CN102706368B - Optical cable metal sheath layer fault detection method based on unipolar coded pulses - Google Patents
Optical cable metal sheath layer fault detection method based on unipolar coded pulses Download PDFInfo
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Abstract
The invention discloses a fault detection method for an optical cable metal sheath layer based on unipolar coded pulses, which takes the pulse time domain reflection principle as the fundamental principle. The method provided by the invention comprises the following steps of: taking the unipolar coded pulses as detection signals, wherein element quadratic sum of a unipolar matrix inversion matrix is less than order of the unipolar matrix inversion matrix; gathering the signals by a data gathering card; performing signal decoding reduction treatment; finding positions of fault points by reading time differences between transmitting signals and reflected signals; and approximately judging the fault type of the optical cable metal sheath layer by identifying a wave shape. The method provided by the invention can effectively detect the fault of the optical cable metal sheath layer.
Description
Technical field
The failure detection schemes that the present invention relates to a kind of optical cable metal sheath layer, belongs to technical field of measurement and test.
Background technology
In communication engineering, all kinds of optical cables (optical cable, submarine optical fiber cable for land) have been widely used in communication trunk circuit.Due to various factor of natural environment and human factor, communications optical cable is usually damaged.The common types of damage of communications optical cable is divided into two kinds: light unit damages and restrictive coating damages.Statistical data showed in the past: fail to repair in time if restrictive coating damages, will probably cause the damage of light unit.The detection and location of optical cable interior lights cell failure at present can be passed through OTDR, and the technology such as BOTDR are realized.But in the time can utilizing light signal to carry out localization of fault to optical cable, fault is very serious, tends to cause communication disruption.Therefore optical cable applying unit wishes, in the time that cable jacket layer is damaged, just can detects and locate, thereby repaired, and prevents the further deterioration of fault.
Current existing cable jacket layer fault detection method has: insulation resistance detection method and sound are visited method.These two kinds of methods can detecting optical cable metal sheath layer insulation fault, but both there is shortcoming: insulation resistance detection method is that cable jacket layer is applied to a DC high voltage, the fault that judges whether that by observing leakage current numerical value change insulation reduces, but but cannot make location to trouble spot, sound spy method needs staff's hand hold transducer along optical cable wiring path manual detection, workload is huge, in growing apart from fiber optic cable maintenance work, is difficult to carry out.
Find under study for action, because TEM ripple may reside in cable jacket structure, so can adopt potential pulse reflectometry to carry out fault detect to optical cable metal sheath layer, if but adopt monopulse as detectable signal, due to decay, the signal of reflected impulse is usually submerged among noise, is difficult to identification.For addressing this problem, usually adopt two kinds of methods: the power that 1, improves pulse; 2, strengthen the width of pulse.But these two kinds of methods have irremediable shortcoming: the power of pulse can not infinitely increase, and when increasing pulse power, also can increase correlation noise; Strengthen pulse width and can sacrifice spatial resolution, can not adopt this method of the very high occasion of localization of fault accuracy requirement.Therefore, need a kind of reduction under the precondition of spatial resolution, improve the method for system signal noise ratio.
Summary of the invention
technical matters:the object of this invention is to provide a kind of method of optical cable metal sheath layer being carried out to fault detect, the method is used coded pulse as detectable signal, can not improve signal power and not reduce under the precondition of spatial resolution, effectively reduce and measure noise raising system signal noise ratio.
technical scheme:the present invention is a kind of method of based on unipolarity matrix coder, the metal sheath layer of optical cable being carried out fault detect, in tested optical cable, launch the pulse of unipolarity coded sequence, gather reflected impulse signal by data acquisition system (DAS), after treated analysis-reduction signal, by reading the mistiming between incident pulse and reflected impulse, draw the position of trouble spot;
Detection method comprises the following steps:
1) utilize Software Create unipolarity encoder matrix, this matrix has such mathematical feature: the quadratic sum of its inverse matrix element is less than this order of matrix number;
2) utilize signal generator to produce and the vectorial corresponding unipolarity train pulse of row matrix in step 1), element " 0 " represents by zero level, and " 1 " represents with high level, this unipolarity train pulse is inputed to modulate circuit as detectable signal; Modulate circuit is inputted train pulse in the protective metal shell of optical cable to be measured, simultaneously using train pulse as trigger pip; Modulate circuit receives the pulse signal reflecting in optical cable to be measured, and data acquisition system (DAS) is got off data acquisition simultaneously;
3) data that collect are carried out to signal processing, signal processing method is: signal is carried out after displacement to progressive mean again, use software to carry out waveform image reduction to the signal of processing, the signal after reduction has higher signal to noise ratio (S/N ratio), and the identification of waveform image is better;
4) calculate the position of trouble spot in cable jacket layer by the mistiming between direct impulse and reflected impulse on measured waveform image;
5) can roughly judge cable jacket layer fault type by the identification of waveform shape: if reflected impulse polarity is identical with direct impulse polarity, fracture defect appears in restrictive coating; If reflected impulse polarity is contrary with direct impulse polarity, cable jacket layer may make moist herein.
