In the last decade, there has been increased interest in photonic technology for new satellite applications. One
critical issue is the high sensitivity to radiative environments of the Erbium Doped Fiber (EDF). It leads to
a radiation-induced absorption (RIA) that is not due to erbium content but mainly to the aluminium that
ensures the erbium inclusion in glass. As the radiation induced losses grow as an exponential function of fiber
length, the principal way so far to reduce EDFA degradation has consisted in increasing erbium concentration
using conventional doping techniques. However, this is limited by the quenching effect, which impacts the fiber
length needed to reach high gain, but also by the Aluminium-induced RIA. It has been recently proposed an
original nanoparticle (NP) doping approach, which allows codopant content decrease with reduced quenching
impact, while keeping EDF amplifying performances. A radiation-resistant amplifier can thus be designed as a
"quenching-free", heavily-erbium-doped amplifier with low RIA.
We demonstrate for the first time an aluminium-free EDF, exhibiting low quenching and low RIA. Despite the
lack of aluminium, using silica NPs allows an erbium concentration close to the one of standard EDFs (200 ppm).
This fiber is compared to a 1400 ppm Erbium-doped optical fiber with a strong aluminium concentration.
Whereas the two fibers exhibit similar initial optical gain (15 dB under saturation conditions), the NP doped
Al-free EDF shows only 2 dB gain reduction after a 600 Gy gamma deposit, while the Al/Er EDF incurs more
than 10 dB gain degradation.