Effect of glow discharge plasma on step index polymer optical fiber parameters

DC glow discharge plasma of power 40 W was applied to step index polymer optical fibers for different exposure times. Nitrogen, oxygen, and hydrogen gases were used to obtain the glow discharge. The fiber core material was poly methyl methacrylate and the cladding was fluorinated polymer. The effect of plasma on the optical parameters, such as core index profile, cladding index, and the numerical aperture, was studied by multiple beam interference fringes and Fourier transformation of infrared spectroscopy spectra. It was found that the plasma treatment affected the optical parameters of both the cladding and the core regions of optical fibers. The optical parameters also changed with the treatment time. The hydrogen plasma had effects greater than those of nitrogen and oxygen plasma. These observed results can be explained by the effect of the electric field during plasma treatment. The studied optical fibers after plasma treatment can be used as inverted-graded index with its important applications.