Embodiments of the present invention disclose an optical repeater and an optical fiber communications system. An implementation solution of the optical repeater includes: a first input end of the optical repeater, a first output end of the optical repeater, a first erbium doped fiber, a first coupler, a second coupler, and a first pump light processing component, where the first input end of the optical repeater is connected to an input end of the first erbium doped fiber, an output end of the first erbium doped fiber is connected to an input end of the first coupler, a first output end of the first coupler is connected to a first input end of the second coupler, and an output end of the second coupler is connected to the first output end of the optical repeater; an input end of the first pump light processing component is connected to a second input end of the second coupler; and an output end of the first pump light processing component is connected to a second output end of the first coupler. In this solution, when all local-end pump lights fail, a reverse pump light can still enter, which can improve reliability of the optical fiber communications system.