Real-time 11.25Gb/s optical OFDM signal transmission over 2000m legacy MMFs using centre launching

In directly modulated VCSEL (DM-VCSEL)-based, end-to-end real-time, 11.25Gb/s optical OFDM (OOFDM) systems utilizing legacy OM1/OM2 multimode fibres (MMFs) as well as simple intensity-modulation and direct-detection (IMDD), detailed experimental explorations are undertaken, for the first time, of the effectiveness of various optical launching conditions including centre 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, centre launching enables an adaptive power-loaded 11.25Gb/s OOFDM transmission over an unprecedented distance of 2000m with an optical power penalty as low as 0.8dB. When centre launching is replaced by conventional offset launching, the transmission distance of the legacy MMF system is reduced to 300m and the corresponding optical power penalty is increased to 2.3dB. 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 centre 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 10Gb/s and beyond.