An optical fiber includes an entrance face that is optically coupleable with a device for transmitting a light beam through the optical fiber. The entrance face includes a core region and a cladding region surrounding the core region. The cladding region is at least partially covered with a coating, which is made of metal, for example. That is, the coating is formed over a whole area of the cladding region or the coating is formed on an area of the cladding region defined in a vicinity of the core region. The coating has a mirror surface to increase the reflectivity thereof and enhances the reflectivity of the entrance face.