Optically powered sensor system

Abstract

An optically powered sensor system includes a plurality of sensors connected to a system optical bus that communicates with a system controller. Optical energy is transmitted along the bus for distribution to all sensors in the system with return pulses from the various sensors transmitted on the bus to the system controller. Each sensor includes a photodiode array for converting optical energy transmitted system-wide by the controller into electrical energy for storage in a storage capacitor associated with each sensor. A transducer, such as a thermistor, and a fixed-value reference, such as a resistor, are connected to a pulse encoder and, in response to power switched from the capacitor, the pulse encoder produces a series of short-duration pulses having a pulse spacing that is dependent upon the fixed value of the reference and the parameter-affected value of the transducer. The pulses are used to drive an optical source for transmitting optical pulses from the sensor to the system controller. The parameter value is determined by multiplying the known value of the reference resistor by a time factor ratio which is related by the reference pulse timing and the parameter-affected pulse timing. An optical sensor system is provided in which the measurement of a parameter by each sensor is immune to variations in the electrical components at each sensor.