Abstract

Detection of strains using modal interferometry in elliptical core two-mode optical fibers is becoming practical. We report two methods of heterodyning this type of strain sensor in order to obtain an rf output signal whose phase is linearly proportional to the axial strain applied to the fiber. Heterodyning the strain gauge greatly improves its sensitivity and overcomes the signal fading problem encountered when directly analyzing the interference pattern.

© 1988 Optical Society of America