Fluke CableAnalyzer DSX-5000, Technical Reference Handbook, Page: 452 / 700

Versiv Series Cabling Certification Product Family
Technical Reference Handbook
416
About Launch and Tail Cords for OSP Links
Launch and tail cords are often not necessary for OTDR tests on
outside plant installations. This is because most of the insertion
loss and return loss of long links is caused by the fiber. The
connectors on the ends of a long link add very little to the total
losses, so it is often not necessary to use launch and tail cords to
include the losses of those connectors in the results.
You should however keep a patch cord connected to the OTDR
port. Use the patch cord, with an adapter if necessary, to connect
the OTDR to links. The patch cord protects the module’s
connector from the wear caused by repeated connections to the
OTDR port.
It may be necessary to use launch and tail cords in these
situations:

The OSP link is short, and you need to see events near the
beginning or end of the fiber.

The tester cannot find the end of an unconnected fiber that
has an APC connector. This can occur because APC connectors
cause very small reflections. OTDRs expect a large reflection at
the end of a fiber, so sometimes the OTDR will not find the
end of a fiber. In this situation, connect an APC/UPC tail cord
or a patch cord to the APC connector to cause a large
reflection at the end of the fiber.
 The customer’s requirements specify the use of launch and tail
cords.
If you must use launch and tail cords, you can use the tester’s
launch compensation function to remove the losses, lengths, and
attenuation coefficients of the launch and tail cords from overall
OTDR results. The compensation function does not remove the
losses of the connections at the launch and tail cords.