This paper presents an investigation of the fatigue life prediction for a dynamic optical cable under a turret-moored FPSO. The commonly used linear model for cable bending behaviors may lead to significant deviations or even mistakes in predicting the fatigue lives of optical cables. Therefore, three types of theoretical models are utilized to simulate the cable bending stiffnesses and stresses, which are introduced respectively into a case study of fatigue analysis. These models are no-slip, full-slip and bilinear, based on different assumptions on the friction effects between the armour wire layers. The difference in the predicted fatigue lives can reach five orders of magnitude, based on the above three models. It indicates that using different models to predict fatigue life may lead to overly conservative or overly risky conclusions, which can have a significant impact on design decisions. Finally, the bilinear bending model is recommended for the fatigue analysis of dynamic optical cables in similar floating systems.