An optimum approach for fabrication of low loss fused fiber couplers

An optimum approach for the fabrication of low loss fused biconical taper c ouplers (FBTCs) is presented. The results show that the taper angle of the device parameter is strongly dependent on the technological parameters of t he filament range, pulling length, and gas flow rate. The FBTC having a sma ller 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 approa ch that the taper angle of the device parameter is strongly correlated to t he 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 c alculation based on the coupled local-mode theory for the analysis of the d ependence of excess loss on taper angle is also presented. Calculated resul t is in good agreement with the experimental data. (C) 2001 Elsevier Scienc e B.V. All rights reserved.