40-Gb/s Wavelength-Division-Multiplexing Passive Optical Network with Centralized Lightwave Source

We propose and experimentally demonstrate a 40-Gb/s wavelength-division-multiplexing passive optical network (WDM-PON) with a centralized directly-modulated laser (DML) source for the first time. In the central office (CO), a DML operating at 42.8- Gb/s with high driven bias and low extinction ratio (ER) is employed for carrying downstream data. In the remote node (RN) or optical network unit (ONU), a narrow-band optical filter is used to re-shape the pulse and optical spectrum for increasing the ER of DML signals and re-set phase correlation between the adjacent bits to increase the dispersion tolerance. On the other hand, the low-ER DML signals before the optical filter are re-modulated by an external intensity modulator driven by the upstream signal and then sent back to the CO. In this way, a 40-Gb/s centralized WDM-PON access system with low-cost configuration is realized.