Transition Networks E-PSW-TX-02 Increasing Network Distance by Installing 100BASE-FX, 10BASE-T

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.)

11 Transition Networks’

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.

Pocket Switch 16