A fully redundant safety interlock system is provided comprising, means for detecting the loss of light on a fiber optic link; controller means, coupled to said means for detecting, for determining the safety condition of the link based on the output of said means for detecting, and for controlling the radiant energy output of an optical transmitter, based on the determined safety condition, via redundant output control signals; and means, coupled to said controller means, responsive to said redundant control signals, for interconnecting the output of said controller means to transmitter drive circuitry to thereby adjust the radiant energy output by the transmitter. According to a preferred embodiment of the invention, the controller means includes an electronic implementation of two independent state machines, each of which redundantly determines the connection state of the optical link between two optical link cards. The output from the state machines is used to adjust (for example, turn on and turn off) the drive circuitry for the transmitter via fully redundant paths which carry the redundant control signals.