Preoxidized Fiber (POF), also known as Oxidized Polyacrylonitrile (OPAN) fiber, is a high-performance intermediate product in the production of carbon fibers. It is derived from Polyacrylonitrile (PAN) precursor fibers through a rigorous pre-oxidation process, which involves exposing the fibers to controlled temperatures in an oxygen-rich environment. This process leads to the formation of a stable oxidized structure, imparting exceptional thermal and chemical stability to the fibers.