Launching condition dependence of graded-index multimode fiber loss and bandwidth

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Abstract
Theoretical and experimental studies of the launching-condition dependence of graded-index 50- mu m core, 0.2-numerical aperture multimode fiber transmission loss and baseband bandwidth are discussed. A combination of a SGS mode scrambler and a mandrel wrap mode filter was used as the launching system. It was found that steady-state fiber loss measurements should be carried out at an approximate mandrel curvature of rho =0.07 mm/sup -1/. This curvature is much smaller than the curvature rho =0.15 mm/sup -1/ which produces an equilibrium-mode distribution as defined by the International Telegraph and Telephone Consultative Committee (CCITT). Measurement at rho =0.15 mm/sup -1/ is shown to underestimate steady-state loss. It was also found that reproducible and reasonable bandwidth measurement can be obtained by choosing rho =0 to 0.07 mm/sup -1/.