What length of launch cable should I use in testing single mode and multi mode fiber?
The length of launch cable used can very depending on the measurement needs. But there are some general rules to follow. The cable should be longer than either of the following specifications, Event Dead Zone or Loss Dead Zone and the pulse length being used. The better of the two to select is Loss Dead Zone as this will meet both. This would meet the minimum length recommendation. Now with that said you may find that the launch cable may need to actually be longer because of the pulse length being used. Another item to watch is that the launch cable is not a small integer length of the cable being tested, i.e. test cable / launch cable = 1, 2, or 3. This is because of Ghosting.
Here are some recommendations.
Multi Mode and Single Mode: The jumper cable needs to be at least 4 to 5 times the length of the pulse width you will be using, 10 times is better. This applies for both a launch cable and a terminating cable. (Terminating cable allows you to see the true loss of the end connector. Because to see the loss of this connector you need to see beyond it.)
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