Optical communication for next generation chip on tip surgical endoscopes

Abstract

The next-generation chip-on-tip surgical endoscopes require small footprint (1-3 French), hyperspectral imaging capability for multi-biomarker quantification with high frame rate to reduce motion artefacts. These innovations demand high data rate links, which could require twisted-pair cables if transmitted electrically. To eliminate bulky electrical wiring, we propose an all-optical powering and communication chip at the distal end consisting of a monolithically series interconnected Photonic Power Converter and a reflective electroabsorption modulator (REAM) based on a p-i-n diode structure with an embedded multiple quantum well (MQW) absorber. Optical sources for the power generator and reflective modulator are provided remotely over optical fiber, thus removing the need to host power-hungry lasers at the distal tip. To simplify the overall design, the communication scheme takes advantage of the REAM's dual functionality as a modulator and detector. Here, we have used a commercial REAM designed to operate at 1550nm and a novel Time Division Duplexing (TDD) communication protocol to demonstrate bidirectional transmission at 500 Mb/s over a singlemode fiber on a benchtop in order to examine the feasibility of the scheme. We found that at shorter wavelength near the MQW band-edge, zero-bias operation of the REAM is possible and the required modulation voltage swing is reduced. Operating under zero-bias at 1520nm instead of 1550nm leads to negligible static energy consumption and about 47% reduction in dynamic energy consumption, reaching an 8dB extinction ratio. Additionally, at 1520nm, the photocurrent generation responsivity increases dramatically at zero-bias, allowing the Transimpedance Amplifier (TIA) to be removed from the receiver circuit. This results in reduced footprint and power consumption of the receiver front end circuit.