  This article describes the Laser calibration system of the Atlas hadronic
Tile Calorimeter that has been used during the run 1 of the LHC. First, the
stability of the system associated readout electronics is studied. It is found
to be stable with variations smaller than 0.6 %. Then, the method developed to
compute the calibration constants, to correct for the variations of the gain of
the calorimeter photomultipliers, is described. These constants were determined
with a statistical uncertainty of 0.3 % and a systematic uncertainty of 0.2 %
for the central part of the calorimeter and 0.5 % for the end-caps. Finally,
the detection and correction of timing mis-configuration of the Tile
Calorimeter using the Laser system are also presented.
