How Fiber Optics Work

check Chicken E one, two three. Okay, then I'm a little okay, all right, let's start well off with a little listener mail. This is your mail comes from Joseph Business. Hi there, Chris and Jonathan. This is Joseph from Dorchester, Ontario. Again. I had an idea and I thought it would be cool for you guys to cover in a blog post or podcast, which you've probably already guessed from the title

of my email, fiber optics. I'm sure you get ten emails a day asking for a podcast on fiber optics, but I look through the list several times and wasn't able to find a podcast on the topic. I have a special interest in this type of data transport, because I have heard that my my town might be getting

some fiber optic lines installed in the near future. I've also seen television shows about installing fiber optic lines along the Pacific coast of North America to link up to Canada and the to link up Canada and the USA with the Central and Southern America's but they didn't really cover exactly how they would work. Of course, everyone knows more or less how fiber optics work, especially since they have almost made the width of the human hair a

standard unit of measurement. However, I and I am sure many of your listeners would like to know exactly how they work, as well as if they are really as good as they are touted as being. Maybe you could also talk about other comparable technologies that we can look forward to. Uh, and I'm going to truncate the rest of his email. He goes on a little bit more, talks about how great we are, But you guys know that already we all know how great we are, So

let's just right into fiber optics. Okay, so the width of a human here. Hey, I think someone's knocking on our ceiling. Um. Oh, what a feeling when all right, let's let's try that again. So fiber optics. Yes. In short, it's a long thin wire of glass yep. And it has a couple of different coatings on it that allow light to pass through this this long wire of glass. Um, and it can go pretty far away without any degradation. And then you have a something on the other end

that detects the light. That's the very basic system of a fiber optic line. Yeah. Now it has to be a very very special glass. You couldn't just basically melt down your window panes and stretch them out. No, that would be a very bad idea, and it would get cold at night, yeah, um, and things could get inside and bats other monsters that begin with be beholders berserker. Oh no, I don't want any berserkers in the bedroom anyhow, scom No. No, No, it's a it's a very very

optically pure glass. It has to be made in a very controlled environment in order for it to be extremely pure. And the reason why it needs to be extremely pure is because the light that is carrying the signals has to be able to to reach as far as it can. Now that's the thing I mean regards there there are a number of different ways to transmit information in a fiber optic line, but without having a very pure medium,

in this case, the the extremely pure optical glass. Um, it's not going to get very far without help, right, So let's uh, let's talk a little bit about fiber optics in general, and then we should talk about the the process of making a fiber optic line, which is actually pretty fascinating. Yeah, it really is. So a fiber optic is made up. Fiber optic line is made up of three parts. You've got the core, which is the glass. Yeah,

that's that's what the light passes through. Around the core, you have the cladding, and the cladding is a reflective coating. It's that's what allows the light to bounce around inside the fiber optic line. So when you shine a light down a fiber optic line, it's reflecting off of this this coating and moving further down the line until it reaches the other end. We can get more into that in a minute. And then around the cladding you have the buffer coating, which is a plastic coating, and that's

what that's just protection. It protects the fiber from any sort of damage. And these these glass wires are so thin that they are actually flexible. You can um use these two to to wire a a connection that requires cornering and that sort of thing. So if you're careful with it, you can actually bend this stuff without having to worry about it breaking. Now that doesn't mean that

it's unbreakable. It is breaking, but if you are careful with it, you can actually corner with this stuff, which is good because otherwise it would not be nearly as useful if you had to do a straight line to line kind of connection. Yeah, that's the whole thing with the cladding, because you know, light travels in a straight line, So if you get to a curve, what are you

gonna do? The light would just pass? Yeah, otherwise the light would just pass right out of the line and it wouldn't get to the other end, and you wouldn't have any information. Yeah. The clouding functions is sort of a imagine yourself in a tunnel if you will, that is completely surrounded, uh, like you're walking through a mirrored tunnel that you know, in this case, you would be the light source and as soon as you get to a curve, uh, you would go straight into the wall.

