An optical bypass switch includes a normal state and a bypass state, a transmission optical fiber having a signal withdrawn therefrom and injected thereto in its normal state so as to be capable of use in a ring or bus architecture. In the bypass state of the switch, the transmission optical fiber is substantially disengaged so that a signal being transmitted thereby can bypass the switch, and in this state optical fibers connected to a transmitter and a receiver of the bypass switch are maintained in a bent attitude so as to allow signals to be withdrawn and injected thereinto. A loop back path, e.g. a connector optical fiber, is provided which allows a path between the transmitter and the receiver to be completed in the bypass state of the bypass switch, and logic circuitry is provided for analyzing signals detected by the receiver which should have originated from the transmitter for evaluating a state of operation of the transmitter, receiver, and connecting means therefor. Whenever the logic circuitry detects a malfunction in any of these elements, e.g. the transmitter, the receiver and connecting structure therefor, the optical bypass switch is kept in its bypass state and prevented from re-engaging the transmission fiber so as to prevent the bypass switch from optically coupling to the transmission fiber when its electro-optic elements are not functioning properly.