Research shows that polarimetric optical-fiber sensors embedded in composite laminates can monitor structural integrity and detect damage while the structure remains in service. An experimental arrangement can be created to monitor strain in composite specimens. Light from a linearly polarized helium-neon laser is converted into circularly polarized light using a quarter-wave plate, and is coupled into a polarization-maintaining optical fiber with a microscope objective lens and three-axis positioner. In order to ensure that the intensity modulation was a maximum, the input beam was polarized at 45 degrees to the axes of the fiber. Although this study used polarization-maintaining fibers, similar results also have been seen for standard single-mode fibers.