Beyondtech e-books and publications are created in order to help fiber optic apprentices eager to improve their techniques and learn everything they can about this amazing topic.
Optical fiber terminations need to be done carefully in order to have low loss and minimal reflectance. But for these procedures to be done perfectly, constant practice is mandatory.
Part I details the steps that have to be followed to do a permanent joint using a mechanical splice, Part II explains how to do a connectorization and Part III describes the way polishing needs to be done. This processes might be used with both multimode and single-mode fiber and with other connectors besides ST.
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A guide for fiber optic terminations, beyondtech
1.
2. Introduction
Optical fiber terminations need to be done carefully in order to have
low loss and minimal reflectance, therefore constant practice is
mandatory to achieve perfection. This E-book is created for optical fiber
apprentices eager to exercise and improve their techniques.
Part I details the steps to be followed to do a permanent joint
using a mechanical splice, Part II explains how to do a connectorization
and Part III describes the way polishing needs to be done.
This processes might be used with both multimode and single-mode optical
fiber and with other connectors besides ST.
Always remember to use safety goggles to avoid optical fiber
fragments to get into your eyes. Letâs start practicing!
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4. The first thing you have to do is strip
the fibers, taking away the coats, buf-
fers and protective layers, leaving the
optical fibers naked. Then, clean the
fiber using an optic clean wipe with
isopropyl alcohol.
Now itâs time to cleave the fiber.
You have to do this following your
cleaverâs instructions. And clean
the fiber using an optic clean wipe
moisturized with isopropyl alcohol.
Place the cleaved ends of the fibers
together into the mechanical splice
device. Now light will travel from one
fiber to another thanks to the index
matching gel. And your fiber splicing
is done!
STEP #1 STEP #2
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STEP #3
MECHANICAL
SPLICING
How to do it?
Mechanical splicing is easy to do if you have all the tools you need, as it only takes three steps to be done. It requires:
A fiber optic stripper A cleaver Kimwipes Isopropyl alcohol The mechanical splice device of your need
Is the process of precisely aligning two fiber optics together using an alignment device
and index matching gel, with refractive index similar to the fibersâ and covers possible
air gaps, helping light travel from one fiber to another with minimal loss and little
back reflection.
However, they are still two separate optical fibers, which is why this method is con-
sidered temporary and is mostly use to rapidly restore short-haul single mode or
multimode cables in FTTH installations.
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If you want to check the signal loss,
you could use a Visual Fault Locator, an
inexpensive small device that shoots
red laser light into the patch cords
and makes high loss points visible.
This method works great with yellow
coated single mode and orange coated
multimode fibers.
Constantly clean your tools:
Particles that you might consider
invisible can cause great damages on
fiber optics. So getting obsessed with
cleaning is never a problem.
Invest in a good quality cleaver:
Cleaving is the most important step
when splicing because a bad cleaves
can increase signal loss. Economic
cleavers generally need more practice
and skills to achieve the appropriate
cleave angle, so if you regularly do
mechanical splices buy a cleaver that
is generally used in fusion splices.
7. FIBER OPTIC
CONNECTORIZATION
Connectorization is the process of adding a connector at the end of an optical fi-
ber cable so it can be temporary joined with another cable or connected to net-
work equipment such as receivers, transmitters or patch panels and be quickly
disconnected when required. Optical fiber connectors guarantee that fibers are
properly aligned, ensuring steady connections.
ST, SC, FC and LC connectors can be terminated with similar processes for both
multimode and single mode fiber.
How to do it?
Before starting, make sure you have all the tools youâll need and organize them in a comfortable way for you to work. The tools are:
The fiber to be terminated The fiber optic connector of your need Epoxy Epoxy syringe Crimp tool
Fiber optic scribe Kevlar cutting scissors Alcohol pads Stripper Ruler Marker Kimwipes
Slide the strain-relief boot onto the
end of the fiber cable, followed by
the crimp sleeve. You can use a piece
of tape to keep them in place.
