Methods for improving the accuracy of optical cable line fault location

Feb 08, 2022

First of all, it is necessary to understand how to use the instrument and master the use of the instrument, which is helpful for accurate measurement.

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

2. Use the magnification function of the instrument. Using the zoom function of the OTDR, the cursor can be accurately positioned on the corresponding inflection point, and the zoom function key can be used to zoom the graph to 25 meters/div, so that more accurate test results with a resolution of less than 1 meter can be obtained.

3. Adjust the accurate test range file. For different test range files, the distance resolution of the OTDR test is different. When measuring the optical fiber obstacle point, the test range file that is larger than the measured distance and the closest should be selected, so as to make full use of the instrument's own accuracy for measurement.

Secondly, accurate and complete original documentation should be established in the maintenance management process. These accurately completed optical cable line files are the basic basis for fault measurement and location. Therefore, the maintenance and management process should not be negligent, and should establish true, credible and complete line information.

When monitoring the optical cable connection, the cumulative length of the optical fiber from the test end to each joint point and the total attenuation value of the optical fiber in the junction section are recorded. At the same time, the model of the test instrument and the set value of the refractive index during the test are also registered. Accurately record various cable residues. Record in detail the length of optical cable reeling at each joint pit, special section, S-shaped laying, room entry, etc., and the optical reeling length of joint boxes, terminal boxes, ODF racks, etc., so as to be deducted when converting the routing length of the fault point.

In addition, the test conditions should be kept consistent during the measurement. During the obstacle test, the consistency of the test instrument model, operation method and instrument parameter setting should be ensured as far as possible, so that the test results are comparable. Therefore, the model of the test instrument and the setting of the test parameters should be recorded in detail each time for future use.

Finally, comprehensive analysis. The test of obstacle points requires operators to have clear thinking and flexible methods of dealing with problems, and clear logical thinking is very useful no matter where they are. Under normal circumstances, the two ends of the fiber optic cable line are tested for bidirectional faults, and then combined with the original data to analyze, and then prepare 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 adopt the measurement method at the nearest joint, and excavate at the obstacle point of the preliminary test, and the terminal test instrument is in a real-time measurement state.

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