An optical cable status monitoring system and method based on DAS and OTDR

Abstract

The present invention discloses a cable status monitoring system and method based on DAS and OTDR, wherein the monitoring system comprises: a monitoring box, the monitoring box comprises a DAS unit, an OTDR unit, an optical switch unit and a wavelength division multiplexing unit, the DAS unit is connected to the OTDR unit through the optical switch unit and the wavelength division multiplexing unit; a plurality of optical cable line branches, each of which is independently connected to the monitoring box interface. The present invention uses DAS to monitor each line in real time, establishes a line distance and pole tower position comparison table for the line according to the return information, wakes up the OTDR distance measurement system in standby state to measure the distance when a breakpoint occurs, and then combines the accurate length information with the pole tower position information to obtain a more intuitive relative position of the fault point.

Description

Technical Field

[0001] The invention belongs to the technical field of laser monitoring, and relates to an optical cable status monitoring system and method based on DAS and OTDR. Background Art

[0002] As an important guarantee for the development of the national economy, it is of great strategic significance to ensure the safe and efficient operation of the power grid. Reliable monitoring of the power line status is an effective way to ensure its safe and reliable operation, and is also an important guarantee for building a controllable, safe, reliable, environmentally friendly and economical smart grid.

[0003] Among them, it is particularly important to monitor the status of optical cables, which are important transmission carriers of optical information, and include the fault status of optical cables such as breakage and external damage in the monitoring. At present, the monitoring of optical cable status mainly relies on manual use of optical time domain reflectometer (OTDR) for distance measurement. However, OTDR generally has technical defects such as short operating life and high price. When used manually, a large number of redundant measurements are always performed, which reduces the service life of OTDR. Secondly, OTDR needs to emit light from one end of the optical cable. When troubleshooting the fault point (break point, loss abnormal point, etc.), the power grid operation and maintenance personnel must first determine the approximate location of the fault point and go to the nearby substation to use OTDR to find the fault point. Finding the fault point requires a lot of manpower. Furthermore, when laying optical cables, there will be extra fiber length at the connection position, which leads to errors in the distance information of the optical cable fault point fed back by OTDR from the OTDR device. The power grid operation and maintenance personnel can only find the approximate range based on the distance length information to conduct inspections and then determine the fault point, which is difficult to achieve accurate positioning. Summary of the invention

[0004] In view of the above problems, the present invention provides an optical cable status monitoring system and method based on DAS and OTDR to solve one of the above technical problems.

[0005] According to a first embodiment of the present invention, the present invention provides an optical cable status monitoring system based on DAS and OTDR, comprising:

[0006] A monitoring box, the monitoring box comprising a DAS unit, an OTDR unit, an optical switch unit and a wavelength division multiplexing unit, the DAS unit being connected to the OTDR unit via the optical switch unit and the wavelength division multiplexing unit;

[0007] A plurality of optical cable line branches, each of the optical cable line branches is independently connected to the monitoring box interface;

[0008] The DAS unit is used to perform full-scale monitoring of the optical cable line and calibrate the optical cable line when the system is started to establish a comparison table between line distance and tower position;

[0009] The OTDR unit is used to accurately measure the distance to the line fault point;

[0010] The optical switch unit is used to switch the optical path channel so that the DAS unit monitors the multiple optical cable line branches in a time division multiplexing manner;

[0011] The wavelength division multiplexing unit is used to multiplex the optical paths of the DAS unit and the OTDR unit so that the lights of the DAS unit and the OTDR unit do not interfere with each other.

[0012] Optionally, each of the optical cable line branches includes a plurality of pole towers, and the plurality of pole towers are distributed at a certain interval on each of the optical cable line branches.

[0013] Optionally, the plurality of towers are evenly distributed at a certain interval on each of the optical cable line branches.

