All-VCSEL Transmitters With Remote Optical Injection for WDM-OFDM-PON

We report on a novel scheme that uses vertical cavity surface emitting lasers (VCSELs) and remote optical injection technique in the hybrid wavelength division multiplexing orthogonal frequency division multiplexing (OFDM) passive optical network. In the proposed scheme, 1.55- μm VCSELs are used as low-cost, directly modulated upstream and downstream transmitters. The slave VCSEL at the optical network unit is remotely injection-locked by modulated downstream signals, and no need for additional injection-locking optical sources and external modulators. In our experiment, bidirectional transmission of 1.25 Gb/s 4-quadrature amplitude modulation (4QAM)-OFDM signal over 26-km single mode fiber has been successfully demonstrated. Moreover, we investigate the residual amplitude modulation (RAM) caused by the conversion of injected AM into slave AM. In addition, the experimental results show that due to this RAM, the power penalty of the 1.25 Gb/s 4QAM-OFDM upstream transmission is deteriorated by 2 dB.