CN113691307A - OPGW fault positioning and early warning method based on BOTDR and OTDR - Google Patents
OPGW fault positioning and early warning method based on BOTDR and OTDR Download PDFInfo
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Abstract
The invention provides an OPGW optical cable fault positioning and early warning method based on BOTDR and OTDR, which comprises the following steps: selecting a plurality of vacant fiber cores of the OPGW optical cable, and respectively testing the loss and Brillouin frequency shift data of the vacant fiber cores by using the OTDR and the BOTDR; determining a welding point based on Brillouin frequency shift data of a plurality of vacant fiber cores; corresponding the determined welding point to the welding tower position in the tower information so as to position the welding tower and the strain constant region; based on the loss of the plurality of spare fiber cores obtained through testing and the corresponding relation between the welding points and the welding tower positions, identifying loss points, larger than a first threshold value, at non-welding points as candidate fault points; and if the candidate fault point is located in the strain abnormal area, early warning of the fault point is carried out, and the type of the early warning is the first type. The method can provide a more accurate early warning means for the operation of the OPGW optical cable, accurately positions the areas with abnormal strain and attenuation, and has important significance.
Description
Technical Field
The invention belongs to the field of Optical Fiber communication, and particularly relates to a fault positioning and early warning method for an OPGW (Optical Fiber Composite Overhead Ground Wire) based on a Brillouin Optical Time-Domain Reflectometer (BOTDR) and an OTDR (Optical Time-Domain Reflectometer (OTDR)).
Background
The electric power OPGW optical cable has the functions of information communication and ground wire, is the basis of power grid production scheduling and enterprise information management, and plays an important role in an electric power system. By 8 months in 2019, the total mileage of the OPGW optical cable of the first-level backbone network in China reaches 8.79 kilometers, and nearly 58 percent of the OPGW optical cable is built in 2003, and the operation life of the OPGW optical cable exceeds 15 years to date.
The OPGW optical cable is easy to be influenced by natural environments such as ice coating, strong wind waving and temperature due to the specific erection mode, so that the OPGW optical cable breaks down. The OPGW optical cable is generally reserved with the excess length of optical fiber of 6-7 per mill during manufacturing so as to overcome the optical fiber overstrain caused by the cable body elongation caused by the reasons of initial elongation, maximum meteorological load, creep deformation and the like during the long-term operation of the optical cable. When the OPGW optical cable is subjected to external force (including ice coating, wind pressure, temperature and the like), the optical cable is stretched, the optical fiber moves towards the inner side, no additional attenuation is generated when the optical fiber is not strained in the excess length range, and if the excess length is exhausted, the optical fiber shows stress to influence the transmission performance or break the optical fiber; when the ambient temperature is lowered, the optical cable contracts and the optical fiber moves outward, and in the moving process, the optical fiber is not bent relative to the loose tube, so that additional loss is not generated, and if the optical fiber is bent, the additional loss is generated. At present, the BOTDA and BOTDR techniques have been applied to the strain test of the optical fiber inside the OPGW optical cable, and a significant test effect is obtained. In 2012, Tengling et al performed tensile test on OPGW optical cables of various structures including layer stranded type and central tube type, and analyzed the changes of transmission performance and optical fiber stress of the optical cables in the process of deformation under the action of external force. The experimental results show that as the tension increases, the strain also increases. When the optical fiber is stressed, the optical power and the OTDR are difficult to measure the change of the optical fiber transmission performance. According to the analysis of the BOTDA monitoring data, the optical fiber strain increase can be known to occur only at a certain point, not the uniform strain of each point on the whole optical fiber, the strain condition of the optical fiber in the OPGW optical cable is monitored by using the BOTDA, and a good early warning effect can be indirectly exerted on the mechanical property change condition of the optical cable. In 2013, Yangyu and the like perform theoretical analysis and experimental research on the strain of the special electric optical cable and the optical fiber, and combine BOTDA test data to obtain that the additional attenuation of the optical cable is still kept within +/-0.05 dB before the optical cable is subjected to 80% RTS under the action of external force and is not broken, the optical fiber of the optical cable generates large strain, and the longer the duration of the strain is, the larger the influence on the optical cable is.
