Distance measurement in air without the precise knowledge of refractive index fluctuation

TL;DR

This paper introduces a femtosecond frequency comb-based method for absolute distance measurement in air that compensates for refractive index fluctuations without needing prior turbulence knowledge.

Contribution

It presents a novel technique using reference interferometers and feedback control to accurately measure distances despite air refractive index fluctuations.

Findings

Achieves accurate distance measurement without prior turbulence data

Uses dual reference interferometers for environmental monitoring

Employs feedback to lock optical path length to stable conditions

Abstract

The accuracy of long distance measurement in air is limited by the fluctuation of refractive index. In this paper, we propose a technique which allows us to measure an absolute distance in air without the knowledge of air turbulence. The technique is based on a femtosecond frequency comb. The fluctuation of the environmental conditions is monitored by two independently operating reference interferometers. The deviations of optical path lengths, caused by the fluctuation of air refractive index, is compensated by feedbacks from the reference interferometers. The measured optical path length is then locked to certain environmental conditions, determined at an optimized moment before the measurement process.