The effects of surface fluorinating on the F/C ratio of polymethyl methacrylate (PMMA) are investigated. The F/C ratio of PMMA increased when the fluorinating temperature was enhanced or the fluorinating time was prolonged and then was apt to be invariable. The attenuation of the polymer optical fiber (POF) was obviously reduced after PMMA POF was surface fluorinated. Finally, the mechanism of reducing attenuation of POF is discussed. (c) 2005 Wiley Periodicals, Inc.