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68

There are a fairly large number of factors to consider and it is also important to accept that not all fiber is the same just like not all twisted pair is the same. Here are a few things that occur to me. Of course these may vary depending on environment. Fiber: Much longer max distances, depending on specification and throughput. No electromagnetic ...


44

Main difference: Singlemode fiber has a lower power loss characteristic than multimode fiber, which means light can travel longer distances through it than it can through multimode fiber. Not surprising, the optics required to drive singlemode fiber are way more expensive, especially considering any varying circumstances. When to use each: Both singlemode ...


40

No, the numbers are right (Page 46). If I can reword your question, it's "Why should I use fiber if the propagation delay is worse than copper?" You are assuming that propagation delay is an important characteristic. In fact (as you'll see a few pages later), it rarely is. Fiber has three characteristics that make it superior to copper in many (but not ...


33

While most other answers have talked about Length limits, Interference issues and are all correct. One important factor while choosing the cable is the speed of the network and the devices you plan to use. The general specifications for currently available ethernet network speeds are as follows Twisted Pair Copper Cable Category 5e 10/100/1000BASE-T ...


31

Multi-mode fiber (MMF) uses a much bigger core and usually uses a longer wavelength of light. Because of this, the optics used in MMF have a higher capability to gather light from the laser. In practical terms, this means the optics are cheaper. Single-mode fiber (SMF) has much tighter tolerances for optics used. The core is smaller and the laser ...


23

If cost is a factor for you, I would look at it like this; Scenario 1 If you are making a short run, say 50M, I would go for copper, simply because of cost (This 50M run is between two comms cabs in an office building for example). Copper is cheaper and using switches would save on the cost of SFPs or GBICs and so on. We obviously aren't talking thousands ...


22

There are a number of things ISP's do: drag bundles of fibers across continents. Since this is very costly, only a small number of very large companies do this and many ISP's rent fiber-pairs from these companies rent capacity (a wavelength, VLAN, MPLS circuit, etc) between to an IXP from a company who owns (or rents) fibers. Since the capacity of fibers is ...


20

The WS-G5484 is a multimode fiber connector. If you're using standard multimode fiber (62.5 micron), you should be about to get around 300m distance out of them. With 50 micron fiber, that number should go up to around 500m.


18

If you ever feel that you are going to run FCoE over the medium then it is better to run fibre than copper as the BER for copper is significantly higher and most of the time will be outside of the tolerance for the 'lossless' nature of FCoe.


17

Twisted pair uses differential signaling - in a pair, one wire is always the negative/complimentary signal of the other. In the simplest example, Transmit+ > Transmit- (higher voltage level) means 1 and Transmit+ < Transmit- (lower voltage level) means 0. Put in another way, each wire is a reference for the other. There is no reference to ground. For ...


16

Generally when you're working with fiber you have to be concerned about two things: 1. Type of fiber: Long-Haul: Single-Mode, used for long distances. Example: Across a city Short-Haul: Multi-Mode, used for generally shorter distances. Example: Internal to your campus/building *Caveat: There are different types of Single-Mode and Multi-Mode. 2. ...


16

I will add another factor that hasn't been mentioned. I can quickly and easily make copper cables, measured and cut to the exact length I need for a run...resulting in neater cable plants. While you can cut to length and put ends on fiber optic cable, I find it considerably more difficult and time consuming...and my experience doing this is with multi-mode ...


16

It all really depends on your requirements and current setup. That being said, here are some of the main ones. Active Pros: Active can fit a lot more wavelengths (colors) onto a single fiber pair. The pro being, the composite signal that is sent over a single fiber pair can carry more bandwidth than a passive of the same size could, in turn you don't ...


15

The distance of the fibre isn't a good indication of whether you'll be able to run a specific optic/speed across it. You need the path loss (measured in dB), which can vary greatly between links of the same distance (due to number of splices, fibre quality etc.) Also, the distance of the fibre in the ground is usually about 25-30% longer than the path it ...


