PROCESS AND APPARATUS FOR MEASURING THE EFFECTIVE DIAMETER OF THE GUIDED MODE IN A MONOMODE OPTICAL FIBRE

摘要

ABSTRACT OF THE DISCLOSUREProcess and apparatus for measuring theeffective diameter of the guided mode in amonomode optical fibre.The apparatus comprises, for example, a lightingsource such as a tungsten filament, quartz-halogenlamp, a monochromator for selecting light of wave-length .lambda. from the lamp, as well as a variableaperture lens. The image of the source isperformed on the input face of the fibre bymeans of the lens, said image having a size greaterthan the diameter of the fibre core. The lightfrom the source falls on the fibre in accordancewith a cone having an apex halfangle 0. Thelighting power P(0) transmitted by the fibre ismeasured as a function of 0 and the effectivediameter 2wo is determined by the formulaP(0) = P? [1 - exp (-2( 2wo2/ 2) sin2 0)]in which P? is independent of 0.Application to the characterization of monomodefibres.(Fig. 1)