What Are Fiber Optic Cables Made Of?

Today we’ll look at the construction of fiber optic cables.

An optical cable contains one or more fibers.

The core, cladding, Kevlar®, ferrule, and polishing are all involved in the construction of a fiber optic cable.

The core is the center part of the fiber cable through which light is transmitted; it is made up of a continuous strand of glass.

The fiber consists of a core surrounded by a cladding layer. The cladding surrounds and reflects light back into the core.  The diameter of the cladding is usually 125 microns.

Kevlar® is the registered trademark for the strong synthetic fiber or “yellow hair” used as a protective outer sheath for fiber optic cables. Its strength protects the cable from damage and kinking.

The ferrule is the protruding portion of a fiber connector. It is the ceramic, plastic or stainless steel part of a fiber-optic connector that holds the end of the fiber and precisely aligns it.

The fiber is inserted into the ferrule and cemented with an epoxy or adhesive. This gives it long-term mechanical strength and prevents contamination.

The ferrule is the most important and costly part of a fiber connector. If its length, hole centering, and inside and outside diameters are not exact, a poor connection will result.

The fiber at the end of the ferrule is then polished to create a flat even surface and to allow two cables to be mated to transfer a signal. Higher grades of polish give less insertion loss and lower back reflection.

More on insertion loss and back reflection to come!