An improved coating for optical fibers is described. The present invention is a dimensionally precise and uniform coating with low-porosity. The improved coating is applied via sputtering within a vacuum chamber. Environmental conditions are monitored within a cylindrical magnetron during sputtering. Sputtering is adjusted or temporarily ceased when environmental conditions approach a damage threshold. Sputtered particles within a plasma cloud are dimensionally similar and adhere to an optical fiber in a volume efficient arrangement forming a more precise, denser, and more adherent coating. Embodiments of the present invention provide improved pull strength by compressively constraining the optical fiber within the coating and by closing microcracks.