Fiber

Pop quiz: Fiber optic LAN and WAN cable basics

Take this quick pop quiz and test your knowledge of fiber optic cabling concepts, such as cable safety, attenuation, splicing, and cable testing.

Although copper still dominates most office LANs, fiber optic cable forms the backbone of many networks. And as prices drop, fiber is gaining popularity for applications once restricted to copper cable.

With these trends in mind, I thought I put together a quick pop quiz on the basics of fiber optic LAN and WAN cabling basics. The quiz covers safety, cable types, common light sources, attenuation, splicing, and cable testing.

I realize this quiz barely scratches the surface of fiber cabling knowledge. Indeed, entire books have been written on designing, building, and managing fiber optic networks. My goal with this quiz is to give you a brief introduction to several important fiber optic cabling concepts.

Note: Unfortunately, our poll tool, which I use to create each pop quiz, doesn't let me indicate a correct answer after each question. To keep from giving away the answers before everyone has a chance to test his/her knowledge, and ruining all the fun, I'm going to hold off posting the answers until later. Update: The answers for my Fiber optic LAN and WAN cable basics pop quiz are now available. If you haven't had a chance to take the quiz, I encourage you to try your luck, before reading the answers.

More TechRepublic resources on fiber optic cabling:

About

Bill Detwiler is Managing Editor of TechRepublic and Tech Pro Research and the host of Cracking Open, CNET and TechRepublic's popular online show. Prior to joining TechRepublic in 2000, Bill was an IT manager, database administrator, and desktop supp...

39 comments
NI70
NI70

Answers would have been nice, but I see you're going to post next week. Had to comment this thread just to get an alert when new posts are added. Not having worked with fiber, I think I did pretty well, may have gotten one or two wrong.

Adrian Watts
Adrian Watts

got all ten right according to the polls and all i know about fibre is what i picked up studying ccna material at uni 6 years ago. weird thing is question 6 "What type of coupling loss occurs..." i know i picked the 40% answer as i had to figure that one out from physics 101 but it was detected as Angluar misalignment. i wonder if that might have something to do with the spread on that question. other than that interesting questions.

337
337

Wicked did better than i expected looks like i got two wrong :-) And it's been ten years or more lol can be happy.

ScarF
ScarF

Hm. Not paying attention when reading this question, made me give the wrong answer - although a key may be the fact that all the answers are correct for attenuation. I'm never learning to read the entire question. Thanks Bill for this nice quiz.

LvTravel
LvTravel

This was an awesome quiz! A little bit of fiber 101. I'll be happy to see the answers when you get them posted.

rvroberts
rvroberts

Pretty good quiz, will be interesting to know what the correct answers are going to be.

oldbaritone
oldbaritone

Fiber is the ONLY way to go between buildings! No problems with ESD or transients. No problems with mismatched grounds. Get a pair of media converters (cheep-cheep on ebay!) and do copper everywhere except between buildings. Piece of cake, easy, safe, not buggy.

Darren B - KC
Darren B - KC

I know that you're not supposed to look at laser light directly, but I've never seen a working fiber optic cable emit a noticable amount of light. I'm not talking about the ones in the ground, I mean the ones that we connect between gigabit switches in our building. Right now, I have to turn off all the lights in the server room so that it is COMPLETELY dark... and even then the light coming out of the connector is barely visible. Why is that? Is it supposed to be really bright?

geoamyk
geoamyk

Ok. Now I want the answers!

Brian.Latta
Brian.Latta

We use Allied Telesyn transceivers to convert 100Mb full duplex ethernet to multimode fiber, and connect individual workstations to the LAN. This allows us to connect deivices up to 2 KM from the switch. It is in use in a large industrial site. The side benefit is it is immune to elecrto-magnetic interference.

Bill Detwiler
Bill Detwiler

Although copper still dominates most office LANs, fiber optic cable forms the backbone of many networks. And as prices drop, fiber is gaining popularity for applications once restricted to copper cable. Take our quiz on the fiber optic cabling concepts: http://blogs.techrepublic.com.com/itdojo/?p=1489 And, let me know how you're using fiber in your networks.

Bill Detwiler
Bill Detwiler

Thanks for the feedback. What other IT topics would you like to see me develop quizzes for?

Bill Detwiler
Bill Detwiler

Thanks for the compliment. I'll post the answers (explanations included) in a new post next week. I'll update this discussion thread and the original post with a link to the new post.

Bill Detwiler
Bill Detwiler

I'm glad you liked the quiz, I'll post the answers (explanations included) in a new post next week. I'll update this discussion thread and the original post with a link to the new post.

Dr Dij
Dr Dij

your two buildings are a couple blocks apart, separated by public streets, who, inconveniently, won' let you you run a backhoe down them. we ran microwave tower (had to get clearance frequency search mil base nearby)

peter
peter

No emp problems:)

johnm
johnm

We had to go with a wireless bridge to the campus stadium (about 200 yards line-of-sight) when the cost of trenching for either fiber or copper would have been more than the campus could afford. It was a lot longer distance to trench because they didn't want to dig across the running track or the football field. The wireless has been fairly reliable but has nowhere near the bandwidth of a fiber or copper connection.

dalentn
dalentn

I had to connect 2 buildings approx 1 km apart for a short term (~1 yr). The cost was very high so I went with a focused wireless transmission. It worked perfectly and was easy to dismantle at the end of the project.

Bill Detwiler
Bill Detwiler

As usual, our members were on the spot with great answers to this question. Many thanks to all those who chipped in.