The described Software Create unipolarity encoder matrix mode of utilizing is as follows:
Wherein
for the Hardmrd matrix of lowest-order,
for
rank Hardmrd matrix,
for
rank Hardmrd matrix; Visible Hardmrd matrix is made up of two kinds of " 1 " " 1 " element;
Then carry out reversal, will own " 1 " and entirely be changed to " 0 ", bipolarity Hadamard matrix just becomes unipolarity matrix like this:
，
for i in Hardmrd matrix is capable, j column element,
for Hardmrd matrix carry out reversal after i capable, j column element;
the first row first row all elements be all " 0 ", after will the first row first row deleting, obtain its maximum nonzero minor:
" 0 " element in matrix is represented by low level, and " 1 " element shows with voltage pulse meter, 5 kilometers of following detection ranges use 5V voltage pulse signals, and more than 5 kilometers detection range uses 10V voltage pulse signal;
Use signal generator that each row vector in s-matrix is emitted in cable jacket layer to be measured by the mode of train pulse successively, and data acquisition is got off with data collecting card.
Described signal processing method, to use unipolarity coded pulse as detectable signal, carrying out signal decoding reduction by the data that data collecting card is collected processes, retrieving algorithm is: cumulative being averaging after signal displacement, signal after reduction has higher signal to noise ratio (S/N ratio), the easier identification of signal waveform that reduction obtains.
beneficial effect:propose a kind of method of optical cable metal sheath layer being carried out to localization of fault, the method is used coded pulse as detectable signal, can not improve signal power and not reduce under the precondition of spatial resolution, effectively reduces and measures noise raising system signal noise ratio.
Brief description of the drawings
Fig. 1 is the optical cable protective metal shell fault detection system schematic diagram in the present invention.
Fig. 2 adopts monopulse as detectable signal, same optical cable protective metal shell to be carried out the effect contrast figure of localization of fault as the employing coded pulse of detectable signal and the present invention's proposition.A is monopulse probe response; B is coded pulse probe response.
Embodiment
Optical cable metal sheath layer fault detection method based on unipolarity coded pulse of the present invention comprises the following steps:
1) utilize Software Create unipolarity encoder matrix, this matrix has such mathematical feature: the element quadratic sum of its inverse matrix is less than this order of matrix number;
2) utilize signal generator to produce the unipolarity train pulse corresponding with row matrix vector in step 1), set it as detectable signal and input to modulate circuit; Modulate circuit is inputted train pulse in the protective metal shell of optical cable to be measured, simultaneously using train pulse as trigger pip; Modulate circuit receives the pulse signal reflecting in optical cable to be measured, and data acquisition system (DAS) is got off data acquisition simultaneously;
3) data that collect are carried out to signal processing, signal processing method is for carrying out after displacement progressive mean again to signal, use software to carry out waveform image reduction to the signal of processing, the signal after reduction has higher signal to noise ratio (S/N ratio), and the identification of waveform image is better;
4) calculate the position of trouble spot in cable jacket layer by the mistiming between direct impulse and reflected impulse on measured waveform image,
5) can roughly judge cable jacket layer fault type by the identification of waveform shape: if reflected impulse polarity is identical with direct impulse polarity, fracture defect appears in restrictive coating; If reflected impulse polarity is contrary with direct impulse polarity, cable jacket layer may make moist herein.
Describe preferred embodiment of the present invention in detail below in conjunction with accompanying drawing.
1, first by Hadamard matrix of Software Create, its make is shown below:
Wherein
for the Hardmrd matrix of lowest-order,
for
rank Hardmrd matrix,
for
rank Hardmrd matrix.Visible Hardmrd matrix is made up of two kinds of " 1 " " 1 " element.
Then carry out reversal, will own " 1 " and entirely be changed to " 0 ", bipolarity Hadamard matrix just becomes unipolarity matrix like this:
，
for i in Hardmrd matrix is capable, j column element,
for Hardmrd matrix carry out reversal after i capable, j column element.
the first row first row all elements be all " 0 ", after will the first row first row deleting, obtain its maximum nonzero minor:
2, by the signal generator in accompanying drawing 1, each row vector in s-matrix is emitted to (this cable jacket layer does truncation at 6 km places in advance) in optical cable metal sheath layer to be measured by the mode of train pulse successively, pulse polarity is positive polarity, and data acquisition is got off with data collecting card.
3, the data that collect are carried out to signal reduction by software approach, obtain equivalent single pulse and survey oscillogram, this equivalence oscillogram and monopulse test design sketch is compared and can find (shown in Fig. 2), the signal power of equivalence oscillogram does not change, but noise power had more originally declined, effectively promote system signal noise ratio.Meanwhile, reflected signal is more prone to identification, just can obtain the position of trouble spot by reading mistiming between reflected impulse and reflected impulse.
4, from accompanying drawing 2, can find out, reflected impulse polarity is identical with incident pulse polarity, illustrates that fracture defect appears in restrictive coating, is consistent with actual conditions.
