| 摘要 |
PURPOSE:To improve the extinction ratio of an optical fiber directional coupler to the ratio much higher than the extinction ratio of the conventional coupler by constituting the input/output ends of said coupler as coil type optical fiber polarizers and operating these polarizers to maintain the absolute single polarization plane. CONSTITUTION:The optical fiber input/output ends of the optical fiber directional coupler 8 are wound at the prescribed bending radius where the absolute single polarization wavelength region exists to constitute the coil type optical fiber polarizers 9. The bending losses of the elliptic jacket type polarization maintaining optical fiber 2 are such that one of the incident waves at the axes of polarization intrinsic to the two directions (X polarized wave and Y polarized wave) is a low loss and the other is a high loss. Only the incident waves of the low loss, therefore, propagate in such coil type optical fiber polarizers 9 formed by winding the optical fibers at the prescribed bending radius so that the polarizers operate to maintain the absolute single polarization plane. The stresses in the polished part are thereby eliminated and the loss of the large extinction ratio of the elliptic type polarization maintaining optical fiber 2 is obviated. |
