two beams of light. Two monochromatic waves are interfered when they vibrate in the same direction, and are not interfered when they vibrates at two directions perpendicular to each other, it can be deduced that, the two light are interfered partly in other circumstances. The directions of the polarization state of two beams of light shall be coincident to make the interference happen in the interferometer. In the principle, when the optical fiber is a perfect column, the polarization states are two modes that individually transmit and do not interfere with each other, but actually, the single-mode optical fiber manufactured is a =
unsymmetrical column. The interferometer applied in the optical fiber system for safety early-warning is the longest interferometer currently utilized, up to about 80 km. Since the environment along the pipelines of 80 km is very complicated, the changes of the phase and polarization of the light beam in the interference during the transmission are very complicated, the change of the pressure and temperature outside make the optical fiber curved or deformed, and the defects during the manufacture will also make the optical propagation constants in the two orthogonal directions different, resulting in the occurrence of so called birefringence, that is, the two polarization states are randomly coupled during the transmission, then, the polarization state of the light output from the optical fiber changes randomly, the interference effect can not be ensured when the two lights are overlapped, finally the signals output presents the blanked state randomly, such phenomena is called polarization fading phenomena. A phenomena is called as phase fading phenomena, wherein the phase of the interference light changes randomly during the polarization state changes randomly, resulting in the signal-to-noise of the system changes randomly, even the signal is fully blanked.
However, the active and passive laser devices applied in the optical fiber system for early-warning have such feature that the polarization and the phase are related, the control on the polarization of the interferometer will change the phase, and the control on the phase will change the polarization state. Therefore, it is one of the most important techniques that coordinately control the polarization and the phase to ensure the two beams of polarization light are interfered steadily and make the phase fading controlled under the requirement of the system.
The principle of the invention is that:
According to the invention, the two beams of polarization light transmitted on the optical fiber interferometer of the optical fiber system for safety early-warning have arbitrary polarization state and random phase, change the signal of light intensity output from the optical fiber interferometer after photoelectric conversion can be written as:
V +J' + J' COO + n + 00 ) (1) Equation (1) can be written as:
V = Vo + Vg cos(0, +0õ +00+ (2) = CA 02664010 2014-09-04 Wherein, V is the output voltage signal, Vg is the visibility of the interferometer, V,õ is the additional noise of the circuit, . is the signal of phase difference due to the acoustic wave of the vibration of soil, that is the signal of the acoustic wave of the vibration of soil to be detected, 00 is the initial phase of the interferometer, it is a constant, çb presents the drift in low frequency of the phase difference due to various interfere and noise, wherein, Vg and 0,, are variable values, which change along with the temperature and the environment outside.
Since the output polarization state of the optical fiber changes randomly due to the slightly curve and distortion of the optical fiber, and the change of environmental temperature, which reflects in the visibility Vg changing randomly between 0-1, when Vg is 0, the signal is fully blanked, this phenomenon is called as signal fading phenomenon induced by the polarization of the optical fiber interferometer.
Moreover, to be convenient in analyzing the problem, equation (2) can be written as:
V = A+V gcos(0, On) (3) Wherein, A=Vi+V 2+ , Vg = 2VV,V2 , is merged into On . Generally, the outside interfere signal 0,õ is a large low frequency signal, 0, is a small high frequency signal, when the signal has a small variation amount AO, :
AV Vg sin 0õ = AO, (4) Since the low frequency interfere 0,, changes randomly and largely, it is easy to learn from equation (4) that signal-to-noise output from the system changes, and when sin 0õ---0 , the signal is fully blanked. The phenomenon of the output signal of the interferometer rises and falls randomly along with the change of outside environment is called as the phase fading phenomenon of the interferometer.
When polarization state control individually performed on the interferometer, the phase of the interferometer will change accordingly. If the interferometer is performed the phase control individually, the polarization state of the interferometer will change accordingly. In addition, if the phase or the polarization state of the interferometer is = CA 02664010 2014-09-04 controlled, the phase difference between the two strands of interference signals detected at the interferometer changes irregularly, which will influence the location precision of the optical fiber of system for safety early-warning.
For these phenomenon, the invention proposes to monitor the polarization state of the interferometer and change of the phase difference between the two strands of interference signals detected at the interferometer, when compensating the phase of the interferometer of the optical fiber system for safety early-warning. The invention compensates and adjusts according to the variation value, such that the phase, polarization state and the phase difference between the two strands of signals of the interferometer reach to the optimal values required by the system.
The output signal of the optical fiber system for safety early-warning after photoelectric conversion is quantified by the A/D collecting card, and can be written as:
V = A +Vg cos(0, 0,7) (3) Generally, signal q5, is a high frequency signal, the outside interfere On is a low frequency signal, it can be obtained the average On of outside interfere On over a period of time by averaging equation (3) over that period of time. A phase modulator is added into one arm of the interferometer, and a feedback control voltage VF is added to the phase modulator, so as to produce control phase difference 0, to counteract the influence of outside interfere, such that the interferometer works at a certain working point, as the following equation:
0, = + 71-12 (n =0,1,2...) (5) When On changes, Oa changes accordingly. By adjusting them circularly, the working point of the hydrophone can be stabilized about 7-c /2, thereby the dependable and steady signal output can be obtained. Therefore, the working point of the system is stabilized at the most sensitive point all the time, such that the phase fading of the optical fiber system for safety early-warning can be overcome.
