The Jiangmen Underground Neutrino Observatory (JUNO) is an experiment designed to measure mass hierarchy and oscillation parameters. To achieve that, a sphere scintillation detector with diameter 34.5m is to be built. To ensure the scintillation light produced by liquid scintillator can travel through the whole detector and be detected by surrounding PMTs, it is important to increase the attenuation length and find an effective way to measure it. By studying the algorithm and background noise, PMT is replaced by CMOS camera. System's structure ...