Half duplex transmission with asymmetric surface normal electro absorption modulator-based optical transceiver for camera-on-tip surgical endoscopes

Emerging camera-on-tip surgical endoscopes supporting hyperspectral imaging with high frame rates to minimize motion artifacts will require alternatives to conventional read-out electrical wiring. We propose an optical communication link utilizing an asymmetric reflective surface-normal electro-absorption modulator (SNEAM) at the distal end of an endoscope, functioning as both a modulator and detector. The light for the communication channel is delivered from a proximal source via an optical fiber, eliminating the need for a power-hungry laser at the distal tip. We designed and fabricated a transfer-printed SNEAM, operating as the modulator at ∼1561 nm, and implemented a half duplexing protocol, demonstrating bidirectional transmission at 320 Mb/s over single-mode fiber on a benchtop setup with device power consumption of about 0.5 mW. The fundamental SNEAM cavity resonance can provide ∼6 dB extinction for a 5 V_pp swing, and a device bandwidth of ∼8 GHz was measured at -6 V bias. By leveraging the enhancement from a cavity side resonance at 1314 nm, the photocurrent responsivity was significantly improved. This, combined with the low optical fiber loss due to the short, few-meter, link length, enabled error-free operation (BER < 10^-9) without transimpedance amplifier or forward error correction, minimizing footprint and power consumption at the distal end.