Two ∆Σ-modulated digital radio-over-fiber (DRoF) transmission systems that employ a multi-pulse Manchester encoder are proposed and experimentally evaluated. With a two-step modulation process comprised of ∆Σ modulation and multi-pulse Manchester encoding, a high frequency replica or image of a ∆Σ-digitized analog communication signal can be transmitted without significant power loss. This is achieved by exploiting the spectral characteristics of the modified Manchester code. For comparative analysis, a conventional ∆Σ-modulation-based DRoF system is also evaluated. Based on the evaluation results, the proposed DRoF systems more significantly improve the reliability and flexibility of the RoF system by providing higher power margins or by making the DRoF system implementation more cost-effective and easier to perform on account of the low-frequency requirement for electronics and optical transceivers.