 in metro applications are considerably lower than long-haul applications because the distances are much shorter. Ten milliwatts of single-mode output power (double the current performance of VCSELs) may be adequate for 40-km rings, which are typical of metro applications. If these power outputs can be achieved, then VCSEL technology will likely be a major cost-reduction factor for optical-networking systems in the metro market. Sub-$1,000 amplifiers Because metro optical systems operate over much shorter distances than long haul, one basic approach of system designers and network planners is to use as little amplification as possible. Perhaps some geographically spread-out metro areas (such as Atlanta, San Jose, and SO on) could need some amplification. However, additional capabilities such as wavelength switching and routing will increase insertion loss and other types of signal degradation in the network. Although large repeater amplifiers, priced at about $20,000, continue to grow in complexity and power, a new class of amplifiers is emerging. These amplifiers are simple and typically have only one pump diode. The major application is overcoming losses due to the proliferation of optical-networking elements, such as OADMs, OXCs, and other equipment, which results in a loss of optical power. There are two major types of metro amplifier, the semiconductor-optical amplifier (SOA) and EDFA. SOAs have an advantage in that they exhibit gain across a much wider wavelength spectrum, specifically over 300 nm versus a less than 100-nm spectrum for EDFAs. However, SOAs have a limitation in that they cannot amplify multiple wavelengths simultaneously without crosstalk between the channels. SOAs will likely find a niche in applications where the wavelengths to be amplified are outside the EDFA gain region and also as optical switch devices. Assuming that there is continued cost reduction, EDFAs should dominate the market for low-cost amplifiers in the 1,500- to 1,600-nm wavelength range. EDFAs targeted for the metro marke