What is the maximum Bandwidth? - Sixty Symbols 

Humility will get you a long way in this field! 10:18

*cough*Neil Dygrasse Tyson*cough*

Its just a number, i dont think anyone is proud of remembering numbers

@@thedude951 Degrasse

@@giorgosd3624 It's* don't*

hehehe

no it didn't

I fapped

Oskar, Do you not know what buffering is?

I conclude that the bandwidth of your line is less than 800 terabits per second. ;-)

Run lots of cables in parallel. Problem solved.

And that's on a single wire. I imagine you could have 1000s of wires on a single cable, yes? Maybe you run into more physical limitations or errors at too small of a size too, though

Run lots of cables in parallel yes but also with slightly different properties allowing them to be a control for overall transmission (plus 'overhead') for further range of frequencies (handling things as a bundle). Ie the different cables extend in part the range of frequencies available resulting in more relative bandwidth per cable.

There is an energy density problem, and mutual coupling between wires. Shannon's theorem says that data rate is given by bandwidth times signal to noise ratio. (For our purposes, dynamic range is a limit on signal to noise ratio.) A one Hertz bandwidth on a single cable can transmit a terabyte per second with a mere 44 teradB of dynamic range, or equivalently 8 x 10^12 bits of resolution.

all we need is to start encoding data in sperms and transmit them through pipes. they carry terabytes of data per teaspoon, so if we want to copy entire massive databases just have a sperm truck go to the new location, then do a memory check to see if everything transmitted and use the internet to make up the tiny difference.

Ali Moeeny I am not sure. He introduced some math, but he steered clear of even naming FT. I think that if he directly went for the concept, explained it, and made it part of the vocabulary, the whole explanation would have sound less sketchy.

+Ali Moeeny What are you talking about, he didn't explain FT at all.

+Ali Moeeny I was kind of surprised that I got to the end of the video and Fourier Transform was never brought up.

*Pee Wee and the audience go apeshit*

That is two words.

harmonics :)

I think our science has gotten to the point where a little Fourier De-synthesis might be just what the doctor ordered.

That's not one word. It's an infinite number of words with varying phases and amplitudes added together. 😉

+Juan Bonnett the moment when someone realise or deeply interiorise that the basic sciences are actually the thing that the modern technology comes from.

+Lazeran that moment when you realise that this is topic is grey and could be found on either one

Bandwidth isn't computerphile? With current technology there is a known maximum bandwidth that we could Mor's Law predict ourselves into a problem with, in a relatively short time frame. At that point laying more wire to fill an exponentially increasing demand isn't plausible, you need better technology with a higher bandwidth or better compression to send less data. This all seems pretty computer related, to me.

i know.... i was like :0

All he talks about is in fact rudimental Computer stuff. *You learn what bandwidth is and how it is “produced“ when you are learning any computer related job!*

I think you missed the point he was trying to convey.

That's not the *type* of information he is referring to. That is nothing more than the nature of the transmission. You need an oscilloscope to translate that. Hes talking about using that like morse code.

@Michael Hall: What you're talking about is the actual binary information that is transmitted. The video is concerned about the physical limits in transmitting information accross a fiber-optic cable. And mind you, as the professor clearly states, a mathematically true pulse requires an infinite amount of frequencies or otherwise an infinite amount of preparation and decay times to form. Fortunately quantummechanics comes to the rescue there giving us a bounded physical world i.s.o. a purely mathematical one. I really love that part.

you say that b/c you saw the bottle of scotch on the desk behind him LOL, that would be a fun class

No one is in his class.

yeah, especially in guitars you can hear beats and harmony off diff. instruments creating non-periodic reverbs, musicians are pretty close to science compared to other non-scientific fields..

That would be whole spectrum from kilometers long radio waves to planck length sized photons. It would be some absurdly large number

I think the lower bound is definitely the size of intergalactic dust (so perhaps IR?) I don't think there is an upper bound tbh, since space can have almost no mattet (a few atoms per m^3).

@@vaibhav1618 what about the bandwidth of a signal sent between two Casimir plates at vacuum? that'd be interesting to graph out.

@@voxelsofsorrow interesting, but what are we charting? Bandwidth vs plate separation?

@@vaibhav1618 exactly! it's kinda interesting because the plates will cut off lower frequencies while allowing higher frequencies as they get closer

That is true. However he's talking about different types of limit. It is also strange that he talked about visible spectrum when fibre optics use only IR.

Well I too mostly understand what is explained, but not quite this time. He lost me at the point that he explained that if you switch a laser on and off, it is a superposition of waves and if you keep it on continuously, it isn't. I understand the Heisenberg uncertaintly principle, and I understand superposition, but I cannot understand what that has to do with it. I also understand the (unmentioned) Fourier analysis, but I cannot make one single image in my mind on what the difference is between switching a laser on/off and leaving it on continuously.

