Underwater Arbitrary Distance Measurement with Laser Frequency Comb for Real-Time Correction of Underwater Refractive Index

With the development of marine science and technology, underwater ranging has been widely applied in underwater remote sensing, detection, and navigation. In this paper, we propose a method aimed at obtaining arbitrary distance underwater using frequency comb, i.e., measuring arbitrary positioned points by using spectral interference and spatial folding optical paths. Moreover, a real-time correction of the water refractive index is implemented in the measurement scheme. The compensation of the refractive index also perfects the measuring mechanism to some extent. The experimental results show that the difference is well within 18.5 μm compared to the reference value over a range of 8 m, and the Allan deviation is 0.96 μm at 100 s averaging time