Picture of input ferrule of the FB on the left. The blue and purple colors at the surface of the ferrule are due to the AR coating that was applied to minimize Fresnel losses. The center and right pictures show the input and output patterns of fibers, respectively, which were obtained by imaging the ferrules under a binocular magnifier. In both cases, the science and reference fibers are lit up by illuminating the other ferrule using a halogen lamp. Some reflections and scratches are visible on the surface of both ferrules. The fibers that are not lit up correspond either to calibration fibers that were not illuminated when taking the pictures or to dummy fibers used to pack the geometry of the pattern (see Fig. 3). The fiber that appears damaged at the bottom right of the output ferrule is a dummy fiber that has no functional purpose.