  Signal-induced noise is observed in Hamamatsu R11265 Multianode
Photomultiplier Tubes, manifesting up to several microseconds after the single
photoelectron response signal and localised in specific anodes. The mean number
of noise pulses varies between devices, and shows significant dependence on the
applied high-voltage. The characterisation of this noise and the mitigation
strategies to perform optimal single-photon counting at 40 MHz, as required by
the LHCb Ring-Imaging Cherenkov detectors, are reported.
