End-to-End Interoperable 400-GbE Optical Communications Through 2-km 400GBASE-FR4, 8 x 100-km 400G-OpenROADM and 125-km 400-ZR Fiber Lines

During many years, the WDM domain was dominated by vendors/system suppliers that logically proposed their proprietary solutions and technologies. This proprietary environment offered the space to innovate and allowed an unbelievable progress of optical transport networks that were able to cope with traffic increase for 25 years. Thereby, coherent technology enabled an incredible growth of data rate carried by wavelengths from 10G in the middle of 2000's decade up to 400G today and soon 800G. However, for data center interconnect (DCI) and metro/regional applications, the lack of openness and interoperability of WDM systems appeared as a real weakness for service providers for both the control (i.e., management) and data (i.e., transceiver) plane. While in the Ethernet area (managed by IEEE) interworking and openness is a reality since a long time, it was not still the case in the WDM domain few years ago. Fortunately, Multi-Source Agreement (MSA) organizations like the Optical Internetworking Forum (OIF), OpenROADM, OpenZR+ and others but also standardization bodies like ITU-T started to break the vendors' lock-in and fostered the emergence of interoperable WDM transceivers at 100G, 200G, 400G and soon at 800G. In parallel, the great progress of microelectronics and photonic integration also paved the way of a miniaturization of WDM interfaces allowing to have ever more powerful digital signal processing (DSP) engines at higher data rates with drastic power consumption reduction authorizing new fundamental applications like IP over WDM. In this paper, we present for the first time an end-to-end interoperable 400-GbEthernet (GbE) optical transmission on 927-km that integrates the most advanced 400G interoperable pluggable optics covering the needs of Ethernet client (IEEE 802.3 400GBASE), data-center interconnect (OIF 400-ZR), and metro/regional (400G-OpenROADM) networks. The generated 400-GbE data flows seamlessly cross three interoperable sections, i.e., 2-km 400GBASE-FR4, 8 x 100-km 400G-OpenROADM and 125-km 400-ZR standard single-mode fiber lines. The 400G optics used here come from various vendors and embed interoperable DSP chips provided by various suppliers, ensuring the full interoperability of the experimental set-up presented here. The sensitivity to a reconfigurable optical add-drop multiplexer (ROADM) cascade insertion in the OpenROADM section is also investigated.