Fiber-Optic Sagnac Interferometry for Gravity Gradient Measurements
Yanjun Chen, Wenbo Wang, Yan He, Yuwen Cao, Lanxin Zhu, Huimin Huang, Xiangdong Ma, Zhengbin Li
Abstract
We report a design for gravity gradient measurements based on Sagnac interferometry. A structure with two masses is designed to convert the effect of gravity gradients into rotational motion. Sagnac interferometry based on optical fibers is introduced to probe its rotational motion. The systematic effects are analyzed theoretically and validated by the static observation of an experimental apparatus. In a 37-day record, we achieve a noise level of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\,\, \times 10^{-12}$ </tex-math></inline-formula> rads <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-2}$ </tex-math></inline-formula> Hz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-1/2}$ </tex-math></inline-formula> under a room temperature environment without any vibration isolation and magnetic shielding devices. The corresponding contribution for the gravity gradient measurement is estimated to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\,\, \times 10^{-2}$ </tex-math></inline-formula> EHz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-1/2}$ </tex-math></inline-formula> .