Optically Injection-Locked 1.55-$\mu$ m VCSELs as Upstream Transmitters in WDM-PONs

The wavelength-division-multiplexed passive optical network is actively being developed to meet the ever-increasing bandwidth demands of end users in a cost-effective and future-proof manner. In this work, we propose a novel scheme that utilizes injection-locked 1.55-mum vertical-cavity surface-emitting lasers (VCSELs) for operation as low-cost, stable, directly modulated, and potentially uncooled upstream transmitters, whereby the injection-locking master source is furnished by modulated downstream signals. Our scheme eliminates the need for external injection-locking optical sources, external modulators, and wavelength stabilization circuitry. We show through experiments that the injection-locked VCSEL favors low injection powers and responds only strongly to the carrier but not the modulated data of the downstream signal, with good upstream transmission performance obtained over 25-km fiber