抄録
Low-loss optical fibers have great potential to make future telecommunications a giant step forward. The main characteristics, the state of the art, and a survey of optical fiber guides are given. A comparison is made between clad fibers and graded-index guides. In single mode guides both of them have no clear difference. In multi-mode guides the graded-index fider is extremely superior to the clad fiber with respect to group delay. However, it is shown that high index-difference and large available radius of the guide are required for stable transmission of light and its practical realization depends on new technique to be developed.
