ishing between WDM and DWDM is more like a traveling circus or moving crap game. Claims of over 1000 lambdas on a single fiber represent one definition of DWDM, while two lambdas spaced 2 nM apart on the same fiber is another hawker's definition. ITU SG 15 wrestles with standards development in an environment where the technical landscape is still evolving at a rapid pace while business development is slow and uninteresting. How to make sense out of all this? Let's have a go at it. First, recognize that optical fiber transmission mimics radio wave and even baseband transmission in many ways. Fundamentally the basics involving transfer of energy are applicable. Optical link per- formance can be modeled with similar techniques and tools as radio links. The optical transmission link has active and passive compon- ents. A light wave is generated and launched into one end of a fiber, gets attenuated on its way to the other end, and a certain level of signal is received and detected. Digital transmission on fiber is simply 1s and 0s, light on and light off. Errors in the detection of the signal at the receive end are a function of the signal in the presence of noise. If the noise is high relative to signal, then errors 4 NETWORK TECHNOLOGY AND METHODOLOGY are more likely. If the noise is low relative to signal, then errors are less likely. The energy spectrum of a lambda is a function of the data rate carried. For example, an OC-192 occupies more bandwidth than an OC-3, or some other data rate in between. This is the same property exhibited by radio systems when comparing bandwidth occupancy of a single DS3 compared to 3 DS3 on a radio channel, bearing in mind the fact that radio channels are intentionally and rigidly band- width limited to prevent out of band radiation. Channel separation, or bandwidth between optical carriers, is as important as separation between radio carriers. If two carriers are close together, one will interfere with the other in a receiver front end and cause errors. The prevailing global fiber