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PA-A6 ATM Port Adapter Installation and Configuration

OL-2672-05

Chapter 1 Overview

Additional Information

A single PA-A6-T3 or PA-A6-E3 contains one ATM T3 or E3 port that consists of two connectors:

receive and transmit. The Cisco 75-ohm coaxial cable has two BNC connectors that attach to the T3 or

E3 port receptacles.

The T3/E3 75-ohm coaxial cable, which comes with attached ferrite bead (see Figure 1-9), is available

from Cisco in lengths of 10 feet (3.04 meters). The typical maximum distance between stations for T3

transmissions is 450 feet (137.2 meters) and for E3 transmissions is 1250 feet (381 meters).

Note To ensure compliance with electromagnetic interference (EMI) and European certification standards for

emission control (EN55022/CISPR22 Class B for radiated emission levels), the TX and RX cables

should be tied together along their entire length, and ferrite beads should be installed on each cable near

the TX and RX connectors.

The PA-A6-T3 and PA-A6-E3 provide an interface to ATM switching fabrics for the bidirectional

transmission and reception of data at rates of up to 45 Mbps (for T3) and 34 Mbps (for E3).

Additional Information

This section describes the SONET specifications for fiber-optic transmissions, defines the power budget,

and helps you approximate the power margin for multimode and single-mode transmissions. This section

includes the following subsections:

• SONET Distance Limitations, page 1-7

• SONET Frame Fundamentals, page 1-8

• Power Budget, page 1-9

• Approximating the PA-A6 Power Margin, page 1-10

• Multimode Power Budget Example with Sufficient Power for Transmission, page 1-11

• Multimode Power Budget Example of Dispersion Limit, page 1-11

• Single-Mode Transmission, page 1-11

• Using Statistics to Estimate the Power Budget, page 1-12

• References on Determining Attenuation and Power Budget, page 1-12

SONET Distance Limitations

The SONET specification for fiber-optic transmission defines two types of fiber: single mode and

multimode. Modes can be thought of as bundles of light rays entering the fiber at a particular angle.

Single-mode fiber allows only one mode of light to propagate through the fiber, whereas multimode fiber

allows multiple modes of light to propagate through the fiber. Because multiple modes of light

propagating through the fiber travel different distances depending on the entry angles, causing them to

arrive at the destination at different times (a phenomenon called modal dispersion), single-mode fiber is

capable of higher bandwidth and greater cable run distances than multimode fiber.

The typical maximum distances for single-mode and multimode transmissions, as defined by SONET,

are in Table 1-5. If the distance between two connected stations is greater than this maximum distance,

significant signal loss can result, making transmission unreliable.

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Cisco CISCO7201 Manual de usuario Pagina 7