"Time Telescope" Could Boost Fibre-Optic Communications 183
An anonymous reader writes "A time lens can focus a chunk of time to a point, rather like a normal lens focuses light rays. Put two time lenses together and you can create what a Cornell University team calls a 'time domain telescope' which can magnify time. They sent a 2.5 nanosecond long light pulse, encoding 24 bits of information, into their time telescope. What came out on the other side was the same 24 bit pulse, but compressed into 92 picoseconds. Squashing more information into a light pulse could help to send more information via optical fibres."
Spacetime, not "squishing time" (Score:2, Interesting)
"A time lens can focus a chunk of time to a point,"
Since einstein we really know that space and time is the same thing, we really should just call it "squishing space", since time is really a measurement of a distribution of matter and energy, we've compressed the space (and hence the time).
"Time and space and gravitation have no separate existence from matter. ... Physical objects are not in space, but these objects are spatially extended. In this way the concept 'empty space' loses its meaning. ... Since the theory of general relativity implies the representation of physical reality by a continuous field, the concept of particles or material points cannot play a fundamental part, ... and can only appear as a limited region in space where the field strength / energy density are particularly high."--- (Albert Einstein, 1950)
WTH? (Score:4, Interesting)
Moving pulses through time has been done with electronic delay lines for about 80 years now. The theory and technology are well worked out, both in the time and frequency/phase domain. A friend of mine worked out an alternate theory around 1961, which left the theorists scratching their heads--- how could there be TWO optimum but different ways of squishing pulses? But it was true.
Anyway, you don't hear much about this technology as it's not a panacea of any sort. Any information you squeeze in time is going to undergo some unavoidable phase distortion-- not anything you want a lot of. And the inverse operation at the other end adds even more distortion. Yep, no free lunch, once again.
Re:Time compression? (Score:3, Interesting)
You've missed the point. The "time telescope" is constructed of two of the frequency-changing lenses. The first lens disperses, the second converges, just like in a normal two-lens telescope. (Except the time telescope does it in frequency/time space instead of position space like your average telescope would.)
The result is a time-compressed pulse at the original frequency. The frequency-shifting is just part of the mechanism that gets this to work.
Re:MUX? (Score:3, Interesting)
The following seems a little better:
http://nanophotonics.ece.cornell.edu/Publications/High-resolution%20spectroscopy%20using%20a%20frequency%20magnifier.pdf [cornell.edu]
Don't ask me to explain it, I'm still searching for an easier explanation. If you have any contemporary optics knowledge you should be able to figure it out.
Re:First descibed in 1834 by John Scott Russell (Score:5, Interesting)
In this case, you start out with an essentially monochromatic long pulse, whose intensity is modulated very slowly compared to the frequency of the light, but as fast as possible using typical telecom electrical modulators. A monochromatic pulse cannot be compressed using a grating or prism. Then the wavelength of the pulse is shifted, with the amount shifted depending on the relative position in the pulse (this is the "time-domain lens"). What you have now is similar to a chirped pulse, which is compressed using a long fiber (I don't know why they don't use prism compression or something else faster here). The time-domain lensing is then undone, "de-chirping" the pulse, leaving you with a much shorter essentially monochromatic pulse at the starting wavelength, with the same amplitude modulation (i.e., carrying the same information).
The point being a huge increase in the amount of information that can be carried in a fiber.
Re:Time compression? (Score:3, Interesting)