Investigation of an underwater clock and data transmission optical wireless link at 650 nm for robotic oriented geodesy applications

Abstract

Underwater geodesy is important for marine studies and seafloor mapping. These studies typically make use of the time of flight, for example SONAR, and collect a lot of data. Furthermore, high map densities require big data collection and transportation, and therefore require high bandwidth underwater networks. In this article, we propose and demonstrate an underwater optical network based on a directly-modulated laser at 650 nm that enables the deployment of underwater robotic systems which are capable of transferring the captured data to a base station and allow the synchronization of the clocking signals. As proof of concept, we demonstrated a unipolar NRZ data transfer from an Arduino at 2 Mbps through an underwater channel measuring about 1 meter in length. A bit error rate value of about 10 − 5 for underwater data transmission was realised by the designed optical network, showcasing its potential for use in underwater data transfer during robotic geodesy surveys. Recovery of the clock signal from the signal generator at 2 kHz was also shown. Phase noise floor values below −90 dBc/Hz were attained for the underwater clock signal transmission.