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 is evident from the calculation results that fibers with a high-index difference and a thin outside diameter are necessary to fabricate the couplers. Fused taper couplers are made of thin fibers with a cladding diameter of 66.0 mu m and an 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 dB and 0.4 dB in the 1.53- mu m and the 0.8 to 1.0- mu m regions, respectively.<
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