Indoor Optical Intercom System: Application of Visible Light Communication system for audio transmission using PDM

Optical Wireless Communication (OWC) using Light Emitting Diode (LED) is a supplement of modern Radio Frequency wireless communication scheme due to high bandwidth (>300 GHz) of the optical domain. It is less harmful compared to RF wave and it fulfils both illumination and data transmission at a time being used for indoors. OWC experiences many schemes starting from Amplitude modulation to Sub Carrier Index Modulation Orthogonal Frequency Division Multiplexing (SIM-OFDM) technique and improvements are still going on for achieving more secured communication system with higher data rate (in Gigabit Class). Here, an audio transmission system in OWC using Pulse Density Modulation (PDM) has been demonstrated. Experiments have been performed using 18W Warm White LED (Correlated Color temperature 2800K) as downlink maintaining the proper light level in the working plane and 850 nm IR LED as uplink for bidirectional communication. Using this scheme, a distance of 9m for communication has been achieved successfully.