PURPOSE: To provide a process for producing a fiber type diffraction grating which increases the reflectivity to the light components of specific wavelengths.
CONSTITUTION: An optical fiber 10 is installed in a furnace core tube 20. Gaseous hydrogen (H2) is made to flow from a valve 21 side toward a valve 22 and a high temp. or high pressure state is maintained in this furnace core tube 20. The optical fiber 10 is an ordinary quartz optical fiber contg. germanium oxide (GeO2) in its core part. The optical fiber 10 is thereafter stored for a specified period of time in a thermostatic chamber. The storage temp. of the optical fiber 10 is preferably included in a range of 0 to 30°C. A great change in refractive index is induced in the region irradiated with UV light by the reduction treatment of an optical waveguide by the gaseous hydrogen and the addition of the hydrogen to the core part. Since the optical fiber is stored in the thermostatic chamber, its characteristics are uniform.
ITO MASUMI
ENOMOTO TADASHI
INOUE SUSUMU
MOBARA MASAICHI
