Silicon Photo-Multipliers (SiPMs henceover) are photo-detectors based on a technology originally invented in Russia (Akindinov et al., 1997). They essentially consist of an array of p-n junctions operated beyond the breakdown voltage (McKay, 1954), in a Geiger-Muller (G-M) regime (Oldham et al., 1972), with typical gain of the order of 106 and on-cell integrated quenching mechanisms. Silicon photo-detectors with internal multiplication are in use since more than a decade (Lutz, 1995). Avalance Photo-Diodes (APDs) (Akindinov et al., 2005) are operated in a proportional regime, with typical gains of 104, Single-Photon Avalanche Diodes (SPADs) (Cova et al., 1996) are endowed with single-photon sensitivity and are tailored for high frequency counting with time resolutions down to 30 ps. However, being made of a single cell operated in binary mode, they do not carry any information about the intensity of the incoming light field.