Design, Calibration and Characterization of a Fiber Optic Triaxial Accelerometer Based on Fiber Bragg Gratings

This work presents the design, calibration and detailed performance characterization of a triaxial accelerometer based on fiber Bragg gratings (FBG), intended for space navigation applications. The sensor employs a single seismic mass architecture, whose acceleration-induced displacement deforms six optical fibers (OFs), forming twelve fiber segments (FSs) that act as elastic elements, with the strain measured by FBGs inscribed in each fiber. The methodology ranges from the manufacturing and spectral characterization of the FBGs to the design of a differential optical interrogation system and a low-noise signal conditioning circuit. A cornerstone of this work is the proposal of an extended calibration model that, in addition to the conventional sensitivity matrix and bias vector parameters, incorporates polynomial terms to actively compensate for the effects of temperature variation. This model was validated through tests in a climatic chamber, subjecting the sensor to different orientations and controlled temperatures. The experimental results validate the design's effectiveness, demonstrating that the accelerometer achieves tactical-grade performance with a bias instability below 1.9 mgE for all axes. The analysis confirmed that the sensor's effective full-scale range is approximately ±20gE, and sensitivity of 112 pm/gE, limited by the nature of the optical interrogation system. Furthermore, a third-order polynomial thermal compensation model was shown to provide the most efficient balance between model complexity and error reduction, reducing errors to a level dominated by the system's intrinsic noise and ensuring the sensor's accuracy over a wide operational temperature range.