-: Fiber media. 2 2
The next type of cable we need to talk about 3 3
is fiber optic cables. 4 4
Now fiber optic cables are going to use light 5 5
from an LED, a light emitting diode, 6 6
or a laser to transmit information 7 7
through a thin piece of glass fiber. 8 8
Now fiber optic cables are great because they're immune 9 9
to electromagnetic interference, or EMI, 10 10
because there's no electricity involved 11 11
in the data transmission as it's going down that cable. 12 12
Also because we're using light instead of electricity, 13 13
our signal can go an extremely long distance 14 14
without much attenuation or signal loss. 15 15
Whereas our copper cables, 16 16
specifically cat 3 through cat 7, 17 17
could only go about 100 meters, 18 18
fiber optic cables can go hundreds of meters, 19 19
or even hundreds of miles. 20 20
After all, we have some really long fiber optic cables 21 21
that are sitting on the ocean floor 22 22
between the United States and Europe, 23 23
and that is a huge distance all the way across the Atlantic. 24 24
Now, this is one of the biggest benefits 25 25
of fiber optic cables. 26 26
It can cover an expansive range and longer distances. 27 27
In addition to that, 28 28
we can turn the light on and off very quickly 29 29
adding to higher beam with applications by using fiber. 30 30
If you remember from our copper media discussions, 31 31
we were talking in terms of 10 megabits per second, 32 32
100 megabits per second, one gigabit per second, 33 33
10 gigabits per second, and things like that. 34 34
But now that we've moved on to fiber, 35 35
we can start talking about things 36 36
in the terabits per second range. 37 37
In fact, all the way back in 2012, 38 38
the Japanese telecommunications company NTT 39 39
was able to send data at one petabit per second. 40 40
Now that is really, really fast. 41 41
And so fiber is starting to be used 42 42
in a lot of extremely fast networks. 43 43
And it's usually not the fiber cable 44 44
that becomes your limitation in the network anymore, 45 45
instead, it's your other networking equipment, 46 46
things like your switches, 47 47
and your routers, and your end user devices, 48 48
they just can't keep up. 49 49
And so for this reason, 50 50
most business class networks 51 51
are still going to use fiber around 10 gigabits per second, 52 52
because of those switches and routers. 53 53
But this is more of a cost benefit decision 54 54
than a technical limitation of the fiber cables themselves. 55 55
So if fiber is so great with a huge expensive range, 56 56
and super high speeds, 57 57
there's got to be some drawbacks, right? 58 58
Why isn't everyone using fiber? 59 59
Well, we really do have two main drawbacks with fiber. 60 60
First, fiber is expensive. 61 61
Now, the price of fiber continues to drop, 62 62
and it has year over year, 63 63
but it's still much more expensive than a copper network. 64 64
For this reason, most businesses only use fiber 65 65
to connect backbones of their networks 66 66
to their edge switches, 67 67
or they're going to use fiber 68 68
if they need to cover a large distance 69 69
that they can't cover with copper. 70 70
Second, fiber is more difficult to work with than copper. 71 71
In fact, when I teach network plus in the classroom, 72 72
I teach my students how to build their own Cat 5e cables. 73 73
Now for less than $10, I can give each student a crimper, 74 74
a set of connectors, and a cable tester, 75 75
and they can take it home with them, 76 76
and they can do it in about 10 minutes 77 77
to learn how to build their own cables. 78 78
It's really easy. 79 79
Now, fiber on the other hand 80 80
is much more difficult to work with, 81 81
and it requires special tools and training 82 82
to learn how to make those fiber cables, 83 83
or to repair broken fiber cables. 84 84
In my experience, 85 85
it costs about five to 10 times more to run a fiber cable 86 86
than it does to run a copper cable 87 87
inside an office building, or between office buildings. 88 88
Now, even with the drawbacks, and expense, 89 89
and difficulty of working with fiber optic cables, 90 90
fiber optics definitely have a place 91 91
in most enterprise networks. 92 92
And so we need to spend some time 93 93
going over the different types of fiber optic cables 94 94
that you may come across. 95 95
First, we need to categorize our fiber optic cables, 96 96
and we do this as either single-mode fibers, 97 97
or multi-mode fibers. 98 98
Now single mode fibers, or SMF, 99 99
is a type of fiber optic cable 100 100
that carries a single beam of light directly 101 101
from one end of the cable to the other end of the cable. 102 102
To achieve this, 103 103
a single mode fiber has a smaller and thinner core 104 104
than does a multimode fiber. 105 105
Now, single mode fiber 106 106
is used for long distance communications 107 107
due to its smaller core size 108 108
of 8.3 to 10 microns in diameter. 109 109
This smaller core size allows 110 110
for a more precise signal transmission 111 111
over a longer distance 112 112
because it forces the light to travel along a single path 113 113
down the center of that cable 114 114
