Increasing Network Distance by Installing
100BASE-FX
Fiber Fast Ethernet, 100BASE-FX, can be used for links to the Transition
Networks’ pocket switch, particularly between buildings or where the
100 meter distance limitation of copper Fast Ethernet, 100BASE-TX,
must be exceeded. Signals move over fiber 10% faster than over
copper.
The 100BASE-FX fiber optic media system uses pulses of light instead of
electrical currents to send signals over the Ethernet medium. Light
pulses propagate faster that electrical signals, with less signal loss, and
provide superior electrical isolation for network devices at each end of
the link. While network devices used in copper segments have
protective circuits designed for protection from typical indoor electrical
hazards, fiber optic media is totally non-conductive. This complete
electrical isolation provides immunity from much larger electrical
hazards, including the effect of lightning strikes and the different levels
of electrical ground currents found in separate buildings. Complete
electrical isolation is essential when Ethernet segments must link
separate buildings.
NOTE: The 100BASE-FX specification requires two strands of
multimode fiber optic cable per link, one to transmit data, and one to
receive data, with the signal crossover (TX to RX) performed in the link.
This allows fiber cable to be used either in half-duplex or full-duplex
mode.
Half-duplex Fiber
The 100BASE-FX media system is designed to allow half-duplex Fast
Ethernet segments of up to 412 meters for the entire collision domain.
In practice, however, half-duplex fiber is limited to 111 meter
distances. and typically is used to connect a server to a workstation
with no intervening hub.
Full-duplex Fiber
The 100BASE-FX media system is designed to allow full-duplex Fast
Ethernet segments of up to 2000 meters in length. The 2000 meter limit
is possible because round trip timing (collision domain) specifications
are not a factor in full-duplex. In full-duplex, the limiting factor for fiber
is optical power loss. (See page 21.)
Installing Network Cable
Use care when installing network cable to ensure that the restrictions
that apply separately to each cable type (10BASE-T, 100BASE-TX, and
100BASE-FX) are satisfied.
10BASE-T
Cable type:
Category 3 or Category 5
(See page 27)
Connector:
RJ-45
(See page 27)
Maximum distances:
100 m
(half-duplex)
(See page 27)
100 m
(full-duplex)
(See page 27)
Restrictions:
5-segment rule
(See page 17)
Straight-through or
Crossover cable
(See page 19)
100BASE-TX
Cable type:
Category 5
(See page 27)
Connector:
RJ-45
(See page 27)
Maximum distances:
100 m
(half-duplex)
(See page 27)
100 m
(full-duplex)
(See page 27)
Restrictions:
512-bit rule
(See page 18)
Straight-through or
Crossover cable
(See page 19)
100BASE-FX
Cable type:
62.5/125 multimode fiber
(See page 28)
Connector:
ST
(See page 28)
Maximum distances:
412 m
(half-duplex)
(See page 28)
2000 m
(full-duplex)
(See page 28)
Restrictions:
Optical loss budget
(See page 21)
NOTE: If the Transition Networks’ pocket switch is installed in a
network that is evolving by increments from legacy 10BASE-T Ethernet
to 100BASE-TX Fast Ethernet and/or to 100BASE-FX Fast Ethernet, refer
again to these cable type restrictions at each upgrade.
Transition Networks’
Pocket Switch
16
11
