10 Gb/s Upstream Transmission in TWDM PON Using Duobinary and PAM-4 Modulations with Directly Modulated Tunable DBR Laser

10Gb/s upstream transmissions in C-band over 40km are demonstrated for symmetric TWDM PON system using tunable DBR lasers. Compared to NRZ, duobinary and PAM-4 signals with direct modulation result in significantly lower dispersion penalty (~1dB).