Subband Index Carrierless Amplitude and Phase Modulation for Optical Communications

Subband index carrierless amplitude and phase modulation (SI-CAP) is proposed and investigated in this paper to improve the performance of multi-band CAP (m-CAP). The bit-error-rate (BER) analysis of the proposed SI-CAP is derived and verified through computer simulations. A detection scheme is also developed for SI-CAP, which achieves maximum likelihood performance at a significantly lower complexity. In addition, an experimental demonstration of the proposed SI-CAP is carried out for optical communication systems. Furthermore, an adaptive equalization technique is implemented to further enhance the performance gain of SI-CAP. It is shown that for the same order of complexity, the SI-CAP exhibits higher spectral and energy efficiency in comparison to m-CAP. Therefore, the performance gain of SI-CAP along with its design flexibility make it a suitable candidate for optical communication systems.