Bounce off the mirror and then bounce off the the opposite side again down the line, so that allows the light to continue to travel through the fiber optic line. Right.

Another way to think about is get like five friends together each uh you know, three of those friends are holding yours, and you put one of your friends at uh you know, at the other end of say um uh an obstacle course or whatever, and you set the three friends so that each one's in line of sight of the of the one person in front of them and the person behind them. So you're at the very front of the line. You can see one person. Okay,

you can see your friend. We'll call him Josh. Okay, so Josh creepy hands Clark is he's holding a mirror, all right, So you have a flashlight and you can see Josh. Now, Josh, he has a direct line of sight to you. And the next person who is Chuck awesome, and Chuck is also holding a mirror, and then uh, Chuck can see Josh and can see the person on the next step down the line, which will say is um Tyler. So Tyler's got a mirror, all right, and Tyler can see Chuck and can see Chris, who's at

the other end. I light up my flashlight aimed over at Josh creepy hands Clark, who then tilts the mirror in such a way so that the light bounces off and goes toward Chuck. Chuck aligns his mirror so that he catches that light, and it bounces off and moves toward Tyler. Tyler then manipulates his mirror so it catches the light and manipulates it toward Chris, and then Chris can see the light that I am shining, even though

we're not in a direct path. Okay, so if I turned that flashlight on and off, Chris will see the light going on and off. I could actually communicate this way if both Chris and I knew Morse code. However, since neither of us do know Morse code, or at least I don't know Morse code, I would just be babbling, uh, complete nonsense, which is okay, granted, part of the course.

But it wouldn't even spell out words. But you could if both people knew Morse code, which that's kind of the basis in a very it's a very simple, yeah, a very simplified version of what is happening in a fiber optic system. You know, there are there are two different types of UH fiber optic lines. One is the single mode, which has a small our core and it uses in a laser light, an infrared laser to transmit information. Yes, laser.

I knew you were going to do that. And the other one is the multimode fiber, which has a larger core, but it uses uh l ED s yes, a light emitting diode YES to to transmit information. And uh there there actually is a you can use a plastic chord version which also uses an LED, but it it uses the visible spectrum red light. But that you know, that doesn't seem to be nearly as common as the glass

core fiber optic lines. Now, when we're talking about things like infrared light, that's light that has a shorter wavelength than visible light. Yeah, all right, And in general, the shorter the wavelength of light, the further it will go on a fiber optic line on its own without degrading, because light signals will degrade over distance. Uh And in general, the distance that most companies use to measure a degrading

effect is the kilometer. So you say, how many you know how how much of a percentage of the light will you lose after a kilometers worth of cable. Oh, we should also mention that these these individual fiber optic threads are often bundled together in a jacket to make

a cable. So you actually have hundreds or even thousands of these fiber optic lines all bundled together, which isn't really It sounds like a lot, but if you think about it, if they're all essentially the diameter of a human hair, you can bundle thousands of these in a reasonably small cable and use that to transmit an awful lot of bandwidth. And I have to agree with Joseph, the human hair measurement is really annoying for those of us who are follically challenged. Well you know, and also

depends on the hair. In my case, it's an imaginary number, so like event twelve or like in um, but minus in diameter. But that's the thing. If if the glass inside the core of a fiber optic line is not pure enough, the signal is going to start degrading even faster um. And there is something that you can do

about that. Uh. Therefore, four parts to a fiber optic system. Um, the transmitter and the receiver, well, I mean those that would be the guy with a flashlight and the guy looking in my other very simple example, and then you get the fiber. Okay, again that makes sense. That's the actual cable. But in the cases when you have very very long connections, like I don't know, if you're trying to connect North America to South America, to use our example,

you stop. You're going to get more emails about that. I love the Canadians, I love them. You you like taunting them. I have to tell you, Okay, apart from my wife, some of the most beautiful women I've ever seen were in Toronto. That is no joke. Okay. So guys, if you're looking for like beautiful women, Toronto toe Okay. So if you were trying to hook up North America and South America were talking about hooking up to Toronto, yeah, you would need an optical regenerator, which is back to

