Structural Monitoring With Fiber Bragg Grating Strain Sensor Array and Optical Frequency Domain Reflectometry

Abstract

In this work, concepts of smart structures, health monitoring systems, and Infrastructure Optics are discussed. This accumulates in the development of the Optical and Structural Simulation software that integrates all key components of Infrastructure Optics. Recent developments in the use of Coherent Optical Frequency Domain Reflectometry (C-OFDR) to interrogate Fiber Bragg Grating Arrays (FBGA) have shown promise in its use in infrastructure health monitoring systems. In this work, the modeling, design, simulation, fabrication, calibration, and testing of a three-element, 15.3 cm fiber Bragg grating strain sensor array with C-OFDR interrogation technique are demonstrated. The FBGA/C-OFDR was initially simulated using in-house software that incorporates transfer matrices. Compared to the previous techniques used, the transfer matrix method allows a system wide approach to modeling the FBGA/C-OFDR system.In the second half of this work, a cavity interference suppression method is used to suppress interferences between fiber Bragg gratings. The cavity interference suppression method is simulated using two transfer matrices, after which, a practical design using a circular polarized source and polarization devices is proposed. Compared to previous techniques, the cavity interference suppression method does not require down shifting the cavity interferences to a lower frequency band, potentially saving fiber material and bandwidth.