An optical transmitter-receiver according to the present invention is an optical transmitter-receiver connected to an optical fiber used for a single-core two-way optical communication channel for making a first optical signal S1 to be sent incident upon the end of the optical fiber and receiving a second optical signal S2 sent via the optical fiber. The above optical transmitter-receiver is provided with emission means for emitting a first optical signal S1, an optical system for making a first optical signal S1 from the emission means incident upon the incident end of the optical fiber in a direction R1 different from a direction in which a second optical signal S2 is outgoing from the end of the optical fiber and light receiving means for receiving a second optical signal S2 outgoing from the end of the optical fiber.