TIA-455-54-B:1998 (R2013)

Introduction

This procedure describes light launch conditions to the test
fiber for the purpose of achieving a uniform overfilled launch with
a laser diode or other light sources. While FOTP-54 can be used to
establish overfilled launching conditions fÓr the measurement of
various fiber parameters, it is principally used in conjunction
with FOTP-30 or FOTP-5 1 for measuring information carrying
capacity. Light launch conditions are established through the use
of a mode scrambler. The mode scrambler is positioned between the
light source and test fiber to produce a radiation distribution
overfilling the test fiber core and numerical aperture,
irrespective of the spatial radiation properties of the light
source.

For many mode scrambler designs, however, the launching
conditions produced depend on the source/mode scrambler alignment
and the interaction with any intermediary optics such as connectors
or optical imaging systems. If the source or any component in the
optical system is changed, the qualification tests must be
repeated. When applied to information transmission capacity
measurements, the overfilled launch gives good measurement
reproducibility; it is not intended to necessarily give the best
bandwidth prediction for concatenated lengths. Also, a particular
light source/mode scrambler combination may be satisfactory for one
size core diameter and numerical aperture test fiber, but not for
another.