The optical fiber attenuation refers to the optical power loss in the optical fiber within a certain length distance, and as the transmission distance increases, the average optical power gradually decreases, and the reliability of the transmission performance also decreases. Therefore, the attenuation of the optical signal determines the transmission quality of the optical fiber, and the failure of the optical fiber is also often reflected in the attenuation change. Therefore, during the operation and maintenance of the power communication system, the OTDR is regularly used for testing the optical fiber attenuation.
Generally, the maintenance method of the OPGW optical cable is to perform an attenuation test by using OTDR, but actually, the optical fiber interruption caused by stress is instantaneous, and an early attenuation test cannot be used to perform effective early warning. The OPGW optical cable is formed by welding a section of optical cable, usually a fault occurs at the welding point of a certain optical cable section, and after the attenuation of the optical cable at the fault section is homogenized by the test result of the whole line, the optical cable cannot show obvious abnormity in the final average attenuation, so that the fault early warning of the OPGW optical cable cannot be comprehensively carried out by simply utilizing the OTDR. The strain data of the line can be obtained by simply using the BOTDR, but whether the attenuation of the strain abnormal area is abnormal or not cannot be judged, and comprehensive and effective safety early warning cannot be realized. In conclusion, the daily maintenance means can only realize the positioning and analysis of the fault when the core is broken or the communication fault occurs, and can not provide more detailed and reliable fault early warning.
Disclosure of Invention
In order to solve the problems, the invention provides an OPGW (optical fiber composite overhead ground wire) cable fault positioning and early warning method based on BOTDR and OTDR (optical time domain reflectometer), so as to solve the defects in the prior art.
The invention provides an OPGW optical cable fault positioning and early warning method based on BOTDR and OTDR, which comprises the following steps: selecting a plurality of vacant fiber cores of an OPGW optical cable, and respectively testing attenuation and Brillouin frequency shift data of the vacant fiber cores by using OTDR and BOTDR; determining a welding point based on Brillouin frequency shift data of the plurality of vacant fiber cores; corresponding the determined welding point to the welding tower position in the tower information so as to position the welding tower and the strain constant region; based on the loss of the plurality of spare fiber cores obtained through testing and the corresponding relation between the welding points and the welding tower positions, identifying loss points, larger than a first threshold value, at non-welding points as candidate fault points; and if the candidate fault point is located in the strain abnormal area, early warning of the fault point is carried out, and the type of the early warning is the first type.
Further, the method further comprises: obtaining an abnormal loss point which is larger than a second threshold value in an OTDR test result, and judging whether the abnormal loss point is caused by strain or not; and if the abnormal loss point is positioned at the welding point of the stressed optical cable section, early warning of a fault point is carried out, and the type of the early warning is a second type.
Further, the method further comprises: the brillouin frequency shift data is converted into strain data by equation (1):
in the formula,. DELTA.vBThe Brillouin frequency shift change quantity caused by temperature and strain,
and
selecting the Brillouin frequency shift of the optical fiber at the down lead as a temperature reference point for the temperature coefficient and the strain coefficient of the Brillouin frequency shift, and realizing the separation of strain and temperature; drawing the strain data and the average attenuation of each section of the OTDR test result in a curve to realize a strain-attenuation corresponding curve; the strain and attenuation early warning threshold value of the OPGW optical cable is drawn in the strain-attenuation corresponding curve so as to provide the corresponding relation between the strain value and the attenuation value of each section of the optical cable and the threshold value,and if the strain and the attenuation exceed a third threshold, early warning of a fault point is carried out, and the type of the early warning is a third type.
Further, the step of determining the fusion joint based on the brillouin frequency shift data of the plurality of vacant cores includes: and drawing the measured Brillouin frequency shift data of the plurality of vacant fiber cores in the same graph to obtain the jumping points existing in a plurality of Brillouin frequency shift curves in the graph as welding points.
Further, the step of corresponding the determined welding point to the welding tower position in the tower information to position the welding tower and the emergency change region includes: and drawing a tower diagram in an equal proportion of 1:1 by combining tower information, drawing the tower diagram and the drawn Brillouin frequency shift diagram in the same diagram, and corresponding the determined welding points to the welding towers one by one to obtain a welding tower corresponding diagram, so that the accurate positioning of the welding towers and the accurate positioning of the abnormal strain area are realized.
Further, the step of testing the plurality of vacant cores for attenuation includes: obtaining the OTDR attenuation curve and the loss point, and the average attenuation value between the adjacent loss points.