without being dispersed around. 115 115
Now, if you see workers with a large roll 116 116
of fiber optic cable in your neighborhood, 117 117
this is usually going to be a single mode fiber, 118 118
and they're going to be able to cover a long distance 119 119
from their internet service providers facility 120 120
all the way into your neighborhood, 121 121
and that's why they do it. 122 122
The second type of fiber we have 123 123
is known as multimode fiber, or MMF. 124 124
Now multimode fiber is a type of fiber optic cable 125 125
that carries a beam of light 126 126
as it's data transmission medium, 127 127
just like a single mode fiber, 128 128
but it uses a thicker core size. 129 129
Now multimode fiber cores 130 130
are between 50 to 100 microns in diameter. 131 131
This makes them about 6 to 10 times larger 132 132
than a single mode fiber's core. 133 133
Now 50 to 100 microns might sound pretty small, 134 134
and it is, relatively, 135 135
I mean, an average human is only about 70 microns 136 136
in diameter, 137 137
this is still an increased core size 138 138
over the size of a single mode fiber, 139 139
and it allows light to start bouncing around and refracting 140 140
as it's traveling down the cable. 141 141
Due to this, multimode fiber 142 142
is usually going to be used in shorter distances, 143 143
up to around two kilometers or less in size, 144 144
and that's about a mile in distance. 145 145
Now multimode fibers are commonly used in the same place 146 146
you're going to normally use a copper patch cable. 147 147
For example, if you're going to be using a multimode fiber 148 148
to connect a router to a switch, 149 149
or a switch to a switch, or switches to servers, 150 150
any place you'd normally use a patch cable, 151 151
or even a cable run between your patch cable 152 152
and your wall jack, 153 153
could be a place you use a multimode fiber instead. 154 154
For the exam, you do not need to memorize the exact size 155 155
of the cores for single-mode or multi-mode fibers, 156 156
they're not going to ask you that. 157 157
Instead, you need to remember the multi-mode fibers 158 158
are going to have a larger core size, 159 159
and therefore they cannot cover longer distances 160 160
the way a single mode fiber can. 161 161
If you need to pick out a cable to cover a longer distance, 162 162
you want to make sure you're selecting a single mode fiber. 163 163
Remember, single mode fibers have a much smaller core size, 164 164
and therefore light can only travel in one direction 165 165
down that cable. 166 166
When you have a multimode fiber, 167 167
the light can bounce around more 168 168
because of the larger core size, 169 169
and therefore, you're going to have less distance 170 170
with multimode fiber because you have more noise. 171 171
This means multimode fibers tend to be less expensive 172 172
to build and buy, 173 173
and they're cheaper to install than a single mode fiber. 174 174
So a lot of network designers 175 175
will actually implement solutions 176 176
that use multi-mode fibers over single mode fibers 177 177
whenever possible. 178 178
And to do that, they'll make sure they have lower distances. 179 179
So maybe they'll go 500 meters between switches, 180 180
instead of two kilometers per switch. 181 181
Now, if you happen to be working in the field, 182 182
and you're trying to identify a cable 183 183
as either a single mode or a multi-mode fiber, 184 184
the easiest way to do this 185 185
is by simply looking at the color of the cable. 186 186
If the cable has a yellow sheath on it, 187 187
it's a single mode fiber, or SMF cable, 188 188
if the cable is an aqua blue or orange color sheath, 189 189
it means it's a multimode fiber, or MMF cable. 190 190
Now, regardless of whether you use single mode or multimode, 191 191
you still have to terminate these cables 192 192
with some kind of a connector, 193 193
so you can plug them in your devices. 194 194
Now, there's going to be four different connector types 195 195
that you're going to come across, 196 196
SC, ST, LC, and MTRJ. 197 197
For the exam, you need to be able to visually identify 198 198
each of these connectors. 199 199
If I showed you a picture of one, 200 200
you need to be able to describe it, 201 201
and pick it out on the exam. 202 202
So how are you going to remember which one is which? 203 203
Well, don't worry, 204 204
I got some memory aids to help you with this, 205 205
and make sure you get it right on the exam. 206 206
First, let's look at SC, 207 207
which stands for subscriber connector. 208 208
Now SC is fairly popular because they're low cost, 209 209
they're durable, and they're easy to install. 210 210
Some people call these the square connector, 211 211
or the standard connector. 212 212
But personally, 213 213
I like to call it the stick and click connector 214 214
'cause it helps remember what it looks like on exam day. 215 215
Now, when you look at an SC, or a stick and click connector, 216 216
you're going to see a little ridge on the top of it, 217 217
a lot like an RJ45 connector. 218 218
And when you push the SC into a network jack or wall jack, 219 219
