Optimal Sensor Placement (OSP) is an optimization problem aimed at identifying sensor positions that maximize the value of information obtained from the employed sensor configuration. The Fisher Information Matrix (FIM) has been widely explored for the development of OSP methods for civil engineering structures. The Effective Independence (EfI) method complements the FIM in OSP by providing information on the contribution of each candidate sensor to the determinant of the FIM, allowing the least important sensor to be excluded during each iteration. By repeating this process, an optimal setup containing the desired number of sensors can be obtained. The FIM and EfI methods have demonstrated their effectiveness for optimal placement of accelerometers in both laboratory and full-scale structures. However, their application to fiber-optic sensors, such as Fiber-Bragg Gratings (FBG), has been limited. In this study, these methods are applied to optimize the placement of FBG sensors for strain-based Operational Modal Analysis (OMA) of a Vierendeel truss bridge. The optimization process aims to identify the sensor configuration that yields the most information on the strain mode shapes of a set of considered modes. Starting with candidate locations determined by a user-specified strain threshold, the methodology iteratively refines the sensor layout to achieve an optimized configuration of 80 sensors—matching the acquisition system's capacity. A calibrated Finite Element model of the bridge is used to determine the candidate locations, ensuring a robust optimization process. This study highlights the potential of combining FIM and EfI for advancing OSP techniques in FBG networks for strain-based SHM.