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."
"A time lens can focus a chunk of time to a point, rather like a normal lens focuses light rays."
no, its not LIKE a normal lens, it IS a normal lens. kind of like how "cloud computing" is the same client/ server model of decades past, a "times lens" is basically, uh, gee, a lens. but made sexy by introducing scifi fantasy terminology for the sake of grabbing attention
"cloud computing" is the "client/server" model like the iPhone is the "rotary phone" model. I certainly agree with your premise that people like to hype things, and this is just a lens with a fancy name. But "cloud computing" is a long-distant descendant of the "client server" model. They aren't the same thing anymore than a nuclear bomb is just "a really strong TNT bomb".
Cloud computing is just client server model on a larger scale with new technologies to make it possible. They are exactly the same conceptually, the only difference is the specific technologies being used to complete the goal. Oh and one is a marketing buzzword used to generate interest while the other is a 'technical' description of a system.
The only reason cloud computing is considered new is because of the scale it is being done on, the markets being targeted, and the technologies being used. So it ma
Client/server is a communications model. Cloud computing is a business model, a management model, a deployment model, etc... You might as well say "networking" is the real concept, and that fancy "cloud computing" is just a PHB term for "networking". Let's just call cloud "computer networking!".
Cloud computing isn't about a "client" and a "server". It's about moving more of your data and business processes off systems and software you support and letting someone else do it.
Cloud computing will have client server components. So what? When I use my Xbox 360 to play games over the internet should I tell people I'm using a "client/server system" or that I'm playing my god damn Xbox 360?
It's fun to mock the Latest Thing, and sometimes it deserves it, but cloud computing is not just a fancy name for Client/Server.
>>>Client/server is a communications model. Cloud computing is a business model
Whatever. It still reminds me of the hellish 1970s/80s VAX machines where you could only access your programs/data from a central source, and if that source or connection went down, you were out of luck. I was much happier when I got rid of that and exchanged it for a computer that ran its own software any time and any place I felt like it.
If it makes you feel better you can use such sophistry to claim they are the same thing. I'm not clear if you're being intentionally dense or just don't understand.
My point about just calling it "computer networking" is that it certainly is "computer networking". It's also "client server". And it's also "cloud computing". They all add meaning. It's not even that hard to grasp.
I'm using "client server" if I have a few hundred netapps in a computer room and use NFS to expose the data to my client machine
It's really the ecosystem of client/server systems provided by many different vendors which together form "the cloud". That's the other part of this - there was originally supposed to be one cloud. Meaning it would be Internet based. Now it's getting diluted and people are applying the same concepts inside a private network.
But again, considering these are networked systems "client server" seems a bit redundant. Like calling client/server "computer networked client/server".
But "cloud computing" is a long-distant descendant of the "client server" model. They aren't the same thing anymore than a nuclear bomb is just "a really strong TNT bomb".
If "cloud computing" is so different from the client-server model (with the server being provided by someone else), then surely you can name some differences between the two models.
The cloud theoretically doesn't have fixed resources, unlike previous excursions into hosted serving. You either had enough capacity for everything, or you needed a faster server that ran idle most of the time. The cloud concept really is a complete rethinking of server balancing by distributing both the software and the data as needed.
But that's just what I get from a bit of reading. I'm not a cloud user, though it'd be something I'd look at if I had a load I thought it could benefit.
So, a normal lens will compress a series of pulses into a shorter series? How, exactly? I didn't realize that normal lenses worked by exciting the atoms in a waveguide with an infrared laser.
...and he got modded up.
"News for Nerds" used to mean the kind of nerds that were like Lisa Simpson and Martin Prince. Now the typical Slashdot nerd is more likely to be the Milhouse van Houten kind of nerd.
"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
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.
That means communications companies will soon be able to bring us 1000+ channels of infomercials and the same sports events for just $60 more per month, while at the same time capping our broadband usage at 2GB a month.
It's shifting the frequency into a shorter wavelength, without going through a chip.
