The structural strains due to external loads have to be measured to monitor the structural health status. For this purpose, the real-time system that can sense deformations of structures without the time delay is needed. The real-time strain measurement system was constructed with 3×3 passive fiber optic Michelson interferometric sensor and digital processing program written in Visual Basic. The strain sensitivities of the fiber optic sensors could be calibrated by tensile tests of specimens with embedded or attached fiber optic sensor. For assuring the operation of the digital processing program, it was performed the off-line simulation that compared strain from the fiber optic sensor with that from a resistance strain gage subject to the tensile loading/unloading test. The noise could be decreased by applying the RC low-pass filter in the fiber optic sensor system. Experiments showed that the constructed real-time fiber optic strain measurement system could successfully track the structural dynamic strain. Also this system can measure the very small strain.
