OPTICAL DEVICE WITH A PIG TAIL OPTICAL FIBER AND ITS PRODUCTION METHOD

摘要

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