Fiber-optic extrinsic Fabry-Perot vibration-isolated interferometer for use in absolute gravity meters

In an absolute gravity meter, a laser interferometer measures the position of a test mass that is falling in a vacuum. The calculated value of gravity is the average acceleration of the mass during a set of drops. Since systematic accelerations of the optical system will bias the measured value of gravity, various interferometer geometries have been implemented in the past to isolate the optical system from ground motion. We have developed and tested a low-finesse fiber-optic extrinsic Fabry-Perot interferometer that is fixed to the mass of a critically damped seismometer in which the effects of systematic ground motion and acoustic vibrations are reduced.