Experimental investigation of DCO-OFDM adaptive loading using Si PN-based receiver

In this paper, an experimental investigation of adaptive bit-loading for DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM) is presented. The carried out measurements demonstrate performance enhancement with DCO-OFDM in a signal-to-noise (SNR) limited environment due to the use of silicon PN photodiode (PD). A PN photodetector usage sets additional bandwidth and SNR constraints that have not been tackled through the majority of published works on visible light communications (VLC). Most of the prior reported works employ commercial-off-the-shelf (COTS) PIN or Avalanche-photodiodes (APD) offering by default higher SNR and larger bandwidth than PN-type PDs. This approach targets at taking one step towards fully integrated low cost fabrication VLC systems. The link utilizes a 650-nm red LED source and a CMOS-compatible reverse-biased PN photodetector receiver. A separation of 4 meters makes the link compatible with indoor VLC applications. A data-rate performance of 172 Mb/s is measured with a bit-error-rate (BER) of 1.9×10−3 which is below the forward error correction (FEC) VLC limit. The effective DC power consumption of the link is about 345 mW. This presents, to the authors' knowledge, a record energy-per-bit performance of around 2 nJ/bit at 172 Mb/s over all reported VLC links to date.