IM/DD Transmission Techniques for Emerging 5G Fronthaul, DCI, and Metro Applications

For short range optical transmissions, the intensity modulation and direct detection (IM/DD) offers the advantages of low cost and low complexity. In this paper, we will review our recent investigation results about IM/DD schemes such as polybinary and discrete multitone (DMT). Polybinary four-level pulse amplitude modulation (PAM-4) system shows better performance than the conventional PAM-4 system for both multimode and single-mode fibers. If the electrical dispersion compensation (EDC) is conducted with DDMZM, the reachable distance can be extended to 80 km which is suitable for the metro access scenario. Single sideband (SSB) polybinary-PAM-4 is also feasible to greatly increase the spectral efficiency (SE) and system capacity. Also, some DMT architectures for metro applications without using dispersion compensating modules will be introduced. SSB-DMT is very simple, while chromatic dispersion (CD) calculation and pre-compensation are not necessary. EDC double sideband (DSB) DMT owns 3-dB better performance than the SSB-DMT. CD can be calculated according to the power fading and the result is sent back to the transmitter for pre-compensation. Twin-SSB-DMT has the highest SE. More than 200-Gb/s data have been successfully generated and transmitted over 80 km single mode fiber (SMF).