With fiber optics, our tolerance to dirt is near zero. Airborne particles are about the size of the core of SM fiber- they absorb lots of light and may scratch connectors if not removed! Dirt on connectors is the biggest cause of scratches on polished connectors and high loss measurements!
1. Try to work in a clean area. Avoid working around heating outlets, as they blow dust all over you
2. Always keep dust caps on connectors, bulkhead splices, patch panels or anything else that is going to have a connection made with it.
3. Use special fiber optic cleaners or lint free pads and isopropyl alcohol to clean the connectors.
4. Ferrules on the connectors/cables used for testing will get dirty by scraping off the material of the alignment sleeve in the splice bushing - creating an attenuator. You can see the front edge of the connector ferrule getting black! Use the metal or ceramic alignment sleeve bulkheads only for testing.
December 2, 2011