Preparation of Elevated NA Fluoride Optical Fibers

Elevated NA fluoride optical fibers having minimum losses of less than 1 dB/km have been prepared using a dry processing technique. NA ranging from 0.19 to 0.24 has been obtained by substituting LiF and/or ZrF 4 in basic core and cladding glasses consisting of ZrF 4 –BaF 2 –LaF 3 –YF 3 –AlF 3 –LiF by NaF and/or HfF 4 , respectively. It has been demonstrated by measuring critical cooling rates for glass-formation that glasses containing NaF applied to elevated NA fibers have high glass-forming ability, It is found that elevating NA enables low OH impurity absorption to be successfully reproduced in FEP coated fibers and that applying glasses containing NaF to elevated NA fibers effectively reduces extrinsic scattering.