A simple and highly sensitive phase-demodulation technique is proposed, and its use for a fiber Bragg grating strain sensor is experimentally demonstrated. Sampling a phase-modulated Mach–Zehnder output with controlled time delay produced two quadrature data streams that have relative quadrature phase difference (90°). The Bragg wavelength-dependent phase information is extracted by application of digital arctangent function and phase unwrapping to the quadrature signals. By use of this technique with a reference grating, strain sensing at as much as a 30-kHz sampling rate was obtained with strain resolution of 3.5 microstrains and 6 nanostrains/ Hz in quasi-static and dynamic strain measurements, respectively.
© 2000 Optical Society of America
Minho Song, Shizhuo Yin, and Paul B. Ruffin, "Fiber Bragg Grating Strain Sensor Demodulation with Quadrature Sampling of a Mach-Zehnder Interferometer," Appl. Opt. 39, 1106-1111 (2000)