In the eight years or so of previous ROADM history, we have witnessed a continuum of advancing capabilities and technologies in ROADMs. In the last 2-3 years, several companies have introduced products that are Edge ROADMs (although the name is only beginning to be standardized), with reduced capabilities, and reuse of existing technology on a cost-reduced basis. Now in mid-2010, ROADMs have become a standard part of long-haul networks — to be included as a matter of course in any new network, and they have become a major update objective for existing networks. They have also become important to metro networks. In addition to the maturity of application, ROADMs have also developed a third-generation technology base — the wavelength selective switch (WSS) — that has quickly become the "gold standard." Now the new application that is driving cost savings is the use of low-cost ROADMs on the edge of the network.