Abstract
Fiber-Optic Gyroscopes (FOGs) are widely utilized in aerospace and navigation systems because of their high precision and operational reliability. Despite these advantages, they remain vulnerable to bias drift caused by vibration and temperature fluctuations, which reduces overall accuracy. This study analyzes FOG performance under simultaneous vibrational and thermal influences. A MATLABbased model was developed to simulate the effect of vibration and the refractive index variations induced by temperature in the fiber coils. Experimental validation was carried out using controlled vibrations in the range of $20-2000 \mathrm{~Hz}$ and thermal cycles from $-30^{\circ} \mathrm{C}$ to $+60^{\circ} \mathrm{C}$. Allan variance served as the primary tool for quantifying bias instability, random walk coefficient, and scale factor error. The findings confirm a decline in accuracy under harsh environmental conditions and highlight the importance of implementing robust compensation strategies.