Distributed strain sensing with a twin-core fiber optic sensor

The purpose of this paper is to introduce a new concept for conducting distributed strain measurements. The device, a twin-core fiber optic sensor, is a single optical filament containing two closely spaced, crosstalking waveguides. An optical source with multiple wavelengths illuminates the single sensor input and a processing unit analyzes the signal from a detector unit that responds to the light emitted from the output of the sensor. For structures bent in the manner of a cantilevered beam, the Fourier transform of the sensor output is the bending moment distribution imposed on the structure. Point load concentrations can also be identified in the sensor signals. Analytic development of the concept will be reviewed, in addition to laboratory experiments which verify a specific model based on the theory.