Theoretical investigation of light coupling phenomena in wavelength-flattened couplers

A study of light coupling phenomena in wavelength-flattened couplers by normal mode analysis is discussed. The effective index method and step approximation of the taper are used to analyze the mode coupling in the fused-taper region. It is shown that coupler parameters such as the dissimilarity of the two fibers, the degree of fusion, the minimum taper waist and the taper length should be optimized to get flat coupling characteristics. The optimum relationship among these coupler parameters is determined for fused-taper couplers employing standard telecommunication fibers.