pter, the main attributes of each type of WDM previ- ously discussed are summarized here: CWDM uses a much wider wavelength range (1,200 to 1,600 nm) with a minimum 20-nm wavelength gap between any two channels. Optical components used for CWDM are less accurate and thus less expensive because of the 20-nm wavelength gap. DWDM refers to the capability to carry a large number of channels, where large may be 100 channels or more. DWDM equipment usually uses the 1,530- to 1,565-nm wavelength range with very high laser accuracy requiring temperature-controlled components. The standards today define a 0.8-nm wavelength gap between any two channels, with some manufacturers demonstrating equipment with 0.4-nm and even 0.2-nm accuracy. BWDM refers to the capability to carry two channels in different directions on a single fiber. Two distinct wavelengths may be used in BWDM technology: 1,310 and 1,550 nm. End Notes 1. J. Christopher Dries, "InGaAs Avalanche Photodiodes Enable Low-Cost CWDM-Based Metropolitan Area Networks," Cahners ECN Cahners Business Information, www.cahners.com. 2. Cisco White Paper, "WDM-Based Metropolitan-Area Deployment of SRP and PoS with the Cisco ONS 15190," 2001. 3. This section is based in its majority on the white paper by Marcus Nebeling, "CWDM: Lower Cost for More Capacity in the Short Haul," Fiber Network Engineering, Inc., Livermore, Calif., www.fn-eng.com. 4. This illustrates that it is rather challenging to make any money with this specific TLS service; typically, carriers have supported 10 Mbps on ATM, not optics. 5. John George, "Optical Architectures and Fibers," IEEE EFM Meeting, Hilton Head, N.C., March 12-15, 2001. 6. R. Michalzik, G. Giaretta, A.J. Ritger, and Q.L. Williams, "10 Gb/s VCSEL-Based Data Transmission over 1.6 km of New-Generation 850- nm Multimode Fiber," IEEE Lasers and Electro-Optical Society (LEOS) Coarse Wavelength Division Multiplexing (CWDM) Technology Annual Meeting, 1999, Postdeadline Paper PD1.6, San Francisco, Calif., November 1999. 7. G. Giaretta, R. Michal