this more or less functions, sort of like an amplifier. Yeah, it's kind of interesting, actually, an optical regenerator. The first time I saw that term, now in my mind, I thought, oh, this must be a a device in the middle of the line that interprets the light and then emits the light on its own, like you know, something that's actually receiving the light and then transmitting the same message but

with at full power. That's not exactly what's happening. What's really happening is that they introduce certain elements into the fiber optic line at a particular distance. It's called doping, all right. Now, Doping is the same sort of thing in a in a sense that you use with semiconductors that let semiconductors do what they do. It's when you insert certain impurities in a very controlled fashion to change

the behavior of that particular substance. Now, in this case, the doping creates this, uh, this material that when the laser light hits it, it energizes the material which and then emits the same light further down the line. Right. The molecules of this substance used to coade the line function as lasers. This blows my mind. It's fascinating and

it's really cool. Yeah, I mean this this was one of those things that I did not know about fiber options before I started to really research this topic for the podcast. And uh yeah, it's it's the special coding that when it absorbs the light and then emits the laser light so that you have a strong signal all the way down, so you know, periodic points along the line. You introduced this doping to make sure that the signal that you put in one end will come out the

other end. And we should go ahead and say that the receivers when they receive a light, they're essentially remember that information is in bits, right, zeros and ones. So how would you transfer light into zeros and ones? What would be the easiest way. The easiest way is to turn it on and off. There you go. If the lights flickering on and off. I mean we're talking like super fast flickering on and off, and you have a very sensitive sensor on the other end that can detect

when it's on and off. That there's your zeros and ones. And that's how you can transmit information. And you're doing it literally at the speed of light. And all you have to do is, you know, plug the cable in one end and to the other, and you don't have to worry about whether or not it's going to get there, because it's gonna get there. Yeah. Well, assuming there's no damage to the line. Yeah, exactly, careful call before you dig.

So here's some here's some other interesting information about fiber optics. Reasons why you might want fiber optics as opposed to say something like copper wire to carry your information. Copper wire, for one thing, is spensive. Copper is not as plentiful as we as we would like. So it's uh, it's it's a precious commodity really and to you know. And the other problem is that you need a lot of

it if you're going to create information lines. And then of course, you know, you have the whole mining, which is a pretty uh, pretty invasive. There's yeah, it's also that's that's the problem. Also, um it generates heat because electricity moving a current moving through a copper wire will generate heat, um but which is not a problem with optical exactly. And it also generates radio frequencies because electric

currents can create uh interference. If you're sheathing around a copper wire is too weak, you can get these radio frequencies emitted as the current is moving through the wire, which means that you can get interference if you have too many uh, too many connections all in one area, or too many wires all in one area. The the information moving through why can start causing interference the uh

for another wire. This is kind of like why you get like a let's say you have a cell phone and you receive a phone call and you happen to have that cell phone next to a speaker that has really poor sheathing. That's where you get the did did didn't noise? Where that's the interference that's coming through the speaker wire because it's generated by the cell phone. Well,

with optic fiber optics, you don't have that problem. If your cell phone goes off next to a fiber optic line, there's no interference with that fiber optic line because it's not it's not reliant upon radio frequencies. It's not gonna affect the behavior at all. Excellent also can hold hold more bandwidth than a copper line can. Yep, And so you start thinking about this like, okay, wait, it's cheaper,

it there's no interference, it can carry more information. You're not gonna lose your signal as much as you would with other forms of transmission. Um it's it doesn't require a lot of power. It's great for transmitting digital information because again you're talking about zeros and ones. Um, it's you know, it's flexible, it's lightweight. What why would a company not use fiber optics. Why would it be so slow to install fiber optics? I can tell you why.

Why Because it costs money to install that stuff and you have to send cruise back out to dig up the grass again. Bingo. So here's the here's the real issue. It's not that fiber optics aren't great or cheap or efficient.