[0014] According to a second embodiment of the present invention, the present invention provides a method for performing optical cable monitoring using the optical cable status monitoring system based on DAS and OTDR as described above, comprising the following steps:

[0015] The optical cable line is fully monitored by the DAS unit, and the optical cable line is calibrated when the system is started to establish a comparison table between line distance and tower position;

[0016] When the DAS unit detects a fault point of the optical cable line, the OTDR unit is started to accurately measure the distance to the fault point through the OTDR unit.

[0017] Optionally, when the DAS unit detects a fault point of the optical cable line, starting an OTDR unit to accurately measure the distance to the fault point by using the OTDR unit includes:

[0018] When the DAS unit detects a fault point of the optical cable line, the preliminary position of the fault point is determined by using the comparison table;

[0019] The OTDR unit is started, and based on the preliminary position of the fault point, the distance to the fault point is accurately measured by the OTDR unit.

[0020] Optionally, the performing full-scale monitoring of the optical cable line by the DAS unit includes:

[0021] The optical switch unit switches the optical path channel, so that the DAS unit uses time division multiplexing to perform full-duty monitoring on multiple optical cable lines.

[0022] Optionally, the time division multiplexing interval is 0.01ms-0.1s.

[0023] Optionally, the calibrating the optical cable line to establish a comparison table of line distance and tower position includes:

[0024] The DAS unit is used to obtain data on the length of the optical cable line, the vibration amplitude and frequency at each position of the optical cable line, and the correspondence between the position of each pole tower from the monitoring box to the end of the optical cable line and the line distance is determined based on the data, and a comparison table of line distance and pole tower position is established based on the correspondence.

[0025] Optionally, when the DAS unit detects a fault point of the optical cable line, the OTDR unit is started to accurately measure the distance to the fault point by the OTDR unit, and then the method includes:

[0026] After the OTDR unit accurately measures the distance to the fault point, the OTDR unit returns to the standby state.

[0027] Optionally, the method further includes: monitoring in real time by the DAS unit whether the length of the optical cable line has returned to a normal state.

[0028] Beneficial effects of the present invention: The present invention adopts a combination of DAS and OTDR to avoid the shortcomings of the two technologies: using DAS to monitor each line in real time, establishing a line distance and tower position comparison table for the line based on the return information, waking up the OTDR ranging system in standby state to measure the distance when a breakpoint occurs, and then combining the accurate length information and tower position information to obtain a more intuitive relative position of the fault point. In this way, the optical cable status monitoring system, while increasing the service life of the OTDR and reducing the line monitoring cost, eliminates a lot of work for the operation and maintenance personnel to find the fault point, greatly improves the operation and maintenance efficiency, and ensures the safe and efficient operation of the optical cable line. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0030] Figure 1 A schematic diagram of the structure of an optical cable status monitoring system based on DAS and OTDR in an embodiment of the present invention;

[0031] Figure 2 A frequency domain schematic diagram of the comparison between the DAS line distance and the tower position in an embodiment of the present invention;

[0032] Figure 3A simplified schematic diagram of a system when an optical cable fails in an embodiment of the present invention;

[0033] Figure 4 This is a flow chart of information feedback in an embodiment of the present invention;

[0034] Figure 5 A schematic diagram of the DAS structure in an embodiment of the present invention;

[0035] Figure 6 FIG. 4 is a simplified diagram of the OTDR structure in an embodiment of the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0038] like Figure 1 As shown, according to the first embodiment of the present invention, the present invention provides an optical cable status monitoring system based on DAS and OTDR, specifically involving distributed optical time domain reflectometry OTDR (Optical Time-Domain Reflectometry) optical fiber sensing technology and optical fiber distributed acoustic detection technology DAS (Distributed optical fiber Acoustic monitoring System).

[0039] OTDR is a test unit device based on the backscattering principle. It is usually used to measure optical fiber loss characteristics, locate optical fiber breakpoints, measure optical fiber length, etc. It is widely used in practical applications such as optical network research, production, construction and maintenance.

