Now take a test trace, and look at the display. Is the trace noisy? If so, more averaging may be needed. Is the end of the fiber at the distance expected based on your knowledge of the length of the cable? If you don’t know the approximate length of the cable, it is easy to become confused by trace artifacts like “ghosts” (see my April 2006 column, “Ghost Busters”). Are the connections visible? Connectors should have high reflection peaks to identify their positions. Are there any peaks where connectors should not be? Those could be ghosts.
Depending on the answers to these questions, you may need to change some of the parameters and take another trace. Once the trace looks good, measure the lengths of individual fiber links and the losses of all the connectors. Save that trace to compare with other fibers in the same cable, to make sure all have similar traces. Fusion splicer manufacturer provides fusion splicer.
Finally, try the autotest function on the OTDR. If the results are similar to the results obtained from the first test, you can feel confident in using it for the other fibers, saving lots of testing time.
The first OTDR parameter to set is the range, which is the distance over which the OTDR manufacturer will measure. The range should be at least twice the length of the cable you are testing, usually 2 km for premises cabling. Longer ranges will make the resolution of the trace poorer, and shorter ranges may create distortions in the trace.
Then set the OTDR test pulse width to the shortest pulse width available, which will provide the highest resolution, giving the best “picture” of the fiber being tested. This is usually listed in nanoseconds (ns), with typical choices of 10 to 30 ns.