Delay Distortion in Weakly Guiding Optical Fibers Due to Elliptic Deformation of the Boundary

Recent results1 indicate that glass fibers are a potential transmission medium for optical communication. For high-capacity systems (in excess of 100 MBaud) dispersion and the associated delay distortion is an important factor to be considered. For such an application the fiber cannot be used in a frequency range where more than one mode propagates, since the difference in group velocity between the various modes causes excessive delay distortion. 2 In the single-mode range the two best known sources of delay distortion are the material and waveguide dispersion.2 In this paper we will treat a different source of dispersion. If the fiber is elliptically deformed two different polarizations with different group velocities are possible. We will calculate the delay distortion due to these elliptical deformations and establish simple relationships between the allowable delay distortion and the tolerances with which the fiber has to be manufactured.