High-speed Flexible Coherent Optical Transport Network

Abstract

In over 30 years, the optical transport network (OTN), the only physical network which actually carries the Internet data from the senders to the receivers, has experienced significant growth in both channel speed and link capacity. During the time period, the network has gone through several major upgrades as technology of optical transmission and networking continuously keeps advancing. In the middle of 1980s, early-stage fiber transmission system emerged as the first equipment for OTN ever introduced to network service providers, i.e., network carriers. The data rate on a pair of strands of fiber at that time was a few hundred Mbps for the system typically [1]. In the later 1980s, synchronous optical network (SONET as an example) began to play its role in carriers’ transport networks [2]. SONET systems provided several hundred Mbps capacity per channel at the beginning and quickly moved to supply 10 Gbps per channel (OC-192) in the middle of the 1990s. Then, 40-Gbps channel (OC-768) was introduced to further increase channel capacity. As the required optical channel capacity became even larger when entering the new century, a new OTN standard, OTN, was introduced in the early 2000s. The new standard includes channels with capacities of 2.5 Gbps (OTU1), 10 Gbps (OTU2), 40 Gbps (OTU3), 100 Gbps (OTU4), and beyond [3, 4].