 which, of course, will be costly. It will involve not only new hardware but also new skill sets and network management solutions. An end-to-end optical network includes the following components: Optical line amplifiers, such as erbium-doped fiber amplifiers (EDFAs), Raman amplifiers, and semiconductor optical amplifiers (SOAs) WDM equipment OADMs, including ROADMs Optical switches Integrated photonic circuits Figure 11.4 shows an example of an optical network that incorporates these components. The following sections describe them, as well as the role of network management systems, in more detail. Optical Line Amplifiers: EDFAs, Raman Amplifiers, and SOAs As mentioned in Chapter 1, EDFAs, which were introduced in 1994, were a key innovation in the fiber world because they meant that an optical signal could be amplified without having to undergo any conversions. Before EDFAs, electronic Optical Fiber Optical Optical Amplifier Amplifier Optical Network Core with Optical Switches Figure 11.4 Optical network components Chapter 11 Optical Networking regenerators had to extract signals, retime them, and then regenerate them. This conversion limited data rates to 2.5Gbps. EDFAs quadruple this speed, providing data rates of 10Gbps. EDFAs have also opened the door to the development of wavelength division multiplexers, which enable incredible expansion of capacity on fiber optics. (Wavelength division multiplexers are discussed in detail later in this chapter.) Composed of erbium metal and doped with special atoms, EDFAs are incorpo- rated in optical fiber at periodic intervals, generally 30 to 60 miles (50 to 100 km), to boost communication signals. The components in an EDFA include an erbium- doped fiber, a laser-pump diode, couplers, and isolators. The light to be amplified is coupled in a section of erbium-doped fiber together with light from a laser-pump diode, normally about 980 nm. The EDFA itself operates in the range of 1,550 nm. The light from the laser-pump diode boosts the 1,550-nm light and is separated on t