you're going to hear a little click 220 220
that tells you it's inserted properly. 221 221
Now this is why I call it the stick and click, 222 222
because you stick it into the jack, 223 223
and you hear the click. 224 224
With SC, you're usually going to see 225 225
two cables bundled together, 226 226
each one with its own SC connector on it, 227 227
and that way you can plug them into the jack. 228 228
Each of these cables is going to be used for transmitting, 229 229
or receiving the data. 230 230
So to transmit and receive, you need two cables. 231 231
Next, we have an ST, or straight tip connector. 232 232
Now the ST connector is also relatively low cost, 233 233
and easy to use. 234 234
The ST is one of the older types of fiber characters we have 235 235
and just like SC, it has a transmit and receive cable, 236 236
each with its own ST connector on it. 237 237
I like to call the ST connectors, 238 238
the stick and twist connector, 239 239
because you're going to insert it into the jack, 240 240
and then turn it about half a turn to the right 241 241
until it locks in place, 242 242
like a BNC connector does with a copper network. 243 243
Now, you're not going to hear a click like an SC connector, 244 244
but you are going to stick it in place, 245 245
and twist it until it locks and stops turning. 246 246
Third, we have an LC, or lucent connector. 247 247
This is a newer and smaller version of an SC connector. 248 248
Like the SC connector, 249 249
it does use a stick and click connection to the jack. 250 250
Now to remember the LC connector, 251 251
instead of the SC connector, 252 252
I like to call this the love connector. 253 253
This is because you're almost always going to find 254 254
the LC connector 255 255
with its transmit and receive sides attached side-by-side, 256 256
like lovers. 257 257
You can actually place them together and they lock together. 258 258
Whereas the SC is often found as two individual cables, 259 259
the LC, or love connector, is almost always married together 260 260
and they're coupled up right next to each other. 261 261
Fourth, we have the MTRJ, 262 262
or mechanical transfer registered jack. 263 263
MTRJ is a fiber optic cable connector 264 264
that's very popular and widely used with networking devices 265 265
because it has a smaller form factor. 266 266
It's much smaller than the other three we talked about. 267 267
Each MTRJ connector is going to have both the transmit 268 268
and receive pins terminated 269 269
inside a single plastic connector. 270 270
And this is about half the size 271 271
of an SC, ST, or LC connector. 272 272
This means that by using an MTRJ, 273 273
you can have a switch that fits 24 fiber ports 274 274
in the same chassis size 275 275
as a regular RJ45 24 port copper switch, 276 276
whereas with ST, SC, or LC, 277 277
you'd only be able to get about 12 switch ports in there. 278 278
Now, often you're going to see MTRJ used on fiber switches, 279 279
and they're going to connect 280 280
to fiber patch distribution panels on one side, 281 281
and the other side, will convert it to SC, ST, or LC, 282 282
for distribution out to a wall jack into an office. 283 283
Now remember, all of these cables are fiber, 284 284
and they're all made of glass. 285 285
And when we connect these cables to the connectors, 286 286
these connectors have two different styles 287 287
that we can contact with those jacks. 288 288
The main difference between these two styles 289 289
is how the fibers end face looks. 290 290
Now, what are these two options? 291 291
Well, they're APC, and UPC. 292 292
First, we have APC, the angled physical contact connector. 293 293
With APC, the fiber end face 294 294
is posed at an eight degree angle. 295 295
This angled face means that the reflected light 296 296
is going to reflected at an angle 297 297
into the clouding of the cable, 298 298
instead of straight back down towards the source of light. 299 299
This provides a better overall signal with less noise. 300 300
Next, we have UPC, or the ultra physical contact connector. 301 301
With UPC, the fiber end face is posed with no angling, 302 302
and instead it has more of a curvature to it 303 303
for better core alignment 304 304
when it goes and gets plugged into a jack. 305 305
Because of this lack of an angle, 306 306
reflected light is going to be reflected straight back down 307 307
towards the light source, and it creates more noise., 308 308
and this causes a bit of signal loss 309 309
over a regular APC connector. 310 310
In general, you're going to see SC connectors 311 311
like to use APC more, while MTRJ tends to use UPC more. 312 312
If you're working in the field, 313 313
and trying to identify a connector as either APC or UPC, 314 314
the easiest way of doing that 315 315
is by looking at the color on the connector. 316 316
If the connector is green, it's APC, 317 317
if the connector is blue, it's UPC. 318 318
Now, the final thing we need to discuss 319 319
is wavelength division multiplexing technologies, 320 320
and these are used with fiber optic cables 321 321
to get more things going over the same line. 322 322
