Sensing properties of the bare FBG have theoretically and experimentally been studied in this study, and then a temperature compensation method for FBG strain sensors was proposed. Due to the fragility of bare FBG, a technique of encapsulating bare FBG in a capillary steel tube was developed and the strain and temperature sensing properties of the encapsulated FBG were furthermore studied. With the consideration of the practical application in civil infrastructures, the technique of FBG to adhere or embed on steel and in reinforced concrete structures was studied. With successfully affixing and embedding bare FBGs and encapsulated FBGs sensors on a steel truss and in a reinforced concrete beam, respectively, the experiment of using the above FBG sensors to monitor the structural strain and deformation process. In order to verify the quasi-distribution sensing ability of FBG, the test that 3 bare FBGs were connected one by one and adhered on a steel truss was done and the independently sensing strain ability was found. Finally, FBGs strain sensors were successfully embedded in a reinforced concrete bridge to monitor the strain history and distribution under construction and in service. The measuring signals indicated that the embedded FBGs could precisely and long-term monitor the strain history, therefore, they can be employed to evaluate the fatigue life for the bridge.