Ericsson FSU 995 F - Page 33

31
ADVANCED OPERATION - Splicing program structure: Splicing process
Mode field matching
Pre-defined programs: 06 & 07
A typical splicing sequence for the mode field matching process
Mode field matching control parameters
current2
current1
pre-fuse
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gap
overlap
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fiber distance
LOSS FACTOR
is a compensatory variable
used in splice loss estimation
to account for the difference
between INDEX LIMIT (the
value entered in the param-
eter) and the measured index
after splicing.
THRESHOLD TYPE
represents the type of com-
parison that should be made
between the hot fiber index
profiles for the two fibers.
The easiest way to set the
Threshold type is by running
the Threshold type test (see
next page).
INDEX LIMIT
represents the value the hot
fiber index will be allowed to
reach before the arc will shut
off, thus ending the splicing
sequence. We recommend
that the first time you splice
a new fiber combination that
you run the Threshold type
test (see next page). See also
Using the index limit param-
eter on p. 33.
The mode field matching
process is intended for splic-
ing fibers with very dissimilar
mode field diameters. That is
to say: Different types of fiber
require different diameter
cores to carry their fundamen-
tal mode. Erbium fiber, for
example, has a smaller than
average core, and when you
want to splice an erbium fiber
with another type of fiber, you
must find some way to make
the transition from one core to
the other as smooth as pos-
sible in order to avoid power
loss around the unmatched
core edges. This is achieved
by means of a hot fiber index
profile. During splicing, a
fiber’s dopants will diffuse into
its core, decreasing its index
profile. With two fibers this
can result in a convergence of
their profiles. With RTC this
process can be observed and
the arc stopped when the best
match of profiles has been
achieved.
A graph from a Threshold type test (see
p.32) plotting of the index profiles for two
fibers. Note how the profiles converge.