From the article:
The Cornell team made their time lenses using a silicon waveguide that can channel light. An information-carrying pulse made from a series of
small laser bursts signalling digital 1s and 0s travels through an optical fibre and into the waveguide. As it enters, it is combined with another
laser pulse from an infrared laser. The infrared pulse vibrates the atoms of the waveguide, which in turn shifts the frequencies of the
data-carrying pulse before it exits the waveguide and passes into an optical fibre beyond.
The abstract of the actual article is a little more informative [nature.com], but still makes strange claims.
I think they can compress a 10Ghz electrical signal into a 270GHz optical signal, with obvious ramifications in multiplexing, as you can then take 27 such signals at a time (theoretically).
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.
This is a complete oversell on a normal everyday phenomenon. This is a simple compression of a lightpulse, and has been done for a long time. Dispersion usually smears out a pulse, but can easily, compress the pulse. There is no "bending of time" here. Look up "Chirped pulse amplification" and also "Prism compressor", and maybe "soliton". First descibed in 1834 by John Scott Russell
No kidding. Its such journalist speak I couldn't figure out what it was talking about.
I think the journalist might have been trying to explain group velocity dispersion aka chromatic dispersion. In a nutshell the speed of light in a vacuum is constant, but in any material it varies a wee tiny bit by frequency, and there is no such thing as a truely monochromatic light source, although we can get pretty close. Work arounds for that problem are VERY OLD NEWS but journalists are always so gullible...
This is not at all an oversell (though admittedly bad journalism). It's not the same as chirped pulse amplification or prism compression.
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.
We're so bad at modulating optical signals that we don't come anywhere near the Shannon limits of the channel. From the sound of it, the 27x increase provided (so far) by this technique also doesn't come anywhere close.
And no, you don't get an article in Nature for regurgitating stuff from old Bell Labs journals.
Doesn't that mean they compressed the amount of time it took light to travel that distance, and therefore changed the speed of light? Or was this simply a compression of the distance between the photons?
Neither. They've created a frequency upshifter (possibly one with interesting spectral properties to preserve the integrity of the encoded information, although the New Sensationalist article is so completely incoherent it's impossible to say if they have actually achieved that result) and given it the most dishonest, misleading name possible to confuse people, as posters above have noted, to grab attention.
They've got attention, but they haven't conveyed any information.
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.
"Please describe how 'time-compressing' a waveform is different than frequency-shifting it"
If I frequency shift a waveform by a factor of 2, then the time compression is also a factor of 2. The article doesn't really mention it, but the frequency shifts in this experiment are much less than a factor of 2, but the time compression is from 2.5 ns to 95 ps, a factor of 27 compression.
This is a real time lens. A spatial lens works by imparting a quadratic spatial phase to light. Diffraction then causes the beam to focus due to the quadratic spatial phase.
A time lens works in analogy to a spatial lens by imparting a quadratic temporal phase to a light pulse. Propagation in a dispersive media then leads to the time compression.
The difficulty is it is very hard to impart a quadratic phase to short light pulses. The only real way to do it is nonlinear optics, which is where the (small) frequency shifts mentioned in the article come from.
Uh, you guys are confusing me. Isn't there still going to be a bottleneck at the point between the output of the laser, and the lens? How do you actually compress anything with that bottleneck?
If you were to just compress the signal in time, the rate of speech would increase, but the frequency (pitch) would as well - it would sound like a chipmunk. This is what a simple resampling program would do.
On the other hand if you were to just frequency-shift the signal (say by heterodyning) then the rate of speech would be the same, but the pitch would change. This is what pitch-correction programs do.
If you do both in series and in opposite directions so the cancel, then the pitch remains the same but rate of speech is now increased. This is what fast playback programs (say for audio books) do.
The researchers figured out how to do the last to light using simple lenses. This could be useful because you can send the data down the same channel (like a frequency multiplexed fiber) as the original signal was intended for.
