Cathodoluminescence Characterization of Point Defects in Optical Fibers

We evaluate the potential of the cathodoluminescence (CL) spectroscopy to characterize the nature and the spatial distribution of point defects in the main classes of optical fibers (OFs): Telecom-grade, radiation-hardened, and radiation sensitive. Canonical samples, that are differently doped in their cores (Ge, N, P, Ce) or their claddings (F), have been investigated through CL technique using a 10-keV electron beam. Obtained results are compared with those obtained by photoluminescence spectroscopy. CL benefits and limits are discussed on the basis of the obtained experimental data. CL is shown to be efficient to investigate the kinetics of defect generation and bleaching under the electron exposure, being the unique technique allowing us to determine in situ the spatial distribution of emitting defects in the fiber transverse cross sections. New insights are given for some of the defects related to the Ge, P, Ce and N dopants.