Further, the candidate failure point is determined by: drawing an OTDR attenuation curve and a corresponding graph of a welded tower in equal proportion, and identifying a loss point exceeding a first threshold value at a non-welded point as a candidate fault point by combining a Brillouin spectrum, an OTDR autonomously determined loss point and the graph of the welded tower; the first threshold is 0.02 dB.
Further, the second threshold is 0.3 dB.
Further, the third threshold comprises a strain threshold and a decay threshold, wherein the strain threshold is 0.1%, and the decay threshold is 105% of the decay average value of the non-stressed region.
The fault location and early warning of the OPGW optical cable are carried out by combining BOTDR and OTDR technologies, a more accurate early warning means is provided for the operation of the OPGW optical cable, and the method has important significance. According to the scheme, the areas with abnormal strain and attenuation can be accurately positioned, the loss point exceeding 0.02dB at the non-welding point and the large loss point exceeding 0.3dB at the welding point of the optical cable section where the abnormal strain area is located can be judged, meanwhile, the strain value and the attenuation value of the abnormal strain area can be compared with the third safety threshold respectively, and fault early warning and positioning of the optical cable are achieved.
In summary, the invention has the following beneficial effects:
(1) the fault positioning and early warning method combining the BOTDR and OTDR technologies can realize positioning of a welded tower and segmentation of an optical cable, realize accurate positioning of a strain abnormal area, realize segmentation and calculation of strain capacity by using BOTDR data, and obtain attenuation information of each section of a line, particularly a strain section by using OTDR. And comparing the strain and attenuation values with corresponding early warning thresholds to realize the fault early warning of abnormal strain and attenuation.
(2) The invention can distinguish the loss point at the non-welding position, judge whether the loss point is related to the stress of the optical cable, and early warn if the loss point is related to the stress of the optical cable.
(3) The invention can distinguish the loss point more than 0.3dB, judge the relation between the large loss point and the strain abnormal area, and realize the early warning of the fault if the loss point more than 0.3dB is positioned in the strain abnormal area.
(4) The OTDR measures the length of an optical fiber, and due to the influence of factors such as excess length of the optical fiber, line sag, down lead and the like, the measured distance of the OTDR is different from the span of a welded tower, which may affect the maintenance of a fault point. The invention can accurately position the welding point and provides great convenience for line maintenance. Meanwhile, the phenomena of line changing, tower increasing and the like exist in the later maintenance process of the OPGW line, information recorded by the tower detail list may not be complete, and the phenomena have great influence on line maintenance and operation and maintenance. The BOTDR is used for measuring Brillouin frequency shift jump, so that a welding point can be identified, the welding point is calibrated by matching with an OTDR attenuation event point, and an important reference is provided for maintaining and verifying a tower detail list.
(5) And establishing a large database of OPGW optical cable operation conditions with multiple dimensions of strain, attenuation and the like, and providing a comprehensive early warning means.
(6) Strain and attenuation data of a C station-D station line are obtained by using BOTDR and OTDR technologies in 8 months in 2020, as shown in FIG. 3, a strain abnormal area of the line is located at a fusion joint of an optical cable, namely, a 157# tower, and loss of 0.342dB is generated, and at the beginning of 1 month in 2021 year, a 15-core 157# tower of the line generates optical receiving-free alarm in a transmission fiber core and is consistent with the strain and attenuation abnormal position height measured by people.
Drawings
Fig. 1 is a flowchart illustrating an exemplary process of an OPGW optical cable fault location and early warning method based on BOTDR and OTDR according to the present invention;
fig. 2A is a schematic overall principle diagram illustrating an embodiment of a fault location and early warning method for an OPGW optical cable based on BOTDR and OTDR in the present invention, where: 1-multiple fiber core Brillouin frequency shift, 2-welding points judged by Brillouin frequency shift jumping points, 3-pole tower diagrams, event points above 4-0.02dB, loss points above 0.02dB of 5-non-welding points, event points above 6-0.3dB, 7-Brillouin frequency shift abnormal areas, 8-Brillouin frequency spectrum jumping points, vertical straight line segments corresponding to pole towers and loss points;
fig. 2B is an enlarged view showing the correspondence of reference numeral 2 in fig. 2A;
fig. 3 is a flowchart illustrating another exemplary process of the BOTDR and OTDR based OPGW optical cable fault location and early warning method of the present invention;
fig. 4 is a flowchart illustrating another exemplary process of the OPGW optical cable fault location and early warning method based on BOTDR and OTDR according to the present invention;
fig. 5 is a diagram showing the correspondence of strain to attenuation, in which: 1-strain early warning threshold, 2-attenuation early warning threshold, 3-strain abnormal region, 4-strain curve and 5-attenuation curve;
fig. 6 is a specific example of the OPGW optical cable fault location and early warning method based on BOTDR and OTDR of the present invention.
