OPTICAL FIBER CABLE

PURPOSE:To prevent an optical fiber cable from being broken by providing a shield plate which has a pinhole whose diameter is smaller than the core diameter of an optical fiber in the incidence part of the optical fiber cable closely to the incidence end surface of the optical fiber in parallel. CONSTITUTION:The shield plate 13 has the pinhole 14 in the center and the diameter of the pinhole 15 is smaller than the core diameter of the optical fiber 7. Further, the pinhole 14 is formed closely to the incidence and surface of the fiber 7 in parallel. Further, a fine adjusting mechanism 15 is a position adjusting mechanism which align the center of the hole 14 with the center of the fiber 7. Projection light from a laser oscillator is incident through a window 10. At this time, when the projection light is at a specific position in a specific direction, the laser light is all passed through the pinhole 14 to be incident on the fiber 7 completely. When the projection light deviates from the specific position or direction, part of the light passes through the pinhole 14 to enter the fiber 7 completely, but the remaining light is cut off by the shield plate 13. At this time, no laser light illuminates the peripheral edge part of the incidence end surface of the fiber 7 and optical damage is evaded.