Self-referencing multiplexing technique for fiber-optic intensity sensors

An all-optical technique for multiplexing and self-referencing a number of intensity modulating fiber-optic sensors is described. The optical transducers are fabricated as integral parts of recirculating optical fiber loops connected in parallel between transmit and receive optical fibers. A portion of an input pulse is tapped off by each sensor loop module. Successive fractions are tapped off on each circulation around the loop and transmitted to a detector. These form pulse trains that characterize each sensor's output. The relative magnitudes of the components of the pulse train are insensitive to lead and connector losses between the sensor modules and the source and detector. Time division multiplexing of the sensor return signals is created by the delays introduced by the fiber leads between the sensor modules. This paper details the response of a single sensor loop versus theoretical performance, and a three sensor system is demonstrated.