A light transmission system has a light transmission module having a light transmission path that transmits a data signal as an optical signal, wherein the light transmission module converts the optical signal transmitted through the light transmission path to an electrical signal and outputs the converted optical signal as a binarization signal, an electrical transmission path that outputs a clock signal as a binarization signal, a reception processing unit that performs a reception process on each of the data signal and the clock signal, and a first delay unit that delays a rise start time of the clock signal with respect to a rise start time of the data signal for the binarization signal. A delay amount of the clock signal by the first delay unit is a time less than or equal to a maximum value of a data dependency jitter (DDJ).