PAM-4 and DMT for Inter-Data Center Connections and 5G Fronthaul Applications

Modulation formats with intensity modulation (IM) and direct detection (DD) are attractive due to the simple optical configuration, the low power consumption and a small footprint. We revisit the performance of 56 Gb/s and 112 Gb/s four-level multilevel intensity modulation (PAM-4) and discrete multitone transmission (DMT) for wavelength multiplexed high speed connections with distances up to 80 – 100 km between data centers and for future 5G fronthaul architectures with a reach of 10 – 20 km. Enabled by digital signal processing (DSP) DMT as well as PAM-4 and its partial response variant are shown to be suitable for the proposed applications. The paper will discuss the specific pros and cons with respect to component properties and the required signal processing effort.