Method for detecting pinholes and incomplete coverage of hermetic coatings on optical fiber waveguides

摘要

A method detects incomplete coverage of hermetic coatings applied to optical fibers during in-line optical fiber fabrication procedures as well as off-line applications. A fluorescent material surrounds the core region of the optical fiber prior to the formation of the hermetic coating on the optical fiber and energy is radiated in the optical fiber to propagate in the cladding mode. This causes an excitation of the fluorescent material to fluoresce in response to the propagated energy. An appropriately disposed detector detects levels of emitted fluorescence along the length of the optical fiber to indicate where the hermetic coating is incomplete or where pinholes in the hermetic coating are located. Optionally, the fluorescent material is located outside of the cladding layer, inside of the cladding layer near its outer surface or throughout the cladding region to fluoresce when excited by the propagated energy. Different wavelengths of radiation can be used which excite different fluorescent materials so that pinholes or incomplete coating coverage can be detected in hermetic coatings that have different chemical compositions.