Abstract

The ultra-dense wavelength division multiplexing (UDWDM)-based fiber-millimeter-wave integration network (FMWIN) is a key enabler for the 6G radio access network (RAN), providing high access density and large capacity. Due to the high density of wavelengths and bandwidth limitations, a modulation format of high spectral efficiency is required in the UDWDM FMWIN. In this article, we propose a spectrally efficient orthogonal odd-even staggered multi-band carrier-less amplitude and phase (OES-m-CAP) modulation. Each sub-band of OES-m-CAP transmits pulse amplitude modulation (PAM) symbols, which is different from the sub-bands of the conventional quadrature amplitude modulation (QAM)-based m-CAP. The center frequency spacing of adjacent sub-bands in OES-m-CAP is half of the baud rate of each sub-band, and the roll-off spectra of adjacent sub-bands can overlap each other. Even if the roll-off factor increases, the center frequency of each sub-band does not shift, and the consumed system bandwidth increases only slightly. Thus, high spectral efficiency and good performance of the pulse shaping filters in OES-m-CAP can both be achieved without compromise. Moreover, we prove the orthogonality of OES-m-CAP in this article. By using OES-m-CAP in a UDWDM FMWIN system of 92-GHz millimeter-wave, we achieve a total data rate of 416 Gbps allocated across 32 sub-bands on 8 wavelengths over a transmission distance of 10 km.