WAVELENGTH-SELECTIVE FUSED FIBER COUPLERS UTILIZING FIELD DIFFERENCE BETWEEN CORE AND CLADDING MODES

It is shown that wavelength-selective fused taper couplers can be made by using the large difference in field distribution between core and cladding modes. It becomes evident from the calculation results that fibers with high-index differences and a thin outside diameter are necessary to fabricate the couplers. Fused taper couplers are made of thin fibers with cladding diameter of 66.0-mu-m and index difference of 0.84%. The splitting ratio of the coupler obtained is more than 20 dB in the 1.53-mu-m region and less than - 20 dB in the 0.8 to 1.0-mu-m region. The loss is less than 0.2 and 0.4 dB in the 1.53-mu-m and the 0.8 to 1.0-mu-m regions, respectively.