The compact size, fast response time and insensitivity to magnetic fields, turn the silicon photomultipliers (SiPM) into a suitable solution for experiments like Mu3e, where time information, with less than a nanosecond precision, is required. In the present talk we report on the performance of $250{\mu m}$ scintillating fibers staggered into ribbons and readout by Hamamatsu MPPCs. The analogue signals were first amplified and then fed to constant fraction discriminators, after which they were digitized through standard VME TDC and QDC modules. We have tested two fiber-SiPM coupling configurations: one with individual fibers matched to single sensors, and another with whole ribbons attached to LHCb-type arrays. The time and position resolving capabilities of the systems were evaluated in conditions where either very low or extremely high number of photons were incident on the photodetectors.

University of Geneva