Finding obstacle points

Update:11 Jun 2018

The method steps for using an OTDR test to determine th […]

The method steps for using an OTDR test to determine the optical fiber line barrier at the endpoint or relay station are as follows:

1) Use the OTDR to test the distance from the obstacle point to the test end.

2) When the optical cable is blocked due to natural disasters or external forces such as external construction, look for personnel according to the obstacle location provided by the crew. If this is not the case, the inspector will not find the location of the obstacle from the road. At this time, it must be checked against the original test data according to the distance from the obstacle point to the test end measured by the OTDR, to find out which obstacle (or which two joints) is between the obstacles, and after necessary conversion, By precisely measuring the length of the ground between them, the specific location of the obstacle can be determined.

3) If the fiber breakage is due to a defect in the optical fiber cable structure or the aging of the optical fiber, it is difficult to accurately measure the break point with the OTDR, and only an obstacle section can be detected, and a section of optical fiber cable should be used instead.

Method for improving fault location accuracy of optical cable

First of all, to understand how to use the instrument, to master the use of the instrument, help to accurately measure.

1. Set OTDR parameters. When using the OTDR test, you must first set the instrument parameters, the most important of which is to set the refractive index and test wavelength of the test fiber. Only accurately setting the basic parameters of the test instrument can create conditions for accurate testing.

2, use the instrument's zoom function. With the OTDR's zoom function, the cursor can be accurately set at the corresponding inflection point. Using the zoom function key, the graph can be enlarged to 25 meters per division. This gives you a more accurate test result with a resolution of less than 1 meter.

3, adjust the exact test range file. For different test range files, the distance resolution of OTDR test is different. When measuring optical fiber obstacle points, you should select a test range file that is larger than the measured distance and closest, so as to make full use of the accuracy of the instrument to measure.

Second, accurate and complete original documentation should be established during the maintenance management process. These accurately completed optical cable file are the basic basis for fault measurement and positioning. Therefore, in the process of maintenance and management, carelessness should be avoided, and true, credible, and complete line data should be established.

In the continuous monitoring of the optical cable, the cumulative length of the optical fiber from the test point to each joint point and the total attenuation value of the hop optical fiber are recorded, and the test meter type and the set value of the refractive index during the test are also registered. Accurately record all kinds of cable remaining. Record the length of the optical cable remaining at each joint pit, special section, S-layout, entry room, etc., and the length of the optical fiber tray at the joint box, terminal box, ODF, etc., so as to deduct the route length when converting the fault point.

In addition, the test conditions should be consistent during the measurement. Obstacle testing should try to ensure the consistency of test instrument model, operation method and instrument parameter settings, and the test results are comparable. Therefore, every test instrument model, test parameter settings have to be detailed records for later use.

Finally, a comprehensive analysis. The test of obstacle points requires that the operators must have clear ideas and flexible methods for handling problems. Clear logical thinking is very useful everywhere. Under normal circumstances, the two ends of the fiber optic cable are two-way fault testing, and then combined with the original data for analysis, and then ready to determine the specific location of the fault. When the link around the fault point has no obvious characteristics and the specific site cannot be determined, then we can use the nearest joint measurement method, which can be excavated at the preliminary test obstacle point, and the end station test instrument is in real-time measurement state.

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