Abstract: A multi-point optical amplification repeating system is disclosed in which an output of a unidirectional amplifier inserted in a unidirectional repeating optical transmission system is branched and coupled to an input of a unidirectional amplifier inserted in another unidirectional repeating optical transmission system, so that bidirectional optical communication can be performed between many points connected to a plurality of first optical transmission lines. If a bidirectional amplifier is employed in a bidirectional repeating optical transmission system, the above bidirectional optical communication can be also realized by fed back the first port of the bidirectional amplifier to the second port thereof through an optical isolator.