| 摘要 |
PURPOSE:To make the wavelength dependency of branching ratio small and to obtain nearly constant branching ratio in a wide waveguide range by forming an optical coupling part between polarization maintaining single mode optical fibers. CONSTITUTION:The coupler is provided with two polarization maintaining single mode optical fibers 1a and 1b having at least one different value among the values of a mode field diameter, a cutoff wavelength and a mode double refractive index and the optical coupling part 5 is formed between the polarization maintaining single mode optical fibers. In this case, the maximum branching ratio can be designed to be an optional value from 0% to 100% corresponding to the degree of the difference of fiber parameter between two optical fibers. Since the wavelength dependency of the branching ratio is small near the maximum branching ratio, the optical fiber coupler having wide band characteristic is obtained. |
