Review and Analysis of Peak Tracking Techniques for Fiber Bragg Grating Sensors.

Daniele Tosi

doi:10.3390/s17102368

Abstract

Fiber Bragg Grating (FBG) sensors are among the most popular elements for fiber optic sensor networks used for the direct measurement of temperature and strain. Modern FBG interrogation setups measure the FBG spectrum in real-time, and determine the shift of the Bragg wavelength of the FBG in order to estimate the physical parameters. The problem of determining the peak wavelength of the FBG from a spectral measurement limited in resolution and noise, is referred as the peak-tracking problem. In this work, the several peak-tracking approaches are reviewed and classified, outlining their algorithmic implementations: the methods based on direct estimation, interpolation, correlation, resampling, transforms, and optimization are discussed in all their proposed implementations. Then, a simulation based on coupled-mode theory compares the performance of the main peak-tracking methods, in terms of accuracy and signal to noise ratio resilience.

Highlights

Since the first demonstrations of the photo-induced periodic modulation phenomenon in optical fibers [1,2,3,4], Fiber Bragg Gratings (FBGs) have become established as one of the most prominent technologies used in fiber optic sensors [5]
While the research on FBG sensors until the 2000s has mainly focused on the fabrication of gratings in photosensitive and standard optical fibers [1,2], using techniques such as phase mask [1], interferometric setup [2], direct inscription through pico/femtosecond lasers [23,24], and draw-tower fabrication [25], FBG sensors have seen a progressive standardization of the optical hardware for their interrogation
Thanks to the advances in low-cost spectrometers and tunable lasers, since the last decade two setups have been consolidated for the FBG interrogation: the first setup is based on a broadband source and a spectrometer [1,4,5,26], and has been commercialized [27,28,29]; the second setup is based on a fast-scanning tunable laser that sweeps a relatively broad wavelength range and a photodetector [30,31,32,33,34,35], and has been industrialized [36,37]

Summary

Introduction

Since the first demonstrations of the photo-induced periodic modulation phenomenon in optical fibers [1,2,3,4], Fiber Bragg Gratings (FBGs) have become established as one of the most prominent technologies used in fiber optic sensors [5]. While the research on FBG sensors until the 2000s has mainly focused on the fabrication of gratings in photosensitive and standard optical fibers [1,2], using techniques such as phase mask [1], interferometric setup [2], direct inscription through pico/femtosecond lasers [23,24], and draw-tower fabrication [25], FBG sensors have seen a progressive standardization of the optical hardware for their interrogation.

Methods

Discussion

Conclusion