Cerenkov pulse dispersion in two low-loss fibers

Abstract

We have measured the material and mode dispersion of a 50‐psec Cerenkov light pulse generated in 500‐m lengths of low‐loss graded and step‐index Corning fibers. The initial 15.7‐nsec full width at half‐maximum (FWHM) transmitted pulse in the graded fiber was reduced to less than 2 nsec with narrow‐band optical filtering. Parallel measurements in the step‐index fiber gave a value of less than 4 nsec for an initial 16.3‐nsec FWHM pulse. Fluorescence induced in the fiber by the electron radiation was less than 1% of the amplitude of the transmitted Cerenkov light in the graded fiber and approximately 2% in the step fiber.