Directly Modulated VCSEL-Based Real-Time 11.25-Gb/s Optical OFDM Transmission Over 2000-m Legacy MMFs

In directly modulated vertical cavity surface-emitting laser (DM-VCSEL)-based, end-to-end real-time, 11.25-Gb/s optical orthogonal frequency division multiplexing (OOFDM) systems utilizing legacy OM1/OM2 multimode fibers (MMFs), as well as simple intensity-modulation and direct-detection (IMDD) detailed experimental explorations, are undertaken, for the first time, for the effectiveness of various optical launching conditions, including center launching and conventional offset launching in maximizing the transmission distances of the legacy MMF systems. It is shown that, in the aforementioned legacy MMF systems, center launching enables an adaptive power-loaded OOFDM transmission at a raw signal bit rate of 11.25 Gb/s over an unprecedented distance of 2000 m with an optical power penalty as low as 0.8 dB. When center launching is replaced by conventional offset launching, the transmission distance of the legacy MMF system is reduced to 300 m, and the corresponding optical power penalty is increased to 2.3 dB. Comparisons of measured maximum achievable transmission distances of various MMF IMDD system configurations subject to different launching conditions show that DM-VCSEL-based, adaptive power-loaded OOFDM at center launching is a viable and cost-effective solution for use in legacy MMF systems. This work may have great potential for upgrading installed MMF local area networks to 10 Gb/s and beyond.