Cleaning Fiber Optic Connections
With 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
Airborne 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 frames.
We 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.
Always clean connectors before mating, whether for testing or making network connections.
When 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.
There are several types of cleaners which can be used.
Many companies sell cleaning kits for fiber optics, including Sticklers, Chemtronics., NetOptics, AFL etc. (Links below) They are readily available from distributors. Some are dry, some us cleaning solutions. They are all good solutions if you follow their directions carefully and always inspect after cleaning.
You may use lint-free pads and isopropyl alcohol to wet-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 insertion. If you wet-clean, use a dry lint-free pad to dry the connector off and then inspect it to ensure it is clean.
Some optical cleaners for lenses may leave residues. Residues usually attract dirt and make it stick.
We have 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.
All "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!)
A 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.
Detectors 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.
Ferrules on the connectors/cables used for testing will get dirty on the sides as well as the ends 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.
- Ed Forrest is the guru of cleaning. He's written a number of books on fiber cleaning - yes, it's a big enough subject for more than one book - and these are THE references on cleaning. His website is http://www.fiberopticprecisioncleaning.com/ and he has videos on YouTube. ( Use Code FVCFR80DX for a 20% discount on all www.createspace.com book orders.
Cleantex Alco Pads
MicroCare Sticklers brand