=
Embodiment 1 The detailed description of the invention will be described according to present embodiment and the invention will be further described. The present example is an experimental prototype, the structure thereof is shown in figures 1 and 2. In the figures, the bold lines present the optical fibers, the fine lines present the electric wires. The specific structure is: the polarization modulator 202 is connected in series between the laser 101 and the multiplex demultiplexer 203 via optical fibers, the multiplex demutiplexer 203 is connected to the two optical inputs of the photoelectric signal processing circuit 309-1 having two inputs/outputs via two optical fibers respectively, the two electric outputs of the photoelectric signal processing circuit 309-1 are connected to the input of a polarization control host 201-1 and the I/O of the phase controller 205-1 respectively, the output of the polarization control host 201-1 is connected to the input of the polarization controller 201-2, one strand of the outputs of the polarization controller 201-2 is connected to the input of a polarization modulator 202 and the other strand of the inputs of the polarization modulator 202 is connected to the input of a phase modulator 206 which is connected in series to optical fiber 1 or 2, the output of the phase control host 205-1 is connected to the input of a phase controller 205-2, the output of the phase controller 205-2 is connected to the input of another phase modulator 206 connected in series to optical fiber 1 or 2. In this electric schematic diagram, the photoelectric signal processing circuit 309-1 having two strands of inputs/outputs performs the function of two photoelectric detectors 309 and 310, A/D 312, AID 313 and the photoelectric signal processing circuit 311, the polarization control host 201-1 and the polarization controller 201-2 perform the function of the polarization controller 201, the phase control host 205-1 and the phase controller 205-2 perform the function of phase controller 205.
Wherein, the type of the single frequency laser is: KOHERAS ADJUSTIK HP E15;
the type of the multiplex demultiplexers 203 and 204 is:
WDM-A-2x2-1550-1-FC/UPC-3*54 of Langguang Company; the type of the polarization control host 201-1 is: NI PXI-1042 8-Slot 3U CPU: PXI-8186 P42.2 I/O: NI PXI-5112, 2 channel, 100 MHz, 32 MB/Channel, 8-bit; PXI-6111 AID 2 channel 12bit, D/A 2 channel 12 bit; the type of the phase control host 205-1 is: NI PXI-1050, PXI/SCXI CPU:
= CA 02664010 2014-09-04 =
P4M 2.5G PXI-6120 A/D 4 channel 16bit, D/A 2 channel 16-hi; the type of the polarization controller 201-2 and the polarization modulator 202 is: OZ OPTICS EPC-400 EPC
DRIVER-04-RS232; the type of the phase controller 205-2 and the phase modulator 206:
OZ OPTICS FICE PZ-STD-FC/PC; the type of the photoelectric signal processing circuit 309-1: general two channel symmetrical photoelectric conversion amplifying circuit, the input range of the light: -20-45dBm, the output range: -3V-43V.
At this, the photoelectric signal processing circuit 309-1 is a photoelectric conversion output circuit, the polarization control host 201-1 in figure 2 implements the A/D 312, the photoelectric signal processing circuit 311 and the polarization controller 201, the polarization control host 201-1 integrates the A/D 312 converting circuit, the phase control host 205-1 implements the A/D 313, the photoelectric signal processing circuit 311 and the phase controller 205.
The monochromatic laser light emitted by the continuous monochromatic laser is transmitted to the Mach-Zehnder optical fiber interferometer via optical fiber, that optical fiber interferometer, as a continuous distributed vibration sensor, picks up the vibration signals of soil along the pipelines, and send them to the photoelectric signal processing circuit 309-1 via optical fiber. The phase control host 205-1, the phase controller 205-2, the photoelectric signal processing circuit 309-1 and the phase modulator 206 compose a phase fading closed control loop, such that the phase difference between the two strands of interference light waves formed by transmission on the optical fiber interferometer can be stabilized at the phase value required by the system. The polarization control host 201-1, the polarization controller 201-2, the photoelectric signal processing circuit 309-1 and the phase modulator 206 compose a polarization fading closed control loop, such that the polarization state difference between the two strands of interference light waves formed by transmission on the Mach-Zehnder optical fiber interferometer can be stabilized at the degree value required by the system.
Embodiment 2 The present example is an experimental prototype of the polarization fading control, the structure thereof is shown in figure 3, and the circuit thereof is shown in figure 4. The laser 101 is connected to the polarization scrambler 410 via optical fiber, and then connected to the multiplex demutiplexer 203 via optical fiber, the multiplex demutiplexer 203 associated with the multiplex demutiplexer 204 and three strands of optical fibers 1,2,3 compose a Mach-Zehnder optical fiber interferometer, the multiplex demutiplexer 203 is connected to the inputs of the polaroid analyzers 412 and 413 via optical fibers respectively, the outputs of the polaroid analyzers 412 and 413 are connected to the inputs of the polarization detectors 407 and 408 respectively, and the outputs of the polarization detectors 407 and 408 are connected to signal processing circuit 411 via electric signal wires, the output of the signal processing circuit 411 is connected to the polarization controller 201, the polarization controller 201 is electrically connected to the polarization modulator 202 via electric signal wires, and is connected via optical fiber to the phase modulator 206 connected in series between optical fiber lor optical fiber 2.
The type of the monochromatic laser 101 is: OHERAS ADJUSTIK HP El 5; the type of the polarization scrambler 410: IQS-5100B of EXFO company; the polaroid analyzers 412 and 413: POL-20-15-PP-1-0 of Phoenix Photonics company; the polarization detectors 407 and 408: polarization component detector PDD-001-13-SM-NC; the signal processing unit 409: is processed by the polarization control host.
