Physical Medium Dependent (Pmd) Protocol; Fiber-Optic; Shielded Twisted Pair (Stp) - 3Com 3C780 - LinkBuilder FDDI Base Unit User Manual

1-4 Overview

Physical Medium Dependent (PMD) Protocol

The Physical Medium Dependent protocol provides all of the services necessary
to exchange data across the cable medium. PMD also specifies an optional
optical bypass facility that enhances reliability. This bypass capability is
invoked when an FDDI station is powered off. (For information on the optical
bypass switch, see Chapter 2, "Installing the Hub.")
The PMD services included for each type of media supported by the
LinkBuilder FDDI Workgroup Hub are listed below.

Fiber-Optic

The PMD standard provides these services for fiber media:

Shielded Twisted Pair (STP)

The PMD standard uses the SDDI de facto standard and provides these services
for STP:
Optical power and cable requirements for 62.5/125 µm fiber-optic cables
Power requirements for optical bypass switches and fiber-optic transceivers
FDDI cable connector (the Media Interface Connector [MIC]), mating
requirements, and keying
Light wavelength of 1300 nm (nanometers)
Transmit signal amplitude of 350–700 mV, peak-to-peak
Cable fault detect
DB-9 cable connector, specifying M as a male connector and A, B, and S
as female connectors