Clifford Pontbriand

Diffuse high-bandwidth optical communications

High speed underwater optical communications has at least three distinct advantages over acoustic communications. The data rates achievable are high (1 to 10 Mbps), the latency from when data is sent to when data is received is low, and there is no acoustic noise associated with transmission. Of course one of the biggest limitations of an optical approach underwater is the rapid attenuation of optical signals due to spreading loss, scattering, and absorption. Nonetheless, communication signals have been broadcast, received, and decoded over distances of 100 to 200 meters. High data rates and low latency make optical communications an attractive human interface to underwater systems, such as wireless control of underwater vehicles. Underwater optical communications is generally well-suited to multiple platform environments, where acoustic silence and limited range avoids interference between platforms. High data rates are advantageous in data retrieval applications, where, for one example, wireless data retrieval would make deployment and recovery of certain systems more economical. Recent engineering developments and accompanying experimental data are put forth in this paper, and the implications for future development are discussed.

Design of Nereid-UI: A remotely operated underwater vehicle for oceanographic access under ice

This paper reports the development of a new underwater robotic vehicle, Nereid-UI, with the goal of being capable of deployments in polar ocean regions traditionally considered difficult or impossible to access such the ice-ocean interface in marginal ice zones, in the water column of ice-covered seas, and the seas underlying ice shelves. The vehicle employs a novel lightweight fiber-optic tether that will enable it to be deployed from a ship to attain standoff distances of up to 20 km from an ice-edge boundary under the real-time remote-control of its human operators, providing real-time high-resolution optical and acoustic imaging, environmental sensing and sampling, and, in the future, robotic intervention.

Wireless data harvesting using the AUV Sentry and WHOI optical modem

The optical communications group at Woods Hole Oceanographic Institution has demonstrated wireless optical transmission of data from a seafloor node to the Sentry AUV. This effort is based on the latest version of the optical modem under continual development at WHOI, and it builds on fieldwork conducted in 2012 and 2013 during which we successfully transferred data from seafloor-deployed optical modem systems using a wire-lowered optical modem from a ship. While our previous work used a high-bandwidth optical modem for the data uplink and an acoustic modem “backlink” to control the file transfer, the optical modem described in this paper supports fully bidirectional optical communication-essentially subsea WiFi. A subordinate objective of our work was to literally map the operational space for an AUV-bottom node optical link. Armed with this spatial map, we can plan for future “connected” AUV operations in support of data mule, inspection, manipulation, and other underwater semi-autonomous tasks.

Autonomous acoustic-aided optical localization for data transfer

The emergence of high speed optical communication systems has introduced a method for transferring data relatively quickly underwater. This technology coupled with autonomous underwater vehicles (AUVs) has the potential to enable efficient wireless data transfers underwater. Data muling, a data transport mechanism in which AUVs visit remote sensor nodes to transfer data, enables remote data to be recovered cheaply from underwater sensors. This paper details efforts to develop a system to reduce operational complexities of autonomous data-muling. We report a set of algorithms, systems, and experimental results of a technique to localize a sub-sea sensor node equipped with acoustic and optical communication devices with an AUV. Our homing system was designed to utilize the long-range, lowpower acoustic signal to determine the sensor location from great distances. When within optical communication range, it exploits the optical power pattern to center the vehicle over the sensor node for optimum data transfer. These implementations were tested over three dives at varying levels of automation. Data collected from the real-time system has been tested in full-automation mode within our simulation environment.