Loop Telecom’s line of SDH/SONET products is designed for high speed transport. These high speed lines are typically fiber optical lines that can travel very long distances without loss. They also use a TDM (time division multiplexing) format like plain old telephone networks. This way much of the same technology and experience can be reused. Ring topologies are also chosen so that when growing the network, the number of links scales linearly with the number of units.
In the above diagram, the O9400R forms the core of the 2.5 Gbps backbone. This type of backbone would be used to connect large cities together. In the bottom two 622 Mbps rings, the O9400R and the O9400S (discontinued) would form a ring across a small or medium sized city. Endpoint devices on this ring can directly serve school, business, or government networks. Low speed access through routers, switches, and AM3440 cards are not shown here, but feed directly to the users’ devices. Also, data from the O9400 can be converted into a different optical format or radio/wireless for further transport.