An optical repeater in a mobile communication system includes a main hub unit (MHU) and a plurality of repeaters connected to a plurality of access points of the MHU, respectively. Each of the repeaters receives subcarrier information and a signal transmitted from a base station, as optical signals, through the MHU or a different repeater connected thereto, processes only a signal corresponding to a subcarrier allocated to a terminal which has accessed according to the subcarrier information, and transmits the processed signal to the terminal which has accessed. Also, each of the repeaters maps a signal of the terminal which has accessed to a subcarrier allocated to the terminal which has accessed, and transmits the same to the MHU or a different repeater connected thereto.