Rare-earth doped optical fibers have been shown to be very sensitive to radiations, limiting the integration of fiber-based systems in space missions. In this paper, we present the characterization of two amplifiers based on a set of prototype active Erbium/Ytterbium codoped double clad fibers developed by Ixfiber SAS. One of these fibers has been codoped with cerium inside its core to enhance its radiation tolerance whereas the other is a classical phosphosilicate Er/Yb fiber. The two amplifiers based on these fibers have been exposed to γ-rays at a low dose rate (0.3 rad/s) and to doses up to 90 krad. Previous studies indicated that Er/Yb amplifiers using this type of fiber suffered significant degradation for cumulated dose above 5-10 krad. We observed, on the contrary, that with our radiation hardened fiber, the degradation of the fiber amplifier's output power can be limited to less than 30% after an exposure dose of …