Phthalocyanine, in general, has some attractive features as a dopant for an acrylic optical fiber core developed for a fiber-optic sensor. Guidelines for achieving a phthalocyanine-doped fiber with a ruled dispersing manner were investigated. A synthesized fiber using a phthalocyanine decorated with tertiary butyl groups had shown a mode-dependent absorption that had suggested a gradual dye distribution in the core radial direction.