Design, preparation, and properties of a boron nitride coating of silica optical fiber for high temperature sensing applications

Boron nitride light-leakage-proof coating was prepared via chemical vapor deposition (CVD) process on silica optical fiber for sensing applications at high temperatures. Compared with the original fiber, the tensile strength of BN coated fiber was more than two times higher at both room temperature and 700 °C. It was found that the critical value of BN coating thickness at which the strength changes from fiber-controlled into fiber-matrix-controlled is 0.5 μm and that at which the strength changes from fiber-matrix-controlled into matrix-controlled is 1 μm. Moreover, BN coated silica optical fiber exhibited favorable creep resistance at 700 °C. Furthermore, BN coated silica optical fiber performed better compared with the uncoated fiber in terms of optical property. Hence, CVD BN is suitable as a light-leakage-proof coating of silica optical fiber.