[0040] The working principle of OTDR is similar to that of radar, and the measurement only needs to be performed at one end of the optical fiber. First, the pulsed laser emits a light pulse into the sensing optical fiber. Rayleigh scattering occurs during the transmission process, and part of the backscattered light power returns to the input end. When the light pulse encounters the gap between glass and air, such as fiber breakpoints, bends, connection points, terminals, and other events, the refractive index changes suddenly, resulting in Fresnel reflection. At this time, the reflected light power is much stronger than the backscattered light power, which is manifested as a sharp reflection signal superimposed on the backscattered signal. When the sensing optical fiber is disturbed by external signals, the backscattering characteristics of that position will change. The distance can be calculated based on the time from the transmitted signal to the returned signal, as well as the speed at which light is transmitted in the optical fiber.

[0041] DAS uses the phase of coherent Rayleigh scattered light rather than light intensity to detect signals such as sound or vibration in the audio range. It can not only use the phase amplitude to provide intensity information of sound or vibration events, but also use linear quantitative measurement values ​​to obtain the phase and frequency information of sound or vibration events.

[0042] DAS can be considered as a mobile interferometric acoustic wave sensor that detects external signals in the sensing optical fiber. When sound or vibration causes a linear change in the phase of the interference light at that position, quantitative measurement of external physical quantities can be achieved by extracting and demodulating the interference signals at different times at that position.

[0043] A structural diagram of an implementation method of DAS is shown in FIG. Figure 5 As shown, the laser emits a light pulse along the optical fiber, and some of the light interferes with the incident light in the pulse in the form of backscattering. After the interference light is reflected back, the backscattered interference light returns to the signal processing device, and at the same time, the vibration sound wave signal along the optical fiber is brought to the signal processing device. Since the speed of light remains unchanged, the measurement result of the sound wave vibration per meter of optical fiber can be obtained.

[0044] A schematic diagram of the structure of an OTDR implementation is shown below: Figure 6 As shown, the laser emits a pulsed laser, which enters the optical fiber through a coupler. After Rayleigh scattering occurs in the optical fiber, the backscattered light power returns to the input end. After the incident light and scattered light enter the detector, the accurate spatial position is calculated.

[0045] like Figure 1As shown, the present invention provides a DAS and OTDR-based optical cable status monitoring system, comprising: a monitoring box 5 and a plurality of optical cable line branches extending from each interface of the monitoring box, such as lines 1-4, each optical cable line branch comprises a plurality of evenly or unevenly distributed towers, for example, towers 11-14 are arranged on line 1, towers 21-24 are arranged on line 2, towers 31-34 are arranged on line 3, and towers 41-44 are arranged on line 4. Among them, the distances between the pole towers 11-14 and the monitoring box 5 are a1km, a2km, a3km, and a4km, respectively, for example, a1km, a2km, a3km, and a4km are 1km, 2km, 3km, and 4km respectively; the distances between the pole towers 21-24 and the monitoring box 5 are b1km, b2km, b3km, and b4km, respectively, for example, b1km, b2km, b3km, and b4km are 1km, 2km, 3km, and 4km respectively; the distances between the pole towers 31-34 and the monitoring box 5 are c1km, c2km, c3km, and c4km, respectively, for example, c1km, c2km, c3km, and c4km are 1km, 2km, 3km, and 4km respectively; the distances between the pole towers 41-44 and the monitoring box 5 are d1km, d2km, d3km, and d4km, respectively, for example, d1km, d2km, d3km, and d4km are 2km, 3km, 5km, and 7km respectively.

