An Optically Linked Telemetry System for Use with Electromagnetic-Field Measurement Probes

A battery-powered optical telemetry transmitter, 2.5 X 2.5 X 3 cm, has been developed for use with various electromagneticfield hazard probes. The electrical outputs from one of these probes, containing three orthogonal sensors, are electrooptically converted to three separate optical pulse trains so that a dc to 2-kHz information bandwidth is established in the transmitter using frequency-modulation techniques. The three optical pulse tains are transmitted over a 4.6-m fiber-optics bundle to one of two types of receivers. These units reconvert the information to either an analog replica of the transmitter input waveform, or to a three-digit, scaled numerical display of the time-averaged value of the input signal. Practical applications involving field-strength measurements in the 1-MHz to 12-GHz region are presented. Advantages over hardwire data links are discussed, and significate reductions in RF interference and cable backscatter during field-strength measurements are described.