Modification of Coupling Power Parameters for High Accuracy Coupling Ratio of Weakly Coupled Fiber

The directional fiber couplers consist of multi fibers joint have been successfully fabricated by heating of torch flame at atmospheric pressure and pulling the fiber coupling region mechanically at micro scale. Good performance of the coupling coefficient and the coupling ratio was obtained by setting the initial parameter of coupler machine such as the coupling coefficient, pulling speed, pulling length, coupling ratio, hydrogen gas flow and pressure and heating temperature during process. The Coupling coefficient of 3-dB fused directional fiber coupler was determined based on perturbation method and coupling mode. A good agreement between theoretical purposed and empirical coupling coefficient from experimental result was reported. The coupling coefficient between the waveguides is significantly induced by the distance of axial separation between parallel fibers and geometrical coupling region. It is exponentially decreases by increasing separation between fibers. However, by controlling the coupling coefficient, the desired coupling ratio can be easily attained.