Claims (3)
1. the optical cable metal sheath layer fault detection method based on unipolarity coded pulse, is characterized in that detection method comprises the following steps:
1) utilize Software Create unipolarity encoder matrix, this matrix has such mathematical feature: the quadratic sum of its inverse matrix element is less than this order of matrix number;
2) utilize signal generator to produce and the vectorial corresponding unipolarity train pulse of row matrix in step 1), element " 0 " represents by zero level, and " 1 " represents with high level, this unipolarity train pulse is inputed to modulate circuit as detectable signal; Modulate circuit is inputted train pulse in the protective metal shell of optical cable to be measured, simultaneously using train pulse as trigger pip; Modulate circuit receives the pulse signal reflecting in optical cable to be measured, and data acquisition system (DAS) is got off data acquisition simultaneously;
3) data that collect are carried out to signal processing, signal processing method is: signal is carried out after displacement to progressive mean again, use software to carry out waveform image reduction to the signal of processing, the signal after reduction has higher signal to noise ratio (S/N ratio), and the identification of waveform image is better;
4) calculate the position of trouble spot in cable jacket layer by the mistiming between direct impulse and reflected impulse on measured waveform image;
5) roughly judge cable jacket layer fault type by the identification of waveform shape: if reflected impulse polarity is identical with direct impulse polarity, fracture defect appears in restrictive coating; If reflected impulse polarity is contrary with direct impulse polarity, cable jacket layer may make moist herein.
2. the optical cable metal sheath layer fault detection method based on unipolarity coded pulse according to claim 1, is characterized in that the described Software Create unipolarity encoder matrix mode of utilizing is as follows:
H
0=[-1]
Wherein H
0for the Hardmrd matrix of lowest-order,
be 2
krank Hardmrd matrix,
be 2
k-1rank Hardmrd matrix; Visible Hardmrd matrix is made up of two kinds of " 1 " " 1 " element;
Then carry out reversal, will own " 1 " and entirely be changed to " 0 ", bipolarity Hadamard matrix just becomes unipolarity matrix like this:
H
ijfor i in Hardmrd matrix is capable, j column element, s
ijfor Hardmrd matrix carry out reversal after i capable, j column element;
The first row first row all elements of S' is all " 0 ", obtains its maximum nonzero minor after the first row first row is deleted:
" 0 " element in matrix is represented by low level, and " 1 " element shows with voltage pulse meter, 5 kilometers of following detection ranges use 5V voltage pulse signals, and more than 5 kilometers detection range uses 10V voltage pulse signal;
Use signal generator that each row vector in s-matrix is emitted in cable jacket layer to be measured by the mode of train pulse successively, and data acquisition is got off with data collecting card.
3. the optical cable metal sheath layer fault detection method based on unipolarity coded pulse according to claim 1, it is characterized in that described signal processing method, to use unipolarity coded pulse as detectable signal, carrying out signal decoding reduction by the data that data collecting card is collected processes, retrieving algorithm is: cumulative being averaging after signal displacement, signal after reduction has higher signal to noise ratio (S/N ratio), the easier identification of signal waveform that reduction obtains.
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| CN112653522B (en) * | 2020-12-15 | 2022-01-14 | 成都陆迪盛华科技有限公司 | Encoding device and method of optical time domain reflectometer |
| CN115412163A (en) * | 2022-09-21 | 2022-11-29 | 佛山市冰蓝科技有限公司 | System and method for detecting and positioning breakpoints of field optical cables |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4370610A (en) * | 1978-08-30 | 1983-01-25 | Bicc Public Limited Company | Locating sheath faults in underground power supply cables |
| CN2096074U (en) * | 1991-07-06 | 1992-02-12 | 天津电力试验研究所 | Fault detector for rubber-plastic cable outer sheath damage |
| CN1598607A (en) * | 2004-08-20 | 2005-03-23 | 淄博博鸿电气有限公司 | Directional and positioning testing device for fault of direct application type cable sheath |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4370610A (en) * | 1978-08-30 | 1983-01-25 | Bicc Public Limited Company | Locating sheath faults in underground power supply cables |
| CN2096074U (en) * | 1991-07-06 | 1992-02-12 | 天津电力试验研究所 | Fault detector for rubber-plastic cable outer sheath damage |
| CN1598607A (en) * | 2004-08-20 | 2005-03-23 | 淄博博鸿电气有限公司 | Directional and positioning testing device for fault of direct application type cable sheath |
Non-Patent Citations (8)
| Title |
|---|
| Fault Location for Underground Power Cable Using Distributed Parameter Approach;Xia Yang,etc;《IEEE TRANSACTIONS ON POWER SYSTEMS》;20081130;第23卷(第4期);第1809～1816页 * |
| Hadamard Transform Image Coding;WILLIAM K.PRATT,etc;《PROCEEDINGS OF THE IEEE》;19690131;第57卷(第1期);第58～66页 * |
| WILLIAM K.PRATT,etc.Hadamard Transform Image Coding.《PROCEEDINGS OF THE IEEE》.1969,第57卷(第1期),第58～66页. |
| Xia Yang,etc.Fault Location for Underground Power Cable Using Distributed Parameter Approach.《IEEE TRANSACTIONS ON POWER SYSTEMS》.2008,第23卷(第4期),第1809～1816页. |
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