Embodiment 3 The present example is an experimental prototype of the phasing fading control, the structure thereof is shown in figures 5 and 6. In the figures, the bold lines present the optical fibers, the fine lines present the electric wires. The specific structure is: the laser 101 is connected to the multiplex demutiplexer 203 via optical fiber, the multiplex demutiplexer 203 is connected to the two optical inputs of the photoelectric signal processing circuit 309-1 respectively via two optical fibers, the two electric outputs of the photoelectric signal processing circuit 309-1 are electrically connected to the inputs of the AID collecting cards 312 and 313 respectively, the outputs of the A/D
collecting cards 312 and 313 are connected to the signal demodulating host; the signal demodulating host has the function of the frequency mixer 517 which is input by signal generator 514, the filter 518, the signal processor 519, the filter 520, the signal demodulator 521; at the same time, the laser 101 is connected to the signal generator 513 via optical fiber, the output of signal generator 513 is connected to the input of the phase controller 205-2, the output of the phase controller 205-2 is connected to the phase modulator 206 which is connected in series between optical fiber 1 or optical fiber 2.
The type of the signal processing circuit 309-1 is: general circuit with two optical fibers as inputs; input range: -20--45bBm, output range: -3V¨+3V; the type of the A/D
collecting cards 312 and 313: PXI-5112, 2 channel, 100 MHZ, 32 MB/Channel, 8-bit; the type of the signal demodulating host 521-1: NI PXI-1042 8-Slot 3U CPU:PXI-8186 P4 2.2 I/O: NI; the type of the signal generator 513: Agilent33250A; the phase controller 205-2: OZ
OPTICS FICE PZ-STD-FC/PC; the phase modulator: OZ OPTICS FICE PZ-STD-FC/PC.
After converted by the photoelectric signal processing circuit 309-1, the interference signals are quantified by the A/D collecting cards 312 and 313, the signal generator 514 generates a modulated signal having amplitude A and frequency F, the modulated signal modulates the laser 101 or the phase modulator 206 on one of the interference arms of the modulation interferometer, producing a phase difference periodically changed in the interferometer, the two light outputs of the interferometer are detected and converted to electric signals by the photoelectric signal processing circuit 309-1, and then are sent to A/D
circuits 312 and 313, after that, the signals with frequency F are sent to the signal demodulation host to be frequency-mixed with the multiple frequency signal thereof. After being filtered, differential and integral calculation, and the addition and subtraction calculation, and then further being filtered, the signals are demodulated to the phase signal produced by the vibration of soil.
Industry Practicality The invention uses the ordinary communication optical fibers laid with the conduit in a same trench or buried underground near the architecture or important districts as the interference arms of the interferometer and transmission optical fibers, so as to form continuously distributed detection sensor of vibration of soil. The vibration signals of the soil nearby the detected object are steadily and reliably picked up, and then are sent to the location system, the occurred position where the event of vibration of soil nearby the =
=
detected object happens is calculated according to the difference between the transmission times of the two strands of the laser signals, and then is sent to a signal identification system so as to determine the feature and sort of the event leading to the vibration of soil. It can be sensed by digging the ground, touching the pipelines, welding at the pipelines, punching.
The location precision is high, the judgment on the feature of the event is exact, and no detection is missed, such that the function of safety early-warning of ministering the pipelines to avoid the happen of pipeline safety accidents. Any vibration signals of soil within 3 meters nearby the optical cables can be efficiently detected, the invention possess high sensitivity. The location precision is up to +10m, which can meet the requirement of the pipeline maintenance and emergency repair. A single system can detect the distance away from about 1201cm, by means of the communication system, a plurality of devices can be connected together to compose a integral seamless detection network, therefore, the detection distance of the invention can be determined according to the requirement.
The present system is not only adapted for using in the system for pipeline safety preventing and early-warning, but also adapted for using in other important architectures and districts for safety preventing and early-warning, for example, the system for safety protecting and early-warning, which is used for communication optical cables, traffic facilities, preservation district of cultural relics, armory, important organs and important industrial areas etc.
An industrial experiment is performed at the pipelines of the west-east gas transmission project at Dongqiao, Suzhou. The detected pipelines are 33.6 km long, the diameter of the pipelines is 01016, the pipelines are located at Yangtze River Regions, the soil is black soft silt, the optical cables are optical cables with silicon tube and are laid with the conduit in a same trench, the optical cables are buried upper-right above the gas direction, the buried depth of the silicon tube is about 1.5m. This segment to be detected passes through the Suzhou Industrial Park which has a plurality of building sites of workshops, bridges, roads etc. The pipelines pass through the plurality of roads and rivers, there are a lot of vibration sources along the pipelines, the environment of experiment site is very complicated. During the experiment, the optical fiber system for early-warning correctly early-warns 5 destroy events, wherein four events are made by workers adjusting the optical . .
, cables, one event is made by construction with machines: the optical fiber system for pipeline safety early-warning detects a vital destroy event at the distance 24.51(m away from Dongqiao, the maintainer arrives at the scene, and find that a digging machine is working above the conduit at the construction site away from the Dongqiao station 25km, the communication silicon tubes has been broken, the maintainer restraints the behavior of destroying the optical fiber pipelines.
Said photoelectric detectors 309 and 310, photoelectric signal processing circuit 309-1, photoelectric signal processing circuit 311, polarization controller 201, polarization control host 201-1, polarization controller 201-2, polarization modulator 202, phase controller 205, phase control host 205-1, phase controller 205-2 and the phase modulator 206 are all products on sale.
In figure 1, regarding three strands of optical fibers 1, 2 and 3, wherein optical fibers 1 and 2 are interference optical fibers, optical fiber 3 is transmission optical fiber, the multiplex demutiplexers 203 and 204 and optical fibers 1 and 2 compose the Mach-Zehnder optical fiber interferometer. The monochromatic laser 101 emits monochromatic laser beam, the monochromatic laser beam is transmitted to the multiplex demutiplexers 203 via optical fiber and then divided into two beams: One beam of the laser is incident at the multiplex demutiplexers 203 of the Mach-Zehnder optical fiber interferometer, and combined at the multiplex demutiplexers 204 to form interference light wave, the interference light wave is sent back to the multiplex demutiplexers 203 via optical fiber 3;
the other beam of the laser is transmitted to the multiplex demutiplexers 204 via optical fiber 3, and incident at the multiplex demutiplexers 204 of the Mach-Zehnder optical fiber interferometer, and combined at the multiplex demutiplexers 203 to form interference light waves.
