Fiber Optic Connections
fiber optics, the tolerance to dirt or contamination on the ends of the ferrules of a connector is near zero.
From left: dirt, contamination, clean connector
dirt particles are about the size of the core of SM fiber and are usually
silica based - they may scratch PC connectors if not removed! Patch
panels have mating adapters that can become contaminated if left open
to the air or scrape off foreign particles under repeated usage. Test
equipment has fiber-bulkhead outputs that need periodic cleaning, since
they may have hundreds of insertions of test cables in short time
recommend you always keep dust caps on connectors, bulkhead splices,
patch panels or anything else that is going to have a connection made
with it. Not only will it prevent additional dust buildup, but it will
prevent contamination from being touched or damaged from dropping.
clean connectors before mating, whether for testing or making network
testing, we recommend that connectors on both the reference and tested
cables be cleaned before every test, as every time the connector is
exposed to air, it can accumulate dust. Typical airborne dust is almost
the size of the SM fiber core, so cleaning every time is even more
important than MM. A secondary effect is that if the connectors are
dirty, it can scratch the end finish (most dirt is silica (sand) based)
and cause higher reflectance if not loss.
are several types of cleaners which can be used.
companies sell cleaning kits for fiber optics, including AFL, NEPTEC,
Chemtronics., NetOptics Etc. They are readily available from
distributors. Some are dry, some us cleaning solutions. They are all
good solutions if you follow their directions.
use lint free pads and isopropyl alcohol to clean the connectors. Some
solvents MIGHT attack epoxy, so only reagent-grade 99% isopropyl
alcohol should be used. Never use cotton swabs or cloth it will leave
threads behind. Clean and dry the end of the ferrule just before
Some optical cleaners for lenses may leave residues. Residues usually
attract dirt and make it stick.
used Alco Pads which are pure isopropyl alcohol on lint-free pads for
over 20 years with no problems. After the alcohol evaporates, they are
good to dry the ends of the ferrules after cleaning.
"canned air" has a liquid propellant and may leave a residue unless you
1. hold them perfectly level when spraying and 2. spray for 3-5 seconds
before using to insure that any liquid propellant is expelled from the
nozzle. These cans can be used to blow dust out of bulkheads with a
connector in the other side or an active device mount (xmit/rcvr).
NEVER use compressed air from a hose (they emit a fine spray of oil
from the compressor!) or blow on them (you breath is full of moisture ,
not to mention all those germs!)
better way to clean these bulkheads is to remove both connectors and
clean with Alco Pads, then use a swab made of the same material with
alcohol on it to clean out the bulkhead.
on FO power meters should also be cleaned occasionally to remove dirt.
Take the connector adapter off and wipe the surface, then air dry or
dry with a lint-free wipe.
on the connectors/cables used for testing will get dirty by scraping
off the material of the alignment sleeve in the splice bushing. Some of
these sleeves are molded glass-filled thermoplastic and sold for
multimode applications. These will give you a dirty connector ferrule
in 10 insertions. You can see the front edge of the connector ferrule
getting black. The alignment sleeve will build up an internal ledge and
cause a gap between the mating ferrules - creating an attenuator!
Use the metal or ceramic alignment sleeve bulkheads only, especially
for testing where you have repeated insertions.
Cleaning contaminated connectors requires aggressive scrubbing on the
ferrule sides with the AlcoPad and tossing the bulkhead away.
Application Notes And Cleaning Video: Westover
has several application notes on inspecting and cleaning fiber optic
connectors. The video is a big file (50+MB) but a good tutorial. Download
Cleantex Alco Pads