OPTICAL FIBER PREFORM AND METHOD OF MANUFACTURING OPTICAL FIBER PREFORM

摘要

PROBLEM TO BE SOLVED: To provide an optical fiber preform which can be drawn into an optical fiber with low loss.SOLUTION: An optical fiber preform 1 includes a core part 10 and a clad part 20 surrounding the core part 10. The core part 10 includes a first core part 11 and a second core part 12 surrounding the first core part 11. The clad part 20 includes a first clad part 21 surrounding the second core part 12 and a second clad part 22 surrounding the first clad part 21. The first core part 11 contains an alkali metal element, a density of oxygen molecules included in a glass being 30 to 200 mol ppb in a part or the whole of an area where an alkali metal atom density is 100 atomic ppm or larger and 10 mol ppb or less in an area where an alkali metal atom density is 50 atomic ppm or less.