Photon detection characteristics and error performance of SPAD array optical receivers

In this paper a novel photon counting receiver for optical communication applications is proposed. The proposed receiver is a single photon avalanche diode (SPAD) array which can provide a significantly improved detection sensitivity compared to conventional photodiodes. First, the detection statistics and main characteristics of a single SPAD receiver is presented, and the effects of the SPAD dead time, which is introduced by the quenching process, on the counting probability and effective count rate are studied. The approach is then extended to account for SPAD arrays. Using a Gaussian approximation, the counting distribution of a large size SPAD array is derived and effective count rate of arrays with different sizes is evaluated and compared. It is found that even in SPAD arrays, dead time still has a significant role in the maximum achievable count rate, and the fill factor of the array greatly affects the performance and count rate and has to be carefully dealt with. The impact of SPAD background counts and fill factor on the error performance of an on-off keying (OOK) modulation optical communication system is also investigated. It is shown that the bit error rate (BER) depends critically on back ground counts and improves with increasing fill factor.