Use the ruler and the marker to mea-
sure and mark 1.3 inches from the end
of the fiber and proceed to remove
that amount of jacket using your
stripping tool. Now cut the aramid
threads using the Kevlar scissors,
but be careful to preserve between
0.20 or 0.40 inches of them.
Mark 0.60 inches on the buffer (mea-
suring from the end of the jacket)
and continue to use the stripper to
remove the exceeding buffer. You
might want to do this by cutting the
buffer in three sections to avoid
scratching the optical fiber. Use a
Kimwipe moisturized with isopropyl
alcohol to carefully clean the bare
fiber, removing any buffer leftovers.
STEP #1 STEP #2
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8. Put the epoxy into the syringe
and remove air bubbles. Place the
needle as far as it can go into the
connector and push the plunger
until you see epoxy coming out the
ferrule top, being careful not to let
any epoxy come out the bottom.
Gently push the optical fiber into
the connector and carefully rotate
the connector back and forth until
its back reaches the Kevlar threads
and the jacket end. You really need
to do this gently in order to avoid
scratching the fiber.
STEP #3 STEP #4 STEP #5
Bring the crimp sleeve to the back of
the connector. Use the proper crimp
tool to crimp the part of the sleeve
that covers the connector body and
the one that covers the jacket. Slide
up the boot so its shelters the con-
nector body. And it is done!
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9. Fast terminations:
Now itâs time to wait for the epoxy
to cure and start polishing. But what
if you donât have time to wait over-
night? You are probably thinking you
can use a fast room temperature
cured epoxy or put the connectors
in an oven to accelerate the process.
And what happens if you have to do
a really quick termination to replace
a few damaged connectors at the
field or in a premises network?
Edward A.Y. Fisher, Application Engi-
neering Manager, says there are two
kind of adhesives you can use in this
cases: cyanoacrylates and anaero-
bics.
Cyanoacrylates Adhesives: Fisher
assures they are used in optical fi-
bers although they donât adhere well
to glass. The recommendation is to
use these instants adhesives in con-
nectors that can later be replaced for
epoxy cured connectors.
If you are using a cyanoacrylate
adhesive, replace Step 3 and do this:
Inject the adhesive into the connec-
tor, place the cable inside and spray
the tip of the ferrule with an acceler-
ator. The curing process will be done
between 30 seconds and 1 minute.
Anaerobic adhesives: These are sub-
stances that harden when they are
set in the ferrule due to the absence
of air. Resistance to extreme envi-
ronments is not as great as epoxyâs.
When working with an anaerobic
adhesive, replace Step 3 by inject-
ing the adhesive into the ferrule,
dip the bare fiber in the accelerator
bottle and insert it into the connec-
tor. It will cure in about 1 minute.
FOA recommends using
the adhesive Loctite 648 and the ac-
celerators Loctite 7471 or 7649.
Before deciding if working with
adhesives instead of epoxies, keep in
mind that epoxy terminated connec-
tors have a better performance and
reliability. FOA advises to use epoxy
because it makes polishing easier
since the hardened epoxy at the fer-
rule tip protects the fiber from get-
ting scratched.
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11. FIBER OPTIC
POLISHING
Polishing is the process that follows connectorization and consists on cleaving
and rubbing the protruding fiber to create a smooth surface, in order to avoid
high loss and reflectance. It needs to be done carefully to not damage or break
the optical fiber.
Singlemode optical fiber polishing needs to be done more carefully than mul-
timode due to the difference between the diameters of the cores, which makes
tiny scratches worst on singlemode connectors. Singlemode fibers are polished
with diamond films, while multimode with alumina films.
How to do it?
It is recommended to work on a dark
mat .....because it helps you see the
fiber. Remember .....to organize your
work place in a comfortable .....way be-
fore starting. Youâll need:
Optical fiber scribe
Fiber polishing plate
Rubber polishing pad
5”m, 3”m and 1”m lapping films
for ceramic ferrules
The polishing puck that suits
your connector
Lint-free wipes
Distilled water
Isopropyl alcohol
Compressed air
200X Microscope
*Keep in mind that although some of these steps are repetitious it
is necessary to follow all of them to get a proper polish.
