###### Abstract  
Signal transmission over optical fibers in the ultraviolet to near-infrared domains remains very challenging due to their high intrinsic losses. In radiation-rich environments, this is made eVen more difficult due to the radiation-induced attenuation (RIA) phenomenon. We investigated here how the number of hydroxyl groups (OH) present in multi-mode (MM) pure-silica core (PSC) optical fibers influences the RIA levels and kinetics. For this, we tested three different fiber samples: one \"wet\", one \"dry\" and one with an intermediate \"medium\" OH content. The RIA of the three samples was measured in the 400-900 nm (\(\sim\) 3 eV to \(\sim\)1.4 eV) spectral range during and after an X-ray irradiation at a dose rate of 6 Gy(SiO2) s\({}^{-1}\) up to a total accumulated dose of 300 kGy(SiO2). Furthermore, we evaluated the H2-pre-loading efficiency in the medium OH sample to permanently improve both its intrinsic losses and radiation response in the visible domain. Finally, the spectral decomposition of the various RIA responses allows us to better understand the basic mechanisms related to the point defects causing the excess of optical losses. Particularly, it reveals the relationship between the initial OH groups content and the generation of non-bridging oxygen hole centers (NBOHCs). Moreover, the presence of hydroxyl groups also affects the contribution from other intrinsic defects such as the self-trapped holes (STHs) to the RIA in this spectral domain. radiations; radiation-induced attenuation; pure-silica core optical fibers; hydroxyl group; ionizing radiations; diagnostics +
Footnote †: journal: Applied Sciences  
Article  
Radiation Effects on Pure-Silica Multimode Optical Fibers in the Visible and Near-Infrared Domains: Influence of OH Groups  
[PERSON]  
1 Laboratoire Hubert Curien, UMR CNRS 5516, Universite Jean Monnet, 42000 Saint-Etienne, France;  
[EMAIL_ADDRESS] (C.C. ); [EMAIL_ADDRESS] (V.D.M. );  
[EMAIL_ADDRESS] (A.M.);  
[EMAIL_ADDRESS] (A.M.);  
[EMAIL_ADDRESS] (A.M.);  
[EMAIL_ADDRESS] (Y.O. );  
[PERSON]  
1 Laboratoire [PERSON], UMR CNRS 5516, Universite Jean Monnet, 42000 Saint-Etienne, France;  
[EMAIL_ADDRESS] (C.C. ); [EMAIL_ADDRESS] (V.D.M. );  
[EMAIL_ADDRESS] (A.M.);  
[EMAIL_ADDRESS] (A.M.);  
[EMAIL_ADDRESS] (Y.O. );  
[PERSON]  
1 Laboratoire Hubert Curien, UMR CNRS 5516, Universite Jean Monnet, 42000 Saint-Etienne, France;  
[EMAIL_ADDRESS] (C.C. ); [EMAIL_ADDRESS] (V.D.M. );  
[EMAIL_ADDRESS] (A.M.);  
[EMAIL_ADDRESS] (A.M.);  
[EMAIL_ADDRESS] (Y.O. );  
[PERSON]  
1 Laboratoire Hubert Curien, UMR CNRS 5516, Universite Jean Monnet, 42000 Saint-Etienne, France;  
[EMAIL_ADDRESS] (F.M. );  
[EMAIL_ADDRESS] (V.D.M. );  
[EMAIL_ADDRESS] (A.M.);  
[EMAIL_ADDRESS] (A.M.);  
[EMAIL_ADDRESS] (Y.O. );  
[PERSON]  
1 Laboratoire [PERSON], UMR CNRS 5516, Universite Jean Monnet, 42000 Saint-Etienne, France;  
[EMAIL_ADDRESS] (C.C. ); [PERSON].D.M. );  
[PERSON]] (A.M.);  
[EMAIL_ADDRESS] (A.M.);  
[EMAIL_ADDRESS] (A.M.);  
[EMAIL_ADDRESS] (Y.O. );  
[PERSON]  
1 Laboratoire Hubert Curien, UMR CNRS 5516, Universite Jean Monnet, 42000 Saint-Etienne, France;  
[EMAIL_ADDRESS] (C.C. ); [EMAIL_ADDRESS] (V.D.M. );  
[EMAIL_ADDRESS] (A.M.);  
[EMAIL_ADDRESS] (E.M.);  
[EMAIL_ADDRESS] (Y.O. );  
[EMAIL_ADDRESS] (A.B.) [EMAIL_ADDRESS] (A.M.);  
jor. by the generation through ionization or displacement damages of point defects in both silica-based fiber core and fluorine-doped cladding. These radiations induced defects possess absorption bands peaking mainly in the UV-Vis explaining the highest RIA levels that are usually observed in this spectral range [14] than in the IR [1,2]. The mitigation of these optical losses represents the biggest obstacle to overcome for the fiber implementation and has been the subject of several previous investigations highlighting that pure-silica core (PSC) and fluorine-doped multimode optical fibers are the best candidates for the steady-state radiation environments (kGy to MGy(SiO\({}_{2}\)) dose levels) [1,15].