Fabrication of UV sensitive single-mode polymeric optical fiber

We report a fabrication process of single-mode polymeric optical fibers (POF) with photosensitive cores which display UV absorption property and may be the suitable precursors to inscribe Bragg gratings. These fibers are composed of polymethylmethacrylate (PMMA) cladding and methyl methacrylate copolymer cores, and processed using the preform drawing technique in our Laboratory. The effects of molecular weight and fabricating techniques on the quality of preform are discussed in detail. Three core systems with enhanced UV photosensitivity are proposed, including benzyl methacrylate (with strong UV absorption) co-monomer contained, benzophenone (photo-initiator) doped, and trans-4-stilbenemethanol (photo-isomerization molecule) doped cores, respectively. Their UV absorption behavior and photosensitivity are analyzed and compared to PMMA. The UV laser induced changes in the UV absorption spectrum and refractive index for trans-4-stilbenemethanol-doped core are detected and the penetration capacity for the photo-induced effect is demonstrated by examining the absorption spectrum change in a film sample being irradiated in presence of a doped core film of 15.5 μm as the shield. In the fiber doped by trans-4-stilbenemethanol, the Bragg grating has been written.