Hold the connector, grab the scribe
and score the fiber above the
epoxy bead without using too much
pressure. Use your thumb and fore-
finger to grab the fiber and pull it up
and away. Put the fiber in a dispos-
al unit. Use an eye loupe to look at
the cleaved end of the fiber. A cleave
is considered optimal if just a fi-
ber diameter of fiber protrudes the
epoxy drop.
STEP #1 STEP #2
Air polish the protruding fiber with
the 5”m lapping film. Grab the
connector steady and gently rub the
lapping film back and forth against it
for about 20 seconds, until the fiber
is leveled with the epoxy bead.Clean
the glass polishing plate with a lint-
free wipe humidified with isopropyl
alcohol.
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12. Clean the bottom of the polishing
puck and the connector ferrule with
a lint-free wipe moisturized with iso-
propyl alcohol and dry it with canned
air. Insert the connector into the
polishing puck while holding both
of them on the air. Do not place the
polishing put on the rubber pad when
inserting the connector because you
could break the optical fiber.
Clean the rubber pad and the shiny
face of the 3”m lapping film using a
lint-free wipe moisturized with iso-
propyl alcohol. Put the 3”m lapping
film on the rubber pad with the shiny
face down.
Add two drops of distilled water on
the 3”m lapping film, softly place the
connector on it and start polishing
the fiber in a figure 8 pattern without
using too much pressure, moving the
puck to the dry part of the film.
About 10 to 15 figures eight should be
made to get a proper polish.
Put the 5”m lapping film on the
rubber pad and gently place the
assembled polishing puck on the
film, taking care not to scratch the fi-
ber. Before following this step, make
sure the surfaces of the plate and the
rubber pad are properly cleaned. If
not, clean them with a lint-free cloth
moisturized with isopropyl alcohol.
Clean the rubber pad and the shiny
face of the 1”m lapping film using a
lint-free wipe moisturized with iso-
propyl alcohol. Put the 1”m lapping
film on the rubber pad with the shiny
face down.
Place two drops of distilled wa-
ter on the 1”m film, gently put the
connector on it and lightly applying
pressure.
Start polishing the fiber in a figure 8
pattern, moving the puck to the dry
part of the film. About 10 to 15 figures
eight should be made to get a proper
polish. Check the ferrule with a 200X
magnification microscope.
Start rubbing the fiber against it in
a figure eight pattern without using
too much pressure, until the sur-
face smooths. The 5”m film can be
reused for 8 to 10 connectors. Once
you finish polishing, remove the
5”m film.
According to the Fiber Optic
Association a properly polished fi-
ber requires from four to five figures
eight.
Remove the connector from the
polishing puck and clean it using a
lint-free wipe soaked with isopropyl
alcohol. Use the microscope to check
if the fiber is leveled with the tip of
the ferrule and if it has any scores. If
it is the case, repeat Step 6 and Step
7.
You need to check that:
* The ferrule endface is free of epoxy.
* The fiber is a the same level with
the end of the ferrule.
* The fiber core has no heavy
scracthes on it.
STEP #3
STEP #6
STEP #4
STEP #7
STEP #5
STEP #8
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13. Recommendations:
* If you are doing terminations in the
field, be sure that your workspace is
as clean as possible and practically
dust free.
* Donât apply excessive of pressure
when air-polishing and polishing
because it could break the fiber.
* Be extremely careful when cleav-
ing the optical fiber with the scribe.
A bad cleave could shatter the fiber.
* Make sure your lapping films arenât
worn out. Excessively used lapping
films could damage the entire pol-
ishing process.
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14. Editor: Marialmi RodrĂguez
Co-Editor: Johann Toirac
Photography and design: Nichott LeĂłn
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