Now, because fiber optics originally used a single light 323 323
to send data down a single fiber core, 324 324
we can only send one zero or one one at a time. 325 325
When the light was on, we got a one, 326 326
when we had it off, we got a zero. 327 327
And so we were sending one bit at a time, 328 328
but we could turn it on and off very fast. 329 329
Now, we also couldn't send or receive things 330 330
over the same cable. 331 331
So we had to have a dedicated cable for sending, 332 332
and another one for receiving, 333 333
otherwise, the light wouldn't be able to tell 334 334
who is sending and who's receiving, 335 335
and we would just see the single light being on or off 336 336
over that single strand of fiber. 337 337
Well, to solve this issue, 338 338
wavelength division multiplexing was created. 339 339
Now, wavelength division multiplexing, or WDM, 340 340
is a technology that allows multiple signals 341 341
to be combined into one signal, 342 342
and then sent over a single fiber optic strand 343 343
using different wavelengths for the laser light source. 344 344
Now, by doing this, 345 345
bi-directional communications over a single strand 346 346
can be accomplished, 347 347
as well as an increase in bandwidth and capacity. 348 348
Now at its core, WDM systems use a multiplexer 349 349
at the transmitter to join several light signals together, 350 350
and then it sends it across the fiber. 351 351
When it gets to the other side, 352 352
it's going to use a demultiplexer at the receiver 353 353
to split that signal back out into the multiple signals. 354 354
Most wavelength division multiplexing 355 355
is run over single mode fibers, 356 356
but there are a few types of WDM 357 357
that can run over multimode as well. 358 358
Now, there are two main types of WDM 359 359
that we need to talk about, namely, CWDM and DWDM. 360 360
The first type is CWDM, 361 361
and this stands for coarse wavelength division multiplexing. 362 362
Coarse wavelength division multiplexing 363 363
can support up to 18 wavelength channels being transmitted 364 364
over a single fiber. 365 365
To achieve this, 366 366
each of these wavelengths is set 20 nanometers apart 367 367
on their own channel. 368 368
Now, CWDM is used mainly in shorter distance applications 369 369
up to about 70 kilometers. 370 370
Now, if you're going to be above 40 kilometers, 371 371
but under 70 kilometers, 372 372
you can only support 8 of those 18 channels 373 373
because the longer distance you go, 374 374
the more the light starts spreading out, 375 375
and it causes noise over the channels, 376 376
so you need more separation. 377 377
Now, CWDM does support speeds 378 378
up to 10 gigabits per second for ethernet, 379 379
and up to 16 gigabits per second 380 380
for fiber channel installations. 381 381
CWDM is sometimes used to connect routers and switches 382 382
using GBIC or SFF transceivers, 383 383
to connect switches and routers over longer distances 384 384
then you could using a copper cable. 385 385
The second type we have is DWDM, 386 386
and this stands for dense wavelength division multiplexing. 387 387
Now it's called D for dense, because we have DWDM, 388 388
that's used to support 80 wavelength channels, 389 389
all being transmitted simultaneously over a single fiber, 390 390
that's right, eight zero, 80, 391 391
instead of one eight, 18. 392 392
Now each of these wavelengths 393 393
is set on a channel only 0.8 nanometers apart, 394 394
and this makes them very dense 395 395
because we don't have 20 nanometers of separation 396 396
like we did with coarse, 397 397
instead we have 0.8 nanometers, 398 398
and that's why we call it dense, 399 399
dense wavelength division multiplexing 400 400
because of the denseness and closeness of these channels. 401 401
Now, DWDM is used to transport data 402 402
over much longer distances 403 403
because these connections can also be amplified 404 404
as we're going across the cable. 405 405
Now, since there are more channels being used, 406 406
DWDM can handle a lot higher speeds as well, 407 407
with top speeds of up to 100 gigabits per second 408 408
per channel, 409 409
and remember, DWDM can handle up to 80 channels, 410 410
therefore, we can have a maximum theoretical speed 411 411
of up to eight terabits per second, over a single cable. 412 412
So where might you find yourself using DWDM? 413 413
Well, if you work for a major internet service provider, 414 414
or a telecommunication service provider, 415 415
you may find yourself working with this type of equipment, 416 416
but you're not going to find it 417 417
in your traditional small office, home office, 418 418
or even corporate office environments. 419 419
These types of solutions are extremely expensive. 420 420
And so they're mainly used as part of the internet backbone 421 421
for large service providers who are running SONET systems. 422 422
For most of us though, 423 423
we're going to be limited to using CWDM, 424 424
which comes embedded into some of our switches and routers 425 425
when we're using fiber for our tracking pass, 426 426
or our connections between devices.