After converted by the photoelectric detectors 309 and 310, the interference signal is analyzed by the photoelectric signal processing circuit 311. The average of the phase due to the disturbance of outside over a period of time is calculated through signal processing and calculation, the phase average is used to control the phase modulator 206 to compensate the phase, so as to counteract the influence of outside and make the interferometer working at a certain working point.
When ensuring the phase of the interferometer maintained at a certain working point, The photoelectric signal processing circuit 311 analyzes and calculates the variable amount of the polarization state of the interferometer to control the polarization controller 201 to send a modulated signal having a frequency F. The interferometer is modulated by the polarization modulator 202, so as to produce a modulated interference wave having a =
frequency F. The photoelectric detectors 309 and 310 detect the polarization state of the two strands of output light of the interferometer, and send them to the signal processing circuit 311 to calculate the polarization state of the interferometer. The polarization state of input light of the interferometer is modified by the polarization controller 201, therefore, the polarization controller 201, the polarization modulator 202 and the photoelectric signal processing circuit 311 form a polarization state closed control loop, such that the difference of polarization states between the two strands of interference light waves produced due to the transmission in the Mach-Zehnder optical fiber interferometer is maintained at the desired degree value of the system. In addition, when the polarization state of the interferometer is controlled, the phase difference between the two strands of interference signals detected at the interferometer will change irregularly, which will influence the location precision of the optical fiber system for safety early-warning. For this, the invention proposes to add a phase modulator 206 at any one of the interference arms of the interferometer, thus the photoelectric signal processing circuit 311 analyzes and calculates the change of the phase difference between the two strands of signals, then modifies the phase difference between the two strands of output signals of the interferometer, such that ensures the phase difference reach to the desired degree while the polarization state is adjusted.
The invention applies Twin Mach-Zehnder optical fiber interferometer, the longest length of the interferometer is up to about 80 km, the vibration signals of the soil long pipelines makes the phase of the interference light wave on the interferometer changed, so as to form a interference signal with vibration information. The principle base of the interferometric Mach-Zehnder optical fiber interferometer is that the interference of two beams of light. Two monochromatic waves are interfered when they vibrate in the same direction, and are not interfered when they vibrates at two directions perpendicular to each other, it can be deduced that, the two light are interfered partly in other circumstances. The directions of the polarization state of two beams of light shall be coincident to make the interference happen in the interferometer. In the principle, when the optical fiber is a perfect column, the polarization states are two modes that individually transmit and do not interfere with each other, but actually, the single-mode optical fiber manufactured is a =
unsymmetrical column. The interferometer applied in the optical fiber system for safety early-warning is the longest interferometer currently utilized, up to about 80 km. Since the environment along the pipelines of 80 km is very complicated, the changes of the phase and polarization of the light beam in the interference during the transmission are very complicated, the change of the pressure and temperature outside make the optical fiber curved or deformed, and the defects during the manufacture will also make the optical propagation constants in the two orthogonal directions different, resulting in the occurrence of so called birefringence, that is, the two polarization states are randomly coupled during the transmission, then, the polarization state of the light output from the optical fiber changes randomly, the interference effect can not be ensured when the two lights are overlapped, finally the signals output presents the blanked state randomly, such phenomena is called polarization fading phenomena. A phenomena is called as phase fading phenomena, wherein the phase of the interference light changes randomly during the polarization state changes randomly, resulting in the signal-to-noise of the system changes randomly, even the signal is fully blanked.
However, the active and passive laser devices applied in the optical fiber system for early-warning have such feature that the polarization and the phase are related, the control on the polarization of the interferometer will change the phase, and the control on the phase will change the polarization state. Therefore, it is one of the most important techniques that coordinately control the polarization and the phase to ensure the two beams of polarization light are interfered steadily and make the phase fading controlled under the requirement of the system.
The principle of the invention is that:
According to the invention, the two beams of polarization light transmitted on the optical fiber interferometer of the optical fiber system for safety early-warning have arbitrary polarization state and random phase, change the signal of light intensity output from the optical fiber interferometer after photoelectric conversion can be written as:
V +J' + J' COO + n + 00 ) (1) Equation (1) can be written as:
V = Vo + Vg cos(0, +0õ +00+ (2) = CA 02664010 2014-09-04 Wherein, V is the output voltage signal, Vg is the visibility of the interferometer, V,õ is the additional noise of the circuit, . is the signal of phase difference due to the acoustic wave of the vibration of soil, that is the signal of the acoustic wave of the vibration of soil to be detected, 00 is the initial phase of the interferometer, it is a constant, çb presents the drift in low frequency of the phase difference due to various interfere and noise, wherein, Vg and 0,, are variable values, which change along with the temperature and the environment outside.
Since the output polarization state of the optical fiber changes randomly due to the slightly curve and distortion of the optical fiber, and the change of environmental temperature, which reflects in the visibility Vg changing randomly between 0-1, when Vg is 0, the signal is fully blanked, this phenomenon is called as signal fading phenomenon induced by the polarization of the optical fiber interferometer.