[0046] The monitoring box 5 includes a DAS unit 51, an OTDR unit 52, an optical switch unit 53 and a wavelength division multiplexing unit 54. The DAS unit 51 is connected to the OTDR unit 52 through the optical switch unit 53 and the wavelength division multiplexing unit 54; multiple optical cable line branches, each of which is independently connected to the monitoring box interface. The specific structure of the optical switch unit 53 and the wavelength division multiplexing unit 54 can refer to any structure of the prior art, and will not be limited or elaborated here, as long as it can meet the above functional requirements. The optical switch is an optical path conversion device. In the optical fiber transmission system, the optical switch is used for the conversion of multiple monitors, LAN, multiple light sources, detectors and protection Ethernet.

[0047] The DAS unit is used to perform full-scale monitoring of the optical cable line and calibrate the optical cable line when the system is started to establish a comparison table of line distance and tower position; the OTDR unit is used to accurately measure the distance to the line fault point; the optical switch unit is used to switch the optical path channel so that the DAS unit monitors the multiple optical cable line branches in a time division multiplexing manner; the wavelength division multiplexing unit is used to multiplex the optical paths of the DAS unit and the OTDR unit so that the light of the DAS unit and the OTDR unit does not interfere with each other.

[0048] like Figure 1As mentioned above, the DAS unit will establish a comparison table of the distance positions of the towers of the four lines. Line 1 has a total of 4 towers, which are respectively a1 km, a2 km, a3 km and a4 km away from the substation. The distance information measured by the OTDR unit can be compared with the positions of these towers to find the relative position of the fault point, rather than only being able to conduct an approximate range inspection based on a single length information. The OTDR unit is responsible for measuring the distance of the line and is usually in standby mode to save the life of the equipment. The optical switch unit is used to switch the optical path channel so that the system can monitor multiple lines in a time-division multiplexing manner, improve the utilization rate of the equipment, and reduce the cost of line monitoring. The WDM unit is used to multiplex the optical paths of the DAS and OTDR so that the light of the two modules does not interfere with each other.

[0049] Optionally, each of the optical cable line branches includes a plurality of pole towers, and the plurality of pole towers are evenly or unevenly distributed on each of the optical cable line branches at a certain interval.

[0050] The present invention adopts a combination of DAS and OTDR to avoid the shortcomings of the two technologies. DAS is used to monitor each line in real time, and a line distance and tower position comparison table is established for the line based on the return information. When a breakpoint occurs, the OTDR ranging system in standby state is awakened to measure the distance, and then the accurate length information and tower position information are combined to obtain a more intuitive relative position of the fault point. In this way, the optical cable status monitoring system, while increasing the service life of the OTDR and reducing the line monitoring cost, eliminates a lot of work for the operation and maintenance personnel to find the fault point, greatly improves the operation and maintenance efficiency, and ensures the safe and efficient operation of the optical cable line.

[0051] According to a second embodiment of the present invention, the present invention provides a method for performing optical cable monitoring using the optical cable status monitoring system based on DAS and OTDR as described above, comprising the following steps:

[0052] First, the optical cable line is fully monitored by the DAS unit, and the optical cable line is calibrated when the system is started to establish a comparison table between line distance and tower position;

[0053] For example, the monitoring system includes four lines, line 1 is provided with towers 11-14, line 2 is provided with towers 21-24, line 3 is provided with towers 31-34, and line 4 is provided with towers 41-44. Among them, the distances between the pole towers 11-14 and the monitoring box 5 are a1km, a2km, a3km, and a4km, respectively, for example, a1km, a2km, a3km, and a4km are 1km, 2km, 3km, and 4km respectively; the distances between the pole towers 21-24 and the monitoring box 5 are b1km, b2km, b3km, and b4km, respectively, for example, b1km, b2km, b3km, and b4km are 1km, 2km, 3km, and 4km respectively; the distances between the pole towers 31-34 and the monitoring box 5 are c1km, c2km, c3km, and c4km, respectively, for example, c1km, c2km, c3km, and c4km are 1km, 2km, 3km, and 4km respectively; the distances between the pole towers 41-44 and the monitoring box 5 are d1km, d2km, d3km, and d4km, respectively, for example, d1km, d2km, d3km, and d4km are 2km, 3km, 5km, and 7km respectively.

