Specialty Optical Fibers Handbook

easily cause surface damage and a precipitous reduction in strength, techniques

were developed very early to enable a protective polymer coating to be applied

in-line without itself causing damage to the fiber surface. Because of the purity of

all of the materials employed, there are rarely any solid impurity particles in the

body of the fiber, so in almost all cases, the strength of the fiber is the strength of

its surface. Thus, the condition of the surface of the fiber determines its strength.

Whatever the situation with regard to the ‘‘starting’’ strength of any given fiber

or fiber type, several things must be kept in mind:

a. Fibers are normally coated in-line with a polymer, which provides protection

from mechanical damage. The strength of