Optical fibers are typically manufactured from a preform consisting of a silica core which may be doped silica or pure silica and a cladding classically of silica having a lower refractive index than the core. An additional layer or coating/buffer is added to prevent the ingress of moisture and other contaminants which would lead to very early failure of the fiber, and increase tensile strength. These coatings/buffers are usually polymers of various types, such as Polyimide, Acrylate, Nylon, and Tefzel™.
Metal coated/buffered fibers were originally developed for ultra high reliability telecommunications applications. The metal coating preserves the high initial mechanical strength and provides resistance against static fatigue (the failure under long term tensile loading), and in particular Aluminum, a hermetic coating to the fiber. In addition to high strength, metal coated fibers can be used at very high temperatures. Aluminum coated optical fibers have a rated operating range of -269°C to +400°C. Tight buffered Gold coated fibers have a rated operating range of -269°C to +700°C. Aluminum and Gold coating can be applied on continuous lengths to a wide variety of multimode, step index, graded index, and single mode fibers.
Note: The fibers in the following table carry a designation “SFS” standing for “Silica Fluorinated Silica” and “AFS” standing for “Anhydrous Fluorinated Silica” followed by the core and cladding diameters (in microns) and concluding with the suffix “G” that designates Gold buffer.
