Method and apparatus for expanding the mode field diameter of an optical fiber

摘要

A method and an apparatus for expanding the mode field diameter of an optical fiber (1) by heating a specified region of the optical fiber (1) with a uniform or desired temperature distribution for forming a thermally-diffused expanded core (TEC). The mode field diameter of the optical fiber (1) is expanded by heating an optical fiber (1) with a burner (11) so as to thermally diffuse the dopant forming the refractive-index profile. The burner (11) has a heating surface (11a) in which a plurality of gas-issuing holes (12) are arranged such that a plurality of parallel rows each of which is composed of a plurality of gas-issuing holes (12) are parallel to the axis of the optical fiber (1).