Installation Guide

10 Prisma Gigabit Ethernet Media Converter Module Installation Instructions 4007998 Rev B
About LinkLoss and FiberAlert
Introduction
The Prisma Gigabit Ethernet Media Converter modules include the troubleshooting
features FiberAlert and TX LinkLoss that help locate "silent failures" on your
network. It is vital to understand how FiberAlert and LinkLoss work, and how they
will react in your network configuration, before attempting to install the module(s).
CAUTION:
Installing modules without understanding the effects of FiberAlert/LinkLoss
can cause perfectly functioning units to appear flawed or even dead
About Link Integrity
During normal operation, link integrity pulses are transmitted by all point-to-point
Ethernet devices. When a media converter receives valid link pulses, it knows that
the device to which it is connected is up and sending pulses, and that the copper or
fiber cable coming from that device is intact. The appropriate “LNK” (link) LED is
lit to indicate this.
The media converter also sends out link pulses from its copper and fiber
transmitters, but normally has no way of knowing whether the cable to the other
device is intact and the link pulses are reaching the other end. The combination of
FiberAlert and LinkLoss allows this information to be obtained, even when physical
access to a remote device (and its link integrity LED) is not available.
What Is TX LinkLoss?
TX LinkLoss is a troubleshooting feature. When a fault occurs on the twisted pair
segment of a conversion, TX LinkLoss detects the fault and passes this information to
the fiber segment. If a media converter is not receiving a twisted pair link, TX
LinkLoss disables the transmitter on the media converter's fiber port. This results in
a loss of link on the device connected to the fiber port.
Continued on next page