Abstract In this paper, we provide a comprehensive discussion focused on the motivation and benefits of providing real-time (RT) signaling mechanisms in multi-channel PONs, outlining several emerging low-latency applications such as Smart Grid, machine-to-machine (M2M) communication, and cloud computing. We expand this discussion to provide a straightforward definition for signaling delay and define that for a signaling mechanism to be considered RT in PONs the majority of the signaling delay should be attributed to the one-way propagation time. We propose backwards compatible mechanisms capable of realizing RT signaling without necessarily requiring additional PHY-layer cost and complexity. Based on frequent signaling data bursts (SDBs) scheduled by the Optical Line Terminal (OLT) for selected upgraded Optical Network Units (ONUs), our proposed mechanisms enable pay-as-you-grow migration from conventional TDM PONs to highly flexible RT signaling for multi-channel PONs capable of supporting emerging low-latency applications. We provide simulation results of system performance with relevant benchmarks showing up to 15% delay reductions with respect to previously proposed OC (Optical Coding) RT architectures, which have already demonstrated significant performance increases with respect to conventional PONs. Finally, we emphasize the flexibility of the proposed mechanisms provided to future RT Dynamic Bandwidth Allocation (DBA) algorithms aimed at achieving efficient Quality-of-Service (QoS) requirements.