Method and apparatus for blocking ambient light in a live fiber optic identifying device

Spurious light is prevented from entering a cover of an optical fiber identification device by placing an opaque, flexible medium such as brush bristles within optical fiber clearance openings in the cover to block the light path around the fiber. Short opposing lengths of strip brushes are placing on either side of each of the slot openings in the cap. The opposing bristles make contact with each other in the slot, keeping out most ambient light. The strip brushes exert very little force on the fiber, permitting it to bend freely.