Ferrule

A precision tube which holds a fiber for alignment for interconnection or termination. Ferrule may be part of a connector or mechanical splice.
The ferrule is a rigid tube used to confine and support the stripped end of a fiber as found in connectors.
The ferrule, usually made of metal or ceramic, is the central part of the male connector. It is designed to both align and protect the fiber core during connection. The ferrule tip is polished to ensure a smooth finish on the fiber end. Polish can also minimize connector loss or backreflection, depending on the angle used. There are four types of polish: PC, super PC (SPC), ultra PC (UPC) and angled PC (APC).