3-23
Catalyst 6500 Series Ethernet Modules Installation Guide
OL-6265-03
Chapter 3 Installing Ethernet Switching Modules
Attaching the Network Interface Cables
Mode-Conditioning Patch Cord
A mode-conditioning patch cord is recommended for use with an LX/LH GBIC or an LX/LH SFP
transceiver and MMF to allow reliable laser transmission.
When an unconditioned laser source designed for operation on single-mode optical fiber is directly
coupled to a multimode optical fiber cable, an effect known as
differential mode delay
(DMD) might
result in a degradation of the modal bandwidth of the optical fiber cable.
This degradation results in a decrease in the link span (the distance between a transmitter and a receiver)
that can be supported reliably. The effect of DMD can be overcome by conditioning the launch
characteristics of a laser source. A practical means of performing this conditioning is to use a device
called a mode-conditioning patch cord.
A mode-conditioning patch cord is an optical fiber cable assembly that consists of a pair of optical fibers
terminated with connector hardware. Specifically, the mode-conditioning patch cord is composed of a
single-mode optical fiber permanently coupled off-center (see Offset in
Figure 3-17
and
Figure 3-18
) to
a graded-index multimode optical fiber.
Figure 3-17
and
Figure 3-18
show a diagram of the
mode-conditioning patch cord assembly.
Figure 3-17
Mode Conditioning Patch Cord with SC (GBIC Transceiver) Connector
1
Beige color identifier
2
To Gigabit Ethernet interface
3
RX (receiver)
4
TX (transmitter)
5
Blue color identifier
6
Multimode fiber (MMF)
7
Single-mode fiber (SMF)
8
Offset junction
9
To cable plant
/ /
/ /
/ /
TX
Offset
RX
57011
1
1
1
2
3
4
5
6
9
8
7
6
Содержание 6513 - Catalyst Switch
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