Ronald de Rooij The thing that he said about continuous wave (CW) is true. It is almost never really exists in real world. I do a lot of EM simulation, and it is a real problem to simulate a CW. We use different kinds of tricks to suppress high frequency signals that permeates from starting the so called 'CW'. These high frequency signals are real problems in our frequency domain analysis.

While I understand the argument being made in the video, it feels like he's contradicted himself. I was under the impression that individual photons represented a packet of energy of a single frequency... What he's saying suggests that a photon itself is a superposition of multiple frequencies?

earthworm768 - actually group velocity dispersion (group delay in the radio world) means that different wavelengths travel through the fibre at different speeds and the frequency components arrive at different times which blurs the pulse edges. it can be partially corrected. it is still a function of bandwidth

Stephen Furr I absolutely didn't get a clue of what you're talking about except the last sentence that I like very much and do agree with :)

allen mathew Thanks :)

+Stephen Furr Advancements in technology only push the speed near and near to the fundamental limits of the media. If the media is for example a CAT5 cable with a given noise floor you can only push so much information down the line (see Shannon theorem).

here here

Stephen Furr there's a limit ;)

When he played two tones of different frequencies, superposition of two signals took place. It will result into wave/signal of different frequency. Therefore, that resulting frequency will be LCM of the two original frequencies.

JFC is a Mexican fast food chain.. right.. right ?

AMGwtfBBQsauce In the future, that might seem like a small amount. In the 1900's, one MB used to be incomprehensibly big.

Jojo Mcguire Which decade are we talking about? Computers didn't even exist in 1900, but multi-gig hard drives were pretty standard by 2000.

AMGwtfBBQsauce I think it's a typo and he meant 1990, however, even then 1 MB wasn't too big. The 80's now, that's a different story.

Ashley Wyatt "Why would we need any more than 50KB of storage?"

+Engineering Nonsense I know right.

+Engineering Nonsense But that will need to be split through the whole population since we share fibre cables

Matthew Lowe its not just one cable, under water, but networks. Right?

Yeah, I was going to say there will be thousands bundled up, but I doubt there will be enough to provide each household within a city with 10TB/s

Matthew Lowe True

+E “Anonymous Nerdfighter” Hernandez The smallest wavelength difference, I would assume, would be one Planck Length. The reason is because the Planck Length is the smallest discrete distance that can be traveled and measured in the universe, so it would be impossible for two wavelengths of light to differ by any less than that.

They don't use square pulses, they shift sine phase one or the other way and use different pieces of sine wave to code 1 and 0. Square pulses will just stretch on the way because they have so many different frequencies

Search for frequency genrator apps on play store or app store. To replicate that pulsing effect, choose a stable frequency let's say 1khz and then play 1.01 khz in other phone.

10 years ago you would be very happy with 56 Kib per second. And in 10 years, once high definition holographic VR movies will start including DNA and psychological information of each character allowing you to create alternative plots as you go and you will try to download something like this, 100 TiB per second might look like a slow connection.

VolodyA! V Anarhist Time for you to write a book. I bet that came off the top of your head, didn't it? Run with it! I also noticed your use of the tebibyte symbol... while I applaud your effort, I don't think it will catch on.

))) About TiB... i don't do that to "catch on", but because otherwise it's ambigous.

VolodyA! V Anarhist As you already know TiB = 1024^4 and TB= 1000^4 bytes... I think the public has spoken with the use of kilo, mega, giga and tera. The only ambiguity would be the public's clear ignorance of the difference and why it's important. That's why I was saying it won't catch on... the general public won't start saying the right thing. But, I applaud your effort to be exact!

VolodyA! V Anarhist you probably meant 20 years ago. 10 years ago was 2005! some of us already had megabyte connections back then (i think i was at 800kbps)

good jorb. *clap*..*clap*..*clap*...

But you'd need the receivers to process the additional cables and compile it all together, which may not actually save time.

Stuart Hull Gamma rays are ionizing radiation so they just smash into atoms and knock electrons off them, often changing the properties of the atoms in the process. It would not be easy to find anything like an optic cable to shove them down. Radio waves have much longer wavelengths and they just pass through many substances or get absorbed. The range we have to work with for fiber optics is pretty much infra red through lower ultra violet.

Mexicano President Many Jobs!

Give Billions to the Bat-Cat!!

Let's see the math.

Google Shannon's Theorem.

KaneLongTroy If we assume 1tb in a millisecond, that will still be done in 0,002 seconds. That's pretty fast.

+GamePhysics Regular computers won't be able to process that much of speed

'application'

Yeah normally i understand everything pretty well too but this time i really struggled to understand anything of substance the first time watching. By now i only understand the first part of the video, where the delta f * delta t = 1 formula comes from.

