Direct-Detection 25 Gb/s PON: PROs and CONs of Digital Signal Processing at the Transmitter Side

We evaluate the performance of direct-detection 25 Gb/s Passive Optical Networks (PON) with adaptive equalization at the receiver side, comparing three transmitter schemes: two including digital signal processing (DSP), namely square-root raised-cosine pulse shaping and pre-emphasis, and the third one without any DSP pre-compensation. We show that DSP at transmitter side can provide a performance advantage only under strong bandwidth limitations and when considering feed-forward equalization (FFE) at the receiver. When including decision-feedback equalization (DFE), the use of pre-compensation at transmitter does not provide any advantage under linear transmission.