The number of unmanned vehicles and devices deployed underwater is increasing. New communication systems and networking protocols are required to handle this growth. Underwater free-space optical communication is poised to augment acoustic communication underwater, especially for short-range, mobile, multi-user environments in future underwater systems. Existing systems are typically point-to-point links with strict pointing and tracking requirements. In this paper we demonstrate compact smart transmitters and receivers for underwater free-space optical communications. The receivers have segmented wide field of view and are capable of estimating angle of arrival of signals. The transmitters are highly directional with individually addressable LEDs for electronic switched beamsteering, and are capable of estimating water quality from its backscattered light collected by its co-located receiver. Together they form enabling technologies for non-traditional networking schemes in swarms of unmanned vehicles underwater.

We have developed an experimental 4-channel stimulator prototype capable of performing voltage controlled stimulation (VCS), current controlled stimulation (CCS), and switched capacitor based stimulation (SCS) all on the same platform for neurological experiments. The stimulator allows changing main stimulation parameters such as amplitude, pulse width, pulse frequency, and output channels in real-time either wirelessly or hardwired. The stimulator was used to objectively evaluate the power efficiencies of each stimulation strategy using platinum epilepsy electrodes with 2.3 mm2exposed area in saline solution. We measured 92%, 65%, and 77% efficiencies for VCS, CCS, and SCS, respectively, on a 962Ω - 810 nF resistive-capacitive load. The motivation behind this research is to find the most power efficient stimulation front-end (SFE) circuitry for implantable neurological stimulators (INS).