An adaptive optical wireless communication (OWC) receiver combining the near-quantum sensitivity of a single photon avalanche diode (SPAD) array and the classical operating performance of a linear photodiode (LPD). The device enables OWC with a single receiver in scenarios requiring a highly extended dynamic range.
With limitations in radio frequency spectrum and technologies increasingly representing a bottleneck for the expansion of wireless communication networks, OWC has attracted significant interest due to its potential advantages such as high data rate, and licence-free spectrum. OWC has diverse application including outdoor Free Space Optics (FSO), indoor Visible Light Communication (VLC), space communication and underwater communication. The nature of OWC means that signals may vary significantly including very low levels which would be below the threshold of conventional optical receivers (e.g. due to adverse weather conditions in FSO or blockage/dimming in VLC). There remains an unmet need for effective OWC receivers which can operate consistently across such an extended dynamic range.
Edinburgh researchers have developed a hybrid OWC receiver for Gigabit transmission that is capable of transitioning from sensitivity levels of classical (e.g., thousand photons per bit) to near-quantum regimes (e.g., ten photons per bit). This is achieved by combining the capabilities of an array of single-photon avalanche photodiodes (SPADs) and conventional photodetectors operating in linear mode (LPD), e.g., pin diode. Notably, the technology incorporates an approach to overcome the inherent operating gap that exists between SPAD array detectors and LPDs in high-speed applications, resulting in a system that provides reliable and smooth operation over a very large dynamic range of incident light intensity.
S. Huang and M. Safari, "Hybrid SPAD/PD Receiver for Reliable Free-Space Optical Communication," IEEE Open Journal of the Communications 10.1109/OJCOMS.2020.3023009
Please note, the header image is purely illustrative. Source: Shaxiaozi via GettyImages