Optical EngineeringInvestigation of open-air laser-induced chemical vapor deposition of carbon on moving optical fibers
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Using a CO2 laser as a heat source, carbon coatings have been successfully deposited on moving optical fibers in an open-air laser-induced chemical vapor deposition (LCVD) reactor. Applications include fusion splice recoat and in-line coating of optical fibers. The relationship between operating parameters and the carbon deposition temperature and rate was investigated. Results indicate that they are strongly dependent on the laser power density and the optical fiber's traverse velocity. In order to provide a deeper understanding of the fundamental principles that govern laser heating and the carbon LCVD processes, a heat transport model was developed to predict the fiber surface temperature during deposition. The surface temperatures obtained from experiments compared well with the predicted temperature. Based on the temperature calculations, various kinetic parameters, including the activation energy EA and pre-exponential factor k0 for the carbon deposition process, are determined. The optical fiber signal loss at 1550 nm induced by the LCVD process is observed to be less than 10–3 dB at low laser power density.