Mode field diameter conversion fiber, optical waveguide refractometer, local change method and optical waveguide preform manufacturing method

摘要

The present invention relates to an optical fiber and relates to a gain spectrum in a cascade mode field diameter conversion fiber, a physical value sensor and an erbium fiber amplifier of a fiber copy collimator, optical waveguide coupler, spectroscope filter, optical isolator, long period diffraction grating, dispersion compensator, May be used in a radiation suppression unit of a predetermined wavelength to smooth it. The present invention facilitates the fabrication of optical waveguides. In order to produce the preform for the optical waveguide 1 by the plasma spray chemical vapor deposition method, the molecular gas mixture supplied to the substrate tube 24 contains three oxygen atoms per silicon atom, one or more nitrogen atoms per 1000 oxygen atoms, . The refraction coefficient is locally deformed by heating the optical waveguide 1. This locally thermally diffuses the elements contained in the core 3 to the cladding 2 or vice versa. The light waveguide 1 is heated by the electric current of the electric arc 10 or by the radiation 16 of the infrared laser 15. The core (3) is doped with nitrogen at a concentration of 0.01 to 5 atomic%. The diameter of the core (3) in the mode field diameter conversion fiber varies along the length of the light pipe (1) and increases toward the end (4).