Preform for optical fiber and method of producing optical fiber

摘要

PCT No. PCT/JP95/00814 Sec. 371 Date Apr. 16, 1996 Sec. 102(e) Date Apr. 16, 1996 PCT Filed Apr. 25, 1995 PCT Pub. No. WO95/29132 PCT Pub. Date Nov. 2, 1995A single-mode optical fiber preform is produced by a process where a porous glass body of a core rod for a single-mode optical fiber is dehydrated and made into a glass to prepare a core rod for the optical fiber, clad layers are deposited on the circumference of the core rod for the optical fiber so as to give an outer diameter of a desired value, and then these are dehydrated and made into glass. At this time, the diameter of a part corresponding to the core rod for the optical fiber in the optical fiber obtained by drawing the preform for optical fiber is controlled to 1.9 times or more the mode field diameter, which is a diameter that allows light having a wavelength of 1.55 mu m to pass therethrough. As a result, a preform for a single-mode optical fiber with which an optical fiber little influenced by defects can be obtained can be produced.