Optimization of the Radiation Response of Backup Optical Fiber Amplifiers for Space Missions

We investigated the X-ray radiation impact on the performances of backup erbium-doped fiber amplifiers (EDFAs) and erbium-ytterbium-doped fiber amplifier (EYDFA). These devices are exposed to the space radiation constraints, unpowered in the OFF mode, up to their hypothetic activation during the mission. This atypical profile of use must be considered as it could lead to a higher radiation vulnerability. To carry out this study, active optical fibers differing in terms of radiation hardness have been exposed to steady-state X-rays under different profiles of amplifier use: the gain degradation is measured by varying the pumping conditions, that drive the photobleaching (PB) phenomenon, during the radiation exposure: ON (100% ON), OFF (0% ON), and OFF-ON-OFF with powering 2% or 10% of the time. Our results show that the impact of the pump and its related PB efficiency depend on the selected active fiber to build the amplifier. An important result is that the backup EDFA designed with radiation-hardened Ce-doped fiber does not suffer from an extra-degradation due to the OFF mode, contrary to the one designed with a nonrad-hard fiber. For this latter one, it is indeed possible to reduce the extra-gain degradation by powering the amplifier for short time periods during the OFF state; otherwise, the EDFA recovers this extra-gain degradation in a few hours after turning ON in our test conditions. For the tested radiation-tolerant EYDFA, an enhanced vulnerability is observed for the OFF amplifier, that can be reduced too by briefly powering the amplifier. The origins of these effects are discussed based on the properties of point defects related to the aluminosilicate (EDFA) and phosphosilicate (EYDFA) glasses of the fiber.

Automated summary

We investigated the impact of X-ray radiation on the performance of backup EDFAs and EYDFA. The study found that the type of active optical fiber used in the amplifiers affects the pumping conditions and photobleaching efficiency. Notably, the backup EDFA designed with radiation-hardened fiber does not experience extra degradation in the OFF mode, while the one designed with nonrad-hard fiber can reduce degradation by briefly powering the amplifier. Similarly, the tested radiation-tolerant EYDFA showed enhanced vulnerability in the OFF mode, but can also be mitigated with brief powering.