Design of a room-temperature, sine-wave gated, InGaAs/InP SPAD based photon counting system with dead-time mitigation

A newly designed room-temperature, sine-wave gated, InGaAs/InP SPAD based photon counting system with dead-time mitigation is described in this work. In this system, an InGaAs/InP SPAD was developed and used as the detector. To mitigate SPAD's dead time and enable room temperature operation, a sine-wave gated quenching circuit is employed for rapid quenching and post-pulse suppression. Furthermore, phase modulation schemes are utilized to mitigate dead-time that enables SPAD to detect incident photons with unknown arrival times when applied in Optical Time Domain Reflectometry (OTDR). Results show that the system developed can operate under room temperature with a dark count rate of less than 8 kcounts/s at bias voltage of 67 V. At this bias voltage, the photon efficiency reaches 9.5% at 1400 nm. A narrow time jitter of 146 ps was achieved and the afterpulsing possibility measured was around 10% at bias voltage of 65 V. To evaluate the system's performance, a photon counting optical time domain reflectometer system was built and tested using FC/PC connectors. It has been proved that the system is able to detect reflected signals from all connectors and accurately measure their position, eliminating the problem of dead-time in the sine wave gated quenching circuit.