Fiber Bragg Gratings have many applications. FBGs can be used like a sensitive element for high temperature measuring. Faber Bragg gratings are sensitive to temperature changes. Hard environment FBGs can be provided as separated or chain of FBGs with different wavelength. Multy - points temperature monitoring are available by use of chain FBGs. Different types of single mode optical fibers and fibers coating are using for writable. High temperature acrylate coating fibers applying for temperature range up to 150⁰C. Polyimide or metal (Cu, Al) coating fibers are used for high temperature application with maximum temperature 300⁰C and 500⁰C respectively. With using for protection of a steel tube, it is possible to use FBGs up to 700⁰C.