A Reconfigurable Single-Photon-Counting Integrating Receiver for Optical Communications

Receiver design for SPAD-based VLC systems under Poisson–Gaussian mixed noise model

“…Since the low-cost intensity modulation with direct detection (IM/DD) is often applied in VLC [3], the signals transmitted by LEDs are constrained to be non-negative and real-valued. Currently, the high-speed integrated optical detectors such as avalanche photodiode (APD) are widely employed in VLC systems [4]. However, these detectors are not applicable in the scenarios of weak illuminance or long-distance transmission where the received optical power is relatively low [5].…”

“…To address the aforementioned issue, the single-photon avalanche diode (SPAD) [4,6] is employed for weak optical signal detection, where the reverse bias voltage is different from classical APDs, causing it to operate in Geiger mode instead of linear mode. In comparison with the classical APD, SPAD is more sensitive to optical signals, and can be employed as a photon counter.…”

“…In [4,9,10,13], the digital SPAD is employed for photon detection, where a digital counter is used to generate discrete outputs. Therefore, the receiver is not influenced by the Gaussian thermal noise.…”

“…Therefore, the receiver is not influenced by the Gaussian thermal noise. However, as is discussed in [4,12,14], for digital SPADs, the counting process is required to be precisely synchronized to the transmitter clock, and additional receiver design work is necessary for recovering the clock and the data from transmitted signals, which may lead to degradation of the system performance and increased overhead at the receiver. Due to this clock synchronization issue of the digital SPAD, the analog SPAD without the counter is considered in this paper, where equally weighted current steering digital-to-analog converters (D/A) [12,15] are employed to generate current signals, and a transimpedance amplifier (TIA) is optionally applied to enhance the bandwidth.…”

“…Therefore, a reduced-complexity GATbased detector with hard decision is proposed, where the corresponding decision thresholds are formulated. In simulations, due to the low output rate of the SPAD [4], an SPAD array consist of enormous diodes used in [4] is adopted to enhance the output rate. Numerical results demonstrate that the reduced-complexity GAT-based detector only suffers negligible performance loss compared with the quasi-ML detector.…”