San Diego, CA
In the Installer Tip, "Powder makes cables easier to pull and terminate" (see March 1997, page 43), the author says the tip is for copper only and does not apply to fiber-optic cables because the powder interferes with light transmission.
Although I do not believe that this is an accurate statement, it may hold some truth. Powder will contribute to optical loss if it gets into a mechanical fiber-optic splice or a fiber-optic connector. Any type of dust or foreign material present where two fibers join is likely to cause excess loss.
On the other hand, an old installation tip for fiber went something like this: If you are working with older at&t ribbon cable, in which ribbons are formed by sandwiching fibers between two layers of Mylar tape, the adhesive remaining on the fibers after you pull back the tape would make it difficult to dress the fibers in the splice tray. Shaking some baby powder on the fibers will improve handling. Again, remember to keep the powder away from fusion or mechanical splicing mechanisms or fiber cleavers.