CN102706368A - 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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- CN102706368A CN102706368A CN2012101555107A CN201210155510A CN102706368A CN 102706368 A CN102706368 A CN 102706368A CN 2012101555107 A CN2012101555107 A CN 2012101555107A CN 201210155510 A CN201210155510 A CN 201210155510A CN 102706368 A CN102706368 A CN 102706368A
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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 present invention relates to a kind of failure detection schemes of optical cable metal sheath layer, belong to technical field of measurement and test.
Background technology
In communication engineering, all kinds of optical cables (land is with optical cable, submarine optical fiber cable) have been widely used in the communication trunk circuit.Because various factor of natural environment and human factor, communications optical cable usually is damaged.The common types of damage of communications optical cable is divided into two kinds: the light unit damages and restrictive coating damages.Statistical data showed in the past: restrictive coating damages if fail in time to repair, with the damage that causes the light unit probably.The detection and location of optical cable interior lights cell failure at present can be passed through OTDR, and technology such as BOTDR realize.But in the time can utilizing light signal that optical cable is carried out localization of fault, fault is very serious, tends to cause communication disruption.Therefore the optical cable applying unit hopes when the cable jacket layer is damaged, just can detects and locate, thereby repair, and prevents the further deterioration of fault.
Present 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 the both has shortcoming: the insulation resistance detection method is that the cable jacket layer is applied a dc high voltage; Through observing the fault that the leakage current numerical value change judges whether that insulation reduces, still but can't make the location to the 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 the TEM ripple may reside in the cable jacket structure; So can adopt the potential pulse reflectometry that the optical cable metal sheath layer is carried out fault detect, but if adopt monopulse, because decay as detectable signal; The signal of reflected impulse usually is submerged among the 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 all 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 be a kind of under the precondition that does not reduce spatial resolution, improve the method for system signal noise ratio.
Summary of the invention
Technical matters:The purpose of this invention is to provide a kind of method of the optical cable metal sheath layer being carried out fault detect; This method uses 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 the metal sheath layer of optical cable being carried out fault detect based on the unipolarity matrix coder; Emission unipolarity coded sequence pulse in tested optical cable; Gather the reflected impulse signal through data acquisition system (DAS); Behind the treated analysis-reduction signal,, draw the position of trouble spot through reading the mistiming between incident pulse and the reflected impulse;
Detection method may further comprise the steps:
1) utilize software to generate the 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 the corresponding unipolarity train pulse of row matrix vector in signal generator generation and the step 1), element " 0 " representes that with zero level " 1 " is represented with high level, this unipolarity train pulse is inputed to modulate circuit as detectable signal; Modulate circuit is imported train pulse in the protective metal shell of optical cable to be measured, simultaneously with train pulse as trigger pip; Modulate circuit receives the pulse signal that reflects in the optical cable to be measured, and data acquisition system (DAS) is got off data acquisition simultaneously;
3) data that collect are carried out signal Processing; Signal processing method is: signal is carried out after the displacement progressive mean again; Use software that the signal of handling is carried out the waveform image reduction, the signal after the 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 the cable jacket layer through the mistiming between direct impulse and the reflected impulse on the measured waveform image;
5) can roughly judge cable jacket layer fault type through the identification of waveform shape: if reflected impulse polarity is identical with direct impulse polarity, then fracture defect appears in restrictive coating; If reflected impulse polarity is opposite with direct impulse polarity, then the cable jacket layer possibly make moist here.
