Quad photodiode array for optical wireless communication

Optical spectrum offers bandwidths far beyond the radio-frequency (RF) technologies. Optical Wireless Communication (OWC) is meant to serve many users in small areas with high-capacity connection. Due to its ultrahigh capacity, OWC can help unload the traffic from the RF channels so that the RF spectrum can be freed for other services. Receivers used in indoor OWC scenario must have a wide field-of-view (FoV) and high sensitivity to be able to capture light from different directions at eye safety levels. VTEC Lasers & Sensors B.V. developed a quad photodiode array with 100 µm diameter. Each photodiode has a shape of 90° sector of a circle and has a separate Trans-Impedance Amplifier (TIA). Such choice allows the system to retain the bandwidth of a single photodiode while increasing the aperture. At -8 dBm incident power, where TIA saturates, the device achieved an error free (BER < 10-9) transmission at 16 Gbps, and 20 Gbps below the error-free FEC floor (BER < 10-3). Incidence angle of the beam was varied between 0° and 16° and no penalty was observed in this range. Hence it can be concluded that the device has a full angle FoV greater than 32°. The results prove that the presented quad photodiode can be used in the indoor OWC communication scenario.