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Installing and Maintaining the Versalar Switch Router 15000
1-36
308684-B Rev 00
Trunk ATM Interface Cards
The Versalar 15000 trunk interface cards occupy chassis slots 11 and 12 and
support network interfaces for TP cards. This section contains information about
the following cards:
• ATM OC-12c/STM-4c single-mode and multimode trunk interface cards
• Quad OC-3 ATM trunk interface card
Single-Mode and Multimode Interfaces
The single-mode fiber (SMF) and multimode fiber (MMF) interfaces operate with
a wide variety of ATM switches and are compliant with Bellcore standards. You
can view modes as bundles of light entering the fiber at a particular angle.
Single-mode fiber allows only one mode of light to propagate through the fiber;
multimode fiber allows multiple modes of light to propagate.
Depending on the entry angles, multiple modes of light propagating through the
fiber travel different distances, thus causing them to arrive at their destination at
different times. This phenomenon is called modal dispersion, and it results in
single-mode fiber being capable of higher bandwidth and greater cable run
distances than multimode fiber. For more information about transmission
distances for single-mode and multimode fiber, see “OC-12c/STM-4c ATM
Interface Card Specifications” on page A-6.
OC-12c/STM-4c ATM Interface Cards
The ATM OC-12c/STM-4c single-mode and multimode trunk interface cards
provide an ATM OC-12c/STM-4c link-level interface. The Versalar 15000
supports one or two OC-12c/STM-4c single-mode cards, one or two
OC-12c/STM-4c multimode cards, or one single-mode and one multimode card.
You can differentiate multimode cards from single-mode cards by their labels, as
shown in Figure 1-12
, which shows a multimode card.