Demonstration of Low-Cost EML Based 240 Gbit/s DFT-Spread DMT Signal Transmission Over Few-Mode Fiber With Cylindrical Vector Beam Multiplexing

In this paper, we experimentally demonstrated the high-speed low-cost mode-division-multiplexed (MDM) discrete multi-tone (DMT) signal transmission based on cylindrical vector beam (CVB) multiplexing over few-mode fiber (FMF) with intensity modulation and direct detection (IM/DD) utilizing electro-absorption modulated laser (EML). Two CVBs (TM01 and TE01 modes) are employed for signal transmission simultaneously with the minimum mode isolation of 16.7 dB between them after transmission over 5 m 4-mode FMF. The digital discrete Fourier transform-spread (DFT-spread) and pre-equalization techniques are implemented in transmitter to improve the system performance. By adopting the proposed schemes, the 240 Gbit/s DFT-spread DMT signal has been transmitted successfully over 5 m FMF below the bit-error-ratio (BER) of $3.8\times 10^{-3}$ which is the hard-decision forward-error-correction (HD-FEC) threshold. The required received optical powers (ROPs) of the two CVBs (TM01 and TE01 modes) are -7.27 dBm and -7.15 dBm, respectively. The experimental results show that CVB-based multiplexing technology combined with advanced modulation format could be a potential candidate for high-speed low-cost server backplane optical interconnection.