Moreover, to be convenient in analyzing the problem, equation (2) can be written as:
V = A+V gcos(0, On) (3) Wherein, A=Vi+V 2+ , Vg = 2VV,V2 , is merged into On . Generally, the outside interfere signal 0,õ is a large low frequency signal, 0, is a small high frequency signal, when the signal has a small variation amount AO, :
AV Vg sin 0õ = AO, (4) Since the low frequency interfere 0,, changes randomly and largely, it is easy to learn from equation (4) that signal-to-noise output from the system changes, and when sin 0õ---0 , the signal is fully blanked. The phenomenon of the output signal of the interferometer rises and falls randomly along with the change of outside environment is called as the phase fading phenomenon of the interferometer.
When polarization state control individually performed on the interferometer, the phase of the interferometer will change accordingly. If the interferometer is performed the phase control individually, the polarization state of the interferometer will change accordingly. In addition, if the phase or the polarization state of the interferometer is = CA 02664010 2014-09-04 controlled, the phase difference between the two strands of interference signals detected at the interferometer changes irregularly, which will influence the location precision of the optical fiber of system for safety early-warning.
For these phenomenon, the invention proposes to monitor the polarization state of the interferometer and change of the phase difference between the two strands of interference signals detected at the interferometer, when compensating the phase of the interferometer of the optical fiber system for safety early-warning. The invention compensates and adjusts according to the variation value, such that the phase, polarization state and the phase difference between the two strands of signals of the interferometer reach to the optimal values required by the system.
The output signal of the optical fiber system for safety early-warning after photoelectric conversion is quantified by the A/D collecting card, and can be written as:
V = A +Vg cos(0, 0,7) (3) Generally, signal q5, is a high frequency signal, the outside interfere On is a low frequency signal, it can be obtained the average On of outside interfere On over a period of time by averaging equation (3) over that period of time. A phase modulator is added into one arm of the interferometer, and a feedback control voltage VF is added to the phase modulator, so as to produce control phase difference 0, to counteract the influence of outside interfere, such that the interferometer works at a certain working point, as the following equation:
0, = + 71-12 (n =0,1,2...) (5) When On changes, Oa changes accordingly. By adjusting them circularly, the working point of the hydrophone can be stabilized about 7-c /2, thereby the dependable and steady signal output can be obtained. Therefore, the working point of the system is stabilized at the most sensitive point all the time, such that the phase fading of the optical fiber system for safety early-warning can be overcome.
=
Embodiment 1 The detailed description of the invention will be described according to present embodiment and the invention will be further described. The present example is an experimental prototype, the structure thereof is shown in figures 1 and 2. In the figures, the bold lines present the optical fibers, the fine lines present the electric wires. The specific structure is: the polarization modulator 202 is connected in series between the laser 101 and the multiplex demultiplexer 203 via optical fibers, the multiplex demutiplexer 203 is connected to the two optical inputs of the photoelectric signal processing circuit 309-1 having two inputs/outputs via two optical fibers respectively, the two electric outputs of the photoelectric signal processing circuit 309-1 are connected to the input of a polarization control host 201-1 and the I/O of the phase controller 205-1 respectively, the output of the polarization control host 201-1 is connected to the input of the polarization controller 201-2, one strand of the outputs of the polarization controller 201-2 is connected to the input of a polarization modulator 202 and the other strand of the inputs of the polarization modulator 202 is connected to the input of a phase modulator 206 which is connected in series to optical fiber 1 or 2, the output of the phase control host 205-1 is connected to the input of a phase controller 205-2, the output of the phase controller 205-2 is connected to the input of another phase modulator 206 connected in series to optical fiber 1 or 2. In this electric schematic diagram, the photoelectric signal processing circuit 309-1 having two strands of inputs/outputs performs the function of two photoelectric detectors 309 and 310, A/D 312, AID 313 and the photoelectric signal processing circuit 311, the polarization control host 201-1 and the polarization controller 201-2 perform the function of the polarization controller 201, the phase control host 205-1 and the phase controller 205-2 perform the function of phase controller 205.
Wherein, the type of the single frequency laser is: KOHERAS ADJUSTIK HP E15;
the type of the multiplex demultiplexers 203 and 204 is:
WDM-A-2x2-1550-1-FC/UPC-3*54 of Langguang Company; the type of the polarization control host 201-1 is: NI PXI-1042 8-Slot 3U CPU: PXI-8186 P42.2 I/O: NI PXI-5112, 2 channel, 100 MHz, 32 MB/Channel, 8-bit; PXI-6111 AID 2 channel 12bit, D/A 2 channel 12 bit; the type of the phase control host 205-1 is: NI PXI-1050, PXI/SCXI CPU:
= CA 02664010 2014-09-04 =
P4M 2.5G PXI-6120 A/D 4 channel 16bit, D/A 2 channel 16-hi; the type of the polarization controller 201-2 and the polarization modulator 202 is: OZ OPTICS EPC-400 EPC
DRIVER-04-RS232; the type of the phase controller 205-2 and the phase modulator 206:
OZ OPTICS FICE PZ-STD-FC/PC; the type of the photoelectric signal processing circuit 309-1: general two channel symmetrical photoelectric conversion amplifying circuit, the input range of the light: -20-45dBm, the output range: -3V-43V.
At this, the photoelectric signal processing circuit 309-1 is a photoelectric conversion output circuit, the polarization control host 201-1 in figure 2 implements the A/D 312, the photoelectric signal processing circuit 311 and the polarization controller 201, the polarization control host 201-1 integrates the A/D 312 converting circuit, the phase control host 205-1 implements the A/D 313, the photoelectric signal processing circuit 311 and the phase controller 205.
