This paper experimentally demonstrates single channel 1.25 Gbps upstream (US) data remodulation by over-modulating 10 Gbps downstream data, based on injection locked Fabry-Pérot laser diodes (FP-LD). In the proposed scheme, non-return to zero (NRZ) or differential phase shift keying (DPSK) modulation formats are used for the downstream data transmission. The injected FP-LD is modulated directly at 1.25 Gbps with NRZ signals and transmitted through 100 km of single mode fiber (SMF) without any error floor in both cases. The experimental results represent total optical power budget of about 30.7 dB for NRZ setup and 29.2 for DPSK setup after 100 km SMF transmission which enables 128 subscribers being connected to the network per λ-channel. The presented configuration provides a cost-efficient solution for WDM-PON since it eliminates the wavelength specific light source at the ONU by using colorless FP-LD. Furthermore, the proposed setup shows a significant improvement in comparison to ASE-seeded FP-LD in terms of transmission distance, intensity noise, and architecture simplicity.