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Fused fiber couplers were fabricated by controlling the coupler waist profile, and the wavelength and the polarization dependences against the waist profile were investigated experimentally. In case of the strongly fused coupler, the coupling is a little stronger for the -polarized light than the -polarized light, and the wavelength dependence increases with fusing more strongly in spite of the shorter effective coupler length. In case of the weakly fused coupler having a dumbbell profile with a narrow neck, the wavelength and the polarization dependences increase rapidly with narrowing the neck, and the wavelength dependence and the coupling become much larger for the -polarized light. The wavelength dependence becomes smallest around a dumbbell profile with the aspect ratio of 1.94.