An integrated sensor system that continuously monitors the structural integrity of an aircraft's critical composite components can have a high payoff by reducing risks, costs, inspections, and unscheduled maintenance, while increasing safety. Hybrid sensor networks combine or fuse different types of sensors. Fiber Bragg Grating (FBG) sensors can be inserted in layers of composite structures to provide local damage detection, while surface mounted Piezoelectric (PZT) sensors can provide global damage detection for the host structure under consideration. This paper describes an example of optimal sensor fusion, which combines FBG sensors and PZT sensors. Optimal sensor fusion tries to find the optimal number and location of different types of sensors such that their combined probability of detection (POD) is maximized. Optimal hybrid sensor networks can be more robust, more accurate, and/or cheaper than networks consisting only of homogenous sensors.