[0054] Second, when the DAS unit detects a fault point of the optical cable line, the OTDR unit is started to accurately measure the distance to the fault point through the OTDR unit.

[0055] Optionally, when the DAS unit detects a fault point of the optical cable line, starting an OTDR unit to accurately measure the distance to the fault point by using the OTDR unit includes:

[0056] When the DAS unit detects a fault point of the optical cable line, the preliminary position of the fault point is determined by using the comparison table;

[0057] The OTDR unit is started, and based on the preliminary position of the fault point, the distance to the fault point is accurately measured by the OTDR unit.

[0058] Figure 3 and Figure 4 This is a system diagram and logic flow chart when a fault occurs in the optical cable line. The tower location information shown in the figure is Figure 2The information in the line distance and tower position comparison table established by the process shown in the figure is that the optical cable length from tower 1 to the substation is a km, the optical cable length from tower 2 to the substation is b km, and so on. When the system is running normally and the line is fault-free, the distance measured by DAS always fluctuates around a normal value. When a fault point occurs in the optical cable, that is, a break occurs at point X as shown in the figure, the distance measured by DAS is between d km and e km, which is not within the normal length range. At this time, the monitoring system will wake up the OTDR in standby mode for precise distance measurement after recording the fault information "the fault point is between towers 4 and 5", and the OTDR will return it and re-enter standby mode after measuring the length information. The system will integrate the precise length information with the previous fault information to obtain relative distance information such as "the fault point is between towers 4 and 5, about x km from the substation, and about (xd) km from tower 4". The operation and maintenance personnel can also use this information to quickly locate the accident site where the break occurred and immediately respond to the accident site for emergency repairs. The spatial resolution of DAS is low only at the end of the line, and the reliability of the rest of the parts is comparable to that of OTDR, so the line distance and tower position comparison table obtained by DAS has a high degree of feasibility. The combination of these two technologies will make optical cable line monitoring more efficient and accurate.

[0059] Optionally, the performing full-scale monitoring of the optical cable line by the DAS unit includes:

[0060] The optical switch unit switches the optical path channel, so that the DAS unit uses time division multiplexing to perform full-duty monitoring of multiple optical cable lines. That is, the optical switch unit switches multiple optical paths continuously at fixed intervals, such as switching and scanning at intervals of 0.01ms-0.1s, so that the interval time of the time division multiplexing is 0.01ms-0.1s.

[0061] Optionally, the calibrating the optical cable line to establish a comparison table of line distance and tower position includes:

[0062] The DAS unit is used to obtain data on the length of the optical cable line, the vibration amplitude and frequency at each position of the optical cable line, and the correspondence between the position of each pole tower from the monitoring box to the end of the optical cable line and the line distance is determined based on the data, and a comparison table of line distance and pole tower position is established based on the correspondence.

[0063] Figure 2The frequency domain diagram of the DAS line distance and tower position comparison. DAS can obtain data on line length, vibration amplitude and frequency at each position, while the optical fiber at the tower position basically does not vibrate, that is, the amplitude is zero. From this, the corresponding relationship between the tower position and the line distance from the substation to the end of the line can be determined, and a comparison table of line distance and tower position can be established. The interval indicated by points 1 and 3 in the figure is the line, and the distance interval indicated by point 2 is the tower position.

[0064] Optionally, when the DAS unit detects a fault point of the optical cable line, the OTDR unit is started to accurately measure the distance to the fault point by the OTDR unit, and then the method includes:

[0065] After the OTDR unit accurately measures the distance to the fault point, the OTDR unit returns to the standby state. After the OTDR performs secondary measurement, the measurement result is fed back to the monitoring box, and then enters the standby state to save energy.

