cols such as the Spa- tial Reuse Protocol (SRP). Therefore, initial optical broadband metro appli- cations could deploy CWDM or BWDM, which present a more cost-effective option for metropolitan area markets. BWDM is a solution based on the transmission of the 1,310- and 1,550- nm wavelengths through a single fiber in opposite directions (see Figure 6-11). With a transmission range of 40 to 120 km (25 to 75 miles), BWDM technology could be used to deliver resilient and cost-effective solutions for metropolitan area deployment. The advantages of BWDM are clear: A 100 percent improvement in fiber utilization. Simplified fiber connection. No resilience penalties. Intelligent protection switching (IPS), enhanced-IPS (E-IPS), and automatic protection switching (APS) are fully supported. Cost-effective. A range of 40 to 120 km (25 to 75 miles), which is suitable for metro deployment. 6.4.1 Cisco Implementation of BWDM Cisco equipment (for example, ONS 15190) integrates the BWDM technol- ogy within their SRP and PoS technologies. The BWDM line card consists of two single SC ports, each fiber transmitting in both directions. The two wavelengths are converted to an electronic signal on the line card and are placed on the internal bus of the equipment. The traffic is then switched to the appropriate standard line card, which in turn is connected to a PoS or SRP device (see Figure 6-12). BWDM offers advantages to both SRP rings and PoS links. In metropoli- tan area environments, BWDM enables the deployment of SRP rings, requir- Figure 6-11 1310 nm BWDM. 1550 nm Chapter 6 Cisco Figure 6-12 ONS 15190 BWDM connections to the Cisco ONS Cisco 15190. ONS 15190 PoS or SRP Device PoS or SRP Device BWDM Link 1310-nm Link Logical Link ing half the fiber required by conventional rings. Because the transmission is in opposite directions, BWDM rings are viewed to be as resilient to resource losses (such as fiber cuts or node failure) as conventional rings. The following section describes various scenarios detailing the events following a