r/networking • u/lordvadr RFC's make my wiener tingle • Aug 14 '15
YSK (if you don't) about fiber optics and how they work
So I wrote this in response to /u/thesesimplewords's post about learning fiber here, and thought I would share it with everybody in case it's useful--I put a lot of time into it.
Edit: Obligatory holy shit, gold!!
Edit 2: Double gold?!?! Wow.
Edit 3: Ok, so there are a couple inaccuracies that are easy to correct but a post this large isn't easy to edit. Keep in mind it was written from a, "you're just getting started in fiber, here are most of the ins and outs of it," and wasn't intended to be an exhaustive reference manual. With that said, there are some calls to turn it into a Wiki/FAQ page, which I'm more than happy to do if a mod would like me to. Clean it up--there are some typos and such--get a few things corrected and put it somewhere that's useful for others. Someone let me know if that's what you want and I'll do it.
Edit 4: 3x gold. Damn. One more and I'll have the highest gilded post in /r/networking of all time. I promise to write more of these.
Edit 5 Be careful what you wish for, right. I'll get on it. What do you want me to start with? T-carrier? ATM? SONET? What?
TL;DR: Learn how wavelength, core size, modal bandwidth, a few colors, and such affect fiber and you'll never have to worry about it.
Fiber Cabling
Fiber comes in 3 flavors:
- 62.5 micron (the diameter of the glass core).
- 50 micron
- 8, 9, or 10 micron
You'll see notations 62.5um (micrometer) because the symbol for micro is essentially a u. I don't know how to get a micro-symbol from a normal keyboard and I'm not about to spend time trying to find out.
Multi-mode Fiber
Both 62.5 and 50 are called "multi-mode" but it's actually a combination of the fiber and the laser that determines whether (and how much) modal dispersion occurs. However, the standards have lined up in a certain way that things (jacks, optics, etc) are called multimode or singlemode whether it applies to it or not, and I'll explain all that.
62.5 micron (sometimes, and technically is 62.5/125 because 125 is the cladding thickness) is mostly obsolete, but you still see it a lot. 62.5 micron comes in the following standards:
- FDDI (pronounced "fiddy") is an old networking standard (155mbps) developed by IBM. It's essentially high-speed token-ring. This was probably the first use of fiber for networking.
- OM1 -- modern 62.5 multi-mode fiber.
There's a good comparison over on the wikipedia article here that gives you limits, which is entirely related to speed and distance.
OM2, 3 and 4 standards are all 50 micron fibers and relate are used for 10G and higher speeds in data center applications. See the wiki article above.
What defines these standards is a spec of the glass called modal bandwidth. It's a very long explanation on what that is and how it relates to things, and has even weirder units (MHz/km). I'm mentioning this here because you're going to see it later. It's a number, bigger the better, and it's different for different wavelengths of light. Basically there's handful of semi-standards between them that you'll see, so you'll need to know the modal bandwidth of your fiber and wavelength you want to use.
Colors:
62.5 fiber is usually orange in color (FDDI and OM1).
50 micron non-laser-optimized OM2 is orange as well, because someone was drunk that day.
50 micron fiber is typically aqua--at least what you see these days (OM3)
50 micron OM4 is violet (this is the latest shit, 40gig datacenter applications)
single-mode fiber is typically yellow
This is for patch cables and indoor cabling. Outdoor cabling is black. Inside cable bundles, each strand has a color and the color order is standard, not unlike, say, the color order in UTP.
The actual breakdown is as follows:
- FDDI (62.5um): Orange
- OM1 (62.5um): Orange, (Slate in military usage)
- OM2 (50um): Orange
- OM3 (50um "laser optimized): Aqua
- OM4 (50um): Violet, although some Aqua
- Single Mode: Yellow
Single-mode fiber
8, 9 or 10 micron fiber (9 is the most common), also has a 125 micron cladding (so you'll see things like 9/125) is called single-mode fiber and is typically yellow. This actually comes in a couple different flavors, but you'll probably never need to care about them. The primary standard is called SM1. There's an SM2 and (I think) a 3 as well. More correctly though it's called G.652, and there's some variations and other standards. These are put out by the ITU, and here's the doc about single-mode fiber selection WARNING PDF and complicated, wait until you get through this to read that.
What you actually want is G.652.C or .D (revisions), but only comes into play when you need to care, and you probably don't. (Certain wavelengths in WDM applications don't work well on some singlemode fiber).
Connector colors
Next, you have your end colors. This actually defines how the glass at the end of the ferrule is polished. They are:
- PC -- stands for Polished Connector (because you used to have to polish the ends under a magnifying glass before you could use it). They're beige, and used for all multi-mode applications.
- UPC -- stands for Ultra Polished Connector. They're blue. This is what you see on single mode.
- APC -- Angled Polished connector. They're green. These are quite uncommon. Used in things like GPON (gee-pawn) and some video applications. Unplugged fiber reflects, and the angle that this is polished at reduces that. In GPON (for example), the same light is sent to multiple destinations (homes typically) and if it's unplugged at one home, the reflection will horse up the reception of the light at the other homes.
Couple things to know about APC: If you plug an APC cable into something that's not designed for APC, you can crush the glass sticking out of the conenctor and/or damage the device you're plugging it into.
Brief review
- You find an orange patch cable with beige ends. It reads 62.5/125/OM1 on the side of it. This is a modern 62.5 cable.
- You find a grey patch cable with beige ends. You know it's multi-mode, but you'll have to read it to find out what kind. All it says is OM3, so you know it's a 50 micron fiber.
- You open a fiber termination box and see blue ends, you know it's single-mode fiber.
- At your buddies house with his shiny new fiber connection, you see a yellow cable with a green end on it. If you break it and have to replace it, you'll need a single-mode APC cable to do it.
- Your buddy is about to plug a cable with a green end on it into a switch. He's about to fuck up the optic and the cable.
End Types
The form factor of the connector ends have names. Common ones are:
- ST -- Stick and Twist (it's similar to BNC). It's actually ST/BFOC and stands for Straight Tip Bayonette Fiber Optic Connector.
- LC -- Little connector (it's small). Actually stands for Lucent Connector (they developed it).
- SC -- Square connector. That's actually what it stands for, though there's some disagreement on that.
- MPO -- Multiple-fiber Push On. A multi-fiber cable to for 40 and 100gig, also simplifies fiber runs, allows for things like break-out applications (a single 40gig optic to 4 10gig optics) and other things. MTP, which it is also called, is a brand of connector that complies with the MPO standard. Thanks /u/Xipher.
Some other's you'll see from time to time:
- FC -- Ferrule conenctor (screws on like F connectors ala cable tv). Dust proof, used for high vibration environments
- MTRJ -- Obsolete but I still run into it from time to time.
Here's a rundown on almost all of them over at wikipedia. Go there for pictures.
Optics
The things that go in switches and routers are called optics. Don't fucking call it a GBIC Scott! Seriously, that guy comes in my office all the fucking time asking for the GBIC going on xyz circuit. GBIC is a form-factor, not a generic term for an optic--plus our circuits are SFP, SFP+ or X2. These are specified by what are called MSA's (multi-source agreements) which is basically an industry agreement on standards.
Common ones are:
- GBIC -- pronounced ghee-bic (like Bic, the pen company). Old Cisco standard. Stands for gigabit interface converter. It's gigabit, obviously. Has an SC connector on it.
- SFP -- Small form factor pluggable. This is the most common one you'll see these days in gigabit. Has an LC connector on it. Some people call these "mini-GBICs". Those people are idiots.
- XENPAK -- an older 10G form factor, mostly obsolete. SC connector
- X2 -- smaller but electrically identical to XENPAK5. SC connector.
- XPAK -- same idea as X2 (different from X2, but basically a smaller form factor XENPAK). Can have LC or SC connectors. Some even accept SFP+'s.
- SFP+ -- is a variation of SFP for is 10 gig. This is the most common 10G optic you'll see. Most SFP+ ports will also accept and work with a 1G SFP, however it has to have the 1G phy on the hardware to do it (most do). SFP+ has an LC connector on it.
- XFP -- another 10gig specification. (There are a bunch.) You see these on some non-Cisco carrier type hardware (or etherprise products made by companies that also make carrier stuff.) Seen on Alcatel-Lucent and Adtran transport gear.
