In this paper, we describe the tensile-strength enhancement of optical fibers obtained by controlling the parameters of the fused biconical tapering process used to produce them. Numerical simulations using the finite-element method show that the internal stress in an optical fiber is related to the cooling time after the tapering process. This stress is reduced by increasing the cooling time, although the internal stress at the edge of the heated area remains significantly higher than that of other areas. Experimental studies based on the simulation results show that the tensile strength of a tapered optical fiber is gradually enhanced as the cooling time is increased from 10 s to 600, 1200, and 1500 s.