OPTICAL FIBER HAVING LOW LOSS AT 1,385 NANOMETER AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To provide an optical fiber having low optical transmission loss in the wavelength region of 1,200 to 1,600 nm and particularly at 1,385 nm, in the correlation of optical transmission loss with wavelengths of transmitted light and also to provide the production of the optical fiber. SOLUTION: This production comprises: forming a core rod 20 by a vapor- phase axial deposition method so as to have a (deposited clad)/core ratio (D/d ratio) of 7.5; dehydrating the formed core rod 20 at about 1,200 deg.C in a chlorine- or fluorine-containing atmosphere; then, solidifying the resulting porous soot base material of the dehydrated core rod 20 in a helium atmosphere to convert it into glass; extending the solidified core rod 20 with an oxygen- hydrogen torch(s); and finally, inserting the extended core rod 20 into a glass tube 40 having a low OH content and then, pressing the glass tube 40 on the extended core rod 20 to form a preform. By producing an optical fiber from this preform, the optical transmission loss at 1,385 nm of the optical fiber is reduced to a level lower than the loss level at 1,310 nm and light in the whole wavelength region of 1,200 to 1,600 nm becomes suitable for optical transmission using the optical fiber.