Fibre Channel Signal Characteristics
Fibre channel electrical signals are sent over a duplex differential interface. This usually consists of twisted-pair cables with a nominal impedance of 75 ohms (single-ended) or 150 ohms (differential). This is a genuine differential signalling system so no ground reference is carried through the cable, except for the shield. Signalling is AC-coupled, with the series capacitors located at the transmitter end of the link.
The definition of the Fibre Channel signalling voltage is complex. Eye-diagrams are defined for both the transmitter and receiver. There are many eye-diagram parameters which must all be met to be compliant with the standard. In simple terms, the transmitter circuit must output a signal with a minimum of 600 mV peak-to-peak differential, maximum 2000 mV peak-to-peak differential. A good signal looks rather like a sine-wave with a fundamental frequency of half the data rate, so 1 GHz for a typical system running at 2 gigabits per second.
The Bit-Error Rate (BER) objective for Fibre Channel systems is 1 in 1012 (1 bit in 1,000,000,000,000 bits). At 2 Gbit/s this equates to seven errors per hour. Therefore, this is a common event and the receiver circuitry must contain error-handling logic. In order to achieve such a low error-rate, jitter "budgets" are defined for the transmitter and cables.
Read more about this topic: Fibre Channel Electrical Interface
Famous quotes containing the words fibre, channel and/or signal:
“The gods are partial to no era, but steadily shines their light in the heavens, while the eye of the beholder is turned to stone. There was but the sun and the eye from the first. The ages have not added a new ray to the one, nor altered a fibre of the other.”
—Henry David Thoreau (1817–1862)
“There may sometimes be ungenerous attempts to keep a young man down; and they will succeed too, if he allows his mind to be diverted from its true channel to brood over the attempted injury. Cast about, and see if this feeling has not injured every person you have ever known to fall into it.”
—Abraham Lincoln (1809–1865)
“Perhaps having built a barricade when you’re sixteen provides you with a sort of safety rail. If you’ve once taken part in building one, even inadvertently, doesn’t its usually latent image reappear like a warning signal whenever you’re tempted to join the police, or support any manifestation of Law and Order?”
—Jean Genet (1910–1986)