Bidirectional optical transcutaneous telemetric link for brain machine interface

A wavelength division multiplexing-based bidirectional optical transcutaneous telemetric data link for brain machine interfaces is reported. By converting the digitised electronic signals to a stream of infrared and visible optical pulses, the optical telemetry wirelessly transmits data between the implanted neural recorder/stimulator and the external control devices. A red visible vertical cavity surface emitting laser (VCSEL) with a peak wavelength of 680 nm is used in the downlink to transmit data from the external base unit to the implant. A near infrared VCSEL with a peak wavelength of 850 nm is utilised in the uplink for data transmission from the implants to the external device. An optical filter is applied to minimise the interference between the two channels. In-vitro experiments show that the uplink is capable of transmitting data at 100 Mbps through 2 mm of porcine skin while the downlink is simultaneously working at a rate of 1 Mbps. The power consumption of the implant part of the telemetry, including the transmitter for the uplink and the receiver for the downlink are 3.2 mW and 290 μW, corresponding to a transmission power efficiencies of 32 and 290 pJ/bit, respectively, which are among the best reported and unseen for bidirectional high-speed transcutaneous communication.