8$\,\times\,$9.95-Gb/s Ultra-Dense WDM-PON on a 12.5-GHz Grid With Digital Pre-Equalization

We first experimentally demonstrate the ultra-dense wavelength division multiplexing passive optical network (UD-WDM-PON) system at 9.95 Gb/s per wavelength on a 12.5-GHz grid, adopting digital pre-equalization considering narrow-band optical filtering effect at the transmitter. Eight optical carriers with 12.5-GHz frequency spacing carry 9.95-Gb/s digital pre-equalized binary signals (on-off keying) and are optically filtered. 25- and 45-km single-mode fiber (SMF)-28 downlink transmissions are experimentally demonstrated. The bit-error ratio for each of the eight channels is less than 1.0 × 10
^-9
after transmission over 25-km SMF-28.