| 摘要 |
PURPOSE:To reduce a cutoff wavelength and to rapidly remove out light other than a basic mode to be transmitted by using an optical fiber in quadruple structure. CONSTITUTION:A 2nd core 2 which has a smaller refractive index than a 1st core 1 is formed as the external layer of the 1st core 1, a 1st clad 3 which has a smaller refractive index than the 2nd core is formed as the external layer of the 2nd core 2, and a 2nd clad 4 which has a larger refractive index than the 1st clad is formed as the external layer of the 1st clad 3. Light from the 1st clad 3 is easily refracted out, the mode field diameter of light in necessary different kind of mode generated by the 2nd core 2 and 1st clad 3 increases, and this mode field diameter reaches the area of the 2nd clad 4 sufficiently. The refractive index of the 2nd clad 4 is larger than that of the 1st clad 3, so light in different kinds of mode is refracted out and easily removed. Consequently, light in unnecessary mode is removed and the cutoff wavelength is reducible. |