The said software generation unipolarity encoder matrix mode of utilizing is following:
Wherein
is the Hardmrd matrix of lowest-order;
is
rank Hardmrd matrix,
be
rank Hardmrd matrix; It is thus clear that the Hardmrd matrix is made up of the two kinds of elements in " 1 " " 1 ";
Carry out reversal then, will own " 1 " and be changed to " 0 " entirely, bipolarity Hadamard matrix just becomes the unipolarity matrix like this:
is that i is capable in the Hardmrd matrix; The j column element;
for the Hardmrd matrix carry out reversal after i capable, the j column element;
First row, the first row all elements of
all is " 0 ", with obtaining its maximum nonzero minor after the first row deletion of first row:
" 0 " element in the matrix is represented with low level " 1 " element shows that with the voltage pulse meter detection range below 5 kilometers uses the 5V voltage pulse signal, detection range uses the 10V voltage pulse signal more than 5 kilometers;
Use signal generator that each row vector in the s-matrix is emitted in the cable jacket layer to be measured with the mode of train pulse successively, and data acquisition is got off with data collecting card.
Described signal processing method; Be to use the unipolarity coded pulse as detectable signal; Carrying out the signal decoding reduction through the data that the data capture card is collected handles; Retrieving algorithm is: add up after the signal displacement and ask average, the signal after the reduction has higher signal to noise ratio (S/N ratio), and the signal waveform that reduction obtains more is prone to identification.
Beneficial effect:Propose a kind of the optical cable metal sheath layer to be carried out the method for localization of fault, this method uses coded pulse as detectable signal, can not improve signal power and not reduce under the precondition of spatial resolution, effectively reduces to measure noise and improve system signal noise ratio.
Description of drawings
Fig. 1 is the optical cable protective metal shell fault detection system schematic diagram among the present invention.
Fig. 2 carries out the effect contrast figure of localization of fault for adopting monopulse to same optical cable protective metal shell as detectable signal as the employing coded pulse of detectable signal and the present invention's proposition.A is the monopulse probe response; B is the coded pulse probe response.
Embodiment
Optical cable metal sheath layer fault detection method based on the unipolarity coded pulse of the present invention may further comprise the steps:
1) utilize software to generate the 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 the corresponding unipolarity train pulse of row matrix vector in signal generator generation and the step 1), it is inputed to modulate circuit as detectable signal; Modulate circuit is imported train pulse in the protective metal shell of optical cable to be measured, simultaneously with train pulse as trigger pip; Modulate circuit receives the pulse signal that reflects in the optical cable to be measured, and data acquisition system (DAS) is got off data acquisition simultaneously;
3) data that collect are carried out signal Processing; Signal processing method is for carrying out after the displacement progressive mean again to signal; Use software that the signal of handling is carried out the waveform image reduction, the signal after the 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 the cable jacket layer through the mistiming between direct impulse and the reflected impulse on the measured waveform image,
5) can roughly judge cable jacket layer fault type through the identification of waveform shape: if reflected impulse polarity is identical with direct impulse polarity, then fracture defect appears in restrictive coating; If reflected impulse polarity is opposite with direct impulse polarity, then the cable jacket layer possibly make moist here.
Specify preferred embodiment of the present invention below in conjunction with accompanying drawing.
1, at first generate a Hadamard matrix through software, its make is shown below:
Wherein
is the Hardmrd matrix of lowest-order;
is
rank Hardmrd matrix,
be
rank Hardmrd matrix.It is thus clear that the Hardmrd matrix is made up of the two kinds of elements in " 1 " " 1 ".
Carry out reversal then, will own " 1 " and be changed to " 0 " entirely, bipolarity Hadamard matrix just becomes the unipolarity matrix like this:
First row, the first row all elements of
all is " 0 ", with obtaining its maximum nonzero minor after the first row deletion of first row:
2, through the signal generator in the accompanying drawing 1 each row vector in the s-matrix is emitted to (this cable jacket layer is done truncation at 6 km places in advance) in the optical cable metal sheath layer to be measured with the mode of train pulse successively; Pulse polarity is a positive polarity, and with data collecting card data acquisition is got off.
3, the data that collect are carried out the signal reduction through software approach; The single pulse that obtains equivalence is surveyed oscillogram; Should the equivalence oscillogram and monopulse test design sketch compare and can find (shown in Figure 2); The signal power of equivalence oscillogram does not change, but noise power had more originally descended, and had effectively promoted system signal noise ratio.Simultaneously, reflected signal is more prone to identification, just can obtain the position of trouble spot through reading mistiming between reflected impulse and the reflected impulse.
