Fiber Optic World Records Broken

Thousands of miles of existing fiber still lie dark, but as schnucki writes, "Bell Laboratories believe they have broken two world records in the use of optical fibres to transmit information." They sent 160 gigabits/sec on one wavelength, and then in a separate experiment sent 1,022 separate wavelengths down one fiber. You do the math. Check it out.

Comments

Sampling rates, digital, and misc cool stuff

[Signal 11]

Just incase you guys didn't know - the reason fiber optic can go so fast is because it transmits analog signals. That means you can layer several hundred harmonics on a single frequency and create a very complex waveform. The trick is in the decoding - converting it to digital. That's where all the sample-rate jazz comes into play.

This isn't really revolutionary new technology.. we've known about stuff like this for awhile. There's a nearly infinite number of ways to encode frequencies, and stack things onto each other.

I find myself wanting of the ability to insert IMG tags here. :( In short, picture a sine wave. Now along the slope of one, picture another sine wave attached to it. And so on. I suspect they're doing something like that. Actually, TVs do something like this - it's how the sync pulses and whatnot work. Very facinating technology. Also very old by today's standard, but still very useful.

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Someone flunked Fourier analysis

[Tau Zero]

Vary the single wavelength's amplitude (intensity) alone, and it's still single frequency while carrying data too.

I see you never studied for a ham radio license or anything else of the sort.

Varying the intensity of a light source creates "sidebands", the same as it does for RF. These "sidebands" are wavelengths slightly longer and shorter than the "carrier". What you see as an amplitude variation is really the interference of the carrier and the sidebands, as they slip in (high amplitude) and out (low amplitude) of phase over time. If you have a carrier frequency of F and a modulation frequency of M, you'll create sidebands at F+M and F-M. If you have really good filters you can suppress one of the sidebands and still carry all the information, and if you have really good frequency references as well you can ditch the carrier and only bother sending one sideband (you can use the frequency reference at the receiving end to supply the "carrier" for demodulation); this is how SSB radios work.

What does this mean for optical fiber? It limits how close together your "colors" can be based on how fast each one is modulated. The sidebands get farther and farther from the carrier as the modulation gets faster, and if the sidebands start clashing you get crosstalk and data errors.
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