Cable engineers may be creative, but sometimes they use that creativity the wrong way. Handling optical signals is one of those ways. But for a long time, nothing made sense. Soon after, I was in one of the operator s hubs and saw a technician cleaning connectors with a bottle of rubbing alcohol from the corner pharmacy. We cleaned all the optical connectors in the hub using proper materials and techniques, and the problems dropped out of sight.
Dirty connectors create several problems.
The most obvious one is signal loss. An optical connection is nothing more than two optical fibres butted against each other. The two fibres must be aligned to extreme precision to couple light from one to the other. It doesn t take much more than a spec of dust or a smudge to block the light. Internally modulated lasers, the dominant type used in cable TV, have some chirp, meaning their wavelengths change with modulation.