The modal noise and distortion caused by a longitudinal gap between two multimode parabolic-index fibers are discussed and quantified by means of modal analysis. It is found that, for coherent illumination and a given loss, the modal noise and distortion due to a gap are generally as severe as or worse than those due to an axial offset between two fibers. It is also shown that, when a partially coherent source is used, the transmission characteristics of a gap can be improved by increasing the operating wavelength. Experimental results have been obtained for modal distortion and are shown to be in close agreement with the theory.
© 1984 Optical Society of America
Santanu Das, Colin G. Englefield, and Paul A. Goud, "Modal noise and distortion caused by a longitudinal gap between two multimode fibers," Appl. Opt. 23, 1110-1115 (1984)