A Vestigial sideband modulation scheme in radio over fiber system using electro-optic modulators

We propose unequal sideband intensity based modulation scheme called vestigial sideband scheme (VSB) for the radio over fiber system (RoF) using concatenated Mach-Zehnder modulator (MZM) and phase modulator (PM). This scheme can be generated with proper adjustment of the modulation indexes of the modulators. MZM-PM configuration can also be used for generating single sideband (SSB) and carrier suppressed double sideband (CS-DSB) schemes. However, SSB scheme suffers from low signal to noise ratio (SNR) due to the strong dc component present in the detected signal. CS-DSB scheme cannot deliver the vector signal without modifying the phase and frequency at the receiver. Proposed VSB scheme can compensate chromatic dispersion (CD) of the RoF link as well as can deliver the vector signal without modification of the carrier frequency and phase at the receiver. We provide the theoretical analysis of the MZM-PM configuration. We illustrate the behaviour of harmonic distortion due to the CD in dispersive RoF link. Finally, we provide the comparison of symbol error rate of the proposed VSB scheme using 4QAM modulation format with DSB and SSB schemes. Simulation results show that VSB scheme can provide better performance than DSB and SSB scheme in dispersive RoF link.