How to polish fiber connectors – Fiber connector polishing Tips and Practices
How to make your fiber optic polishing
work to be correct and how to revise your fiber connector polishing
When you polishing a fiber connector or
several connectors in polishing holder, by fiber polishing machine or fiber
polisher, there are procedures and setting parameters designed to leverage the
machines best practices as well as previous developments and experience.
Additionally, there are tips to
consider applying during daily production to improve first pass yield,
efficiency and results to avoid scrapping costs.
The standard polishing process includes
three steps:
Epoxy Removal
Geometry checking
Final Step: finishing the fiber
connector end-face, check optical surface
Below we share tips for each step of
the fiber polishing process:
Epoxy removal
Pre- Polish
When connectors are loaded on the
polishing fixture or fiber polishing holder jig after cleaving, there are
large, sharp edge fibers and inconsistent fiber protrusion due to different
fiber cleaves. This can result in fiber
breaks if polishing, by machine, is started immediately.
Tip: start polishing the connectors
loaded on the jig with SC Film mounted on the rubber pad and then by hand/air
delicately, with little hand pressure making few rotations (around 10). Next the fiber protrusion has more consistent
length distribution over all ferrules resulting in less fiber breakage (fiber
into ferrule bore hole). After this
initial operation, one can start polishing with the machine using the same film
used for air polishing.
LC Conical
The available surface of the 1.25 mm
connector is small and sometimes due to this limited surface, epoxy is also
going to the base of the chamfer area that you cannot remove using the
polisher.
Tip: After the epoxy removal step on
the polisher, if some epoxy is still present on the chamfer area, use a little
scalpel to remove residues. This will allow to move to the next step (Geometry)
avoiding any contamination on D films.
For other types of ferrule (2.0 or 2.5
mm) it is a good practice to check, after epoxy removal, if all the epoxy has
been polished away (checking the front face of the ferrules).
Fiber Polishing Jig Holder Locking
Mechanism with Individual Ferrule
A fiber
polishing fixture or holder jig where the ferrules are independently
moving from the each other is called Individual Pressure Control (IPC) fixture
and is recognized by the use of spring loaded adapters to lock and to keep the
ferrule in place.
Tip: after checking if there are not
any epoxy residues left, it is a good practice to verify if all the connectors
are well positioned (same height) and if the spring of each adapter is working
properly with the ferrule moving freely – not stuck due to polishing residue.
This guarantees each ferrule will be under the defined fiber polisher pressure
in the polishing steps offering more consistent geometry results.
Geometry Checking
Air Bubble Under Fiber Polishing Film
A common occurrence after positioning
on the rubber pad is air bubbles under the fiber polishing lapping film.
When this occurs, it must be removed
because during the geometry polishing process as the air cushion can modify the
ferrule geometry (radius and/or apex).
Tip: to avoid this effect, use a roller
to press down the lapping film on the rubber pad. It is important to have a
different roller for each type of film to avoid contamination especially from D
film to final film. If one uses the same
roller, it is essential to clean it before moving to the smaller film grid.
Tip: when using just one roller, to
avoid contamination, take two films one on top of the other (one on top upside
down) and then use roller. The lapping film that will used for polishing
connector will not be effected by any cross-contamination.
Fiber Polishing Film Longer Life
Diamond fiber lapping film is the most
expensive film we use on the polishing process and one consideration when
selecting a supplier is the number of times you can use it. There are fiber polishing films used for 10,
15, 25 times, or even longer depending on the process and specific customer
specifications.
Tip: after a certain number of usage,
typically 10 times, if you clean the surface with alcohol you are able to
extend the life of this film (using alcohol removes debris from previous
polishing).
VIEW: Diamond Films Product Matrix
Fiber Polishing Rubber Pad
In a polishing process, we use rubber
pads typically 60 to 80/85 durometer.
Keeping consistent geometry can be a challenge.
In principle, a rubber pad that is too
soft can help to reduce radius but effect negatively the apex.
Using a harder pad with higher pressure
should be better to get positive radius and apex results.
Tip: always try to develop a process
using pads with same durometer throughout the entire process. Changing the
hardness of the fiber polishing pad will effect radius and/or apex and can make
it difficult to bring both parameters within the specification. Usually adjusting pressure and timing, using
the same pad, can achieve desired results.
If you do need to change to a softer pad, decrease the durometer maximum
by approximately 10 durometer.
Choice of APC connector holder/Jig
According to Connector Style
In the market there are two different
types of ferrules: Stepped and Conical.
As soon as you select the connector style,
you need to consider the related fiber polishing fixture holder jig.
Tip:
Stepped Ferrule – require a jig with an
APC angle of 8°
Conical Ferrule – require a jig with an
APC angle of 8.3°
FINAL STEP
CLEAN, CLEAN, CLEAN
Scratches are a fiber optic assembler’s
nightmare because if it occurs, they jeopardize all of the previous activities
and are costly due to the waste of time and additional material.
Tip: each step requires good
cleanliness to avoid contamination especially when you move from D film to
Final polishing film. Quite often this
activity is underestimated but if you make this a priority, you can avoid
costly issues.
Tip: use spray water to remove all the
debris on the ferrule and mainly at the jig’s bottom surface. Follow this by wiping the operation using
Cleaning Wipes or similar paper moving from the center of the jig to the
outside.
Final Fiber polishing Film Choice
In addition to the nice smooth surface,
final film is extremely important to define the right fiber protrusion. Based on the requested specification, you can
choose different types of film that provide various results.
Tip: important to know the different
specifications and what your requirement is: Fiber protrusion, Undercut,
Flatness with respect to the Ferrule. Basically, fibers can protrude or stay
below the ferrule surface according to the described parameter to guarantee the
best fiber physical contact terminated in a connector.
Tip: if you don’t have access to
different final lapping films, adjusting time and pressure, can also achieve
specified results with some limitations.
Polishing-Tips-and-Best-Practices-for-Single-Fiber-Connectors-fig-1
Fiber optics requires physical contact
between the two mating parts because if you have an air gap between, it will
cause high back reflection. The physical
contact will happen when you have fiber protrusion but considering the
compression force made by the connectors, you could have some physical deformation
of the fiber and ferrule. When that
happens, there is physical contact with flat and undercut if the related values
are according to the specified parameters.
One might ask, why not only use
protruding fiber and the answer is that concern is about fiber breaks when the
two fibers are pushed against the others?
They specify undercut or flat fiber vs. end face the ferrule to better
protect the fiber but still having physical contact. It is clear the parameters have to be
according to the specifications (as seen on the graphic) otherwise you will
experience air gap.
Polishing-Tips-and-Best-Practices-for-Single-Fiber-Connectors-fig-2
CONCLUSION
Hundreds of fiber optic patch cable
assembly facilities around the world use Fibermart’s Fiber polishing films,
including multiple Fortune 500 companies. Fibermart has polishing process
technical experts on staff as well as lapping film experts.
Please note a few of our resources
whether you are implementing a new polishing process, fine-tuning your process
to ensure it produces repeatable results, or looking for help to resolve a
polishing issue by writing to us: sales@fiber-mart.com or support@fiber-mart.com
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