The main objective of this proposed research is to develop and test optical fiber strain and stress sensor systems for on-line, accurate, and real-time monitoring of critical components of structural systems under service load conditions. In this proposed research the combined resources of Rutgers' Civil Engineering Department and those of its center for Fiber Optic Material Research Program (FOMRP) will be devoted for development and implementation of both discrete and continuous optical fiber strain / stress sensors for detection and warning of imminent structural failures for both concrete, and steel structures. In the case of concrete structural components, the sensor system will be evaluated under both embedded (internal) and exposed (external) condition; where the latter is attached to existing structures and the former is embedded in the structure during its construction.