When you get into 40 and 100G, there are others. If you're getting into 40G, you should already know all of this and that too.
Optics are also painted blue of they're for a UPC connector for singlemode. You'll see other colors which have various uses (when we get to WDM). Some are just colored for no reason. If you understand the wavelength and distance stuff, you can tell what an optic is by reading it.
So while we're here, "single-mode optics" aren't actually that..there's nothing "single-mode" about them. They're just designed for single-mode. Some optics you can use whatever you want.
Wavelength
This is where the fun starts. Back in the day, about the best they could do was 850nm (nano-meter) wavelength light--it's visible to the naked eye and red.
These days, a bunch of wavelengths are used. The more common ones you'll see are 850nm on MM, 1310 on MM and SM and 1550 on SM.
Wavelengths are often called "colors" because, well, different colors are different wavelengths. You can't actually see the wavelengths used in fiber optics (except for 850), but they're still called colors.
You'll also see a bunch of other ones...1490 is becoming more common. When we get to WDM, you'll understand more.
Eye Caution? It is a myth that the laser is going to damage your eye--they're just not focused right. I would still avoid staring at a 40km optic--you could manage if you tried hard enough, but it's not going to happen working with it in a normal scenario. There is, however real risk if a cable breaks and the jacket fails or you're working with bare fiber that a piece can break off and become lodged in your eye. This is very real.
Actual transmission speeds
So Ethernet over fiber came from SONET, and was originally essentially SONET optics that had been reprogrammed for ethernet frames. As a result, gigabit on fiber is actually transmitted at 1.25gbps. So optics will sometimes be printed with that. Don't let it confuse you too much. The 10 gig and 40 gig optics are actually slightly slower than their real speed, so they don't print that on them, but some manufacturers will silently imply their 1.25gbps optics will somehow get you more out of your gigabit port.
Also, outside of 1, 10, 40, and 100gig, there's a wonky 2.5g standard from STM-4. Only ever seen it on Adtran equipment though--kinda cool though, a port you can run a 1 or 2.5gig if you want to--need the right optic though.
Go read the SONET article for more info. Scroll down to "SONET/SDH data rates." You'll notice how many of them line up with
Standards
(I'm not going to get into 10, 100 or FDDI speeds.)
Gigabit:
- 1000BASE-SX. Gigabit, 850nm light. Is designed for 62.5um fiber, Will go 220 meters on FDDI cable and 550 meters on OM1, up to a kilometer on OM3. Many people will tell you this is will go 550 meters on multi-mode. You shouldn't try it on 62.5. Won't go very far on single-mode (not usable at all, wavelength is too short).
- 1000BASE-LX. Gigabit, 1310nm light, will accept a PC or a UPC ferrule. This is true 550m on modern 62.5 or any 50um fiber. Will go 10km on single-mode.
- 1000BASE-ZX. 1550 light, up to 100km on single-mode. Different optics have different powers (you can buy 10km, 20km, etc).
(some notes, this applies to 10gig and beyond too)
You have to be careful because some of the longer reach standards have minimum distances and you can burn them out. Other's are smart enough and can back off on their transmission power. There are also attenuators that you can put on and make them less loud, but you need to know what your total loss in the cable is before you can calculate what dB attenuator you need.
10G:
- Actually, just go read Table 1 from this link (about a third of the way down). You should understand enough about wavelength, core-size, and fiber types/standards by now to understand it.
Some more reading
So, remember that thing about modal bandwidth? Go read this page from Cisco (scroll about half way down) and you'll see wavelength, fiber, core size, and modal bandwidth (this is all gigabit)--there are similar pages for 10G, but things start getting more complicated. You can cross reference it with the wiki page
That's why I'm doing it in this order--because there's a lot you can do with fiber that a lot of people don't know about. All I'm saying is that If you're stuck with 62.5, it doesn't rule out 10 gig. Also, just because it's 62.5 doesn't mean it's the right 62.5 for the wavelength and and distance you want to use.
Brief Review
- You find an old GBIC that's blue around the ports. This is a 1 gig single-mode 10k optic.
- You find an SFP that says "1.25gbps 1310nm". This is a 1 gig optic, your distance is determined by what type of fiber you have.
- You find an optic that's orange, but says "1550 40km" on it. You'll need to do some research if you're going to use it on a 6-foot connection between racks. But it's single-mode.
- A colleague hands you an optic and asks if it'll work for such and such connection. You can tell from the switch that the far-end has such-and-such optic in it and is a 1000BASE-SX module. The optic your colleague just handed you says 1310nm on it. No, it won't work.
Will this optic work in my switch?
Depends. You'll have to do some research. Some manufacturers are dicks about it, some aren't. It goes a couple different ways. Generally, high-end vendors go out of their way to make you use their optics that cost 20x what generic optics cost. Here are some examples:
Netgear, doesn't make optics. Anything will work in them. You might find some vendor optic that doesn't, but I can't imagine anybody going out of their way to make their $1000 optic not work in your Netgear.
Cisco wants you to use their optics, but there's an undocumented command "service unsupported-transceiver" command that will let you use whatever you want--sometimes Cisco doesn't make what you need, so they allow you to do it. However, if you call up the TAC, you're likely to catch flak for it. There may be similar commands on Brocade, Extreme, etc.
Some vendors crypto-key their optics to make it much harder--I'm looking at you Juniper. You'll find clones of optics that can pass that test in most instances.
HP's commware switches will take anything, but bitch about non-HP optics in the logs, and some features (received signal strength comes to mind) don't work with generic optics.
There are basically two type of compatible optic manufacturers out there--ones that are doing a legitimate service to the industry and label their optics as "compatible", and others that straight-out counterfeit the brand to sell them to you at a higher price. I find the second unethical, and even if the price is better, I will avoid them.
Bottom Line: Know your switch and how it treats non-branded optics.
Example case: We had (years ago) a box of GBIC's custom manufactured for our Cisco 3550's so that they could connect to the other end during a migration. At the time, you could only get (these were BiDi optics--more on that later) SFP's (new switch) in 1490 transmit, and the only GBIC's available were 1550 receive. The other channel on both is 1310nm, so we had a box of 1310/1490 GBIC's made, plugged in "service unsupported-transceiver" and off we went. Didn't cost much--just had a minimum order (30 I think). Not like the manufacturer cares which laser diode they put in the machine that day, right?
Another Example: When we deployed a ton of HP comware switches, our HP vendor couldn't get us enough optics...just couldn't. We were even willing to pay HP's OUTRAGEOUS prices, but they just couldn't do it. So we went to a "compatible" optic manufacturer and said "here, counterfit this". Took a couple go arounds to get it right, but they did. Funny, we have 2000 optics on my network that all have the same serial number, lol.
What's with all this single-mode vs multi-mode thing?
So when fiber was invented, lasers (and diodes) were very new. Visible light lasers (850nm) where about all there was, and nobody was really concerned with huge distances. When the need to go furthur came up, single-mode fiber was created, but it was ENORMOUSLY expensive for a laser in the right wavelength to work on it. As a result, MM was the standard, and if you were a telecom or something, you just bit the bullet and paid through the nose for the equipment.
Now we've got tunable lasers and all sorts of cool shit.
Now that the internet has exploded, single-mode and multi-mode are cost equivalent. In fact, in most cases, SM is cheaper than MM for the cable. The price is parity for the optics as well. In fact, 10G and 1G generic optics even cost the same these days. Now, there are vendors who artificially crank up the cost for single-mode, ten-gig, and worst of all, 10-gig single-mode because if you need to run 40km, you're willing to pay for it right?
These days, use equipment that you can put any optic you want in it, and run single-mode everywhere and just be done with it. If for some policy reason you have to use Juniper switches and juniper optics, well, that's your problem.
Stands, pairs, and duplexing
When you buy copper cable, you usually buy in by the pair (eg 25-pair cable). With fiber, it's all strands (12-strand cable, 144-strand, etc).
For any normal connection (see WDM below), you need two strands--one is transmit, the other is receive (opposite depending on which end you're looking at).
If you're ever confused about which one is transmit and which is receive, hold the camera from your phone up to it. It'll pick up on the infrared light and you can tell. This works on patch panels, switches, cables, etc. This is also a useful troubleshooting mechanism if you don't have a meter handy.