(1) The speed of your fiber connection is how much information can travel through (2) Information is 1s and 0s (3) "1" and "0" are basically "pulse" and "no pulse") (4) The shorter in duration the pulses the more pulses can travel through your fiber within a given period of time (5) A short (duration) pulse can only be created by combining loooots of waves of different frequencies (6) There is a limitation on what range of frequencies (bandwidth) your fiber can support (7) Since the range of frequencies is limited, the duration of the supported pulses is also limited, because of (5)

+Роман Плетнев I like your thinking. I imagine the time we would see the laser as "on" would decrease as we decreased the number of frequencies allowed through the filter. As we decrease the frequencies allowed through it essentially becomes opaque which makes sense as then the time we perceive the laser as on would be zero. So the delta t (time of perceived pulse) through the filter is proportional to delta f of the filter (i.e range of frequencies allowed through)? No idea, just speculating...

+Роман Плетнев since the filter can physically not be that precise, you would only cut the end and the beginning of each pulse. if you switch fast enough, the time until it is close enough to your target frequency would be longer than the length of the pulse, if you know what i mean. If the totally unrelated mental image helps, think of the sound an organ makes if it turns on while you are pressing the keys (it is one of my favourite sounds :D)

+Роман Плетнев +Ross Sullivan +Maric I understand your confusion, it's because the vid explain it poorly. The vid is only 11 min it cannot cover everything of a 2 h class on the subject. Here the explanation: every signal that is not pure can be written as a sum of a pure signal, when I say pure I mean it contains only 1 frequency, and it means the signal can be drawn as a perfect sinusoide. Now when you switch on a off periodically the green laser, if you look at the signal as a whole you will see (if for example the period is 1s) 1s there is a pure sinusoide then 1s there is nothing, and so on until you decide to stop it. It is then impossible to mathematically describe the whole signal with one and only one frequency (the frequency of the green laser). Only by using the sum of many frequency you can mathematically reconstruct the whole signal. In other word, by using a lot of different frequency, and add them together you can achieve the same result as if you were turning on and off the laser. Hence the "it contains a lot of different frequency". As for how can adding different frequency can result in total darkness (equivalent to when you turn off the laser) you can look into interference. So to answer your question if the signal was obtained by turning on and off then you will see nothin, but if the signal was obtained by the addition of many frequency, you will filter the green light and obtain all the other. For more info look into Fourier series.

Роман Плетнев same light but with just less energy because you filtered some of it off

And what in case we are capable of sending a single photon. We put a filter. And what does even very long lasting sine wave of light freq mean? That photons come in an extremely ordered fashion one after another without any differences in space gaps between them in a straight path?

Well, there is a problem with the "easy with computers" part. So far with the word "it" we are outside the frequency range of digital audio, so you will need special hardware to digitize the incoming 26996 Hz signal. And "it" is a very short word. I'll let you calculate the frequency of the word "information" with your system, but I guess we would in the 10^27 Hz range... By the way, an unchanging sine wave has to be infinite in time, to be unchanging. Otherwise it'll contain other frequencies. As you said, having some fun.

There is also the problem of having the different peaks and valleys of different frequencies smearing together and also losing the information.

LOL

your computer won't be able to handle it.

i wonder if it would melt the fiber

Those crazy levels of speed are more commonly found in trans-oceanic cables, where billions of people's bits are going over a single bunch of fibers (like a shared cable internet connection on steroids).

G4mm4G0bl1n I never said it was a single fiber. I said "cable" and "bunch of fibers". Those cables are massive bunches of fibers. My point was that the only real need for anywhere near theoretical single fiber bandwidth is in those transoceanic fibers. No home or business network, metro net, ISP, etc. needs that at this point.

G4mm4G0bl1n Not at all. I specifically said "at this point" not "never". As long as LANs are capped at 1 maybe 10 Gbps, WANs need not be faster. Will the need be there soon enough, of course. But not today.

If we only had infinite time.

Correct!

very interesting. Can you tell more about it? Do you mean a light-speed electrons movement? a simple wire faster than optical? then why? whaaaaaa ????

DC is zero frequency. A signal that is DC never changes. But the universe has only finite time, therefore the signal can only be DC if we make assumptions about its border conditions at the beginning and end of time.

Mike Page no, i didnt) DC is undestandable. never changing dc is not information. the universe and time is not understandable. if you want infinite, never changing, dc then you just need an infinite energy for this useless circuit. wtf

Information limit is reached when spikes as just barely high enought to be detectable as something different from zero. Any higher than that and you are wasting time that the spike needs to climb and then fall again.

Are you sure that you don't have a DSL connection? Considering the fact that the slowest speed i can get with fiber optic connection is 10 down and 5 up makes me wonder.. I can get, depending on the speed/plan you pick, anything from 10Mbit/s and all the way up to 1Gbit/s both up and down, for a fairly low cost. I currently have 100Mbit/s and pay about $45/month (USD).

Gnagarn 100 mbit/s in USA or the world, dl and ul???

750Kb/s keep whining

I think the full explanation would take many times longer... I did watch another video explaining the same concept only marginally better - probably minutephysics...