The monochromatic laser light emitted by the continuous monochromatic laser is transmitted to the Mach-Zehnder optical fiber interferometer via optical fiber, that optical fiber interferometer, as a continuous distributed vibration sensor, picks up the vibration signals of soil along the pipelines, and send them to the photoelectric signal processing circuit 309-1 via optical fiber. The phase control host 205-1, the phase controller 205-2, the photoelectric signal processing circuit 309-1 and the phase modulator 206 compose a phase fading closed control loop, such that the phase difference between the two strands of interference light waves formed by transmission on the optical fiber interferometer can be stabilized at the phase value required by the system. The polarization control host 201-1, the polarization controller 201-2, the photoelectric signal processing circuit 309-1 and the phase modulator 206 compose a polarization fading closed control loop, such that the polarization state difference between the two strands of interference light waves formed by transmission on the Mach-Zehnder optical fiber interferometer can be stabilized at the degree value required by the system.
Embodiment 2 The present example is an experimental prototype of the polarization fading control, the structure thereof is shown in figure 3, and the circuit thereof is shown in figure 4. The laser 101 is connected to the polarization scrambler 410 via optical fiber, and then connected to the multiplex demutiplexer 203 via optical fiber, the multiplex demutiplexer 203 associated with the multiplex demutiplexer 204 and three strands of optical fibers 1,2,3 compose a Mach-Zehnder optical fiber interferometer, the multiplex demutiplexer 203 is connected to the inputs of the polaroid analyzers 412 and 413 via optical fibers respectively, the outputs of the polaroid analyzers 412 and 413 are connected to the inputs of the polarization detectors 407 and 408 respectively, and the outputs of the polarization detectors 407 and 408 are connected to signal processing circuit 411 via electric signal wires, the output of the signal processing circuit 411 is connected to the polarization controller 201, the polarization controller 201 is electrically connected to the polarization modulator 202 via electric signal wires, and is connected via optical fiber to the phase modulator 206 connected in series between optical fiber lor optical fiber 2.
The type of the monochromatic laser 101 is: OHERAS ADJUSTIK HP El 5; the type of the polarization scrambler 410: IQS-5100B of EXFO company; the polaroid analyzers 412 and 413: POL-20-15-PP-1-0 of Phoenix Photonics company; the polarization detectors 407 and 408: polarization component detector PDD-001-13-SM-NC; the signal processing unit 409: is processed by the polarization control host.
Embodiment 3 The present example is an experimental prototype of the phasing fading control, the structure thereof is shown in figures 5 and 6. In the figures, the bold lines present the optical fibers, the fine lines present the electric wires. The specific structure is: the laser 101 is connected to the multiplex demutiplexer 203 via optical fiber, the multiplex demutiplexer 203 is connected to the two optical inputs of the photoelectric signal processing circuit 309-1 respectively via two optical fibers, the two electric outputs of the photoelectric signal processing circuit 309-1 are electrically connected to the inputs of the AID collecting cards 312 and 313 respectively, the outputs of the A/D
collecting cards 312 and 313 are connected to the signal demodulating host; the signal demodulating host has the function of the frequency mixer 517 which is input by signal generator 514, the filter 518, the signal processor 519, the filter 520, the signal demodulator 521; at the same time, the laser 101 is connected to the signal generator 513 via optical fiber, the output of signal generator 513 is connected to the input of the phase controller 205-2, the output of the phase controller 205-2 is connected to the phase modulator 206 which is connected in series between optical fiber 1 or optical fiber 2.
The type of the signal processing circuit 309-1 is: general circuit with two optical fibers as inputs; input range: -20--45bBm, output range: -3V¨+3V; the type of the A/D
collecting cards 312 and 313: PXI-5112, 2 channel, 100 MHZ, 32 MB/Channel, 8-bit; the type of the signal demodulating host 521-1: NI PXI-1042 8-Slot 3U CPU:PXI-8186 P4 2.2 I/O: NI; the type of the signal generator 513: Agilent33250A; the phase controller 205-2: OZ
OPTICS FICE PZ-STD-FC/PC; the phase modulator: OZ OPTICS FICE PZ-STD-FC/PC.
After converted by the photoelectric signal processing circuit 309-1, the interference signals are quantified by the A/D collecting cards 312 and 313, the signal generator 514 generates a modulated signal having amplitude A and frequency F, the modulated signal modulates the laser 101 or the phase modulator 206 on one of the interference arms of the modulation interferometer, producing a phase difference periodically changed in the interferometer, the two light outputs of the interferometer are detected and converted to electric signals by the photoelectric signal processing circuit 309-1, and then are sent to A/D
circuits 312 and 313, after that, the signals with frequency F are sent to the signal demodulation host to be frequency-mixed with the multiple frequency signal thereof. After being filtered, differential and integral calculation, and the addition and subtraction calculation, and then further being filtered, the signals are demodulated to the phase signal produced by the vibration of soil.
Industry Practicality The invention uses the ordinary communication optical fibers laid with the conduit in a same trench or buried underground near the architecture or important districts as the interference arms of the interferometer and transmission optical fibers, so as to form continuously distributed detection sensor of vibration of soil. The vibration signals of the soil nearby the detected object are steadily and reliably picked up, and then are sent to the location system, the occurred position where the event of vibration of soil nearby the =
=
detected object happens is calculated according to the difference between the transmission times of the two strands of the laser signals, and then is sent to a signal identification system so as to determine the feature and sort of the event leading to the vibration of soil. It can be sensed by digging the ground, touching the pipelines, welding at the pipelines, punching.
The location precision is high, the judgment on the feature of the event is exact, and no detection is missed, such that the function of safety early-warning of ministering the pipelines to avoid the happen of pipeline safety accidents. Any vibration signals of soil within 3 meters nearby the optical cables can be efficiently detected, the invention possess high sensitivity. The location precision is up to +10m, which can meet the requirement of the pipeline maintenance and emergency repair. A single system can detect the distance away from about 1201cm, by means of the communication system, a plurality of devices can be connected together to compose a integral seamless detection network, therefore, the detection distance of the invention can be determined according to the requirement.
