This document discusses the evolution from 10G to 100G networks for metro applications. It describes how 100G technology can complement existing 10G infrastructure by utilizing unused wavelengths on fibers. A key consideration is maintaining economic viability while providing greater bandwidth efficiency. Direct detection is seen as more suitable than coherent detection for metro due to lower cost and complexity. The document outlines various technological requirements for a 100G network such as 100G transceivers, DWDM multiplexers, optical amplifiers, dispersion compensation, and FEC. It provides an example architecture for upgrading an existing 10G system to incorporate 100G services over longer distances.