EXFO FTB-7000 OTDR Series for FTB-500 - Manual (Page 69)

Setting Up Your OTDR
OTDR 55
Launch Conditions for Multimode Measurements
Launch Conditions for Multimode
Measurements
In a multimode fiber network, the attenuation of a signal is highly
dependent on the mode distribution (or launch condition) of the source
that emits this signal.
In the same way, the attenuation reading performed by any test instrument
will also depend on the mode distribution of its light source.
A single light source cannot be conditioned for both 50 μm (50 MMF) and
62.5 μm (62.5 MMF) fibers at the same time:
³
A source conditioned for 50 MMF testing will be under-filled for
62.5 MMF testing.
³
A source conditioned for 62.5 MMF will be overfilled for 50 MMF testing.
TIA/EIA-455-34A (FOTP34, Method A2) is providing a target launch
condition that is obtained when using an overfilled source followed by
mandrel-wrap mode filter (five close-wound turns around a mandrel tool
of a given diameter).
Your product has been conditioned for 62.5 MMF testing. However, you can
also test with 50 MMF fibers.