METHOD FOR MANUFACTURING IMPROVED MULTIMODE OPTICAL FIBER AND FIBER MANUFACTURED BY THIS METHOD

摘要

PROBLEM TO BE SOLVED: To provide a method for manufacturing multimode silica-based optical fiber and to provide fiber manufactured by this method. SOLUTION: The method for manufacturing the multimode optical fiber of wide range silica-base contains provision of noncircular preform and drawing of fiber of chiral structure from the preform. The noncircular preform can be manufactured by maintaining the inside of a tubular preform under reduced pressure during at least a part of breaking and consequently obtaining a noncircular core and a cladding. The noncircular preform can be also manufactured by removing proper parts of the preform (by grinding or by plasma etching, for example) and obtaining a circular core and a noncircular cladding. The chiral structure is given to the fiber, for example, by twisting the fiber alternately in a clockwise direction and in an anticlockwise direction with respect to the preform during drawing of the fiber.