Question

what does REF's surface contains
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Answer 1

Answer:Reference surface

In fiber optic technology, a reference surface is that surface of an optical fiber that is used to contact the transverse-alignment elements of a component such as a connector or mechanical splice. For telecommunications-grade fibers, the reference surface is the outer surface of the cladding. For plastic-clad silica fibers, which have a strippable polymer cladding, the reference surface may be the core.