Microbending loss in optical fibers

The loss induced in optical fibers by random bends in the fiber axis is studied by winding fibers under constant tension onto a drum surface that is not perfectly smooth. The tension forces the fibers to conform to slight surface irregularities, which can result in an increase in the optical loss on the order of 100 dB/km. This microbending loss may be a significant design consideration in system applications of low-loss optical fibers. Data are presented on the reduction of the effect by means of coatings and increased numerical aperture.