A 250Mbps 24pJ/bit UWB-inspired optical communication system for bioimplants

This paper presents an optical communication system, implementing a UWB-inspired pulsed coding technique, for emerging high throughput bio-applications such as brain machine interfaces. The proposed solution employs sub-nanosecond laser pulses that, compared to the state-of-the-art, allows for high bit rate transmissions and reduced power consumption. The overall architecture consist of a transmitter and receiver that employ a pulsed semiconductor laser and a small sensitive area photodiode. This can allow for CMOS integration into a compact silicon footprint (estimated lower than 1 mm² in a 0.18 μm technology). The analogue circuits presented herein have been implemented using discrete off-the-shelf components. These provide the bias and drive signals for laser pulse generation, photodiode signal detection and conditioning. Moreover, the digital sub-system for data coding and decoding processes have been implemented on a FPGA board through VHDL description language. Experimental results validate the overall functionality of the proposed system using a diffuser between transmitter and receiver to emulate skin/tissue. This shows the capability of operating at bit rates up to 250 Mbps achieving BER less than 10^-9 and power efficiency as low as 24pJ/bit. These results enable, for example, the transmission of a 1000-channel neural recording system sampled at 16kHz with 16-bit resolution.