High-Precision Optical Transfer Delay Measurement Using Optical-Comb-Assisted Phase-Derived Ranging

Abstract

We propose and experimentally demonstrate an approach for high-precision optical transfer delay measurement based on phase-derived ranging powered by a frequency-agile electro-optic comb. When the optical comb passes through a Mach-Zehnder interferometer, a reference frequency-shifted comb and a probe comb carrying distance information of targets are created. After filtering and heterodyne detection, two electrical signals are generated and sent to a narrowband phase detector for phase extraction, from which distance information or transfer delay can be recovered. Thanks to the broad comb spectrum, high-order comb lines exhibit high sensitivity to propagation distance and transfer the phase to the generated low-frequency electrical signals, significantly enhancing measurement precision. Experimental demonstrations show that a precision of ±10.5 fs is achieved, with a measurement range up to 50 km. Furthermore, a free-space distance measurement is performed, and a precision as small as $2.8~\mu $ m is realized. The proposed system holds great potential for widespread use in distributed network systems and 3D imaging systems.