Light transport is in general reciprocal, and therefore the statement "if I see you, you see me" is in general true. The magneto optical Faraday effect is one way to break reciprocity, and it is used in optical isolators for instance. In our group, we are interested in more fundamental questions raised by the presence or not of reciprocity and its consequences on multiple scattering, and we work in particular with optical fibers as the propagation medium. The Faraday effect, and thus reciprocity breaking, is proportional to the external applied magnetic field and to the length of the Faraday active medium. The proportionality constant—called the Verdet constant—is for most materials quite low, meaning that reciprocity can only be substantially broken over very large distances for the magnetic fields achievable in the lab. We would therefore like to fabricate an optical fiber with a large Verdet constant. Silica optical fibers doped with a small concentration of Gadolinium seem to be good candidates, as the Verdet constant of Gd-doped fibers was reported to be 2 orders of magnitude larger than standard telecom optical fibers, with reasonably low losses. For this work, we propose to fabricate Gd-doped optical fibers, and then characterize then both optically and magneto-optically.