Method and system for detecting dirt on optical fibres

摘要

When splicing optical fibres, it is necessary that the fibre ends to be spliced together are clean and that no contaminants will be enclosed in the splice after fusing the fibre ends together. The mantle surfaces and sliced surfaces of the fibre ends (2) are illuminated with coherent light (1) wherewith diffraction of the light is indicative of the presence of dirt and dust. Dirt and dust on the mantle surfaces and sliced surfaces of the fibre ends functions as irregular disturbance sources which produce secondary waves having mutually short optical wave differences whose interference forms an irregular pattern with strong contrast that can be recorded on a screen (4) placed behind the fibres. The secondary light fields that are formed when light is diffracted through clean optical fibres are homogenous and their interference forms a periodic and regular pattern. The difference detected between a regular pattern obtained from a clean fibre end and an irregular pattern obtained from a dirty fibre end can then be used in a dirt-detection system.