Detailed Description
Exemplary embodiments of the present invention will be described hereinafter with reference to the accompanying drawings. In the interest of clarity and conciseness, not all features of an actual implementation are described in the specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the device structures and/or processing steps closely related to the solution according to the present invention are shown in the drawings, and other details not so relevant to the present invention are omitted.
The embodiment of the invention discloses an OPGW optical cable fault positioning and early warning method based on BOTDR and OTDR, which comprises the following steps: selecting a plurality of vacant fiber cores of an OPGW optical cable, and respectively testing attenuation and Brillouin frequency shift data of the vacant fiber cores by using OTDR and BOTDR; determining a welding point based on Brillouin frequency shift data of the plurality of vacant fiber cores; corresponding the determined welding point to the welding tower position in the tower information so as to position the welding tower and the strain constant region; based on the obtained attenuation of the plurality of vacant fiber cores and the corresponding relation between the welding points and the welding tower positions, identifying loss points, larger than a first threshold value, at non-welding points as candidate fault points; and if the candidate fault point is located in the strain abnormal area, early warning of the fault point is carried out, and the type of the early warning is the first type.
In the following, some embodiments of the invention are described separately.
Fig. 1 shows an exemplary processing flow of the OPGW optical cable fault location and early warning method based on BOTDR and OTDR of the present invention.
As shown in fig. 1, in step 1, a plurality of vacant fiber cores of an OPGW optical cable are selected, and the OTDR and BOTDR are used to test the loss and brillouin frequency shift data of the plurality of vacant fiber cores, respectively.
For example, the spare cores of the OPGW optical cable may be selected in the substation communication room, and the number of the spare cores may be 2, 3 or more, may be all the spare cores, or may be part of the spare cores.
And respectively testing attenuation and Brillouin frequency shift data of the vacant fiber core by using the OTDR and the BOTDR, and storing complete test data according to the number of the test fiber core.
For example, the fiber core selected in step 1 should be a vacant fiber core without service occupation, the OTDR should test the lengths and attenuations of all vacant fiber cores, and identify loss points, and main event point information such as average loss, end reflection, core breakage and the like of adjacent loss points, where an event point judged in the OTDR report is a point where the loss is greater than 0.02dB, usually a fusion point, and meanwhile, a loss point exceeding 0.3dB in the OTDR report is highlighted, and the stored test result should include an attenuation curve graph (i.e., an OTDR attenuation curve), an event table, average loss of adjacent loss points (i.e., cross-section attenuation) and the like. The BOTDR should be used for testing the lengths and Brillouin frequency shifts of all fiber cores, and the stored data should include main data such as positions and Brillouin frequency shift values.
Next, in step 2, the fusion point is determined based on the brillouin frequency shift data of the plurality of vacant cores.
For example, the plurality of core brillouin frequency shift data measured in step 1 may be plotted in the same graph, as shown in 1 in fig. 2A, and if at least one trip point exists in a plurality of brillouin frequency shift curves at a certain position in the graph, it may be determined that the point is a fusion point, as shown in 513# and 493# towers 2 in fig. 2A and 2B.
In the embodiment of the invention, step 2 is to compare several groups of Brillouin frequency shift curves drawn by drawing software, and mainly compare and observe the step-shaped jump points, because the step-shaped jump points do not appear after two sections of optical fibers with similar Brillouin frequency shifts are welded, Brillouin frequency shifts of a plurality of fiber cores need to be compared, the position can be judged as a welding point when one Brillouin frequency shift jump appears, Brillouin frequency shift jumping points can be more accurately identified by more Brillouin frequency shift data as much as possible, and the welding tower can be more accurately positioned.
In step 3, the determined welding point corresponds to the welding tower position in the tower information so as to position the welding tower and the emergency change area.
