An optic sensor system comprising an optic sensor (10), a pair of photoelectric devices (12,14) and a pair of optic fibers (16,18) that transmit light respectively between the photoelectric devices (12,14) and the sensor (10). The photoelectric devices (12,14) serve as both a source of input light for the sensor (10) as well as a light detector for the light returned from the sensor (10). A control circuit is used to switch the photoelectric devices (12,14) on and off, thus determining the periods of time that each operates as a source or detector.