A single channel 100 Gb/s dual-polarization quadrature phase shift keying transmission based on injection-locked broadband quantum-dash Fabry-Pérot laser, and employing external modulation, has been demonstrated. By employing a far L-band ~1621-nm sub-carrier, -17.4-dBm sensitivity at the bit error rate 3.8×10 ^-3 has been obtained after 10 km standard single mode fiber transmission. Besides, an injection locked mode wavelength tunability of ~23 nm, which translates to ~50 sub-carriers, is accomplished. These results favor the viability of deploying broadband quantum-dash lasers as unified upstream and downstream transmitters in next generation wavelength division multiplexed-based passive optical networks.