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Citation information: DOI 10.1109/TNS.2019.2953645, IEEE Transactions on Nuclear Science 1 Radiation Effects on WDM and DWDM Architectures of Pre-Amplifier and Boost-Amplifier Marine Aubry, IEEE Student Member, Ayoub Ladaci, Sylvain Girard, Senior Member IEEE, Luciano Mescia, Arnaud Laurent, Thierry Robin, Benoit Cadier, Mathieu Boutillier, Julien Mekki, Member IEEE, Adriana Morana, Member IEEE, Cosimo Campanella, IEEE Student Member, Jeoffray Vidalot, IEEE Student Member, Emmanuel Marin, Youcef Ouerdane and Aziz Boukenter Abstract—We investigated the X-ray (40 keV, 700 Gy(SiO2), ~80 mGy/s) radiation effects on the performances (gain) of Er- Doped Fiber pre-Amplifier (EDFA) and Er/Yb codoped Fiber boost Amplifier (EYDFA). Various EDFA and EYDFA architectures have been designed to operate either in Wavelength Division Multiplexing (WDM) or Dense WDM (DWDM) schemes. We compare the performances of amplifiers based on conventional or radiation hardened versions of the active Er-doped or Er/Yb- codoped fibers. Our results show that for all amplifier architectures, the various channels undergo similar gain degradation levels and kinetics, as expected from the measured spectral dependence of the radiation-induced attenuation of the phosphosilicate (ErYb-doped) and aluminosilicate (Er-doped) glass matrix of these fibers. This degradation remains very limited for the amplifiers based on radiation hardened fibers, with gain decrease of less than 0.3 mdB.Gy -1 for the EDFA (~30 dB initial gain) and less than 0.8 mdB.Gy -1 for the EYDFA (~18 dB initial gain) in the DWDM architecture. Index Terms—Radiation effects, optical fibers, erbium, amplifiers, X-rays, EDFA. I. INTRODUCTION uring the last decades, optical fibers have strongly improved the performances of telecommunication systems. Indeed, their ability to guide light over long distances allows an improvement of the data transfer rate reaching Tbits/s instead of a few Mbit/s in case of the conventional coaxial cables [1]. However, due to the continuous increase of the bandwidth needs, several solutions were proposed in order to increase even more the data transfer capacity. One of the most effective solution remains the Wavelength Division Multiplexing (WDM) configuration. WDM and later Dense WDM (DWDM) [2] strongly increase communication bandwidths by adding numerous communication channels into a single optical fiber. A similar challenge is today faced by the space industry with the development of free space telecommunications. One of the most promising solutions remains the optical communication systems [3]. Indeed, this photonic technology can be used for the inter-satellite and/or satellite-ground links. However, to ensure the signal propagation through the atmosphere and for long distances, high signal power amplification at both transmitter and receiver levels are required [4]. This can be achieved using Rare Earth Doped Fiber Amplifiers (REDFAs) which are getting a high interest for the space applications due to their high performances such as high gain, low noise figure, electromagnetic immunity, low weight and power consumption. [5]. However, the conventional REDFAs have shown a high radiation sensitivity leading to a strong degradation of their performances in space [6, 7]. It was demonstrated that the Rare Earth Doped Fibers (REDFs) are the most radiation sensitive component of the whole system [8]. In fact, those fibers are generally co-doped with Phosphorus or/and Aluminum to prevent the clustering of RE ions that limits the amplification processes and then reduces the amplifier performances [9]. The presence of Al and/or P is associated with higher Radiation Induced Attenuation (RIA) levels as the point defects related to those dopants have absorption bands that directly affect the signal and pump propagations [10, 11, 12]. To overcome these drawbacks, many studies were carried out and several solutions were identified allowing the development of radiation tolerant systems for today space missions based on new doped fiber compositions or/and fabrication processes such as the Ce co-doping or nanoparticles deposition process [13, 14, 15]. Moreover, the addition of hydrogen in the active fiber core shifts the absorption bands out of the pump and signal wavelengths range by passivating some of the point defects [16, 17, 18]. Another strategy consists in defining the whole system architecture combining experimental and simulation approaches to optimize the amplifier parameters such as the pumping configuration, the doped fiber length, etc. for a better radiation resistance [19, 20]. Up to now, radiation hardened REDFAs were tested and space qualified in a single wavelength amplification configuration (one communication channel). To the best of our knowledge, no study has been yet performed to investigate the effects of D Manuscript received July 05, 2019, revised September 11, 2019. Part of this research has been produced in the framework of the Joint Laboratory “LabH6” between University of Saint-Etienne and iXblue (https://photonics.ixblue.com/labcom/labh6). M. Aubry, A. Ladaci ,S. Girard, A. Morana, C. Campanella, J. Vidalot, E. Marin, Y. Ouerdane and A. Boukenter are with the Université de Lyon, Lab. Hubert Curien, F-42000 Saint-Etienne, France (E-mail: marine.aubry@univ-st-etienne.fr; sylvain.girard@univ-st-etienne.fr). M. Aubry, A. Ladaci, A. Laurent, T. Robin, B. Cadier are with iXBlue Photonics, Lannion, France (arnaud.laurent@ixblue.com). M. Aubry, J. Mekki and M. Boutillier are with the CNES, Toulouse, France (julien.mekki@cnes.fr) M. Aubry A. Ladaci and L. Mescia are with Politecnico di Bari, Bari, Italy. (luciano.mescia@poliba.it).