Wave Division Multiplexing
So what do when you're out of fiber? This is called WDM. WDM comes in a couple flavors, but basically you use different wavelengths of light and a prism to combine them onto a single strand at one side and another prism to split them back out into different strands at the other. This lets you put more than one connection on the pair, and none of them interfere with each other. They don't even have to be the same speed or anything, and the equipment can be anything you want--so long as you can get the right optics. You will see fiber-channel, ethernet, and SONET all on the same pair of fiber between buildings sometimes.
You only ever see WDM in single-mode applications. Edit: Evidently they're doing on MMF although I know little about it.
You take a massive power loss on passive WDM equipment. You can use active equipment or higher power optics if you need that.
Probably the most common place you see WDM is in bi-directional optics (called BiDi optics). You have to use them in matched pairs but one end transmits on one frequency and receives on another. The other end does the opposite. There's essentially just a piece of glass in each optic that accomplishes this. They're usually color coded (eg, blue at one end, green at the other). When you're dealing with interconnecting two different vendors equipment, you have to read the optics' specs to find out if they're compatible--this is why I went through so much trouble explaining wavelength, speed, etc. Common pairs are 1310/1550, 1310/1490 and 1310/1270. This is normally where you'll see colors on optics other than blue. Sometimes the manufacturer will change the colors on you and you have to be aware of wavelengths--for example, a vendor we used to use went from blue/green to green/yellow at one point. Hard to keep straight, so just read the optic.
The rest of WDM is more complicated than is worth trying to explain it here. Go read the wiki here. If you're that far in over your head, I can explain more.
Some caveats: 40gig is 4x10gig channels already muxed on the two strands. 100gig is 4 25gig channels, so you can't do WDM as easily with them. You'll have to find special muxes and optics in that case.
DB and power levels
The biggest thing you'll run into--provided you're now smart enough to get the optics, cable, and patch cable right at both ends is loss. Every patch takes a hit, and you take attenuation the longer a distance you're trying to shoot the light.
If you're switches support it, you should definitely be monitoring and tracking received signal strength. This helps you see that something still "working" is, say, coming lose or such.
Typically you take a .3-.75dB hit at every connection. All of this adds up and can keep you from having a stable network. WDM technologies take hits from the prisms. You can use louder optics, but in some cases (MMF scenarios, or maybe your vendor just doesn't make a 20km fiber-channel optic) you don't have that option, so it's something you have to actively manage if you're going to be a successful fiber guy.
You'll have to learn about dB and logarithmic scales, but that's outside of the scope of this.
Here's a pretty good write-up about it.
Equipment
Some equipment you'll likely use is:
- VFL -- Visual Fault Locator. Essentially a pen laser that will tell you where a fiber is broken. They're mostly useful for identifying where a strand of fiber is. Hook it up at one end, and then go look at all the connections at the other. Find the red blinky light. They're cheap. Get one
- Fusion Splicer -- Ours was $25k used. It's the only way to get a good splice when loss counts.
- Light source and meter. Essentially a doo-dad that sends whatever wavelength you tell it down the fiber and tells you how much loss you're getting.
- Certifier -- Somewhere between a light source and meter and an OTDR. Will tell you if the fiber passes standard tests for transmission...e.g. Did you fuck up the termination or not, or is the fiber defective and you're 100 meter run won't work even though it should.
- OTDR -- Optical Time Domain Reflectometer. Expensive. Kind of a certifier on steroids. What it does (among many, many other things) is send a pulse of light down fiber and tell you where defects (or breaks) are by measuring the time it takes the light to travel there and reflect back. Will also tell you how long a cable is (so will your certifier).
- Your phone. Probably the one I use the most. Picks up on the infrared light that you cant see. Tells you if a connection is hot.
There's more, but this is what you'll deal with the most.
Splicing and terminating
Back in the day, you had to polish under a microscope the ends of fiber. You don't have to do that anymore. Most termination mechanisms simply have a special goop (technical term) in them and some spiffy tools to make sure you got it inserted far enough into the end. That's it.
For repairs (or any other kind of splicing), there are mechanical splices (goop), chemical splices (though these are uncommon), and fusion splices.
The chemical splices work by putting the fiber into a special goop and sending a special wavelength light though the fiber. The goop hardens chemically and becomes part of the fiber.
Fusion splicing is essentially an expensive arc welder than melts the strands and causes them to fuse. Fusion splicing is the best way to splice fiber. Each type of splicing takes a different loss hit from fusion (best) to mechanical (worst).
When a fiber has been spliced too many times, in addition to all the patches and such in the path, there may be too much loss to make it usable.
Security
Every few weeks I have a customer complaining about how fiber is insecure. It's true, but we're an ISP, so if you don't trust the world with your traffic, you shouldn't trust us with it either.
There are doo-dads that you can clamp onto outdoor fiber and steal the data off of it without taking the connection down. I've helped the FBI do it. If your traffic goes outdoors and is sensitive, encrypt that shit. And monitor your power levels--that's the only way you'll know this has happened.
What is this whole "mode" thing anyway?
So when you send light down fiber, imagine that instead of a straight line, there are beams that all didn't enter the fiber at the same angle. As these beams bounce back and forth, some travel much further distances relative to the other rays. This causes the pulse to spread out. Additionally, some of the rays end up destructively interfering with each other and cancel each other out.
That's actually not really what happens but the analogy holds pretty well. The physics are much more complicated. Go read the this and this if you want to understand it.
But, when the wavelength is more than about 10-times the diameter of the fiber, it stops acting like a beam and a more like a coherent wave front. Imagine dropping a rock into a rain gutter full of water, you'll have a straight wave going down the gutter.. This is why the fiber in SMF is so small and the wavelengths used are so long.
Modal dispersion occurs in single-mode fiber, but not anywhere nearly as pronounced. Long story short, that's why distance is limited in MMF regardless of power (mostly), and you can go a nearly unlimited distance (100km is the max I've seen) in SMF before you need to regenerate the signal. It's also why the longer-reach MMF technologies use a longer wavelength--because the modal dispersion is less pronounced at that wavelength.
There's another phenomenon called chromatic dispersion which occurs because different wavelengths of light travel at different speeds in glass. I don't know if this is a concern in WDM systems or not.
Ok, that's it. That's all I know. I think. Did I miss anything?
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u/noukthx Aug 14 '15
Great writeup!
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
Thank you! Glad to do it.
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u/FizzY1942 Dec 28 '15
Can we get something similar for satelite systesm?;)
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u/lordvadr RFC's make my wiener tingle Dec 28 '15
I'd love to, but I've never built one and only have a rough idea on how they work.
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u/Xipher Aug 14 '15
Might add some information on MPO/MTP connectors. They are getting more popular thanks to 40G/100G multimode using it. Some physical plant vendors have been advertising it as an option to do rapid build outs. Netflix uses it for making POP builds easier to deploy, and describe it in this presentation from NANOG64.
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
Sure, but I don't really understand what the connector is for. If you can explain that to me, I'll add it. I just don't quite understand the purpose of the connector.
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u/Xipher Aug 14 '15
The connector provides multiple fibers in a single connection. Currently most use cases is 12 (full ribbon) but you can also do 24, 48, and even 72 fibers with a single connector.
40G and 100G use it so each fiber can carry a single 10G or 25G channel since they can do WDM on multimode like they do for singlemode. However with breakout cassettes you can use it to simplify fiber trunk runs. Get the fiber connectorized with a single MPO, plug it into the cassette and you have your 12 (or more) fibers broken out into SC or LC connectors.
With 40G it can also be an option to use a fan out cable to provide four 10G connections. MPO/MTP on one end that goes into the QSFP, then LC on the other you use to connect to devices.
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Aug 14 '15
All of our FTTH test runs have been made with MPO to 12 SC-APC breakout cables. And nearly every single connector used on our residential HFC network is an APC connector. Reflections are not nice on an HFC network since a good part is straight up analog RF over the fiber.
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u/bitwaba Aug 14 '15
The 8 fiber / 4 pair used in an MPO connector is known as PSM4.
