8.2 Gbps Optical Wireless Link Using SiPM at NIR Wavelength

Silicon Photomultipliers (SiPMs) can provide optical wireless communication (OWC) receivers with better sensitivities than PIN photodiodes, thanks to their photon counting capabilities. The commercial availability of SiPM with fast output pulse width allows high-speed data transmission at low irradiance levels. This article investigates the use of a commercially available SiPM with an active area of 1 mm² and fast output pulse width of 0.6 ns in a Near-infrared (NIR) OWC link and compares the performance of a 3 mm x 3 mm SiPM with a fast output pulse width of 1.4 ns. Although both SiPMs have maximum detection efficiency at 450 nm, a wavelength of 850 nm is used owing to the availability of high-speed VCSELs, higher eye safety limit and ability to filter ambient light when using this wavelength. The OWC link is designed and tested at a 35 cm transmission distance using On-Off-Keying (OOK) and Decision Feedback Equalization (DFE), and a maximum data rate of 8.2 Gbps at a BER of 3.8 × 10⁻³ was obtained with 15.34 W/m² irradiance at the SiPM. These results are achieved in the dark and under 500 lux of White Light Emitting Diode (WLED) ambient light. A long pass colour glass filter is used to reject light up to 700 nm wavelength, thus rejecting most of the interference from WLEDs, resulting in data rates similar to dark environments. This is the highest data rate achieved using SiPMs in an NIR link.