Robust Transmission of 29-Gb/s OFDM Signal Over 1-km OM1 MMF Under Center Launching

Center launching is a simple and straightforward method to couple optical signals to a multimode fiber (MMF), and able to preferentially excite a few lower-order modes with reduced modal dispersion. However, system imperfections and mechanical perturbations will excite undesired higher order modes, leading to a selectively faded channel frequency response. For this reason, center launching is conventionally less favorable than offset launching when on-off keying is used. This problem can be circumvented by leveraging on the fine frequency granularity of the orthogonal frequency-division multiplexing (OFDM) signal, which is inherently less sensitive to the frequency fading. We have experimentally demonstrated the transmission of a 40-Gb/s OFDM signal (net data rate of 29.48 Gb/s) over 1-km G62.5/125 MMF without using complicated bit-and-power loading. The channel bandwidth is less than 9.1 GHz. We also demonstrate the robustness of the system against fiber bending, polarization variation, unmatched launch beam spot size, as well as its long-term stability.