Fluke Networks CertiFiber Pro Users Manual - Manual (Page 416)

Versiv Cabling Certification Product Family
Technical Reference Handbook
394
Use a Launch Cord of the Correct Length
To do an OTDR test on a long fiber, the tester uses wider pulse
widths to increase dynamic range. Wider pulse widths make
wider dead zones, which can hide the first connector and the
fiber at the near end of the link.
To make sure you see measurements for the near end of the link,
use a launch cord that is longer than the dead zone. Table A-1
shows examples of minimum lengths of launch cords for typical
links.
Table A-1. Minimum Length of a Launch Cord
Use a Launch Cord that Has the Correct
Connectors
One end of the launch cord must have the same type of connector
as the OTDR. The other end must have the same type of
connector and polish as the link. Do not use hybrid patch cords to
connect launch cords to the OTDR or to the link.
Maximum Length of Link (km) Typical Pulse
Width (ns)
Minimum Launch
Cord Length
(meters) *
1310 nm 1550 nm only
0 to 35 0 to 50 1000 130
35 to 45 50 to 65 3000 400
45 to 50 65 to 75 10000 1000
50 75 20000 2400
* For fiber with typical attenuation (  0.35 dB /km at 1310 nm;  0.2 dB /km at
1550 nm) and event loss less than 0.8 dB .