Fig. 1. Google intra-datacenter network.

Fig. 2. Datacenter optical transceiver evolution.

Fig. 3. Historical view on the (a) pluggable optics front panel BW and (b) energy efficiency scaling.

Fig. 4. Technology options to scale the BW. WDM, wavelength division multiplexing; PDM, polarization division multiplexing.

Fig. 5. Impact of modulator drive swing on supported link loss and relative power consumption for two 400 G designs: 4×100  Gb/s PAM4 and 1×400  Gb/s PM-16QAM.