The problem is that we already have a lot of these systems in place using older technology, and it costs a lot of money to rip all a lot of money and a lot of time to rip all that stuff out and replace it with a new system, which is why fiber optic lines are pretty still pretty rare in the United States. I mean there are different There are cities that have a very very you know, strong fiber optic presence, like the fiber optics uh from the

curb all the way to the home. But um, but I would say for the majority of the United States that's not the case. Yeah, that's that's true. Um, But it is it is an option, you know, and it's something it's starting to roll out. Yeah, I mean people

are demanding more bandwidth. So before long you're gonna have a lot of companies, a lot of sp s saying that fiber optics are definitely a good investment because otherwise, I mean, eventually you're gonna have companies say, you know what, if they're not going to provide the fiber optics to

their customers, there's an area of opportunity for us. If we move in there and we're willing to build the infrastructure that we need, we can steal all those customers away because we can provide something that the other company can't. So ultimately, I think we will be moving more to uh fiber optics infrastructure throughout the United States. UM, I still think it's gonna take a while, especially in regions where competition is practically non existent. I mean, in my neighborhood,

that's pretty much the case. You you have your choice of one major I s P or nothing, unless you want to go uh wireless with y Max, which you know, that's a totally different animal because you're not using cables at all in that case. But yeah, uh so let's I mentioned that we you know, it might be interesting to talk a little bit how about how they make fiber optic threads. I thought i'd kind of walk through them the process because it is pretty cool. Yeah it is,

and we actually have a pretty detailed right up about that. Yeah. Yeah, there's a there's a great article on how fiber optics work on how stuff Works dot com. So if you want to look into this more thoroughly and see some really cool illustrations that help you visualize what's going on, I highly recommended. All right, But first, what they start with is a gas deposition system, a modified chemical vapor deposition system m c VD. So you've got these materials

that are all in liquid format. You gasify them and you move them into a tube where they then kind of combined and cols, and you use a a it's actually in a lathe, so it turns you've got a flo aim on that lathe. And it's a fairly complicated chemical process. But you're using silicon chloride and germanium chloride and uh, eventually this forms um silicon dioxide and germanium dioxide, and then together these two chemicals form deposits within the

lathe and that ultimately is what makes the glass. Now it's not a wire yet. It's it's a sort of a cylinder of glass and it has to be basically extruded out into a long, thin fiber. Right So what they do is they put the cylinder of glass, this this very pure glass um into it's kind of like a little oven. It heats it up and it makes the end of it kind of bead up until it grows large enough for gravity to pull it downward. So then it starts to droop and it pulls hind it

a very thin thread of glass. Right now, you feed this through a very special system of of of guiding devices all the way down into a tractor what they call attractor. It's just a simple gear that will pull the thread in a very regular way, and it can actually react to how thick or thin the thread is at any particular time to make certain that you have

a uniform thickness once it gets to the end. Now, when you're putting it through these little guides, the guides help shape the wire to make sure it's the right thickness, and you use lasers to measure the thickness of that wire along the pathway to make certain that you've got the right length that those readings are what tell the tractor how quickly to turn, and they can turn pretty fast. Um. Yeah, I think it's something like sixteen thirty three revolutions per second.

I mean that's pretty fast. So it has to be pretty precise, yes, precise, in order for it to to be you know, the right diameter and the you know, the right quality of the glass, they have to be very careful how they do this. Yeah, you want the diameter to be as precise as possible so that you can use the correct wavelength of light through the fiber optic line. Otherwise, again, you're gonna have some real problems with the signal degrading UM over a shorter distance than

you had anticipated. So once you're done with this process, one cylinder of this stuff can create more than one point four miles of fiber optic thread. Because that's how we're talking about the thickness of a human hair. So, uh, taking a cylinder of glass and reducing it to that thickness, obviously the length is going to be quite impressive. And one point of our miles is that's long two point two kilometers to our friends in Europe and overseas, So um,

that's your basic rundown of fiber optics. It is a really good system for carrying information. Um. And it has other applications too. I mean it's used in in well a lot of medical applications. Um. And uh, actually I believe that my plumber, as he was trying to figure out exactly what was clogging the line U to the sewer from my house, used fiber optic line to see what was going on. As it turned out, there were roots growing in my pipes. Radical. Yeah, nice, thank you.

