Contamination effects in butt coupled and expanded beam singlemode fibre optic connectors

Singlemode fibres will be required for airborne applications such as sensor systems, RF over fibre and wavelength division multiplexing of data. Deployment of singlemode fibres on aircraft has been slower than multimode. This is partly because of concerns over maintaining core alignment within connectors in harsh environments (vibration, shock, temperature variations etc.) but also the perceived effects of contamination given the small core size. These concerns apply to butt-coupled connectors where fibre cores are in intimate contact at a connection. Mitigation of these effects is often suggested by the use of expanded-beam technology. However, quantitative data generated using real contaminants is not freely available.