OPTICAL FIBER PREFORM, METHOD FOR PRODUCING OPTICAL FIBER, AND OPTICAL FIBER

摘要

An easily producible optical fiber preform which is drawn to an optical fiber having a core containing a sufficient concentration of alkali metal is provided. An optical fiber preform 10 is composed of silica-based glass and includes a core portion 20 and a cladding portion 30. The core portion 20 includes a first core portion 21 including a central axis and a second core portion 22 disposed on the perimeter of the first core portion 21. The cladding portion 30 includes a first cladding portion 31 disposed on the perimeter of the second core portion 22 and a second cladding portion 32 disposed on the perimeter of the first cladding portion 31. The core portion 20 contains an alkali metal at an average concentration of 5 atomic ppm or more. The concentration of the OH group in the perimeter portion of the first cladding portion 31 is 200 mol ppm or more.

主权项

1. An optical fiber preform, which is composed of silica-based glass, comprising:
a core portion containing an alkali metal at an average concentration of 5 atomic ppm or more; a first cladding portion which is disposed on the perimeter of the core portion and which has a OH group having a concentration of 200 mol ppm or more in the perimeter portion; and a second cladding portion disposed on the perimeter of the first cladding portion.