A protective Coating applied directly on the fiber. Primary buffers encompass the 125 um cadding up to 250 um. Secondary buffers typically buffer from 40 0um to 900 um.

In a Fiber optic communication cable, the buffer encompasses one or more optical fibers in order to provide mechanical isolation, protection from physical damage and fiber identification. The buffer may take the form of a miniature conduit, contained within the Cable and called a loose buffer, in which one or more fibers may be enclosed, often with a lubricating gel.