Field evaluation of a portable whispering gallery mode accelerometer

Abstract

An accelerometer utilising the optomechanical coupling between an optical whispering gallery mode (WGM) resonance and the motion of the WGM cavity itself was prototyped and field-tested on a vehicle. We describe the assembly of this portable, battery operated sensor and the field-programmable gate array automation. Pre-trial testing using an electrodynamic shaker demonstrated linear scale-factors with <0.3% standard deviation (±6 g range where g = 9.81 ms−2), and a strong normalised cross-correlation coefficient (NCCC) of rICP/WGM = 0.997 when compared with an integrated circuit piezoelectric (ICP) accelerometer. A noise density of 40 µg Hz−1/2 was obtained for frequencies of 2–7 kHz, increasing to 130 µg Hz−1/2 at 200 Hz, and 250 µg Hz−1/2 at 100 Hz. A reduction in the cross-correlation was found during the trial, rICP/WGM = 0.36, which we attribute to thermal fluctuations, mounting differences, and the noisy vehicle environment. The deployment of this hand-fabricated sensor, shown to operate and survive during ±60 g shocks, demonstrates important steps towards the development of a chip-scale device.