Metro area optical networks: technologies and trends

The term "metro network" encompasses the part of the network that lies between long haul networks and end customers. Although often thought to be smaller than about a hundred miles, some metropolitan networks can extend much farther. Contrary to long distance networks, which mostly carry SONET flows, metro networks can carry a variety of traffic formats, for example Ethernet, ESCON or Fibre Channel. Network nodes also have an aggregation function, combining lower speed tributaries into high-speed pipes.