Optical device with a pig tail optical fiber and its production method

摘要

An optical waveguide with a specific refractive index difference DELTA 1 has a constitution in which a core with a high refractive index and having a rectangular section is built in a cladding layer with a low refractive index formed on a substrate. A pig tail optical fiber, formed by a first fiber serially connected to a second fiber, each having a different specific refractive index difference, is connected to an input terminal of the optical waveguide. The second fiber has a specific refractive index difference DELTA 2 (< DELTA 1) and is connected to a terminal of the first fiber which has a specific refractive index difference nearly equal to DELTA 1. A diffusion region in the neighborhood of the connection is formed by diffusing a dopant for refractive index control in the core of the second fiber by heat addition. Due to the diffusion region, the diameters of the first fiber and the second fiber are adjusted so as to be nearly equal.