In a typical optic fiber Bragg grating (FBG) strain measurement, unless made in an ideal static laboratory environment, the presence of vibration or often disturbance always exists, which often creates spurious multiple peaks in the reflected spectrum, resulting in a nonunique determination of strain value. We attempt to investigate the origin of this phenomenon by physical arguments and simple numerical simulation. We postulate that the fiber gratings execute small-amplitude transverse, vibrations changing the optical path in which the reflected light traverses slightly and nonuniformly. Ultimately, this causes the multipeak reflected spectrum.
"In search of multipeaked reflective spectrum with optic fiber Bragg grating sensor for dynamic strain measurement," Optical Engineering 46(10), 104401 (1 October 2007). https://doi.org/10.1117/1.2799181