The present system is not only adapted for using in the system for pipeline safety preventing and early-warning, but also adapted for using in other important architectures and districts for safety preventing and early-warning, for example, the system for safety protecting and early-warning, which is used for communication optical cables, traffic facilities, preservation district of cultural relics, armory, important organs and important industrial areas etc.
An industrial experiment is performed at the pipelines of the west-east gas transmission project at Dongqiao, Suzhou. The detected pipelines are 33.6 km long, the diameter of the pipelines is 01016, the pipelines are located at Yangtze River Regions, the soil is black soft silt, the optical cables are optical cables with silicon tube and are laid with the conduit in a same trench, the optical cables are buried upper-right above the gas direction, the buried depth of the silicon tube is about 1.5m. This segment to be detected passes through the Suzhou Industrial Park which has a plurality of building sites of workshops, bridges, roads etc. The pipelines pass through the plurality of roads and rivers, there are a lot of vibration sources along the pipelines, the environment of experiment site is very complicated. During the experiment, the optical fiber system for early-warning correctly early-warns 5 destroy events, wherein four events are made by workers adjusting the optical . .
, cables, one event is made by construction with machines: the optical fiber system for pipeline safety early-warning detects a vital destroy event at the distance 24.51(m away from Dongqiao, the maintainer arrives at the scene, and find that a digging machine is working above the conduit at the construction site away from the Dongqiao station 25km, the communication silicon tubes has been broken, the maintainer restraints the behavior of destroying the optical fiber pipelines.
Claims (3)
1. An optical fiber system for safety early-warning for at least one of a phase fading control and a polarization fading control, comprising:
three strands of optical fibers laid with a conduit in a same trench;
a Mach-Zehnder optical fiber interferometer comprising two of the three strands of optical fibers, and two multiplex demultiplexers, wherein a first of the two multiplex demultiplexers is connected to a second of the two multiplex demultiplexers by means of the three strands of optical fibers;
a laser;
a polarization modulator connected in series via first and second optical fibers between the laser and the first multiplex demultiplexer, respectively;
a first photoelectric detector and a second photoelectric detector connected to the first multiplex demultiplexer via third and fourth optical fibers, respectively;
a first A/D (analog to digital) converting circuit and a second A/D converting circuit electrically connected to outputs of the first photoelectric detector and the second photoelectric detector, respectively;
a photoelectric signal processing circuit connected to outputs of the first and second A/D converting circuits;
a polarization controller connected to one output of the photoelectric signal processing circuit, a first output of the polarization controller being connected to the polarization modulator;
a phase modulator connected in series to at least one of the two of the three strands of optical fibers, the phase modulator being connected to a second output of the polarization controller; and a phase controller connected to another output of the photoelectric signal processing circuit, an output of the phase controller being connected to the phase modulator, wherein the phase controller, the photoelectric signal processing circuit and the phase modulator realize a feedback control of phase fading, so a phase difference between two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired value, wherein the polarization controller, the polarization modulator, the phase modulator and the photoelectric signal processing circuit compose a polarization fading closed control loop, so a difference of polarization states between the two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired degree.
three strands of optical fibers laid with a conduit in a same trench;
a Mach-Zehnder optical fiber interferometer comprising two of the three strands of optical fibers, and two multiplex demultiplexers, wherein a first of the two multiplex demultiplexers is connected to a second of the two multiplex demultiplexers by means of the three strands of optical fibers;
a laser;
a polarization modulator connected in series via first and second optical fibers between the laser and the first multiplex demultiplexer, respectively;
a first photoelectric detector and a second photoelectric detector connected to the first multiplex demultiplexer via third and fourth optical fibers, respectively;
a first A/D (analog to digital) converting circuit and a second A/D converting circuit electrically connected to outputs of the first photoelectric detector and the second photoelectric detector, respectively;
a photoelectric signal processing circuit connected to outputs of the first and second A/D converting circuits;
a polarization controller connected to one output of the photoelectric signal processing circuit, a first output of the polarization controller being connected to the polarization modulator;
a phase modulator connected in series to at least one of the two of the three strands of optical fibers, the phase modulator being connected to a second output of the polarization controller; and a phase controller connected to another output of the photoelectric signal processing circuit, an output of the phase controller being connected to the phase modulator, wherein the phase controller, the photoelectric signal processing circuit and the phase modulator realize a feedback control of phase fading, so a phase difference between two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired value, wherein the polarization controller, the polarization modulator, the phase modulator and the photoelectric signal processing circuit compose a polarization fading closed control loop, so a difference of polarization states between the two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired degree.
2. An optical fiber system for safety early-warning for a polarization fading control, comprising:
three strands of optical fibers laid with a conduit in a same trench;
a Mach-Zehnder optical fiber interferometer comprising two of the three strands of optical fibers, and two multiplex demultiplexers, wherein a first of the two multiplex demultiplexers is connected to a second of the two multiplex demultiplexers by means of the three strands of optical fibers;
a laser;
a polarization scrambler connected in series via first and second optical fibers between the laser and the first multiplex demultiplexer, respectively;
a first polaroid analyzer and a second polaroid analyzer connected to the first multiplex demultiplexer via third and fourth optical fibers, respectfully;
a first polarization detector and a second polarization detector connected to outputs of the first polaroid analyzer and the second polaroid analyzer, respectively;
a signal processing circuit connected via electrical signal wires to outputs of the first and second polarization detectors;
a polarization controller connected to one output of the signal processing circuit, a first output of the polarization controller being electrically connected to the polarization scrambler; and a phase modulator connected in series to at least one of the two of the three strands of optical fibers, the phase modulator being connected via a fifth optical fiber to a second output of the polarization controller;
wherein the polarization controller, the polarization scrambler, the phase modulator and the signal processing circuit compose a polarization fading closed control loop, so a difference of polarization states between the two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired degree.
