Radiation effects on rare-earth doped optical fibers
Résumé
In this paper, we reviewed our previous work concerning the responses of rare-earth (RE) doped fibers (Yb, Er and Er/Yb) to various types of radiations like gamma-rays, X-rays and protons. For all these harsh environments, the main measured macroscopic radiation-induced effect is an increase of the linear attenuation of these waveguides due to the generation of point defects in the RE-doped core and silica-based cladding. To evaluate the vulnerability of this class of optical fibers for space missions, we characterize the growth and decay kinetics of their radiation-induced attenuation (RIA) during and after irradiation for various compositions. Laboratory testing reveals that this class of optical fibers is very sensitive to radiations compared to passive (RE-free) samples. As a consequence, despite the small length used for space applications, the understanding of the radiation-induced effects in this class of optical fibers becomes necessary before their integration as part of fiber-based systems like gyroscopes or communication systems. In this paper, we more particularly discussed about the relative influence of the rare-earth ions (Er3+ and/or Yb3+) and of the glass matrix dopants (Al, P, ...) on the optical degradation due to radiations. This has been done by using a set of five prototype optical fibers designed by the fiber manufacturer iXFiber SAS to enlighten the role of these parameters. Additional spectroscopic tools like confocal microscopy of luminescence are also used to detect possible changes in the spectroscopy of the rare-earth ions and their consequences on the functionality of the active optical fibers.