 These wavelengths fall within two bands: a blue band between 1,529 and 1,541 nm and a red band between 1,549 and 1,557 nm. Each band is dedicated to a particular direc- tion of transmission. Nortel's S/DMS TransportNode offers bidirectional DWDM solutions for OC-48, OC-192, and hybrid OC-48/192 applications. Figure 3-63 illustrates a short-reach bidirectional eight-wavelength OC-192 configuration. To permit extended reach in DWDM applications, Nortel's S/DMS Trans- portNode's optical amplifier portfolio includes a leading-edge bidirectional multiwavelength optical repeater (MOR) that handles the associated wave- lengths in both the blue and red bands. This topic is discussed in more detail in Chapter 5. Outside Plant Figure 3-63 Nortel's S/DMS TransportNode OC- Mixed Mixed 192 bidirectional Tributaries Tributaries DWDM configuration (short reach). 11 through 18 Single-Fiber OC-192 Bidirectional Channel S/DMS TransportNode Wave Division Wave Division S/DMS TransportNode OC-192 Multiplex Coupler Multiplex Coupler OC-192 Network Elements Network Elements Red Wavelengths Blue Wavelengths Red + Blue Wavelengths OC-192 Wavelength Plan Blue {X2,4,6,8} Red {X1,3,5,7} 1529, 1530 1550, 1552 1532, 1533 nm 1555, 1557 nm Chapter 3 3.4.7 Using SONET Rings to Manage Bandwidth in Small-City Networks Efficient management of DS1 traffic is a critically important function in just about every interoffice network since most services are transported in the VT/DS1 layer. Effective solutions for traffic routing, grooming, consoli- dation, and the like must be put in place to avoid escalating operational costs, congestion, and a premature need for network expansion. Bandwidth management strategies range from manual rearrangement of crossconnect panels in smaller offices to sophisticated DCSs in offices with heavy traffic demand. Although DCSs offer a high degree of flexibility and substantial labor savings, their cost-effectiveness begins to diminish as traffic demand falls below 36 STS-1s/DS3s that require VT/DS1-layer grooming. As can