Visible Light Communication in the Dark

We present a new visible light communication (VLC) primitive: VLC in the dark, where the communication sustains even when the LED light appears dark. We achieve the goal by reducing the duty cycle of the light source to an extremely low level (0.0019%) such that the illuminance is imperceptible to human eyes and yet can still be sensed by photodiodes to decode data. VLC in the dark consumes much lower energy than the conventional VLC links and thus is appealing for enabling VLC uplink or communication among Internet-of-Things devices with tight energy budget. We build a preliminary prototype to demonstrate its feasibility. Our current single link achieves 190.7 bps data rate with 46.8 mu W power consumption at the LED.