Interrogation of fiber Bragg grating arrays by illumination using a low coherence interferogram

Interrogation of multiplexed arrays of fiber Bragg grating (FBG) sensors is generally limited on several fronts, for example, the number of sensors in an array can be restricted by the bandwidth of illuminating source, and simultaneous interrogation of all of the sensors in an array can be limited depending on the technology adopted. Interferometric interrogation overcomes the simultaneous interrogation problem through the Fellgett advantage, but conventional interferometric systems cannot easily interrogate multiple arrays. The work described in this paper implements an interferometric interrogation scheme for fiber optic sensors based on the filtering of a high coherence interferogram from a low coherence interference pattern generated by a scan of an optical path difference in a two beam interferometer illuminated with a broadband source. This filtering technique can address multiple arrays of FBG sensors in a single scan while simultaneously addressing all of the sensors in the individual arrays. Experimental data yielded a system resolution of ∼9.03pm/⁰C and ∼9.23pm/⁰C for two gratings for short delay scans of ∼13mm.