EML based real-time 112 Gbit/s (2 × 56.25 Gbit/s) PAM-4 signal transmission in C-band over 80 km SSMF for inter DCI applications

We report on an electro-absorption modulator (EAM) integrated laser (EML) based real-time 112 Gbit/s (2 × 56.25 Gbit/s) 4-level pulse amplitude modulation (PAM-4) signal transmission in the C-band over 80 km of standard single-mode fiber (SSMF). Various operating conditions of the EAM were investigated to find the optimum driving conditions for PAM-4 modulation. When the EAM reverse bias was set to the inflection point of the transfer curve, which was −2.35 V, we obtained a bit error ratio (BER) of 4 × 10−8, which is well below the forward error correction (FEC) limit. The results demonstrate the feasibility of using EMLs for implementation in PAM-4 transceivers for inter-datacenter interconnection (inter-DCI) applications.