Perhaps all the information is there, but its been compressed by a time telescope to the point it is now a black hole. Since the information is within the event horizon, you cannot see it.
The other issue which nobody seems to be bringing up is that at the other end the light has to be uncompressed and corrected for errors so that it can be read properly. This takes time and essentially negates any savings. I suppose this sort of thing would be useful if vast distances were involved, but on the Earth, the distances are short enough where it's really a neat science trick rather than anything useful.
Both. They vary the frequency over the light pulse so that different parts of the pulse travel with different speeds, thus causing the back of the pulse to catch up with the front.
Not quite. It's like you driving your 12' long car along the highway. When you drive through a tunnel your car (and you) come out perfect, functional, but only 3' long. After going through another tunnel you regain your original length.
The time lens terminology does seem a little sensational, but it is kind of descriptive. It's also very useful - we're not good at modulating light. We can completely saturate the bandwidth of an RF channel but we can only use a small fraction of the bandwidth of an opti
salesman speak (Score:4, Insightful)
"A time lens can focus a chunk of time to a point, rather like a normal lens focuses light rays."
no, its not LIKE a normal lens, it IS a normal lens. kind of like how "cloud computing" is the same client/ server model of decades past, a "times lens" is basically, uh, gee, a lens. but made sexy by introducing scifi fantasy terminology for the sake of grabbing attention
Re: (Score:2)
Re: (Score:3, Insightful)
Cloud computing is just client server model on a larger scale with new technologies to make it possible. They are exactly the same conceptually, the only difference is the specific technologies being used to complete the goal. Oh and one is a marketing buzzword used to generate interest while the other is a 'technical' description of a system.
The only reason cloud computing is considered new is because of the scale it is being done on, the markets being targeted, and the technologies being used. So it ma
Re:salesman speak (Score:5, Insightful)
Client/server is a communications model. Cloud computing is a business model, a management model, a deployment model, etc... You might as well say "networking" is the real concept, and that fancy "cloud computing" is just a PHB term for "networking". Let's just call cloud "computer networking!".
Cloud computing isn't about a "client" and a "server". It's about moving more of your data and business processes off systems and software you support and letting someone else do it.
Cloud computing will have client server components. So what? When I use my Xbox 360 to play games over the internet should I tell people I'm using a "client/server system" or that I'm playing my god damn Xbox 360?
It's fun to mock the Latest Thing, and sometimes it deserves it, but cloud computing is not just a fancy name for Client/Server.
Parent
Re:salesman speak (Score:4, Insightful)
Agreed, it is more like fancy name for a mainframe with RJE.
Parent
Re:salesman speak (Score:4, Insightful)
>>>Client/server is a communications model. Cloud computing is a business model
Whatever. It still reminds me of the hellish 1970s/80s VAX machines where you could only access your programs/data from a central source, and if that source or connection went down, you were out of luck. I was much happier when I got rid of that and exchanged it for a computer that ran its own software any time and any place I felt like it.
Parent
Re: (Score:3, Informative)
If it makes you feel better you can use such sophistry to claim they are the same thing. I'm not clear if you're being intentionally dense or just don't understand.
My point about just calling it "computer networking" is that it certainly is "computer networking". It's also "client server". And it's also "cloud computing". They all add meaning. It's not even that hard to grasp.
I'm using "client server" if I have a few hundred netapps in a computer room and use NFS to expose the data to my client machine
Re: (Score:3, Informative)
It's really the ecosystem of client/server systems provided by many different vendors which together form "the cloud". That's the other part of this - there was originally supposed to be one cloud. Meaning it would be Internet based. Now it's getting diluted and people are applying the same concepts inside a private network.
But again, considering these are networked systems "client server" seems a bit redundant. Like calling client/server "computer networked client/server".
Re: (Score:2)
But "cloud computing" is a long-distant descendant of the "client server" model. They aren't the same thing anymore than a nuclear bomb is just "a really strong TNT bomb".
If "cloud computing" is so different from the client-server model (with the server being provided by someone else), then surely you can name some differences between the two models.