For example, a tower diagram can be drawn in an equal proportion of 1:1 by combining tower information, as shown in 3 in fig. 2A, the tower diagram and the brillouin frequency shift diagram drawn in step 2 are drawn in the same diagram, the welding points determined in step 2 correspond to the welding towers one by one, a corresponding diagram of the welding towers is obtained, and accurate positioning of the welding towers and accurate positioning of abnormal strain areas are achieved.
In one example, step 3 is combined with tower information to draw a tower diagram, image comparison is carried out on the tower diagram and the Brillouin frequency shift diagram drawn in step 2 in an equal proportion of 1:1, a vertical straight line segment is drawn at all the Brillouin spectrum jump points, and the corresponding relation between the vertical straight line segment and the tower diagram is observed. Because newly-added poles and towers may not be recorded in the pole and tower detailed list, brillouin frequency shift jump positions may not correspond to poles and towers, and the poles and towers can be rechecked to operation and maintenance personnel at the home or on-site, and meanwhile, the calibration of pole and tower information can be realized. Here, 7 in fig. 2A is a brillouin frequency shift abnormal region corresponding to a strain abnormal region in spatial position, that is, the brillouin frequency shift abnormal region is a strain abnormal region.
In this way, in step 4, based on the loss of the plurality of vacant fiber cores and the corresponding relation between the welding points and the welding tower positions obtained through testing, the brillouin frequency shift data is combined, and loss points with non-welding points larger than a first threshold value are identified and used as candidate fault points; and if the candidate fault point is located in the strain abnormal area, early warning of the fault point is carried out, and the type of the early warning is the first type.
For example, the OTDR attenuation curve obtained in step 1 and the welding tower corresponding diagram obtained in step 3 may be drawn in equal proportion, and a brillouin spectrum, a loss point autonomously determined by OTDR, and the welding tower diagram are combined, so that a loss point exceeding 0.02dB (as an example of a first threshold) at a non-welding point may be identified, as shown in 5 in fig. 2A, if the loss point is located in a strain abnormal region, a fault point early warning is performed, and the type is counted as the early warning type one, that is, the first type described above.
Therefore, by comparing the loss point autonomously determined by using the OTDR in the step 4 with the corresponding map of the welding tower obtained in the step 3, the loss point at the non-welding position can be identified, the relation between the loss point and the abnormal strain area is compared, whether the loss point is caused by strain or not is judged, and if yes, early warning is carried out (early warning type I).
Fig. 3 shows another exemplary process flow of the OPGW optical cable fault location and early warning method based on BOTDR and OTDR of the present invention.
As shown in fig. 3, this processing flow includes step 5 in addition to steps 1 to 4 shown in fig. 1.
In step 5, obtaining an abnormal loss point which is greater than a second threshold value in the OTDR test result, and judging whether the abnormal loss point is caused by strain; and if the abnormal loss point is positioned at the welding point of the stressed optical cable section, early warning of a fault point is carried out, and the type of the early warning is a second type.
For example, the abnormal loss point highlighted and marked in the OTDR report obtained in step 1 and greater than 0.3dB may be marked in the image obtained in step 4 by using a cross, as shown in fig. 2A at 6, to achieve accurate positioning of the abnormal loss point, and determine whether the loss is related to the stress, and if the abnormal loss point is located at the fusion splice of the stressed optical cable segment, perform fault point early warning, and count as the early warning type two, that is, the second type described above.
Therefore, in this embodiment, by comparing the loss point exceeding 0.3dB (as an example of the second threshold value) determined autonomously by the OTDR in step 5 with the brillouin frequency shift data measured by the BOTDR, the relationship between the large loss point and the strain abnormal region can be visually observed, whether the large loss point is in the strain abnormal region or the welding point at both ends is observed, whether the large loss point is related to the stress is determined, and if so, an early warning is performed (early warning type two).
Fig. 4 shows another exemplary processing flow of the OPGW optical cable fault location and early warning method based on BOTDR and OTDR of the present invention. As shown in FIG. 4, in this example, steps 6 to 8 are included in addition to steps 1 to 5 shown in FIG. 3.
