Abstract
We report on latest version of the calibration and monitoring system developed for the scintillator tile hadron calorimeter (AHCAL) for the ILC. System is based on original fast (3.5 ns pulse width) and precise LED driver board called QMB. One UV-LED can illuminate 72 scintillating tiles with SiPM. Distribution of the light pulses uses notched fibres, developed at our laboratory. All parts of the system are continually upgraded to get better results. The system is flexible to all necessary monitoring and calibration of SiPM detector tasks. It has high dynamic range of precise a few nanosecond pulses. Low intensity LED pulses are needed to obtain SiPM single photoelectron spectra. A routine monitoring of all SiPMs during the test beam operations is achieved with mid-range a fixed-intensity light pulse. The full SiPM response function is cross-checked by varying the light intensity from zero to the saturation level. In calibration systems we developed, we concentrate especially on the aspect a high dynamic range of precise a few nanosecond pulses. Calibration system has been tested with 2.2 m long slab of engineering AHCAL prototype, which uses 864 SiPM embedded in 3 by 3 cm scintillator tiles and represents a part of the biggest foreseen detector using SiPMs.