I was feeling a little rancid there. Apparently you were okay. So that was a reference. That was not an inside joke. I just wanted to point that out. Punk rock thing, Yeah, it is a punk rock thing. Well, hopefully that answers your question, Joseph about the fiber optics I think, um, you know, I I really enjoyed our article on the site. You know, it's excellent. It really is really good. It

really is. It's one of the stronger, stronger articles. I mean, we have a lot of great articles on the site, but this one, uh you can tell was there was a lot of care and research put into this particular aler of one. So um, I was very impressed, So yeah, definitely go and check it out if you're if you're interested in learning more about fiber objects, you can read more about the detailed process of how they build fiber

optic lines and the different uses and applications. And uh, I guess that leads us to our second round of listener mail. This listener mail comes from Timothy, who says, Hey, John and Chris, I love solving the Rubik's cube, and then it occurred to me that I had no idea how they work? Could you explain how the Rubik's cube works, especially variants like the four by four by four and the five by five by five. Love the podcast. Keep

up the good work, well, Timothy. Better than explaining how Rubik's cube works, I would like to recommend to you a podcast called The Stuff of Genius because recently The Stuff of Genius focused on er No Rubik, inventor of the Rubik's Cube, among other puzzles. Um, so check that out.

Watch that video, and uh, I think, um, you know it does and go into real strong detail about how the Rubik's cube itself works, But it does give you an indication of, you know, where Rubik was coming from when he started to design this crazy thing that ended up being a huge fad. So uh as for solving Rubik's cubes, Oh, dear lord, I was hopeless. I was one of those people who would slowly peel the stickers

off and then put them on the different faces. Yeah, well you could have been one of the people that took them apart. Yes, I've seen that too. I've seen that too. Yeah. Essentially there essentially there's a ball in the center and the center pieces are static, they don't

really move. Some pieces that move around them on channels with ball bearings in them that get get the pieces where they need to go right, And so it's just the four by four by four and the five by five by five that was just a larger ball with more ball bearings in it, and that's pretty neat. Yeah. I've actually seen a really cool video about how to solve a Rubik's cube and it talks about the algorithms have to follow. Yeah, there's actually several algorithms. Um, Yeah,

there's several, depending on you have. You have several that you follow in order to get certain squares in certain locations. And if you follow that series of algorithms, then you will always be able to solve the Rubik's cube. Now, Grant, the way the guy was flipping this Rubik's cube around his hands was like, I was like, you need to go slower for the liberal arts majors in the audience. No, I'm a liberal. I was a liberal arts major to saying that, as you know, slow down people. I don't

think in three dimensions. I've said this before. Personally, I find it puzzling. Ha ha. Well, he's quite the enigma, Mr Pilette. So we're going to wrap this up now. If any of you have any email that you would like to send us, our address is tech stuff at how stuff boards dot com. Remember we have a live show every Tuesday one pm. That is, you can find the link to that on our blog. Which if you want to find a blog, where would they go to on the blog, Chris, that would be blogs dot how

stuff works dot com. Right, that is the direct U r. L. I always tell people just to go to houstof works dot com and follow the links on the right hand side. But if you want to go straight there, blogs dot how stuff works dot com. Well, and you can also check out all the other blogs that are here, not just ours. Yeah, there's some good ones. There are people

who write stuff, and that's good. If you're you know, if you're into good stuff, you know there there are lots and lots of really good blogs on there, so check it out. If you haven't stopped by, give it

a try. I think you might enjoy it. If you don't, you can write to Stuff podcast at the house stuff Works dot com and Chris and I will talk to you again really soon for more on this and thousands of other topics how stuff works dot com, and be sure to check out the new tech Stuff blog now on the House stuff Works homepage, brought to you by the reinvented two thousand twelve cameras. It's ready, are you