Cisco 12008, Installation And Configuration Manual, Page: 123 / 382

Preparing for Installation 2-21
Site Wiring Guidelines
Synchronous Optical Network Connection Guidelines
The Synchronous Optical Network (SONET) specification for fiber-optic transmission
defines two types of fiber:
•
Single mode
•
Multimode
Data transmission in either mode occurs by means of bundles of light rays that enter 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 through the fiber.
Multiple modes of light propagating through the fiber travel different distances, depending
on entry angles, causing the light to arrive at destinations at different times. This
phenomenon is called modal dispersion.
Single-mode fiber provides higher-bandwidth transmission and supports greater cable
distances than multimode fiber. Table 2-3 lists the maximum distances for single-mode and
multimode fiber-optic transmissions, as defined by SONET.
If the distance between two connected stations is greater than the maximum distance
specified in Table 2-3, significant signal loss can result, making fiber-optic transmission
unreliable.
Table 2-3 SONET Maximum Fiber-Optic Transmission Distances
Transceiver Type Maximum Distance between Stations
1
1. Typical results; you should use the power budget calculations to determine the
actual distances.
Single-mode Up to 9 miles (14.5 km)
Multimode Up to 1.5 miles (2.4 km)