tion signals using only 2 fibers. However, unless there is a major underlying engine continuously driving the demand through the roof, this kind of technology is a one-time upgrade, which has obvious market sizing implications. The pertinent question for the current discussion is whether DWDM has practical application in the metro space. There has been a lot of hype in the Chapter 5 Figure 5-3 Practical migration: Fiber increasing demand Fiber but with multiple Fiber systems already deployed. Fiber Before Traditional Ring Configuration After Ring Configuration with WDM New Demand New Demand New Demand New Demand recent past about metro DWDM. It is true that long-haul analog carrier techniques developed in the 1940s were later adopted by analog loop carrier techniques in the 1950s. The N1 and N2 carrier terminals supported 12 channels, whereas the N3 and N4 carrier terminals supported 24 channels. The long-haul transmission systems, however, supported 600 (L1), 1,860 (L3), 3,600 (L4), 10,800 (L5), and 13,200 (L5E) channels. Similarly, T1 (24 channels), T2 (96 channels), and T3 (672 channels at 44.736 Mbps) carrier systems developed in the early 1960s were later used in the 1970s for access in metropolitan digital loop carrier environments. However, T4-NA (2,016 channels at 139.264 Mbps) and T46 (4,032 channels at 274.176 Mbps) were not used in loop applications because they were overkill. The reality is that in its general form DWDM has some applicability to metropolitan environments, probably for a handful of point-of-presence-to- point-of-presence (POP-to-POP) rings.7 If DWDM systems now in the mar- ket were redesigned to be optimized according to the requirements for metropolitan environments, there could be increased applicability. If the Dense Wavelength Division Multiplexing (DWDM) Systems systems were redesigned to meet specific price points (see Section 5.2 "Overview of Technology"), their applicability would be enhanced. (Section 5.4, "Example of Optimized Edge Equipment" briefly discusses what some metro