Interrogation techniques for π-phase-shifted fiber Bragg grating sensor: A review

Abstract

π-phase-shifted fiber Bragg gratings (πFBG) have been extensively explored by various research groups in the recent past as a high-resolution optical fiber sensor for both static and dynamic strain measurement applications. A phase-shifted FBG exhibits very sharp resonance in its spectral response which offers enhanced dynamic strain measurement capability in comparison to regular FBG sensors. External perturbation induced modulation in the centroid wavelength of the resonance is estimated from the wavelength-shift measurements. The interrogation system that measures the wavelength-shift represents a key element in terms of both cost and performance as it has to determine relatively small shifts in central wavelength of πFBG spectra. This article gives a review of the current state-of-the-art for πFBG sensor interrogation principles with a systematic and complete overview of the available experimental configurations and their working principles. A detailed description of the existing interrogation architectures is provided together with analysis in terms of measurement sensitivity, dynamic range and complexity of the different experimental configurations. The associated advantages and the limitations of different architecture are also touched upon. It is expected that πFBG sensors will be widely applied in practice in near future due to the availability of cost-effective interrogation and multiplexing techniques as well as its low-cost fabrication and high-resolution sensing capability. The present article can be used as a future guideline for differentiating the various interrogation principles of πFBG sensor to be utilized for small amplitude dynamic strain perturbation measurement.