Fusion Splicing of Optical Fibers

It is the most widely used method for splicing optical fibre. There are a number of fusion welding machines manufactured by different companies, some of them are fully automatic and controlled by a microprocessor and some are partly automatic and manually controlled. In some cases, the fibre ends & the fusion process can be seen on a TV monitor screen.

The process can be sub-divided into the following three steps:

(a) Axial alignment.
(b) Prefusion
(c) Actual fusion welding.

In some of the machines the axial alignment is done manually by manipulating a number of knobs and is observed with the help of a high power microscope. This is normally followed in case of multimode fibre. In some modern machines, pre-aligned, V-grooves are provided & finer adjustment is done, if necessary. For single mode fibre, other techniques are followed. The best one is fully automatic core alignment method which is used now a days.

After aligning is done, the ends of the fibres are fire polished by an electric are and this method is called pre-fusion. During this process, the fibre ends are kept separated at a distance, after this they are brought closer and the process is called as fibre end feeding. This feeding process is continued during actual fusion by electric arc to prevent a reduced section at the point of welding.

The process of prefusion, fibre ends feed and actual fusion are critical to a good weld and are automatically controlled by the fusion machine. The fusion time of single mode fibre is less than that of multimode fibre.