Frequency response of graded-index multimode fibers, whose index profile parameter α deviates from the optimum value, is investigated both theoretically and experimentally. The frequency response of the fiber with optimum α diverges periodically. However, that of the fiber with nonoptimum a does not exhibit periodic divergence but has periodic curvature changing points whose period is inversely proportional to the amount of α deviation. The period is about a fifth of the divergence period of the fiber with optimum α when the α deviation is 0.1. The optimum a difference between λ = 0.82 and 1.27, µm is found to be 0.07 for GeO2-P2O5-doped silica fibers by measurement of frequency responses at these wavelengths.
© 1980 Optical Society of America
Mitsuhiro Tateda, Shigeyuki Seikai, and Naoya Uchida, "Frequency characteristics of graded-index fibers," Appl. Opt. 19, 765-769 (1980)