[0066] Optionally, the method further includes: monitoring in real time by the DAS unit whether the length of the optical cable line has returned to a normal state. If it has returned to normal, the DAS unit performs the previous interval scan; if it has not returned to normal, the DAS unit continues to report an error to remind the maintenance personnel to perform maintenance.

[0067] The present invention adopts a combination of DAS and OTDR to avoid the shortcomings of the two technologies. DAS is used to monitor each line in real time, and a line distance and tower position comparison table is established for the line based on the return information. When a breakpoint occurs, the OTDR ranging system in standby state is awakened to measure the distance, and then the accurate length information and tower position information are combined to obtain a more intuitive relative position of the fault point. In this way, the optical cable status monitoring system, while increasing the service life of the OTDR and reducing the line monitoring cost, eliminates a lot of work for the operation and maintenance personnel to find the fault point, greatly improves the operation and maintenance efficiency, and ensures the safe and efficient operation of the optical cable line.

[0068] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0069] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for monitoring optical cables using an optical cable status monitoring system based on DAS and OTDR, characterized in that: The DAS and OTDR optical cable status monitoring system comprises: A monitoring box, the monitoring box comprising a DAS unit, an OTDR unit, an optical switch unit and a wavelength division multiplexing unit, the DAS unit being connected to the OTDR unit via the optical switch unit and the wavelength division multiplexing unit; A plurality of optical cable line branches, each of the optical cable line branches is independently connected to the monitoring box interface; The DAS unit is used to perform full-scale monitoring of the optical cable line and calibrate the optical cable line when the system is started to establish a comparison table between line distance and tower position; The OTDR unit is used to accurately measure the distance to the line fault point; The optical switch unit is used to switch the optical path channel so that the DAS unit monitors the multiple optical cable line branches in a time division multiplexing manner; The wavelength division multiplexing unit is used to multiplex the optical paths of the DAS unit and the OTDR unit so that the light of the DAS unit and the OTDR unit do not interfere with each other; The method comprises the following steps: The optical cable line is fully monitored by the DAS unit, and the optical cable line is calibrated when the system is started to establish a comparison table between line distance and tower position; When the DAS unit detects a fault point of the optical cable line, the OTDR unit is started to accurately measure the distance to the fault point through the OTDR unit.

2. The method for monitoring an optical cable according to claim 1, characterized in that: When the DAS unit detects the fault point of the optical cable line, the OTDR unit is started to accurately measure the distance of the fault point by the OTDR unit, including: When the DAS unit detects a fault point of the optical cable line, the preliminary position of the fault point is determined by using the comparison table; The OTDR unit is started, and based on the preliminary position of the fault point, the distance to the fault point is accurately measured by the OTDR unit.

3. The method for monitoring an optical cable according to claim 2, characterized in that: The full-scale monitoring of the optical cable line by the DAS unit includes: The optical switch unit switches the optical path channel, so that the DAS unit uses time division multiplexing to perform full-duty monitoring on multiple optical cable lines.

4. The method for monitoring an optical cable according to claim 2, characterized in that: The time division multiplexing interval is 0.01ms-0.1s.

5. The optical cable monitoring method according to claim 2, characterized in that: The calibrating of the optical cable line to establish a comparison table of line distance and tower position includes: The DAS unit is used to obtain data on the length of the optical cable line, the vibration amplitude and frequency at each position of the optical cable line, and the correspondence between the position of each pole tower from the monitoring box to the end of the optical cable line and the line distance is determined based on the data, and a comparison table of line distance and pole tower position is established based on the correspondence.

6. The optical cable monitoring method according to claim 2, characterized in that: When the DAS unit detects the fault point of the optical cable line, the OTDR unit is started to accurately measure the distance of the fault point by the OTDR unit, and then the method includes: After the OTDR unit accurately measures the distance to the fault point, the OTDR unit returns to the standby state.

7. The optical cable monitoring method according to claim 2, characterized in that: Also includes: The DAS unit monitors in real time whether the length of the optical cable line has returned to a normal state.

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