Sapphire optical fiber with SiBCN coating prepared by chemical vapor deposition for high-temperature sensing applications

To prevent the oxidation of BN-coated sapphire optical fiber (SOF) at 800 °C, a SiBCN ceramic coating was used as an outer coating owing to its excellent high-temperature oxidation resistance. Compared with BN/SOF, the tensile strength of SiBCN/BN/SOF increases from 500 to 723 MPa at 1200 °C. The optical properties of double coating indicate that the addition of SiBCN does not diminish the total reflection of the BN coating. Furthermore, SiBCN-coated fibers indicate lower residual stress and performed better compared with other coated fibers in terms of mechanical and optical properties. Hence, SiBCN is highly suitable as an outer coating of SOF.