The influence of fiber dispersion on the transmission performance of a quadruple-frequency optical millimeter wave with two signal modulation formats

This paper reports investigations of the transmission performance of a 40 GHz dual-tone optical millimeter (mm) wave by quadrupling a radio-frequency local oscillator via a single dual-electrode Mach–Zehnder modulator based on the transmission function of the dispersive fiber. The theoretical analysis and simulation results show that, although the fiber chromatic dispersion does not cause a fading effect on the optical mm wave with the two signal modulation formats, the bit walk effect caused by the time shift of the sidebands due to fiber dispersion limits its transmission distance as the signal is modulated on the two tones. The limitation of transmission distance caused by the bit-walk effect can be overcome if the signal is modulated on only one of its two tones, and, in this way, the transmission distance is greatly extended. Moreover, the dual-tone data modulation format is more suitable for a radio-over-fiber link with transmission distance less than 40 km owing to the good signal performance and ease of implementation, while single-tone data modulation can be applied for a longer fiber link, even up to 120 km.