Dynamic strain measurement at high frequencies by using portable fiber Bragg grating (FBG) interrogator

In this work, we demonstrate the interrogation of fiber Bragg gratings (FBGs) for strain measurement of a metallic object by using 4- channel optical interrogator with sampling rates of 250 kSa/s per channel. The interrogator, which is packaged in a portable unit, applies a real-time active phase demodulation scheme based on multitone mixing on the signal coming from a fiber-optic Sagnac interferometer. The measurements from our interrogator show excellent agreement when compared with strain gauge-based sensors serving as reference system, and a dynamic strain resolution below 10 nε/√Hz.