Hybrid WDM-PDM visible light communication system incorporating compressed spectrum return to zero advance modulation format

Abstract

Abstract Hybrid wavelength division multiplexing (WDM) and polarization division multiplexing (PDM) technology is a promising candidate for high capacity and extended reach in visible light communication (VLC) systems. However, multilevel modulations and direct modulation are suffered from two predominant limitations in VLC such as high complexity and frequency chirping respectively. Therefore, in this work, a high-capacity VLC system is presented by employing a hybrid WDM-PDM and compressed spectrum return to zero (CSRZ) advanced modulation format. Moreover, direct modulation is replaced with external modulation employing Mach-Zehndar modulators and red/green/blue (RGB) laser diodes (LDs). A detailed comparison of non-return to zero (NRZ) and CSRZ is performed at varied VLC lengths in terms of bit error rate (BER) and Q factor. Results revealed that CSRZ is far better than NRZ and external modulation offered an edge over direct modulation. The maximum VLC distance achieved using CSRZ is 229 cm within acceptable BER limits (10−3) without forward error correction (FEC).