FIBEROPTICS BY JIM HAYES
Last month, we stripped the fiber we
planned to terminate, so we are almost
ready to attach the connector. But first,
we have to clean the fiber to remove any
dirt and scraps of the stripped buffer.
Since we are dealing with such small
components, cleaning is one of the most
important tasks in fiber optics. Cleaning
the fiber before inserting it into a connector does not just involve cleaning;
it must be done in a way that does not
adversely affect the adhesive we use in
Most manufacturers of connectors
and adhesives for fiber optics recommend
using a lint-free wipe and pure isopropyl
alcohol, which is 99 percent pure and
quite different from typical drugstore
isopropyl rubbing alcohol, which is 70
percent alcohol and 30 percent water.
The water in rubbing alcohol is bad
for fiber and adhesives. Water migrates
into the glass fiber and can affect strength
and attenuation. Water also can affect the
strength of adhesives used in the termination process and the length of time it
takes some adhesives to cure.
I found this out the hard way. I was
teaching students using supplies provided by a distributor and discovered the
anaerobic adhesive would not harden. I
recognized that the alcohol wipes I had
received were medical wipes, the ones a
nurse uses to disinfect your skin before
an injection. The moisture content of the
rubbing alcohol prevented the adhesive
from hardening. Switching to the correct
alcohol wipes solved the problem.
Once we have the proper products,
we can set aside our clean fiber and pre-
pare the connector for termination. Be
sure to place the fiber in a clean loca-
tion (on top of a clean, lint-free wipe is
good) and somewhere you won’t touch
it by mistake.
Since we are focusing on adhesive-polish connectors, we have three types
of adhesives to consider, each requiring
a different technique. Epoxies are usually
heat-cured, but some types set overnight
at room temperature. Heat-cured epoxies are used for factory-made patchcords
because of their ease of termination and
Epoxies are easier to use because
the connector will have a small bead of
adhesive on the end of the fiber that supports the fiber during the cleaving and
polishing process. This support makes
it nearly impossible to get a poor cleave
The drawback of the epoxy-termination
method is you need a curing oven. While
they are not expensive, almost all of
them require power at the work site;
there is only one battery-powered oven
(I designed it 20 years ago).
Anaerobic adhesives are simpler to
use but harder to get right. The adhesives
can cure in about 30 seconds with a two-chemical system that pairs the adhesive
with a setting agent, or in about 5 minutes for an adhesive alone. The drawback
is you do not have the adhesive bead on
the end of the connector supporting the
fiber, so you have to be more careful when
cleaning and polishing.
The 3M Hot Melt connector comes
with the adhesive inside the connector. A high-temperature oven melts the
adhesive so you can insert the fiber.
These connectors also have the adhesive
bead on the end of the ferrule to make
them almost foolproof to cleave and pol-
ish. If you mess up a Hot Melt connector,
you can usually reheat it and try again.
The choice between these three types
of connectors is really a matter of personal experience and economics. I have
found that students often prefer to use
what they learn in class when in the field.
Those of us who have tried all of them
generally agree that the epoxy and Hot
Melt methods are easier, but an analysis
of termination time and cost makes the
anaerobic or epoxy methods cheaper,
mainly because the connectors themselves are much cheaper.
Some installers prefer to avoid the
adhesive-polish connectors entirely.
Instead, they use the prepolished-splice
connectors that are sold on the premise
of quick termination. Don’t be fooled.
The Fiber Optic Association has done
time and motion studies of fiber optic
termination, and the speed claims don’t
always make sense. By the time you go
to a work site, do your setup, make the
terminations, clean up and leave, the type
of termination hardly affects the time it
takes for the whole job.
Next month, the process continues.
Cleaning Fibers Is Crucial
The art of installing fiber optic connectors, part 3
IN SEVERAL RECENT COLUMNS, I discussed the process of fiber optic terminations. I examined each step in detail and shared some of the things I have learned
from experience and teaching students. As they say, one learns from one’s mistakes.
HAYES is a VDV writer and educator and the president of The Fiber Optic Association. Find
him at www.JimHayes.com. T H