 an ampli- fier that is capable of operating over a range of 300 to 450 miles (480 to 725 km). However, runs in MANs are typically no longer than 70 miles (110 km), SO these expensive amplifiers are often overkill. As a result, the next generation of MAN products, designed to address the MAN core-that is, metro access, cable TV, and enterprise networks-has been introduced. These CWDM products are used for building citywide rings, covering distances of up to 37 miles km). They gener- ally support longer distances and greater capacity than do metro access products. Metro access products, such as passive optical networks (PONs), are designed to bring fiber closer to the customer. Enterprise products address building high- capacity campus networks. In all three of these MAN sectors, the issues are the same: pricing, scalability, access, and flexibility. As far as pricing and scalability issues go, the lower carrying capacity and dis- tance requirements in the metro area allow providers to reduce costs by using less Chapter 11 Optical Networking expensive lasers. The price of a transponder board, which represents 90% of the cost of a laser, can vary by 25%, depending on the quality of the laser. Shorter- distance lasers use less-expensive modulation and amplification techniques. Whereas long-haul lasers are externally modulated, enabling the signal to travel up to 450 miles (725 km), shorter distances may allow direct modulation, where the laser runs only 50 to 60 miles (80 to 100 km) but costs 30% to 40% less than a long-haul laser. But less expensive lasers also mean less capacity. The lower grade of light sources requires greater spacing between the wavelengths, thereby reducing the number of channels or wavelengths that can be derived by up to 50%. To meet these new demands, we need a very dynamic network that has the capability to accommodate huge capacity requirements and to change the configu- ration of that capacity dynamically. Subscribers want to connect at the current speed of their backbone. They want to m