In step 6, the brillouin frequency shift data obtained in step 1 is converted into strain data by equation (1):
in the formula, Δ T is the amount of change in temperature, Δ ∈ is the amount of change in stress (amount of strain), and Δ vBThe Brillouin frequency shift change quantity caused by temperature and strain,
and
for example, the temperature coefficient and the strain coefficient of the brillouin frequency shift may be 1.12MHz/° c and 0.0482 MHz/. mu.epsilon.respectively, and the brillouin frequency shift of the optical fiber at the down-lead (i.e. the down-lead is the optical cable down from the top of the tower for fusion) is selected as a temperature reference point, so as to realize the separation of the strain and the temperature.
In the step 6, the formula (1) is a relational expression of Brillouin frequency shift, temperature and strain, and a good linear relation is formed between the Brillouin frequency shift and the temperature and the strain. From the fusion points determined in step 3, the brillouin frequency shift value at the down-lead of each optical cable section can be obtained (the optical cable at the down-lead is not in principle stressed), and this value is used as the brillouin frequency shift change amount affected only by temperature, and is set as Δ νB1The expression is shown as formula (2).
The temperature compensated Brillouin frequency shift change amount can be obtained by subtracting the formula (1) and the formula (2), and the strain amount of the line can be obtained by dividing the temperature compensated Brillouin frequency shift change amount by the strain coefficient, as shown in the formula (3).
In step 7, the strain data obtained in step 6 and the average attenuation of each segment of the OTDR test result obtained in step 4 are plotted in a curve to realize a strain-attenuation corresponding curve.
For example, step 7 may divide the attenuation data measured by the OTDR into segments with adjacent welding points as boundaries according to the welding points determined in step 3, form a segmented attenuation curve, and plot the attenuation curve and the strain curve in a graph to realize a strain-attenuation curve.
In step 8, a strain and attenuation early warning threshold value of the OPGW optical cable is drawn in the strain-attenuation corresponding curve obtained in step 7, as shown in fig. 51 and 2, to provide a corresponding relationship between the strain value and the attenuation value of each optical cable and the early warning value, so as to facilitate direct observation, and when providing strain and attenuation abnormality early warning, the accurate positioning of the optical cable in the relevant section is directly realized by combining fig. 2A and 2B, and if the strain and the attenuation exceed a third threshold value, fault point early warning is performed and the type of early warning is a third type (or called early warning type three).
It should be noted that the first threshold, the second threshold, and the third threshold may be determined according to empirical values, for example, or may be determined by an experimental method, and are not described herein again.
The strain and attenuation early warning threshold set in step 8 is influenced by the type, material and structure of the cable, and is not a fixed value. When the strain and attenuation exceed the early warning threshold, positioning of strain and attenuation abnormal points can be realized by combining the results of fig. 2A and 2B, and fault early warning and positioning of the OPGW optical cable are realized.
In the embodiment of the invention, the OTDR can be used for testing the vacant fiber core so as to eliminate the fiber core damaged by the port flange, complete data including an event waveform diagram, an event table and the like are stored, and a proper fiber core is selected for the BOTDR test. And then testing by using a BOTDR, storing data, drawing a Brillouin spectrum, and primarily confirming the welding points and the positions thereof by using the stepped jump points of the Brillouin spectrum of different fiber cores. And then, drawing and comparing the OTDR image and the Brillouin spectrum in an equal proportion of 1:1, drawing a vertical straight line segment at all the jump points of the Brillouin spectrum, observing the corresponding relation between the vertical straight line segment and the OTDR attenuation points, and further confirming the welding points and the positions of the welding points. And finally, drawing a tower diagram in an equal proportion of 1:1 by combining tower information, comparing the tower diagram with the previously drawn diagram, observing the corresponding relation between the towers and the vertical line sections, and finally determining all the welding points and the positions thereof if the tower diagram corresponds to the vertical line sections one by one, or finally determining the welding points and the positions thereof by site reconnaissance if the difference is too large. Meanwhile, the event point of 0.02dB at the loss point and the non-fusion point of the strain abnormal region exceeding 0.3dB and the position of the event point are determined, and if the event point of the non-fusion point in the strain abnormal region or the optical cable section of the strain abnormal region has a large loss point of more than 0.3dB, fault early warning is carried out.