Well?
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But that's just what I get from a bit of reading. I'm not a cloud user, though it'd be something I'd look at if I had a load I thought it could benefit.
Salesmen guy who didn't RTFA. (Score:4, Insightful)
So, a normal lens will compress a series of pulses into a shorter series? How, exactly? I didn't realize that normal lenses worked by exciting the atoms in a waveguide with an infrared laser.
Parent
Re:Salesmen guy who didn't RTFA. (Score:4, Insightful)
Parent
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> It's just yet another technology invented in a lab for academics' sake.
Yeah, and what's that ever given us?
http://www.physics.ucla.edu/~ianb/history/ [ucla.edu] ...
http://www.research.ibm.com/about/past_history.shtml [ibm.com]
http://www.research.ibm.com/resources/awards.shtml [ibm.com]
http://www.parc.com/about/milestones.html [parc.com]
Re: (Score:3, Funny)
As it turns out, "part for the course" is "par for the course" when you hit one of the letters immediately adjacent to the "r".
Deceptive Name (Score:5, Informative)
I'm used to these physics guys doing all kinds of crazy things with invisibility cloaks and such so I took the title to be a literal time lense.
After RTFA, the "time lense" is a frequency up-shifter. Still impressive, but not supernatural as I had hoped.
Re:Deceptive Name (Score:4, Informative)
After RTFA, the "time lense" is a frequency up-shifter.
So an Auto-Tune, basically.
Parent
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"Deceptive name" is even better, but... hey, it got them on Slashdot!
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
Re:Spacetime, not "squishing time" (Score:4, Informative)
Hrm....
Don't you mean time dilation [wikipedia.org]?
Parent
These future Slashdot comments are hilarious... (Score:4, Funny)
.. I should know since I read them 70 picoseconds ago using my time telescope.
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.
Fantastic (Score:2)
That means communications companies will soon be able to bring us 1000+ channels of infomercials and the same sports events for just $60 more per month, while at the same time capping our broadband usage at 2GB a month.
It's shifting the frequency. (Score:4, Informative)
It's shifting the frequency into a shorter wavelength, without going through a chip.
From the article:
The Cornell team made their time lenses using a silicon waveguide that can channel light. An information-carrying pulse made from a series of
small laser bursts signalling digital 1s and 0s travels through an optical fibre and into the waveguide. As it enters, it is combined with another
laser pulse from an infrared laser. The infrared pulse vibrates the atoms of the waveguide, which in turn shifts the frequencies of the
data-carrying pulse before it exits the waveguide and passes into an optical fibre beyond.
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heh I'm certainly Stoked [wikipedia.org] that this will give us all faster internet.
Ironic (Score:5, Funny)
MUX? (Score:4, Informative)
Re: (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.
Know what it would be good for? (Score:4, Funny)
I can think of a myriad of uses ..|||..|.||. eady using it for that.
First descibed in 1834 by John Scott Russell (Score:5, Informative)
This is a complete oversell on a normal everyday phenomenon. This is a simple compression of a lightpulse, and has been done for a long time. Dispersion usually smears out a pulse, but can easily, compress the pulse. There is no "bending of time" here. Look up "Chirped pulse amplification" and also "Prism compressor", and maybe "soliton". First descibed in 1834 by John Scott Russell
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No kidding. Its such journalist speak I couldn't figure out what it was talking about.
I think the journalist might have been trying to explain group velocity dispersion aka chromatic dispersion. In a nutshell the speed of light in a vacuum is constant, but in any material it varies a wee tiny bit by frequency, and there is no such thing as a truely monochromatic light source, although we can get pretty close. Work arounds for that problem are VERY OLD NEWS but journalists are always so gullible...
http:// [wikipedia.org]
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.
Parent
Re: (Score:3, Informative)
We're so bad at modulating optical signals that we don't come anywhere near the Shannon limits of the channel. From the sound of it, the 27x increase provided (so far) by this technique also doesn't come anywhere close.
