Definitions of Hermetic Coated Fibers and Carbon Coated Fibers and Metal Coated Fibers

hermetically coated fiber
In order to keep the mechanical strength and loss of the optical fiber stable for a long time, inorganic materials such as silicon carbide (SiC), titanium carbide (TiC), and carbon (C) are coated on the glass surface to prevent water and hydrogen from outside. Diffusion produced fiber (HCFHermeticallyCoated Fiber). Commonly used in the production process of chemical vapor deposition (CVD) method, high-speed deposition of carbon layers is used to achieve sufficient sealing effect. This carbon-coated fiber (CCF) can effectively cut off the intrusion of the fiber and the outside hydrogen molecules. It has been reported to last for 20 years in a hydrogen atmosphere at room temperature without increasing losses. Of course, in the process of preventing moisture intrusion and delaying the fatigue process of mechanical strength, its fatigue coefficient (Fatigue Parameter) can reach more than 200. Therefore, HCF is used in systems that require high reliability in harsh environments, such as submarine optical cables.
Carbon Coated Fiber
The fiber coated with carbon film on the surface of silica fiber is called carbon coated fiber (CCF: Carbon Coated Fiber). The mechanism is to use the dense film layer of carbon to isolate the surface of the optical fiber from the outside world, so as to improve the mechanical fatigue loss of the optical fiber and increase the loss of hydrogen molecules. CCF is a type of Hermetic Coated Optical Fiber (HCF).
Metal Coated Optical Fiber
Metal Coated Fiber is an optical fiber in which metal layers such as Ni, Cu, and Al are coated on the surface of the fiber. There are also plastic coated on the metal layer, the purpose is to improve heat resistance and can be energized and welded. It is one of the optical fibers that are resistant to harsh environments, and can also be used as a component of electronic circuits. Early products were made by coating molten metal during the wire drawing process. Because this method is too different in the expansion coefficient of the glass and the metal, it will increase the micro-bending loss, and the practical rate is not high. Recently, the performance has been greatly improved due to the success of low-loss electroless coating on the surface of glass fiber.