Specialty Optical Fibers Handbook

noncontinuous process just like the preform technique. In the spin-melt process,

a volume of ready-to-use polymer pellets is melted and pressed through a spin

head that incorporates many holes. The holes serve to form the core and apply

the cladding. This process is very efficient but also very expensive.

20.7.2 Production of Graded-Index Profiles

A number of processes for the manufacture of GI profiles are described in the

technical literature:

. Surface gel polymerization technique

. Centrifuging

. Photochemical reactions

. Extrusion of many layers

In most of these techniques, the principle is to initially create a preform of up

to 50-mm diameter and then to subsequently draw this preform down to the

desired fiber size.

20.7.3 Interfacial Gel Polymerization ...