These methods are primarily applicable to measuring the geometry of opaque fiber coatings and buffers. Although FOTP-55 can be used for fibers having translucent coatings, the side-view methods of FOTP-173, -119 and -163 are the preferred methods for measuring such coatings.

This method covers only the dimensions of the protective coating or buffer. Although the uncoated cladding diameter may also be determined with this method the measurement is generally not made to the degree of accuracy that is obtainable with other tests methods, such as FOTP-45 and -176.

This document describes a manual method using an optical microscope (Method A) and an automated gray-scale method (Method B) that uses computer data processing techniques.

A means of quality control on a go-no-go basis using a template is given in Annex A.