Brian.Latta
Brian.Latta

The wavelength of light used in fibre optics is not visible to the human eye. It can permanently damage your retina. see the posting at: http://www.thefoa.org/tech/wavelength.htm Some inspection scope utilize a filter to let through the visble wavelenght but block the damaging higher wavelength. But it is never a good idea to look directly into an active fiber optic cable.

Bill Detwiler
Bill Detwiler

I'll post the answers (explanations included) in a new post next week. I'll update this discussion thread and the original post with a link to the new post.

mgottberg
mgottberg

In our public school, a small K-12 school in rural southern Minnesota, we have about 90+% of our building as fiber to the desktop. We currently have (the now dead standard) 3M volition product line. We are looking for a new electronic product line. Any suggestions? Have looked at Transition Network (Milan) - also looking at HP Procurve and Cisco both kind of out of our price range. Any ideas/suggestion would be greatly appreciated

Brooks Fancher
Brooks Fancher

We only use it for MetroE. My backbone is run over copper since everything is in one room and everything is within 10 feet of the switch.

dmmillr1
dmmillr1

we have a fiber backbone from building to building and use it in a few facilities for the main backbone. I have copper mirroring the in building runs as a failsafe

DMambo
DMambo

We use fiber to run from our WAN demarc to our 3 IDF's in our single building that's like a maze because it's had many additions over the years. The only problem I have had with it in almost ten years was when a mouse ate through one of the cables near the connector. I know it was a mouse because I saw the little bast@rd when I opened the enclosure to investigate the problem. I got him the next day! Thanks, DCon! As far as the quiz goes, I don't know if I got the answers right, but I got all but one of the most popular answers!

FAST!!!
FAST!!!

At least that's what my wife keeps telling me... Seriously, who doesn't use fiber in todays networks. We have a lot of temporary fiber runs installed to construction trailers setup around the perimeter of our buildings. Lightning strikes are the primary reason for this. Keeps people and equipment safe.

Mohammad Oweis
Mohammad Oweis

We use it as a backbone to connect all switches to the core switch, and to connect buildings together, specially in the factories where buildings are very far from each other and there is a high voltage cables on the way.

Chris_Muncy
Chris_Muncy

We use it to interconnect buildings and ago around electrically noisy environments. Its too easy now not to ignore using fiber in your infrastructure.

darpoke
darpoke

I'd be keen to also see quizzes on subjects like: -Network security/SSL -Domains, routing and firewalls -IPv6 -RAID -VMs -UNIX command line admin -Software binaries + compilation It's actually nice to see a quiz, as opposed to an opinion poll. Difference being, you can post answers to one! Good call.

Zeppo9191
Zeppo9191

If the majority is any indication, I got all of them right. Of course, it's entirely possible that the majority is incorrect... Thanks, Bill - having never worked with fiber, I hope I learned something.

al
al

Horizontal drilling and bad weather (heavy snow) changed our minds about the use of wireless between buildings (875 yards). We were able to pull multi-core fiber, a multi-line copper, and some specialty "cables" through the 1.5" tube put in by the drillers. Worked great, went under several locations akin to your football field, and cost far less in both money and recovery time of the disturbed ground than a trench.

whopper
whopper

I agree it is a very bad idea to look into a fiber, especially if you don't absolutely know what is on the other end of it. I have been told that it is much more dangerous to look into a single-mode fiber than into a multi-mode. The reasoning was that multi-mode transmitters were usually lower-power such as LED and were often visible while single-mode transmitters were usually of much higher power and were outside the visual spectrum. Any comment from someone wh actually knows about this?

337
337

Especially since things have improved so much since i first learnt it woosh and the prices. Even at home i want to give it a go because i'm wanting to run radio gear near computers cat5 ethernet causes birdies at a lot of frequencies. Dam nuisance having clock pulses and whatever ripping through. I'm guessing utilising fibre will help reduce spurious in that case. Pity about the PC itself lol :-) And not forgeting crosstalk with cable trays etc full of cat5 which you mentioned that and dud copper in the cat5-6 TP had some batches like that (resistivity to high). The joys of cabling.

Darren B - KC
Darren B - KC

I should clarify my original statement and say that even in a dark room, I'm not looking into the ends of the connectors dead on, but rather at an angle just to see if the plastic on the very tip of the connector is illuminated at all. Sometimes they are, but most of the time they are not. However, in 99% of the cases where there's no illumination, there's also no signal. (Broken cable or a bad GBIC.) On the up side, I don't work with fiber that terribly often. Our network is relatively small and doesn't go through very many changes. On the down side, I work for a company that is unwilling to spend money on fiber test equipment, so when we DO have to work with fiber, there's a lot of trial-and-error going on.

peter
peter

Singelmode fibres operate at a higher frequency than multimode and are more energetic (e=hf where e is energy h is Plank's constant and f is frequency). The light produced from a singlemode source is synchronous and contained in a very tight angular range - the power density from a single mode source will typically be much higher than that from a non synchronous source like a led. It's a good idea never to look directly at a laser output. Note that a led is not a laser and transmits omnidirectionally - concentrate the light and send it down a fiber and the power density can still be enough to damage your eyes. There are better ways to tell if it's night or day than trying to stare directly at the sun.

Brian.Latta
Brian.Latta

Multi mode generally uses LED emitters with 850nm or 1300nm wavelength. Single mode uses 1310nm or 1490-1625nm laser emiiter. Hard to descibe in words but the basics are the Laser produces a far brighter light with a narrrower bandwidth ( turns on quicker and gets brighter ) so produces more punch.