OPTICAL FIBER AND PREFORM IMPROVED IN CHARACTERISTICS OF OH-RADICAL AND BENDING LOSS AND FABRICATION METHOD THEREOF

摘要

PURPOSE: A base material for optical fiber, the optical fiber, and a method for manufacturing the same are provided to substantially eliminate hydroxyl groups and to modify curving loss characteristic by applying a trench type index profile. CONSTITUTION: Clad layers(2, 4) are formed by depositing soot on the inner wall of a quartz tube. A trench region(3) is formed on the clad layers. The refractive index of the trench region is relatively lower than those of the clad layers. A core layer(1) is formed on the clad layers. The refractive index of the core layer is relatively higher than that of the clad layers. While the core layer is formed, soot forming gas is introduced with carrier gas. The temperature of the quartz tube is heated to a temperature between 1200 and 1500 degrees Celsius to generate soot. The soot is deposited on the clad layers. Dehydration reaction gas is introduced into the quartz tube, and the temperature of the quartz tube is heated to a temperature between 700 and 1200 degrees Celsius in order to eliminate the soot and hydroxyl groups, and moisture from the quartz tube. The soot is sintered and vitrificated.