Noise in a phase sensitive strain monitoring system

Noise measurements indicate that the strain resolution of our 3/spl times/3 detection system is limited by the phase noise due to the source /FFP combination. The shape of the noise distribution suggests that noise in the filter wavelength dominates at frequencies above 100 Hz. The noise floor supports previous measurements of nanostrain resolution in this instrument. Significant improvement to the resolution of a sensor system based on this approach, therefore, will require low-noise drive voltages for the FFP (fiber Fabry-Perot filter) up to the limits of the digitization process.