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:
“I see now our fireside formed into a groupe, no one member of which has a fibre in their composition which can ever produce any jarring or jealousies among us. No irregular passions, no dangerous bias, which may render problematical the future fortunes and happiness of our descendants.”
—Thomas Jefferson (1743–1826)
“For, rightly, every man is a channel through which heaven floweth, and, whilst I fancied I was criticising him, I was censuring or rather terminating my own soul.”
—Ralph Waldo Emerson (1803–1882)
“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)