  We report on several versions of the calibration and monitoring system
dedicated to scintillator tile calorimeters built within the CALICE
collaboration and intended for future linear collider experiments. Whereas the
first, a 1 m3 analogue hadron calorimeter prototype, was already built and
tested in beam, second-technological prototype-is currently being developed.
Both prototypes are based on scintillating tiles that are individually read out
by new photodetectors, silicon photomultipliers (SiPMs). Since the SiPM
response shows a strong dependence on the temperature and bias voltage and the
SiPM saturates due to the limited number of pixels, it needs to be monitored.
The monitoring system has to have sufficient flexibility to perform several
different tasks. The self-calibration property of the SiPMs can be used for the
gain monitoring using a low intensity of the LED light. A routine monitoring of
all SiPMs during test beam operations is achieved with a fixed-intensity light
pulse. The full SiPM response function is cross-checked by varying the light
intensity from zero to the saturation level. We concentrate especially on the
last aspect - the high dynamic range.
