Daya Bay Calibration System

$\theta_{13}$ is the last unknown mixing angle in the neutrino mixing matrix. Knowledge of $\theta_{13}$ is essential for understanding the phenomenon of neutrino oscillations and CP-violation in lepton sector. Through observing the disappearance of reactor antineutrinos, the Daya Bay Reactor Neutrino Experiment aims at probing $sin^2 2 \theta_{13}$ with a sensitivity of 0.01 at 90\% C.L. in 3 years of running. To reach such a sensitivity, we need to understand the performance of our detectors using various methods, including the use of radioactive sources and LEDs manipulated by automatic calibration units. In this talk, the calibration system will be introduced.