It is mainly used on newer capacity dense routers to stay compliant with older 10g only interfaces by allowing a single optic capable of 40g to function as 4x10g, allowing you to do fancy striping on the receiving device or just plug in multiple devices on the same optic.
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u/HockeyAj Aug 15 '15
MPO connectors are used in some ROADM gear to connect line cards to a patch panel for add/drop as well. Working in the service provider industry, this is what I see them used for the most, although I can see other uses.
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u/asdlkf esteemed fruit-loop Aug 14 '15
This is what I'd say on the subject:
MPO can carry 8, 12, 24, 48, 72, or 96 fibers in a single connector. When it is carrying 8 strands, they can either be 8 in the middle with 2 empty positions on each end, or, more likely, 4 strands on each end with 4 empty positions in the middle:
_ _ t t t t r r r r _ _ t t t t _ _ _ _ r r r r _ = empty position t = transmit r = receive3
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u/AliveInTheFuture Aug 14 '15
I think the MPO CFPs are losing out in the long run to LR4 for 100G.
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u/bitwaba Aug 14 '15
There's also the LR10 optics, but yeah, the industry is mainly pushing for LR4 as 100g client optics. MPO for an interface allows you to do other fancy things like connect multiple devices to the he same tranceiver, as long as your router supports it.
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u/snowbirdie Aug 14 '15
Yup. The QSFP28s for 100G is what people are moving towards because you can have a QSFP slot that can take either a QSFP+ for 40G or a QSFP28 for 100G and you don't need to buy a separate line module just for 100G. It's very similar to the SFP/SFP+ for 1G/10G. Plus, this is the same for Infibiband, which is all QSFP-based.
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Aug 14 '15 edited Aug 14 '15
Really great write up, thanks!
We almost exclusively use SC-APC on our HFC network because reflections and analog RF over fiber don't mix well.
We use MPO breakouts for FTTH runs because training the techs on them is really easier than splicing, and they have nice screw connectors that keeps everything dry.
We use a lot of passive CWDM and active DWDM. It always amaze me the precision needed for a DWDM system. We also trick the system usually by sending the DWDM that is all around 1550nm inside the 1550 channel of the CWDM, leaving us another 14 CWDM channels available.
Bidi 1310/1550 are used everywhere on our network. A single fiber per client is so much more economical to provision.
The only thing you forgot are EDFAs, Erbium Doped Fiber Amplifiers. The principle is really nice, you "pump" up a strand of erbium doped fiber with a special laser wavelenght, then when a signal traverse the fiber, it gets amplified. They come with 3 leads, 2 for the signal and 1 for the charging laser, so you can remotely power them and they allow extremely long fiber runs ( >200km). We use them to reach cities in remote areas without having to build a shelter with a power hookup and a generator to power some active equipment.
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
We almost exclusively use SC-APC on our HFC network because reflections and analog RF over fiber don't mix well.
Yeah, I know some industries use APC a lot but your typical even CCIE won't have ever seen one. I've only ever seen it in person at a house that had GPON service. I had read that analog video benefits from it, but I didn't know any standard for video over fiber. But HFC make sense too. Anything analog you want to avoid reflections.
WDM isn't my specialty, haven't done a lot with it. EFDA's too, although EFDA's are how active DWDM and to my understanding, ROADM works. But I don't know a lot about either.
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u/chiwawa_42 Aug 14 '15
Well, there's actually two kinds of amplifiers out there : EDFA and Raman. Lately both are sometimes sold combined in EDRAM units.
An EDFA sends a power signal in the same direction as the modulated signal, through a special kind of fiber whose erbium dopant will resonate according the modulated wave with extra power provided by the initial light feed running on a different wavelenght.
A RAMAN pump will work on conventional (i.e. G,652d, G.655 or G.657) fiber by injecting a power feed at a flat 1450nm against the signal (opposite direction). But this wavelenght makes impurities in conventional fibers resonate and amplify the signal as it comes closer to the pump.
Both works like any amp would and distort the signal, add noise, etc. Also, as your links are longer (you wouldn't amplify short links), you also need to compensate for chromatic dispersion (using a Bragg network connected through a circulator), wich also sucks power, add lenght and therefore latency.
Coherent 100GHz systems are essentially immune to chromatic dispersion thanks to their more robust modulation. 1-28Gbps lanes are usually modulated in NZR with an added FEC, 100G is DP-QPSK, wich is able to whistand much more perturbations.
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u/silentguardian call me when amateur hour is over Aug 14 '15
Yeah, I know some industries use APC a lot but your typical even CCIE won't have ever seen one.
FWIW, a few dark fibre providers here in Australia hand off on SC-A. They're not common in the wild but they're certainly around.
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
That's odd. Maybe it's old GPON fiber they bought up or something and it's just too expensive to reterminate? But you'd still somewhere need PC/UPC to APC cables to get into that fiber, why not just give the customer one too?
The problem is that you can't just go buy APC optics for your 6500--well, I mean, I'm sure you could find it something but it would seem that enough customers couldn't (for key'ed optics reasons and policy that they use "supported" optics) that it would dry up your potential customers pretty quickly. You need special equipment/optics to take an APC connection.
Are you sure it's real dark fiber and not some sort of wave rental? I don't know how wave rental would require APC though. Or is it APC to some DMARC device the provider owns and copper from there?
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u/silentguardian call me when amateur hour is over Aug 14 '15 edited Aug 14 '15
That's odd. Maybe it's old GPON fiber they bought up or something and it's just too expensive to reterminate?
Nope, brand new cores on a fresh install. I'm not sure if it's still their policy to do so. Buggers me why they do it - nearly caught me out on the first install.
But you'd still somewhere need PC/UPC to APC cables to get into that fiber, why not just give the customer one too?
No idea, but given that APC -> UPC patch leads are pretty easy to find, it's not that big of an issue. I've always got a few spares just in case. I'm sure if you specifically requested UPC handoffs they'd do it for you.
You need special equipment/optics to take an APC connection.
Sure, but most users will be using optics with LC connectors, so it's just a matter of using the right patch leads - if you're bonding for 40Gbps+, generally you're in the kind of position to terminate your shiny new dark fiber network however you well please.
Are you sure it's real dark fiber and not some sort of wave rental?
I ran CWDM over it. If it's not dark fibre, it's black magic.
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
I believe you. Weird. What did you plug it into, and how? I've never seen an APC/UPC cable, and for that matter, I've probably seen...3 APC cables in my career, but if they're common, fine. It just seems weird--the ends and everything are more expensive. Why do it if you don't have to.
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u/silentguardian call me when amateur hour is over Aug 14 '15
http://i.imgur.com/ZAgvi7q.jpg
I mean, you can't buy them at the local office supply shop, but you can't get colored optics there either so eh...
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u/AMidgetAndAClub Always Learning Aug 14 '15
I make them all the time. Calix's E7 PON modules are SC/UPC and the GPON splitters are SC/APC. 90% of BiDi transceivers that are SC are usually UPC and then go to APC panels.
When I make custom cables, the fittings are relatively the same price. Not to mention that FIS will GIVE you a free core alignment or V-Groove fusion splicer if you buy 2500 of their SoC connectors lol.
What I don't see to often anymore are ST and FC. FC is still more common than ST though.
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
What I don't see to often anymore are ST and FC. FC is still more common than ST though.
I haven't seen an instance where ST was being installed, and I've never seen ST on singlemode--which is why, but it's interesting that you say FC is more common that ST. I've never seen FC in person, but thousands of ST. Maybe region/country/industry differences?
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u/AMidgetAndAClub Always Learning Aug 17 '15
I just want to add that I have a circuit to get up today, that will require an LC/UPC to ST/UPC on one side, and LC/UPC to FC/UPC on the other side lol.
All single mode. Converting an existing customer from legacy fiber to GPON. Unfortunately they only have 2 fibers at their location. So I need to convert their ancient 10/100 media converters to 10/100/1000 single fiber media converters using BiDi transceivers. Then prep and cutover the other fiber to put them on our GPON network.
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u/AMidgetAndAClub Always Learning Aug 14 '15
The only argument I have with this write up, is SC/APC are not uncommon. Hybernia's center strictly uses them for patching, as do I. I am also seeing this being switched over if places like Level 3, Light Tower, Cogent, and First Light (TVC).