Can find out from accompanying drawing 2 that 4, reflected impulse polarity is identical with incident pulse polarity, explain that fracture defect appears in restrictive coating, be consistent with actual conditions.
Claims (3)
1. optical cable metal sheath layer fault detection method based on the unipolarity coded pulse is characterized in that detection method may further comprise the steps:
1) utilize software to generate the 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 the corresponding unipolarity train pulse of row matrix vector in signal generator generation and the step 1), element " 0 " representes that with zero level " 1 " is represented with high level, this unipolarity train pulse is inputed to modulate circuit as detectable signal; Modulate circuit is imported train pulse in the protective metal shell of optical cable to be measured, simultaneously with train pulse as trigger pip; Modulate circuit receives the pulse signal that reflects in the optical cable to be measured, and data acquisition system (DAS) is got off data acquisition simultaneously;
3) data that collect are carried out signal Processing; Signal processing method is: signal is carried out after the displacement progressive mean again; Use software that the signal of handling is carried out the waveform image reduction, the signal after the 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 the cable jacket layer through the mistiming between direct impulse and the reflected impulse on the measured waveform image;
5) can roughly judge cable jacket layer fault type through the identification of waveform shape: if reflected impulse polarity is identical with direct impulse polarity, then fracture defect appears in restrictive coating; If reflected impulse polarity is opposite with direct impulse polarity, then the cable jacket layer possibly make moist here.
2. the optical cable metal sheath layer fault detection method based on the unipolarity coded pulse according to claim 1 is characterized in that the said software generation unipolarity encoder matrix mode of utilizing is following:
Wherein
is the Hardmrd matrix of lowest-order;
is
rank Hardmrd matrix,
be
rank Hardmrd matrix; It is thus clear that the Hardmrd matrix is made up of the two kinds of elements in " 1 " " 1 ";
Carry out reversal then, will own " 1 " and be changed to " 0 " entirely, bipolarity Hadamard matrix just becomes the unipolarity matrix like this:
First row, the first row all elements of
all is " 0 ", with obtaining its maximum nonzero minor after the first row deletion of first row:
" 0 " element in the matrix is represented with low level " 1 " element shows that with the voltage pulse meter detection range below 5 kilometers uses the 5V voltage pulse signal, detection range uses the 10V voltage pulse signal more than 5 kilometers;
Use signal generator that each row vector in the s-matrix is emitted in the cable jacket layer to be measured with 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 the unipolarity coded pulse according to claim 1; It is characterized in that described signal processing method; Be to use the unipolarity coded pulse as detectable signal, carry out the signal decoding reduction through the data that the data capture card is collected and handle, retrieving algorithm is: add up after the signal displacement and ask average; Signal after the reduction has higher signal to noise ratio (S/N ratio), and the signal waveform that reduction obtains more is prone to identification.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112653522A (en) * | 2020-12-15 | 2021-04-13 | 成都陆迪盛华科技有限公司 | Encoding device and method of optical time domain reflectometer |
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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2012
- 2012-05-18 CN CN201210155510.7A patent/CN102706368B/en not_active Expired - Fee Related
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 (4)
| Title |
|---|
| WILLIAM K.PRATT,ETC: "Hadamard Transform Image Coding", 《PROCEEDINGS OF THE IEEE》 * |
| XIA YANG,ETC: "Fault Location for Underground Power Cable Using Distributed Parameter Approach", 《IEEE TRANSACTIONS ON POWER SYSTEMS》 * |
| 仇胜美: "海底光缆故障判定及测试方法", 《海洋工程》 * |
| 殷杰: "海底光缆护套层故障监测技术", 《光纤与电缆及其应用技术》 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112653522A (en) * | 2020-12-15 | 2021-04-13 | 成都陆迪盛华科技有限公司 | Encoding device and method of optical time domain reflectometer |
| 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 |
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