Abstract: According to the principle of volumeconservation, a differential equation of tapering shape function has been derived for a fused fiber. A closedform solution is obtained under the boundary conditions and from the effective length of the fused zone for the fused tapering process. For different tapering processes with various torches, the tapering shape function can be described by the solution completely, accurately and conveniently. Experimental data in the form of relevant charts show good agreement with the theoretical results. Especially, given the initial length of the fused zone, the solution can predict the diameter distribution of the taper zone for the fused tapering fiber with arbitrary elongating length.

Key words: differential equation, fused tapering, passive devices, tapering-shape function
, optical fiber