An optimum approach for the fabrication of low loss fused biconical taper couplers (FBTCs) is presented. The results show that the taper angle of the device parameter is strongly dependent on the technological parameters of the filament range, pulling length, and gas flow rate. The FBTC having a smaller taper angle and hence a lower excess loss, has a lower filament speed, longer pulling length, a higher gas flow rate than those of a larger taper angle and a higher excess loss. Therefore, by applying this optimum approach that the taper angle of the device parameter is strongly correlated to the technological parameters, I-in. long FBTCs with low loss of 0.13 dB and high yield of 90% have been fabricated successfully. A simple theoretical calculation based on the coupled local-mode theory for the analysis of the dependence of excess loss on taper angle is also presented. Calculated result is in good agreement with the experimental data.