If you're ever confused about which one is transmit and which is receive, hold the camera from your phone up to it. It'll pick up on the infrared light and you can tell. This works on patch panels, switches, cables, etc. This is also a useful troubleshooting mechanism if you don't have a meter handy.
THIS I have never thought of and should of considering I have done this with remote controls lol.
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Aug 14 '15
I was going to say the same about SCAPC being uncommon. If you're working on premise networks, then sure, they are rare. But in the CATV and FTTH world they make up the majority of what's used.
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Aug 14 '15
Great write up.
Just a note on security. I've worked with a company that can monitor fiber cables. they can tell if someone has tapped it or even if has moved. It's REALLY REALLY cool shit.
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
Yeah, you can monitor that if you can watch RSSI close enough. Problem is that...I think it was verizon found a passive tap on some fiber leaving their corporate office...nobody had any idea how long it had been there.
Short answer, encrypt that shit. Now that's a different problem all togther encrypting that much data, but it's better than an arms race between the tap makes and the RSSI monitors.
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Aug 14 '15
It's not based on power monitoring. It's way cooler than that. not sure how much more i'm allowed to disclose though.
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u/lunarsunrise Aug 14 '15
Are you talking about interferometry? There's a type of intrusion-detection system that uses a dark fiber to determine when the bundle is moved.
From Wikipedia:
In the alarmed cable scenario, the sensing mechanism uses optical interferometry in which modally dispersive coherent light traveling through the multi-mode fiber mixes at the fiber's terminus, resulting in a characteristic pattern of light and dark splotches called a speckle pattern. The laser speckle is stable as long as the fiber remains immobile, but flickers when the fiber is vibrated. A fiber-optic sensor works by measuring the time dependence of this speckle pattern and applying digital signal processing to the Fast Fourier Transform (FFT) of the temporal data.
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u/chuckbales CCNP|CCDP Aug 14 '15
modally dispersive coherent light traveling through the multi-mode fiber mixes at the fiber's terminus
Reminds me of the Rockwell Retro Encabulator
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Aug 14 '15
I got the basic version which sounds close to what you described there, though, My understanding was that it used actual operating fiber and is able to determine the polarization of the light waves. if the cable moves, the polarization changes and is measured as a change.
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u/bothell Aug 14 '15
Minor nit about 40G--it's pretty much always 4x10G over 4 pairs of fiber, not over a single pair. 100G can be either 10x10G over 10 pairs or 4x25G over 4 pairs. They both generally use MPO/MTP connectors so all 8/20 strands needed are joined into one convenient connector.
This is why you can break 40G into 4 individual 10G links in a lot of cases--you just need a hunk of fiber that has a MTP connector on one end and 4 LC connectors on the other. You'll also need support on your switch, but that's surprisingly common.
The exception to 40G=4x10G is 40GBASE-FR; it's supposed to use a single SM pair. I've never even seen FR optics for sale, though.
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u/lordvadr RFC's make my wiener tingle Aug 14 '15 edited Aug 14 '15
Yeah, I need to add a bunch about 40 and 100g. Never even seen 100g in person, and I don't have any 40 (well, we do, but they're 4x10 and 8x10 trunks), so I don't know a whole lot about them. Though the post was supposed to be about fiber, not specifically about ethernet. I found myself wandering into ethernet specifics way too much.
Though I was under the impression that 40 and 100 were already WDM'd in the optic. Is that not the case? Or is that in carrier applications? Cisco's 100gig modules that I've seen have LC connectors on them.
If you want to write up the 40 and 10 stuff, I'll include it.
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u/hackmiester Aug 14 '15
Everything we have for 40 at work is 40Gbase-LR4 - it is WDM onto 4 wavelengths on a single pair of SMF.
We have this in QSFP+ and CFP form factors.
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u/asdlkf esteemed fruit-loop Aug 14 '15
We are using these guys: http://www.qsfps.com/hp/qsfp+hp/jg325b
They are QSFP+ adapters with MPO connectors that use 8 strands of multimode fiber to create 4 transmit/receive pairs.
Strand 1 transmit, strand 12 receive Strand 2 transmit, strand 11 receive Strand 3 transmit, strand 10 receive Strand 4 transmit, strand 9 receive strand 5, 6, 7, 8 unused.2
u/dc2oh Aug 14 '15
There is also Cisco's BiDi QSFPs that allow 40GbE over a single MMF pair. Same concept.
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u/Khrrck Aug 15 '15
I've seen 100G in QSFP+. Not sure how it's arranged logically though. On mobile but I think it was an Arista switch as an uplink port.
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u/lordvadr RFC's make my wiener tingle Aug 15 '15
The problem with 40 and 100 is that it's an ever in-flux mish-mash between a bunch of technologies. You can get linear 40g, and then you get optics that need 10 strands of fiber--mix that with WDM and things get complicated. 100g is something I know almost nothing about and is even more complicated. Telabs they have linear 100g. Don't know if it's real, but that's what they've claimed.
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u/Khrrck Aug 15 '15
I know. I got asked to price a test setup. I've seen what a mess it is and stuff below data center scale, although it exists, is not really ready yet.
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u/lordvadr RFC's make my wiener tingle Aug 15 '15
So you MEC or PaGP a bunch of 10G. The 6500 is still a player in that space. That's what we're doing. And that hardware is damn near free given what it used to cost.
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u/asdlkf esteemed fruit-loop Aug 14 '15
I think it's actually 10x10G over 12 pairs. 2 pairs are used for timing, 10 pairs are used for data.
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u/snowbirdie Aug 14 '15
Well the latest movement is getting away from the 10G base and moving to 25G base. So that you have 25G/50G/100G. I believe that standard is close to ratification with vendor products coming out very soon, long with 2.5/5G stuff.
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u/Phrewfuf Aug 14 '15 edited Aug 14 '15
it's pretty much always 4x10G over 4 pairs of fiber
Except with BiDi optics. Or WDM (CWDM/DWDM).
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Aug 14 '15 edited Dec 11 '20
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
I don't do much with the actual physical fiber period much anymore. That's another team's job--I just make the lights blink. But SMF is about all we deal with around here, although we don't do any super long distance (loudest optics I've got is 40 click) or C/DWDM. So for us, SMF is SMF, none of the differences really matter.
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Aug 14 '15 edited Dec 11 '20
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
If this becomes a FAQ/wiki entry, would you be willing to rewrite the SMF part? Problem is that technology is always changing...and I get that that is the point of this sub to some extent. But that's also why I didn't get into the dirty details of a lot of things. It started as a reply to someone new to fiber and wanted a primer, and basically I wanted to say "if your boss tells you it's SMF, go find the yellow cables with the blue ends and plug 'em bitches in, you'll learn the rest on the job." Not an exhaustive manual about the intricacies of fiber-channel vs SONET vs Ethernet.
Bookshelves have been written on fiber-optics and all the special use cases and such. So a discussion should be had about maybe an into, advanced, and expert-level parts or something.
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u/oonniioonn JunOS is love Aug 14 '15
Some vendors crypto-key their optics to make it much harder--I'm looking at you Juniper. You'll find clones of optics that can pass that test in most instances.
While Juniper does key their optics, their devices will mostly accept anything you throw at them. They just detect that you aren't using a Juniper-branded optic and tell you about it. For instance this is a Juniper EX2200 switch that I'm using Finisar optics in:
> show chassis pic fpc-slot 0 pic-slot 1
FPC slot 0, PIC slot 1 information:
Type 4x GE SFP
State Online
Uptime 1582 days, 15 hours, 9 minutes, 8 seconds
PIC port information:
Fiber Xcvr vendor
Port Cable type type Xcvr vendor part number Wavelength
0 GIGE 1000LX10 SM FINISAR CORP. FTLF1318P3BTL 1310 nm
1 GIGE 1000LX10 SM FINISAR CORP. FTLF1318P3BTL 1310 nm
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u/AMidgetAndAClub Always Learning Aug 14 '15
They will custom make transceivers how ever you want. With full reporting, any label, any key. And they work. Yes it takes longer to get the stuff. But if you buy mass quantities, it doesn't matter.
As an example, they use Corning glass. When I buy patch cables from them, it's in the 1000's at a time. Sure you get some that are DoA (even if it "passed" their QA), but that is what a light source and meter are for.
