Ethernet was first developed as a low cost multi-access protocol for local area networks (LANs). In the last 15 years, there has been tremendous development in the Ethernet technology. Modern Ethernet is no longer just a LAN protocol. As a result of the Internet proliferation, Ethernet has taken a much broader meaning in today's fast growing telecommunication world. High speed Ethernet standards using optical fiber as the transmission medium have been developed to meet the increasing bandwidth demand. These systems are penetrating into metropolitan area networks (MANs) and wide area networks (WANs). They will also be used with DWDM technologies. In this paper, we describe the development and application of modern Ethernet technologies.