three strands of optical fibers laid with a conduit in a same trench;
a Mach-Zehnder optical fiber interferometer comprising two of the three strands of optical fibers, and two multiplex demultiplexers, wherein a first of the two multiplex demultiplexers is connected to a second of the two multiplex demultiplexers by means of the three strands of optical fibers;
a laser;
a polarization scrambler connected in series via first and second optical fibers between the laser and the first multiplex demultiplexer, respectively;
a first polaroid analyzer and a second polaroid analyzer connected to the first multiplex demultiplexer via third and fourth optical fibers, respectfully;
a first polarization detector and a second polarization detector connected to outputs of the first polaroid analyzer and the second polaroid analyzer, respectively;
a signal processing circuit connected via electrical signal wires to outputs of the first and second polarization detectors;
a polarization controller connected to one output of the signal processing circuit, a first output of the polarization controller being electrically connected to the polarization scrambler; and a phase modulator connected in series to at least one of the two of the three strands of optical fibers, the phase modulator being connected via a fifth optical fiber to a second output of the polarization controller;
wherein the polarization controller, the polarization scrambler, the phase modulator and the signal processing circuit compose a polarization fading closed control loop, so a difference of polarization states between the two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired degree.
3. An optical fiber system for safety early-warning for phase fading control comprising:
three strands of optical fibers laid with a conduit in a same trench;
a Mach-Zehnder optical fiber interferometer comprising two of the three strands of optical fibers, and two multiplex demultiplexers, wherein a first of the two multiplex demultiplexers is connected to a second of the two multiplex demultiplexers by means of the three strands of optical fibers, a laser, a first output of which is connected via a first optical fiber to the first multiplex demultiplexer ;
a first photoelectric detector and a second photoelectric detector connected to the first multiplex demultiplexer via second and third optical fibers, respectively;
a first A/D (analog to digital) collecting card and a second A/D collecting card connected via electric wires to outputs of the first photoelectric detector and the second photo electric detector, respectively;
a signal demodulating host including:
a frequency mixer connected to outputs of the first and second A/D collecting cards; and a signal generator to which an output is connected to the frequency mixer, a first filter connected to an output of the frequency mixer, a signal processor connected to an output of the first filter, a second filter connected to an output of the signal processor, and a signal demodulator connected to an output of the second filter,;
a signal generator connected to a second output of the laser;
a phase modulator connected to at least one of the two of the three strands of optical fibers, the phase modulator being connected an output of the signal generator;
and a phase controller connected to an output of the signal generator, an output of the phase controller being connected to the phase modulator, wherein the phase controller, the signal demodulating host and the phase modulator realize a feedback control of phase fading, so a phase difference between two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired value.
three strands of optical fibers laid with a conduit in a same trench;
a Mach-Zehnder optical fiber interferometer comprising two of the three strands of optical fibers, and two multiplex demultiplexers, wherein a first of the two multiplex demultiplexers is connected to a second of the two multiplex demultiplexers by means of the three strands of optical fibers, a laser, a first output of which is connected via a first optical fiber to the first multiplex demultiplexer ;
a first photoelectric detector and a second photoelectric detector connected to the first multiplex demultiplexer via second and third optical fibers, respectively;
a first A/D (analog to digital) collecting card and a second A/D collecting card connected via electric wires to outputs of the first photoelectric detector and the second photo electric detector, respectively;
a signal demodulating host including:
a frequency mixer connected to outputs of the first and second A/D collecting cards; and a signal generator to which an output is connected to the frequency mixer, a first filter connected to an output of the frequency mixer, a signal processor connected to an output of the first filter, a second filter connected to an output of the signal processor, and a signal demodulator connected to an output of the second filter,;
a signal generator connected to a second output of the laser;
a phase modulator connected to at least one of the two of the three strands of optical fibers, the phase modulator being connected an output of the signal generator;
and a phase controller connected to an output of the signal generator, an output of the phase controller being connected to the phase modulator, wherein the phase controller, the signal demodulating host and the phase modulator realize a feedback control of phase fading, so a phase difference between two interference optical waves transmitted on the Mach-Zehnder optical fiber interferometer is stabilized at a desired value.
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| Application Number | Priority Date | Filing Date | Title |
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| CN200610090901XA CN101692137B (en) | 2006-06-30 | 2006-06-30 | Optical-fiber security early-warning polarization-phase combined control system |
| CN200610090599.8 | 2006-06-30 | ||
| CN200610090901.X | 2006-06-30 | ||
| CNB2006100905998A CN100487509C (en) | 2006-06-30 | 2006-06-30 | Optical fiber safety early warning polarization control system |
| CNB2006100905926A CN100460913C (en) | 2006-06-30 | 2006-06-30 | Optical fiber safety early warning phase control system |
| CN200610090592.6 | 2006-06-30 | ||
| PCT/CN2007/001866 WO2008003224A1 (en) | 2006-06-30 | 2007-06-13 | An optical fiber control system for safety early-warning |
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2007
- 2007-06-13 WO PCT/CN2007/001866 patent/WO2008003224A1/en active Application Filing
- 2007-06-13 CA CA2664010A patent/CA2664010C/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CA2664010A1 (en) | 2008-01-10 |
| WO2008003224A1 (en) | 2008-01-10 |
| WO2008003224A9 (en) | 2009-05-28 |
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