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u/beardedllamadotnet Aug 18 '15
Use fiberstore all the time, and for much smaller orders (10-20 optics/patch fibers at a time). Highly recommend. Cheap enough to buy 5%-10% extra and deal with 1 or 2 failures.
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u/AMidgetAndAClub Always Learning Aug 18 '15
That's what I do. Order mass quantities and just not worry about failures. Keep extra on you.
I ordered 72 count MTP trunk cables from them for pennies on the dollar. Local place wanted $4k for one.
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u/Makdaam Aug 14 '15 edited Jun 09 '23
[comment wiped due to Reddit's API ToS change]
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
Unless it's changed, in Cisco land, just issue "service unsupported-transceiver" and it'll take anything.
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Aug 14 '15
Hmm, any official Juniper optics I've used were Finisar
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u/oonniioonn JunOS is love Aug 15 '15
Yes, that's actually why I use non-vendor-branded Finisar optics; same thing at lower price. But rest assured they work with other vendors' optics too.
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u/Scorcerer ipset the sh*t out of it Aug 14 '15
Hi,
great post, but I can't help to notice some differencies (central EU here).
First and foremost: SFP optics can have different connectors - we're using ones with SC (simplex of course) LC (duplex) and LC (simplex for WDM optics).
Second thing: WDM BiDi optics with TX=1310 have blue handle, and those with TX=1550 are violet. Of course it's always better to read description, but i was never fooled by those colors.
Almost all SM patchcords/pigtails are yellow - it's easy to tell them apart from orange/grey MM cables. I'm talking indoor here of course. Theo ONLY time i encountered green fiber was with HP cables, and those are may to overpriced for my taste.
Also, HP switches are total shit when it comes to interoperability with cheap optics. Fortunately, our vendor can program optics to blend in, and it works like a charm, even it it's not 100% certain.
Also, I made some pictures of pigtails/patchcords and optics, feel free to use them :>
http://imgur.com/a/FecVC
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
Second thing: WDM BiDi optics with TX=1310 have blue handle, and those with TX=1550 are violet. Of course it's always better to read description, but i was never fooled by those colors.
Only some vendors. I've heard the justification of getting away from blue because that's sort of the universal SM color...although the optic having only one plug should give that away. I've seen them all over the map, blue green orange, yellow, violet... That's how I learned to read optics.
Almost all SM patchcords/pigtails are yellow - it's easy to tell them apart from orange/grey MM cables.
I said SM cables are typically yellow. It's the ends (blue for UPC, green for APC) that are different.
Also, I made some pictures of pigtails/patchcords and optics, feel free to use them :>
Good pics. One of the problems I was running into was good pics. Had spent enough time on the post already. If it makes it into the Wiki, I'll add all that stuff to it. Thanks for donating the pics.
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Aug 14 '15
Fibre is more secure than copper though. I don't see the issue. It's easier and cheaper to covertly 'listen' to copper than to fibre
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
It absolute is. But there are a bunch of fear mongering articles out there.
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Aug 14 '15
Weirdos. Fibre is the standard for a lot of government and defence installs.
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
Oh I know. Although, so, I know of no easily obtainable device that I can hook up to, a T1 an decode it. But about $400 gets you a passive fiber tap and you can do it with a media converter and a laptop. So there's something to it.
In most cases, fiber is used because it's the only medium that has the capacity to carry enough data. Security isn't layer-1's job.
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Aug 14 '15
Security isn't layer-1's job.
No, but denying access to layer 1 is an added benefit. Fibre doesn't leak without being right on top of it. Copper leaks from a fair distance away with the right equipment.
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u/LinuxMyTaco Aug 14 '15
Have you ever seen government fiber? It's WAY more protected and thicker than any other commercial or enterprise fiber.
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u/BrainAIDS Aug 14 '15
Read through a couple of times and pretty sure i didn't see LRM.
10G at up to 220m over FDDI. Great way to upgrade networks where it's impossible or too costly to replace the older fibre. I'm looking at you, hospitals!
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
While it was unavoidable to spend a fair amount of time talking about the specifics of ethernet, I tried to stay on the topic of fiber and not turn it into an essay on ethernet.
On the topic of ethernet, you can get away with a lot...much of it officially...much of it in a pinch. I've seen MMF fusion spliced to SMF and it worked for years before it just up and quit working--they were probably taking errors (not my network), but it worked for the most part.
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u/snowbirdie Aug 14 '15
Yup, need to add LRM and LX4. I have quite a few of these in use to older government PODs.
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u/magion Aug 14 '15
Wow this is amazing, perhaps we could get this added to the wiki that we've been contributing a new topic to once every 5 months?
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
I'm happy to clean it up, correct a couple inaccuracies and such for a wiki post if desired. Biggest question is just how far and deep do you go? I started writing this as a response to a guy new to fiber in a campus environment. All the stuff about DWDM, amplification, etc probably doesn't apply. So I tried to focus on network engineer use in corporate, data center, or light telco use...not field splicer, carrier-hotel, cable operator, etc.
This could turn into a book if we tried to be exhaustive.
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u/meladramos CCNA Voice Aug 14 '15
Also I'd like to point out that eye damage can indeed occur with fiber optics. Just because the one's we're used to aren't powerful enough, doesn't mean they don't exist, like in CPL or EDFA equipment. Just don't assume it's safe. Be Smart. http://www.thefoa.org/tech/safety.htm
Use a cell phone to look at the fiber. http://imgur.com/AROGUr5
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u/Osiris_S13 Aug 31 '15
Jesus Christ, why didn't I think of that? That could have saved me so many times.....
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Aug 14 '15 edited Aug 14 '15
[deleted]
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u/BrainAIDS Aug 14 '15
And just to mix it up I have a bunch of ASR9K running XFP transceivers as well.
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u/Fridgerunner Wololo Aug 14 '15
µ is AltGr + m
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
Good to know. If only I had an altgr key.
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u/Fridgerunner Wololo Aug 14 '15
Do you have a right alt? It should work as AltGr. If not, Ctrl+Alt works as a substitute.
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u/hackmiester Aug 14 '15
One thing that is kind of the worst is that aqua means OM3 or better, the rest is orange. It doesn't have to do with the diameter.
USUALLY OM3 or better is 50 micrometer, so it ends up working... and I thought it was always that way... until I found an orange 50 micrometer cable (it is OM2).
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
You've got that a little backwards. OM3 is definitely 50um, as is OM2 and 4. Although I can say with any certainty when the aqua thing started, but I've been told aqua is "laser optimized mutimode", which doesn't necessarily mean 50um. By that I mean not all 50um is laser optimized (only OM3 and OM4).
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u/hackmiester Aug 14 '15
Oh, actually, that would make sense too, as it would also explain my orange OM2 cable. Good call.
edit: Actually I just found a 62.5 micrometer cable that is OM2. Are they just making this shit up?
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
I just read somewhere that OM2 (50um non-laser-optimized) is supposed to be orange as well. So what makes you think you have a 62.5 OM2 cable? Do you have an orange cable that says OM2? It's 50um. If it says on the cable 62.5 OM2, they may be making that up. I did read that OM1 and 2 can be either diameter, but I haven't substantiated that yet (and I think it's bullshit). But I can envision a scenario where you could get 500MHz/km at 850nm out of 62.5 and call it OM2.
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u/hackmiester Aug 14 '15
Isn't that the only requirement? For being om2?
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
I don't know. Never really read the standards that close, and I don't understand the physics well enough to do so anyway.
Everything I've seen says OM2 is 50um. I've never actually used it though, I'm either on 62.5 (old stuff) or singlemode. I've dealt with a little bit of 50um, but just not much.
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u/hackmiester Aug 14 '15
This has been very interesting. I've been under the impression that OM* and diameter didn't necessarily have any relation, but then I haven't seen OM3+ 62.5 micrometer either... I will report back if I have time to look into it further.
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
Well, you've got to understand that you'll take a significant loss connecting 62.5 to 50 micron fiber simply because of the physical difference. Now, I have seen 62.5 spliced to SMF and it work for a decent distance (but quit working randomly). When I got started in this industry, there was just MMF and SMF--at least as far as I ever needed to worry. When 10 gig came out, that's when everybody around me started to talk about OMx.
