Fluorinated Polymer Claddings for Optical Fibers

The standard process to coat glass optical fibers with polymers consists of applying a liquid coating with a die and UV-curing it. It is not straightforward to employ this procedure with low-index fluorinated coatings because of their very low viscosity. This work shows that the viscosity of fluorinated diacrylates can be increased by two orders of magnitude by controlled crosslinking with a tetrafunctional silane. The resulting material has a viscosity that is high enough for a fiber coating operation. Photocured coatings with very low refractive index (1.323) have been obtained and employed as claddings for glass optical fibers. Losses as low as 3 dB/km were measured on these fibers.