The company says it achieved two milestones using its interoperable pluggable 400ZR coherent modules and its specially designed athermal arrayed waveguide grating (AWG) multiplexers (MUX) and de-multiplexers (DMUX). First, data rate per channel increases from today’s non-interoperable 100Gbps direct-detect transceivers to 400Gbps interoperable coherent 400ZR modules. Second, the current DWDM infrastructure can be increased from 32 channels of 100 GHz-spaced DWDM signals to 64 channels of 75 GHz-spaced DWDM signals. The total DCI fiber capacity can thus be increased from 3.2 Tb/s (100Gb/s/ch. x 40 ch.) to 25.6 Tb/s (400Gb/s/ch. x 64 ch.), which is a total capacity increase of 800 percent. The 400ZR signal uses an approximately 60 Gbaud symbol rate and 16 QAM modulation, resulting in a broader transmitting signal spectrum compared to that of a standard 100 Gb/s coherent or PAM4 signals. Furthermore, it is recognized that the center frequencies of the lasers, MUX and DMUX will all drift due to temperature changes and ageing. Consequently, as the channel spacing is reduced from 100GHz to 75GHz, adjacent channel interference (ACI) becomes more critical, and can potentially degrade the optical signal-to-noise ratio of 400ZR signals.