Ron Karjian
If you think you`re seeing the numbers 50/125 bandied about more often these days, it`s not your imagination. You`ll be seeing that combination used a lot more for premises-cabling installations in the years ahead.
"I`m surprised that there has been such a great deal of interest on the part of end-users and manufacturers to move to 50/125-micron multimode fiber cabling," says Eric Lach, research analyst for network technologies at the Gartner Group. "Most people are more comfortable with 62.5-micron because it`s accepted by the tia and it`s selling in volume." Yet, even though 62.5/125-micron multimode is more widely deployed in North American premises-cabling systems, Lach says that "there are inherent advantages in 50-micron fiber because it`s technically better and cheaper than 62.5-micron fiber."
The installed base of 62.5/125-micron fiber cabling "is optimized for use with light-emitting diodes," explains Tony Beam, global systems marketing manager for netconnect premises-cabling systems at amp netconnect (Winston-Salem, NC). But, he says, amp`s research shows that when other light sources such as vertical-cavity surface-emitting lasers (vcsels) are used in combination with multimode fiber, "50/125-micron multimode fiber does not exhibit the performance limitations sometimes seen in 62.5/125-micron fiber." Beam expects 50/125-micron fiber to be recognized in the next issue of the tia/eia-568a standard.
Fiber-optic cabling systems for network backbones and horizontal cabling runs are increasingly offering 50/125-micron fiber-optic cable and compatible equipment instead of--or in addition to--62.5/125-micron. "Fifty-micron fiber has the ability to support Gigabit Ethernet up to the recommended 500 meters for both long- and short-wavelength sources," says John Siemon. "It`s less susceptible to differential modal delay and is specified in addition to 62.5-micron fiber in iso/iec-11801 international cabling standards."
