Abstract

Improvements in graded-index multimode optical fiber sensor performance caused by an on-axis dip in the parabolic index of refraction profile of the fiber are considered. The effects of such a dip on fiber multimode propagation are first reviewed.¹ Effects on both the modulation mechanisms and the resulting sensitivities of intrinsic bend loss and extrinsic coupling sensors are then analyzed. Experimental measurements of both of these observables obtained using specimens having two different degrees of such a central refractive-index profile dip are compared with this analysis. Analytical and experimental results indicate that sensor sensitivities are increased by ~10% for the specific fiber profiles considered. It is shown that by further increasing the severity of the central dip from the nominal parabolic index profile, an additional sensitivity increase of 20% is attainable.

© 1985 Optical Society of America