Detection statistics and error performance of SPAD-based optical receivers

This paper presents the characterization of single photon avalanche diodes (SPADs) for optical communication applications. SPAD-based optical receivers can provide a significantly improved single-photon detection sensitivity compared with conventional photodiodes. However, an undesirable dead time introduced by the quenching circuit decreases the performance of these receivers. Using a precise analysis, we show that in the presence of dead time, the photon arrival process does not follow a Poisson process. Also, the effective count rate is evaluated and shown to depend critically on dead time. The effect of SPAD dead time on the error performance of an on-off keying (OOK) modulation optical communication system is also investigated. It is shown that, when background counts due to dark current and afterpulsing are small, the performance degradation of the SPAD-based receiver due to dead time losses is negligible. However, for systems with considerable background counts, the bit error rate (BER) degrades rapidly with increasing dead time.