Editing Mode scrambler (section)

== Types ==
There are two common types of mode scramblers: the "Step-Graded-Step" (S-G-S) and the "step index with bends". The S-G-S mode scrambler is actually an assembly, a fusion-spliced concatenation of a step-index profile, a graded-index profile and another step-index profile fiber.<ref>[https://patentimages.storage.googleapis.com/d2/08/c7/9eb780e387fdbb/US4229067.pdf United States Patent]</ref> Typically, each segment is approximately 1 meter long, and may use segments of unconventional size to produce the distribution required according to core size of fiber to be tested.  Unconventional fiber size was not an issue, as they were developed by fiber manufacturers, but some test equipment has difficulty complying with revised qualification standards, and now use "Step Index with Bends" mode scramblers, which can be adjusted to purpose. Step Index with Bend mode scramblers are created simply by routing a specially designed step-index multimode fiber through a series of small radius bends, or by compressing fiber against surfaces with specific roughness.  The implementations are simple, but generally less reproducible, and require care to avoid over-stressing the fiber.

A mode scrambler can be characterized and qualified by measuring its near-field and far-field distributions, as well as by measuring one of these distributions while restricting the other. Guidelines for constructing a mode scrambler and qualifying its output can be found in the ANSI/TIA/EIA-455-54 fiber optic test procedure ('''FOTP''').