| 摘要 |
PURPOSE:To enable axial alignment of optical fibers to be readily accomplished without degrading their transmission characteristics by inserting a focusing type cylindrical lens at the butt portions of the fibers and inserting an absorption elements giving attenuation in the lens. CONSTITUTION:When a conventional attenuator constituted by optical fibers alone and an attenuator inserted with a focusing type cylindrical lens having a lens of 1/2 pitch are compared, the accuracy of axial alignment is determined by the area ratio R of the ray propagation region expressed by formula I. If, for example, the length of the focusing type lens of 1/2 pitch is let 20 mm, the refractive index nf1 of core 1.46 by taking an example of a quartz fiber 1% and the core radius a 60mum, then the maximum axial deviation quantity rt of the focusing type cylindrical lens is 1.86 mm and its area ratio R is 961. Hence, the axial alignment of the attenuator inserted with the foregoing focusing type cylindrical lens becomes extremely easy and further there is no degradation of transmission characteristics such as the occurrence of mode conversion or other. |
