A spool or box of fiber, typically 100 m to 1 km for singlemode and 50 to 300 m for multimode, matching the fiber under test and terminated with high-quality connectors. It lets the OTDR recover from its own initial dead zone and provides clean backscatter before and after the first connector of the link, so that connector's loss can be measured. In loss testing, the reference jumper attached to the source is also called a launch cable.
Hook the 1 km launch cable on the front, I want the first panel connector on the trace, not buried in the dead zone.
Also heard as
- launch box
- pulse suppressor
- launch fiber
Do not mix it up with
- Receive cable: The receive cable goes on the far end so the last connector can be measured; the launch cable goes on the OTDR end.
Related terms
Receive cable
A reference fiber attached at the far end of a link so an OTDR can measure the loss of the last connector.
OTDR
Optical Time Domain Reflectometer: a tester that maps a fiber's loss and events by timing light reflected back along it.
Event dead zone
The distance after a reflective event during which an OTDR cannot detect a second, separate event.
One-jumper reference
A loss-test reference set with a single launch jumper between source and meter, so both link end connectors are counted.