JPS6017084B

PURPOSE:To obtain superior polarization characteristics by providing a core and clad with an intermediate player which has a less refractive index in between and forming a stress generating part which has a specific coefficient of thermal expansion in the location where the both are opposed to each other. CONSTITUTION:The intermediate layer 6 having the less refractive index than the core 4 and clad 5 is provided between the core 4 and clad 5 and the stress generating part 7 which has the coefficient of thermal expansion different from that of the clad 5 is arranged at the opposing position on both sides of the core 4. Then, the difference in refractive index between the core 4 and clad 5 is set to 0.5-1.0%, and the core 4 and intermediate layer have such diameters and widths corresponding to the difference in refractive index that the total dispersion in a wavelength range with at least 0.1mum width close to 1.55mum wavelength is