Optical MC-CDMA System for IM/DD based Optical Wireless Communications

The optical waves and radio waves, both follow same laws of Physics. However wavelength of optical waves is much smaller as compared to radio waves. There is exponential growth in the demand for data access, but the RF spectrum is already congested. Optical Wireless Communication (OWC) emerges as an alternative solution for today's high-speed data communication. Optical Orthogonal Frequency Division Multiplexing (O-OFDM) with intensity modulation and direct detection (IM/DD) is a modulation scheme commonly used in OWC systems. There are two common families of O-OFDM signal structures mostly used in OWC systems. First one is bipolar Gaussian signal called DC-biased optical OFDM (DCO-OFDM) and the second is unipolar half Gaussian signal called asymmetrically clipped optical OFDM (ACO-OFDM). In this paper a novel modulation scheme based on O-OFDM and code division multiple access (CDMA) is proposed. The new technique enables the implementation of simple and spectrally efficient OWC system. The proposed scheme support simultaneous transmission of multi-user data. Simulation results illustrate that Optical-MC-CDMA provides an excellent performance complexity trade-off.