Velocity Conference 2015 (New York, NY)

About this course

good morning everyone we know that communication is always important it involves a transmitter and a receiver in a face-to-face communication if you want

to try to tell me something you need to be within my hearing distance as we're the four apart from each other as the distant grows often time we want to rely on some additional helps some time is

also involving other species but what if we cannot afford the extra latency what if we need to maintain the nature of this real-time information transfer fortunately throughout humans particular

session we learned several techniques that allows us to do so for start we start to rely on our eyes and less on our voice in our ears we can convert the information into some sort of coded

message and use any kind of signaling system everything from smoke signals to fire beacons or similar still over a great distance if you're on the receiver end you need to have this bionic eyes

with superhuman vision what if we can shift responsibility to the transmitter what if the transmitter project the information to the receiver this is the whole idea behind heliograph focused ray

typically from the sunlight is reflected by a mirror in the transmitter modulated by signal for example Morse code and sent down to the receiver a spot close to the receiver Morse code is not always

fun this is why Alexander Graham Bell best known for his invention telephone came up with a different idea he called it photo phone remember this was back in 1880s Madison Square Garden

was opened for the first time and America Civil War just ended photophone works were similar like a telephone instead of electricity he was using like his voice modulates light sorts centered

the receiver and converted back to the audio with the technology available at that time he managed to transfer his voice vine line over distance of 700 field this is quite profound this is

remarkable this is a milestone in the history of wireless voice communication Bell was so fascinated by fora phone if it wasn't for his wife intervention you will have named his second daughter

after him for the one heliograph they belong to this freespace optical communication system it suffers from two problems first the line of sight is crucial so you can only communicate in

straight line second the medium itself is extremely lossy it's hardly surprising that it's hard to maintain a communication link over a great distance is why electricity won the battle for

the next hundred years people just started to use telegraph and later on telephone it wasn't until about 50 years ago that optical communication gained traction again it was for the invention

of laser now if you grew up in the 90s and read comic books you know that laser is pretty amazing in real life laser is much more than just this powerful and destructive

weapon laser is different than any other light source for start is highly monochromatic its exhibit one single pure color if you put the prism behind it there won't be any rainbow one color

one frequency one wavelength that also means all the photons the particles light carries the same amount of energy on top of that laser is also extremely coherent all the rails they do not cross

each other's the travel all the way from our imperfect thing this allows us to build an optical interferometer a crucial component in any high sensitive optical receiver being monochromatic and

being coherent sets laser up as the perfect carrier for any modern optical communication system another achievement we've done is fiber optic is made of silicate glass it's very light it's low

cost in maintenance in many aspects is superior than copper wire if you cut a fiber optic cable the cross-section looks like this the jackets and buff are there for the protection but the magic

happen inside that core it's 8 micron of silica glass the thinnest strain of your hair is really 16 this is just half of it thanks to the difference in the refractive index between the core and

the cladding this established of an optical phenomenon called the total internal reflection if you launch a photon into the 8 micron of take a glance it gets flat there forever

if you launch a photon from this base to the JFK Airport and come back again it's going to lose most of its power only 1% remains but thanks to modern optical receiver that's 1% it's necessary it's

sufficient to recover all the formations no amplification SSE no booster needed imagine doing this with electricity and copper wire it's just impossible this is why our Internet backbone reliance on

this massive network of undersea fiber-optic cable all over the world in fact life streaming of the skin on this conference will not be possible if it's not from millions of photons flying

around in these tiny little tubes if you think of Internet as a series of tubes there is some truth to them if you choose one cables from this place to Europe it has this staggering amount of

capacity 3.2 rabbit per second how much is 3.2 turbit percent forbidden it's essentially the content of a stack of blu-ray discs how fast is 3.2 turbid per second imagine that entire content

appears across the pond somewhere in Europe in just a second how do we achieve this compared to Bell's experiment years ago today's we have the luxury of modulating several different

attributes of light we can modulate this amplitude its frequency and its face combining all these aspects allows us to multiply the total capacity of any photonics transmission system it gets

even better I mentioned earlier that laser is monochromatic there's almost zero overlap between one frequency another in other words we can lounge for different

signal like in this diagram that has four different frequency of the carrier's launched into the same single fiber optic no chance in the insulation necessary and then at the receiver end

we can be matched up and get the individual channel this dragon source for but in practice we can have as many as 10 or 20 or 40 once we start to get into this high bit

rate we start to be facing the law of physics there will be some impairments and that decreases the signal quality take for example a chromatic dispersion this causes pulse broadening so one bit

will not be easily distinguishable from another one but rest assure some of the brightest mind in our industry we work really hard to solve this problem in the result speaks for itself today for our

undersea fiber-optic communication system we have our base bit rate of 10 gigabit per second but we start to see a deployment of 100 and 200 and why stop there when we start to modify the medium

itself to improve the state of the fabrication of the fiber-optic cables we can have 255 terabit per second are we gonna see that a bit per second or extra bit per second anytime soon only time

will tell it was barely hundred fifty years ago when both struggle with his voice for invention over life low signal quality low bandwidth short distance but thanks

to the hard work of all the scientists in the last hundred years everyone from physicists to mathematicians optical communication has turned from the way we communicate attention from our

civilization today we can talk to anyone on this planet wherever there are whenever we like if you know someone who's a scientists you owe it to yourself to give them a hug a big hug

we have to remember that we stand on the shoulders of the Giants the man and the woman before us it is therefore in our best interests to show our gratitude to be thankful and to stay humble thank you

you