9 Double breaks in both primary and secondary fibers can Slave be resolved by creat- ing two separate rings when there are Slave multiple master devices in a ring. Slave Slave Master 2 Overview One common problem that network managers experience is the need to support a new application while the existing infrastructure consists of optical fiber unsuitable for the application. In fact, this author, while serving as a consultant on a network analysis project for a college, came across this situation. The college had previously installed multimode fiber many years before to support 155-Mbit/s ATM (asynchronous transfer mode) communications from a switch located in one building to all other buildings on the campus. A few years later the college was considering upgrading to Gigabit Ethernet; however, the ability transmit via multimode using Gigabit Ethernet could not support the distance between the building where the ATM switch was located and several buildings on campus. The solution to this problem was to use multimode where the transmission distance was capable of supporting Gigabit Ethernet. For those locations where the distance precluded the ability to use Gigabit Ethernet or multimode cable, the use of a fiber- optic mode converter provided one solution to the distance problem. This is because some fiber-optic mode converters use LEDs or lasers that have a higher level of optical power than provided by the Gigabit Ethernet standard. Thus, you could use a single-mode/multimode con- verter to extend the transmission distance. For one product it is possi- ble to obtain a transmission distance of up to 3 km over multimode, which was sufficient for the college. Fiber in the Building Operation Figure 8.10 illustrates the use of a single-mode/multimode fiber-optic converter. Because the converter receives and regenerates light pulses, it also functions as a repeater. In examining Figure 8.10, note that the single-mode transceiver repre- sents a port on a Gigabit Ethernet switch that would replace the ATM switch used 