EXFO iOLM - Manual (Page 12)

Introducing the intelligent Optical Link Mapper
6 iOLM
Performing Multimode Measurements
Performing Multimode Measurements
If your module supports multimode measurements, it can test both
62.5 m and 50 m fibers. The internal multimode fiber for an EXFO OTDR
is 62.5 μm.

When a 62.5 μm fiber is connected, the loss at the connector can be
correctly characterized just like in the case of a singlemode fiber. It is
then simple to evaluate a pass/fail criterion in this case.

When a 50 μm fiber is connected, the loss at the connector depends
on many factors:

the connector loss itself

the 62.5 m to 50 μm core fiber difference

the RBS difference between 50 m and 62.5 μm fibers
The measured loss between the OTDR connector and the fiber is
typically around 3.3 dB.
With 50 μm fibers, since the connector loss measurement at the OTDR
is imprecise because of major other factors, the iOLM excludes the first
connector from the link rather than providing inaccurate information.
With a launch fiber, the connector at link start (connector A) is “On-Link”.
When characterizing a multimode link or a singlemode fiber, launch fibers
are recommended. In multimode, the launch and receive fibers must have
the same core size as the link under test. Using an unfitting launch or
receive fiber would lead to inaccurate results.
The use of an external EF-compliant device such as the SPSB-EF-C30 will
ensure a fast and easy way to get accurate loss measurements. For more
information about encircled flux compliance, refer to the encircled flux test
solution specification sheet.