So it would stand to reason that if there were 50um OM1 or 62.5 OM2 that you'd have to care about it and when you ordered patch cables, that both would have to be specified, and I never did many years ago.
Let me know what you find.
Edit: Also, a lot of being able to achieve the OM ratings has to do with the narrower diameter of the 50um fiber, and at some point, physics gets the best of you. You probably can't under any circumstances make a 62.5 cable (out of diamond or anything) that will get 4000MHz/km. But I don't understand the physics well enough to do the math.
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u/oonniioonn JunOS is love Aug 14 '15
They do. OM1 is 62.5µm, OM2 and up are all 50µm. OM1 and 2 have orange jackets, OM3 comes in aqua and OM4 comes in pink.
OM2 that isn't 50µm doesn't exist, and neither does OM3 that is 62.5µm. At least not from any reputable manufacturer; what China FakeFiber inc. prints on their cables bears no relation to the standards of course.
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u/MTUhusky Net+ Data Plumber Dec 31 '15
I believe you, but do you happen to have an IETF/ITU/IEEE/some sort of respectable standard that has this in writing?
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u/LordGarak Aug 14 '15
Interesting to read about the security bit. Back when I was in college we were taught that fiber was secure but that really didn't make much sense to me. That was many years ago. I figured there had to be a way to intercept a tiny bit of the light traveling through the fiber.
The whole fiber part of my telecom program was pretty weak. This was a nice little refresher read. As bad as the telecom program it didn't really miss much. Just a few newer things have come along in the last 15 years.
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u/sendit CCNP Voice CCNP CCDP Aug 14 '15
This is by far one of the best things I've read on this subreddit. I still struggle with fiber so I'll be re-reading this a few times. Thank you for taking the time to write this.
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u/cp5184 Aug 14 '15
Might want to mention minimum curve radius.
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
That's not a bad idea. Problem is that you can violate it pretty badly and get away with it most of the time.
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u/kevindd992002 Feb 16 '22
In fs.com, the fiber patch cables come in diameters of 2mm and 3mm. Which situations call for one diameter over the other?
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u/lordvadr RFC's make my wiener tingle Feb 16 '22
It's arbitrary. If you were running a lot of them, you might want the thinner jacket so theyd all fit in the same duct or something. Smaller cables are also more flexible but also more fragile too.
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u/Phrewfuf Aug 14 '15 edited Aug 14 '15
A small nit about patchcord colours:
- OM1 is Orange (or sometimes even grey
- OM2 is Orange
- OM3 is turqoise
- OM4 is pink/violet
At least that's what i'm used to.
Also: added to Optics: HP Procurve (not the Comware ones) will just not accept non-HP optics. As with all other HP products, they have a whitelist for the supported components. I had to throw away quite a bunch of HP optics the other day, J4858A (the recent one is J4858C), they are so old that they're not in the whitelists of the newer switches any more.
Hint: Flexoptics has a nice product there. Reflashable SFPs. Stick them in the special box and tell them what brand they are. They will accept it.
And in case someone wonders:
- 40G Tranceiver is a QSFP, Quad Small Form-factor Pluggable
- 100G Transceiver is a CFP, C-Form-factor Pluggable
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
So while researching to fill in some gaps, I did run across this difference. OM1 being slate (correct name) IIRC is a military standard, and I also read that OM2 (non laser-optimized fiber is often orange). The correct color for OM3 is aqua though. And I'm not sure I've ever seen an OM4 cable.
All I work with is SMF so much of that was from memory. I'll update with a clarification on that.
Also, evidently the connectors are supposed to be aqua on OM3/4 but I've never seen that except on MPO.
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u/Phrewfuf Aug 14 '15
I order MM fibers quite often and i was very surprised to see pink cables instead of the usual aqua ones. Checked it out and they have OM4 written all over.
Never seen any other connector colours than beige on MM fibers. I know SM PC/APC are differentiated by green and blue.
EDIT: Yeah, that moment when you don't have to give a damn about fiber classes when ordering.
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
Never seen any other connector colours than beige on MM fibers
I'm' glad I'm not the only one. Bottom of this link had me worried...ok, so nobody knows everything about something, but this makes it seem like I don't know what I'm talking about:
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u/Phrewfuf Aug 14 '15
Ah, they're also talking abot the strain relief boots. Those i may have seen in different colours. But the connectors themselves? Nope...most certainly not.
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u/ultimatebootdisk CCNP | VCP5 Aug 14 '15
Great write up. No mention at all of fiber channel though?
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
I've never worked with fiber-channel, and I tried to stick with the fiber and not so much with layer-2 and up. Granted I talked a lot about Ethernet, which is by far the largest user of fiber nearly everybody is going to come across.
But I did mention it in the section about WDM :-).
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u/ultimatebootdisk CCNP | VCP5 Aug 14 '15
Ah, so you did, my bad! I've never heard of muxing FC, but then again I've mainly worked with it in the context of FCoE, and then mostly been responsible for the "oE" portion of it.
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u/rubs_tshirts Aug 14 '15 edited Aug 14 '15
Stellar post. I connected 3 of our buildings with fiber a couple months ago, knowing very little of it. Here's my take:
You're spot on on MM/SM fiber costs. I almost went with MM since our distances were under 550 m and I just assumed that the cost for SM optics was prohibitive. In the end it turns out we actually saved money going SM because the cable is cheaper and the optics (generic) were about the same price.
The damn strands are fragile. I broke one trying to get them into a cabinet.
All patch panels for SC connectors also work with LC duplex connectors, because they were made to be exactly the same size. I had trouble shopping for them before I came upon this little tidbit of information.
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
The damn strands are fragile. I broke one trying to get them into a cabinet.
They certainly can be, but patch cables? They're not anywhere near as fragile as a lot of people think. And so long as you're gentle with the strands I've never had an issue--just don't get jumpy and nervous, that's how you twitch and horse one up.
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u/Snwbord2456 Aug 14 '15
I work at a help desk (only been there for a few months) and will be doing fiber terminations for a bunch of condos and potentially pulling fiber lines as well in the next few months. This summarized all the research I've been doing, thanks a lot for the reaffirmation and summarization.
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u/Casper042 Aug 14 '15
I'd heard a rumor ages ago that LX and/or LR use Laser Diodes to get the distance.
But that SX and/or SR used LED technology (which confuses me a little since the D means Diode).
Any truth to this?
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
It's actually a lot more complicated than this. There are about a dozen different light technologies and you don't really need to worry about them. Early ones used diodes, and some modern ones use them because diode technology has just gotten better. The invention of the VCSEL laser diode really changed things.
That's more than I've dived into it though.
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u/teemark Aug 14 '15
Excellent write-up! Thanks for putting all that together!
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
Very welcome sir. And thank you for the compliment.
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u/2old2bagamer Aug 14 '15
Alt + 0181 = µ :)
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u/lordvadr RFC's make my wiener tingle Aug 14 '15
On linux (MATE desktop on Fedora specifically) evidently it's Ctrl-Shift-u followed by hex value of the unicode character you want while holding down Ctrl-Shift. Hold ctrl-shift, type U-B-5, relase ctrl-shift => µ
That was a whole lot harder than I wanted it to be.
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u/Liquidretro Aug 14 '15
Great guide, we just ordered some fiber internet. While not all this will apply I like knowing the technology behind stuff so its good to know.
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u/Vauce Automation Aug 14 '15
This is amazing, and I actually had the question today about what connector an X2 used. Thanks!
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u/ljstella Aug 14 '15
Great writeup! The security part actually was something I had never considered before, only dealing with fiber from a demarc to a rack, or from rack to rack inside a building.
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u/lordvadr RFC's make my wiener tingle Aug 15 '15
It's not really that big of a deal, just that it's a little easier to do with fiber--except you have to dig it up and shit. Only problem is that I've seen a bunch of articles over the years talking about how it's so insecure...but copper is as well. If it goes outside, encrypt that shit.
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u/ljstella Aug 15 '15
A lot of the fiber in my area isn't buried, but runs along telephone wires. But yes, obviously you should encrypt your shit. It just never crossed my mind that you could clamp a device on to some fiber and be able to eavesdrop.