The method comprises the steps of calculating a strain quantity distribution diagram of the whole line by using a Brillouin frequency shift curve measured by BOTDR (Brillouin optical time Domain reflectometer) according to a Brillouin frequency shift value at a down conductor as a temperature reference, arranging the attenuation of each divided section and the strain quantity curve measured by the BOTDR in a graph by combining with an OTDR report, analyzing the relation between the strain, the attenuation and an early warning value, and carrying out early warning if the strain quantity is greater than the early warning value.
Claims (8)
1. An OPGW optical cable fault positioning and early warning method based on BOTDR and OTDR is characterized by comprising the following steps:
selecting a plurality of vacant fiber cores of an OPGW optical cable, and respectively testing the loss and Brillouin frequency shift data of the vacant fiber cores by using OTDR and BOTDR;
determining a welding point based on Brillouin frequency shift data of the plurality of vacant fiber cores;
corresponding the determined welding point to the welding tower position in the tower information so as to position the welding tower and the strain constant region;
based on the loss of the plurality of spare fiber cores obtained through testing and the corresponding relation between the welding points and the welding tower positions, identifying loss points, larger than a first threshold value, at non-welding points as candidate barrier points; and if the candidate obstacle point is located in the strain abnormal area, early warning of the fault point is carried out, and the type of the early warning is a first type.
2. The OPGW optical cable fault location and early warning method based on BOTDR and OTDR as claimed in claim 1, wherein the method further comprises:
obtaining an abnormal loss point which is larger than a second threshold value in an OTDR test result, and judging whether the abnormal loss point is caused by strain or not; and if the abnormal loss point is positioned at the welding point of the stressed optical cable section, early warning of a fault point is carried out, and the type of the early warning is a second type.
3. The OPGW optical cable fault location and early warning method based on BOTDR and OTDR as claimed in claim 1 or 2, characterized in that the method further comprises:
converting the brillouin frequency shift data to strain data by:
in the formula,. DELTA.vBThe Brillouin frequency shift change quantity caused by temperature and strain,
and
selecting the Brillouin frequency shift of the optical fiber at the down lead as a temperature reference point for the temperature coefficient and the strain coefficient of the Brillouin frequency shift, and realizing the separation of strain and temperature;
drawing the strain data and the average attenuation of each section of the OTDR test result in a curve to realize a strain-attenuation corresponding curve;
and drawing a strain and attenuation early warning threshold value of the OPGW optical cable in a strain-attenuation corresponding curve so as to provide a corresponding relation between the strain value and the attenuation value of each section of the optical cable and the early warning threshold value, and if the strain and the attenuation both exceed a third threshold value, carrying out fault point early warning and the type of the early warning is a third type.
4. The OPGW optical cable fault locating and early warning method based on the BOTDR and the OTDR as claimed in claim 1, wherein the step of determining the fusion point based on the Brillouin frequency shift data of the plurality of vacant fiber cores comprises:
and drawing the measured Brillouin frequency shift data of the plurality of vacant fiber cores in the same graph to obtain the jumping points existing in a plurality of Brillouin frequency shift curves in the graph as welding points.
5. The OPGW optical cable fault location and early warning method based on the BOTDR and the OTDR as claimed in claim 1, wherein the step of corresponding the determined fusion point to the fusion tower position in the tower information to locate the fusion tower and the strain constant region comprises:
and drawing a tower diagram in an equal proportion of 1:1 by combining tower information, drawing the tower diagram and the drawn Brillouin frequency shift diagram in the same diagram, and corresponding the determined welding points to the welding towers one by one to obtain a welding tower corresponding diagram, so that the accurate positioning of the welding towers and the accurate positioning of the abnormal strain area are realized.
6. The BOTDR and OTDR based OPGW optical cable fault location and early warning method according to claim 5, wherein the step of testing the loss of the plurality of vacant cores comprises:
and obtaining an OTDR attenuation curve, and judging a loss point through the OTDR.
7. The OPGW optical cable fault location and early warning method based on BOTDR and OTDR as claimed in claim 6, wherein the candidate obstacle point is determined by:
drawing an OTDR attenuation curve and a corresponding graph of a welded tower in equal proportion, and identifying loss points exceeding a first threshold value at non-welded points by combining a Brillouin spectrum, the OTDR autonomously determined loss points and the graph of the welded tower to serve as candidate obstacle points; the first threshold is 0.02 dB.
8. The OPGW optical cable fault location and early warning method based on BOTDR and OTDR as claimed in claim 2, wherein the second threshold is 0.3 dB.
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