This core wire has a high-accuracy metal ferrule at the optical-fiber end. It is fixed by fusion in the optical module with the center aligned without the use of a connector. It is designed and manufactured according to the customer requirements including the shape of the end. Features The material can be selected from SUS 303, SUS 304 and others. The end surface can be AR-coated. The end of the ferrule is obliquely polished at an angle, 4°, 6°, 8°, 10°, 12° or the like for the prevention of the reflection of light. A flat-polished end is also available. The shape of the ferrule can be modified by request.