And no, you don't get an article in Nature for regurgitating stuff from old Bell Labs journals.
What happens when you combine them? (Score:5, Funny)
What happens when you take four Time Lenses and align them to be 90 degree angles to each other?
ONE MAN KNOWS THE TRUTH! [timecube.com]
Re:I think I saw a movie about this... (Score:5, Funny)
...Ben Affleck starred.
We're boned.
So you were the guy who saw it.
Parent
Re:Time compression? (Score:5, Insightful)
Doesn't that mean they compressed the amount of time it took light to travel that distance, and therefore changed the speed of light? Or was this simply a compression of the distance between the photons?
Neither. They've created a frequency upshifter (possibly one with interesting spectral properties to preserve the integrity of the encoded information, although the New Sensationalist article is so completely incoherent it's impossible to say if they have actually achieved that result) and given it the most dishonest, misleading name possible to confuse people, as posters above have noted, to grab attention.
They've got attention, but they haven't conveyed any information.
Parent
Re: (Score:2, Funny)
They've got attention, but they haven't conveyed any information.
They've conveyed the information, but it's encoded in the 24 bits of the light pulse
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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:Time compression? (Score:4, Informative)
"Please describe how 'time-compressing' a waveform is different than frequency-shifting it"
If I frequency shift a waveform by a factor of 2, then the time compression is also a factor of 2. The article doesn't really mention it, but the frequency shifts in this experiment are much less than a factor of 2, but the time compression is from 2.5 ns to 95 ps, a factor of 27 compression.
This is a real time lens. A spatial lens works by imparting a quadratic spatial phase to light. Diffraction then causes the beam to focus due to the quadratic spatial phase.
A time lens works in analogy to a spatial lens by imparting a quadratic temporal phase to a light pulse. Propagation in a dispersive media then leads to the time compression.
The difficulty is it is very hard to impart a quadratic phase to short light pulses. The only real way to do it is nonlinear optics, which is where the (small) frequency shifts mentioned in the article come from.
Parent
Re: (Score:3, Interesting)
Re:Time compression? (Score:5, Informative)
Imagine a speech audio signal.
If you were to just compress the signal in time, the rate of speech would increase, but the frequency (pitch) would as well - it would sound like a chipmunk. This is what a simple resampling program would do.
On the other hand if you were to just frequency-shift the signal (say by heterodyning) then the rate of speech would be the same, but the pitch would change. This is what pitch-correction programs do.
If you do both in series and in opposite directions so the cancel, then the pitch remains the same but rate of speech is now increased. This is what fast playback programs (say for audio books) do.
The researchers figured out how to do the last to light using simple lenses. This could be useful because you can send the data down the same channel (like a frequency multiplexed fiber) as the original signal was intended for.
Parent
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Which means the IPO should be right around the corner.
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Perhaps all the information is there, but its been compressed by a time telescope to the point it is now a black hole. Since the information is within the event horizon, you cannot see it.
Go ahead. Disprove it.
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The other issue which nobody seems to be bringing up is that at the other end the light has to be uncompressed and corrected for errors so that it can be read properly. This takes time and essentially negates any savings. I suppose this sort of thing would be useful if vast distances were involved, but on the Earth, the distances are short enough where it's really a neat science trick rather than anything useful.
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Both. They vary the frequency over the light pulse so that different parts of the pulse travel with different speeds, thus causing the back of the pulse to catch up with the front.
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Re: (Score:3, Funny)
Last Night
You Beer
Girl Hideous
You Horny
Taxi Ride
Whale Ride
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Not quite. It's like you driving your 12' long car along the highway. When you drive through a tunnel your car (and you) come out perfect, functional, but only 3' long. After going through another tunnel you regain your original length.
The time lens terminology does seem a little sensational, but it is kind of descriptive. It's also very useful - we're not good at modulating light. We can completely saturate the bandwidth of an RF channel but we can only use a small fraction of the bandwidth of an opti