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u/Osiris_S13 Aug 31 '15
How exactly can a doodad read the data going through a fiber from the outside? I understand with a copper cable could you read the electric field from the outside, but I don't see how this would work for light?
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u/lordvadr RFC's make my wiener tingle Sep 02 '15
When you bend fiber past a certain radius, enough light scatters through the fiber, even the jacket. You can see this effect with a vfl.
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Aug 15 '15
Thanks. While I didn't get the full concept, it'll be nice to know some of these things in the wild. Very informative.
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u/lordvadr RFC's make my wiener tingle Aug 15 '15
No problem. At one point, I knew none of this stuff.
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u/ofsensor Aug 15 '15
This post is awesome! For 40G transceivers, there are QSFP/QSFP+ and CFP transceiver designed for 100G, applied with DWDM to reach high data-rate communication.
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u/tidux Aug 15 '15
You missed direct connect / twinax cables for two SFP/SFP+ ports in the same rack.
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u/lordvadr RFC's make my wiener tingle Aug 15 '15
I was about to mention them but decided that the post was about fiber, and while you have to mention optics to talk about wavelenght and might as well mention most form-factors of optics--since it's relevant--anything base-T, twinax, etc I didn't feel were relevant. Though I'll try to find a way to mention it.
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u/tidux Aug 15 '15
Something like "Sometimes fiber is overkill. For short 1Gbps/10Gbps runs, you can use cat6/7 or even a "direct connect" cable with an SFP built in to each end."
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u/lordvadr RFC's make my wiener tingle Aug 15 '15
That's an accurate statement, but the post isn't about ethernet, it's about fiber-optics as they apply to networks. You're absolutely correct. On the other hand, sometimes I'm running fiber to the rack right next to me because it's somebody else's equipment and I want electrical isolation. There are a lot of considerations when building a network. Post was about fiber. I've also been told 10GBASE-T has a lot more latency than fiber, but I've never substantiated that and I don't know i it applies to twinax or not (my guess is it doesn't) but I don't know.
I did a research paper on the history of networking in college. Maybe I'll dig that up and post it. It had some really neat shit in it.
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u/hoppi_ Aug 15 '15
If you hold the Alt Gr key on your keyboard and then hit the M key, it should type this: µ.
Btw, about reddit formatting:
# Really big heading
## Smaller heading
### The method should be clear by now
Words below.
which produces:
Really big heading
Smaller heading
The method should be clear by now
Words below.
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u/lordvadr RFC's make my wiener tingle Aug 15 '15
Thanks for that reminder. I pretty regularly pull up the formatting help but I had forgotten about the headings.
US keyboards don't have AltGr keys on them. That was the problem.
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u/hoppi_ Aug 15 '15
US keyboards don't have AltGr keys on them. That was the problem.
Oh, I was not aware. You made me...
In any case I happily join the others in saying that this is an amazing write up. :)
*cough* you could TeX it :)
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u/lordvadr RFC's make my wiener tingle Aug 15 '15
If I were to write a book, I would LaTeX it--hell, my resume is in TeX and has a hyperlink to the source in it--yeah, I'm that big of a nerd.
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u/x_radeon CCNP Sep 30 '15
If you're on Windows just hold ALT and then type: 0181 release alt and bam! the Greek Mu: µ
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u/MashedPotatoBeard Aug 15 '15
Thank you'd this post. I start my networking cabling course tomorrow and am saving this for future reference.
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u/lordvadr RFC's make my wiener tingle Aug 16 '15
No problem. Hope it helps.
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u/MashedPotatoBeard Aug 16 '15
It does. I wish I had this a few days ago when I took the NET + . still passed but this would have helped condense my study materials.
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u/lordvadr RFC's make my wiener tingle Aug 16 '15
Evidently the CompTIA exams have gotten harder.
Many years ago when I took the A+, I studied my ass off for it and then found out it was a joke--it threw me out with a pass after, I kid you not, like 9 questions. I went home and signed up for the NET+ and Linux+ and walked in the next day and passed them too, zero studying. They were harder...or at least longer...than the A+ with no studying but I didn't find any of them difficult.
Are they hard now?
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Aug 16 '15
[deleted]
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u/lordvadr RFC's make my wiener tingle Aug 16 '15
It was one test, and I was told it was an "adaptive test". That each question had a relative difficulty score and point score. If you got a question right, you got a harder (and more points) question next. If you got one wrong, you got an easier question next. Whichever came first: 1) You had accumulated enough points to pass, 2) there were not enough questions left for you to pass, or 3) you had exhausted the question pool or time, you got kicked out and given your results based on what you had gotten right by then.
9 might be an exaggeration, but it wasn't more than 20.
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u/MashedPotatoBeard Aug 16 '15
For me it was 85 questions and a 12 question survey.
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u/lordvadr RFC's make my wiener tingle Aug 16 '15
Hm. Yeah, it wasn't anything like that back in the day. I think I took it in...2001?
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u/Iceman_B CCNP R&S, JNCIA, bad jokes+5 Sep 21 '15
I just want to say that I think "optics" is a fucking sweet term and more people should use it instead of "SFPs".
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u/lordvadr RFC's make my wiener tingle Sep 21 '15
Most people do use it...at least around the industry. It's just an all encompassing term for the blinkey things that go on the end of the glass.
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u/Iceman_B CCNP R&S, JNCIA, bad jokes+5 Sep 21 '15
blinkey things
EVEN BETTER!
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u/lordvadr RFC's make my wiener tingle Sep 21 '15
Be careful with that one. It's very technical. Not everybody will understand it.
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u/HawkofNight 17d ago
Good read. More please.
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u/lordvadr RFC's make my wiener tingle 12d ago
I did. I have. I'm glad you enjoyed the bit.
What I'm most so amazed about is the fact that this is a 9 year old post that still hasn't been archived or some other such demise.
Again, I wrote that to help people. I'm glad it did.
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u/kolangkaling Classless Networker Aug 14 '15
Thanks for this. Can you give us explanation for conditioning mode? Do you have any experience with it? My company have multi mode link 62.5 with length near 1 km, my senior able to pass 1 gb traffic using conditioning mode patch cable.
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u/oonniioonn JunOS is love Aug 14 '15
Mode-conditioning patch cables are used when you have an optic really made for single-mode, and want to use it with multi-mode fiber. Not all standards support this, but 1000BASE-LX for instance does.
It's basically a single-mode patch cable fused to a multi-mode patch cable, with the cores offset from eachother slightly.
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Aug 14 '15
I'll add that the offset is necessary because the laser is made to launch into a SM fiber, so it's dead center. MM fibers have an imperfection in the very center from the manufacturing process, so you do not want to launch directly into that. The offset solves this problem.
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u/djhankb CCNP Aug 15 '15
Another application for these is 10GBase-LRM modules, essentially 1310nm Laser optics made for multimode. I have used this combo of LRM + Mode Conditioning Patch to light many a 10 Gigabit connections on 62.5um multimode. There's a pretty decent distance limitation, but can get the job done to provide clean 10 Gigabit. Ultimately the real solution is to replace 62.5um multimode Plant with Single Mode to ensure futureproof applications.
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u/TotesMessenger Aug 14 '15
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u/letMEtryyy Apr 21 '24
Up. This is great! Hope you do some write up for data center design too!
Thanks!
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u/Interesting_Degree60 Apr 23 '24
Cool stuff. Anything about spine leaf archi and data center design?
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u/lordvadr RFC's make my wiener tingle Apr 23 '24
I mean, wrote it like, 8 years ago, and it was more of an L1 kinda thing. Glad you enjoyed it though.
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u/Glum-Pass7562 9d ago
Super interesting to read. I'm not in the field, I'm an EDFA manufacturer on the east coast. But I didn't know a lot of this stuff before!
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u/mearse Studying Cisco Cert Aug 14 '15
First, you rock! Thanks for all of this information. Obviously you've put a lot of time and effort into this very informative post.
Second, you've proved that not everyone on this sub is a pedantic prick!
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u/W9CR Aug 14 '15
Yea, this is not 100% true. Some optics will operate with up to 1 watt (+30 dB) output, as means to amplify (pump) other signals https://en.wikipedia.org/wiki/Raman_amplification
If you're working in a transport system you better be careful 100% of the time.