In this investigation, we propose and demonstrate a wavelength-tunable self-seeding 1.2 GHz reflective semiconductor optical amplifier (RSOA)-based transmitter in each optical network unit for colorless wavelength-division-multiplexed passive optical network access. The output wavelength of the proposed RSOA-based laser can be tuned in the whole C-band. Here, we apply an orthogonal frequency division multiplexing (OFDM) modulation with bit-loading algorithm on RSOA laser to modulate 3.5 Gbps data rate directly for upstream traffic. In addition, we employ a 2.5 GHz direct modulation laser in the head-end to generate 10 Gbps 16-QAM OFDM signal for downstream traffic. Therefore, after transmitting through 20 km single-mode fiber, power penalties of 1.4 and 2.8 dB are observed for downstream and upstream traffics, respectively, under the forward error correction threshold [bit error rate = 3.8 × 10−3].