The document discusses the evolution of 100G and beyond networking technologies. It notes that 100G found adoption in core and metro networks by leveraging existing ecosystems through coherent and direct detect solutions. Pressure to lower costs while increasing capacity continues. The next technologies being developed include 400G using higher symbol rates and software-defined optics leveraging techniques like flexible grid, multi-level modulation, and discrete multitone transmission. This will enable the transition from fixed DWDM networks to software-defined optical networking with more programmability and efficient use of spectrum.