Non-contact surface vibration analysis using a monomode fibre optic interferometer incorporating an open air path

Abstract

A very high sensitivity non-contacting vibration analysis system based upon a monomode fibre optic Mach Zehnder interferometer incorporating an open air path is described. The system was operated in both a closed loop limited tracking range (>105) homodyne mode and an effective infinite tracking range novel pseudo-heterodyne mode. For periodic signals, amplitude detection sensitivities of approximately 2*10-10 m at 10 Hz to 5*10-11 m at 10 kHz have been demonstrated for both modes of operation.