Radiation influence on Er/Yb doped fiber amplifiers performances: High power and WDM architectures

The actual challenge for space researchers is to increase the free space telecommunications data speed transfer. One of the most promising solutions is the optical communication systems. This technology can be used for the inter-satellite and/or satellite-ground links, reaching the TB/s speed for data transfer in the case of Dense Wavelengths Division Multiplexing (DWDM) based technologies. However, to achieve such systems, two main issues need to be overcome: the first one is to validate that no unexpected radiation effect appears when the optical amplifier is working in the DWDM configuration and the second one is to estimate the degradation of the Erbium/Ytterbium co-doped boost (High Power - HP) fiber amplifier performances during the space mission lifetime. In this last case, the used high powers will result in a complex response of the amplifier due to photobleaching, photodarkening and thermal effects. In this work, we estimate the radiation effects on an Er/Yb co-doped boost fiber amplifier operating in a Dense WDM configuration. Both radiation hardened and a conventional versions have been considered. The obtained results allow estimating the performances of our fibers under exposure in such amplification setup and also to validate its potential for use in an actual space mission. We demonstrate the good radiation resistance of Er/Yb co-doped 12 mu m core diameter fibers reaching 20 W of output power for telecommunication applications. This core diameter provides a few-mode optical output signal (with low dispersion) managing enough power to ensure the signal propagation trough the atmosphere. This study is fundamental as several phenomena such as Photo/Thermal bleaching, photo-darkening etc. are in competition due to the high-power light density in the fiber core and the system radiation response cannot be predicted by actual simulation tools yet.