ABSTRACT
The basic structure of optical fiber WLI strain measurement system based on Michelson interferometer is shown in Figure 1. The light emitted from the SLED light source passes through the circulator, and then reaches a semi-transparent mirror. After that, the transmitted light reaches the reflective mirror through the sensing optical fiber, which is reflected and reaches the circulator through LS, semi-transparent mirror and L1. In the circulator, the transmitted light is recoupled with the reflected light. The recoupled light enters the 50/50 coupler, and is divided into two beams. One of them enters L3 and is reflected to the detector by a reflective mirror. Another beam enters the L2 through the selffocusing lens and is also reflected by the reflective
1 INTRODUCTION
In the process of bridge construction and service, the cable force will be affected by the construction, cable corrosion, wind load and bridge deck vehicle load and so on. Because the bridge is a statically indeterminate structure, once the cable force deviate from the designed value, bridge internal force distribution will be changed, which will enable the pylon and girder to generate additional moment and bury next hidden trouble to the safe operation of the bridge.