13

Some things that I haven't seen mentioned: 1) 10GBASE-T uses a lot of power compared to fiber to DAC. 2) 10GBASE-T transceivers have much higher latency than other options. This could be important in a compute cluster or other low latency environment like automated financial trading.


13

Neither, really. Replacing a copper link with a fiber link might lower latency a tiny bit (assuming an uncongested link), but what you really get when you replace a "core" link with a higher bandwidth link is less possible congestion. In your example scenerio, it doesn't matter, because there is only one device on each end. In a live network, though, moving ...


12

Have you looked at using a separate external mux? I've run parts of our rings on pairings of ordinary (but colored) 10G optics and passive CWDM muxes with a single strand on each side. This let us also do multiple parallel links at the same time (we used 8 channel muxes).


12

Per the ANSI/TIA/EIA 568, Commercial Building Telecommunication Standard, UTP cabling is limited to 100 meters. That length assumes up to 90 meters of solid-core (better performance, but fragile) horizontal cable, and no more than 10 meters of stranded (poor performance, but less fragile) patch cord divided between both ends. Installation is critical, and ...


11

[MMF] longer wavelength (850nm), much wider beam vs. [SMF] short wavelength (1310nm-15??nm), narrow beam. The key difference that no one has touched is "modal dispersion", which is a fancy term to describe how the light moves through the fiber. This page goes into far more detail. The first picture sums it up... MM is bouncing off the edge of the fiber ...


11

Signal travels roughly same speed in copper and fibre, copper being slightly faster. Fibre is determined by refractive index, typically speed being about 0.65c, i.e 200km per 1ms (single direction, not RTT). Maximum theoretical throughput is hard to determine, maybedivide wavelengths to Planck length difference and light each up, so absurd amount. But in ...


11

You can use short range SFP optics for this. The Cisco part number is GLC-SX-MM, and the cost is about $75-$100 each (you'll need two). The person installing your fiber should use 50uM multimode fiber (62.5uM is also useable, but you're getting close to the maximum range) with LC type connectors.


11

EDIT: Fixing answer now that I'm on a real laptop. Yes, OM3 is just "laser optimized" multimode, it will work with both your optic and distance. What are the limitations in terms of bandwidth/distance? Max Distance @ 1Gbit/s (per the product page): 550m This also lines up with the OM3 specification http://en.m.wikipedia.org/wiki/Multi-...


10

Here's a few things not yet covered. Using only single mode lets you use one fibre type for everything (fewer optics, cable types to spare) No likelihood of obsolescence (eg, OM3 seemed like it was current for ~3 years) Offers single-pair options for 40 & 100g Offers single-fibre options at 1 & 10g Although the optics are more expensive they're < ...


10

Please read Everything You Always Wanted to Know About Optical Networking – But Were Afraid to Ask :)


10

Lots of people have answered already; and I agree: Fiber beats copper as soon as distance becomes a factor. But beware of multimode fiber; it also has serious distance issues. You can only go 550 metres on GE (1000BASE-SX), and some of the 10GE modes manage 330 metres on really good multimode fiber (OM3 or OM4). In a larger colo or CO or in a campus ...


10

Cross on one of your patch cables. You want your installed fiber plant to be labeled correctly at both ends (Strand 1 at Site A = Strand 1 at Site B).


10

Common practice would be just to cross everywhere since you will always get an uneven number of crosses which will result in an overall cross. But this only works if your fibres were installed by a sane company. Basically you need to know that: a) Couplings cross b) You need crossed cables/trunks everywhere (which *should* be default) So let's test that: ...


10

Absolutely: NO Think about it for a second... you're firing a 62.5um (or 50um) laser into a 9um fiber. That means ~85% of the signal is gone from the very start. (The opposite will work: SM launched into a MM fiber, but it takes good fiber, a Mode Conditioning Cable, and your distance will be compromised. But it can work.)


10

Wavelength and rate are the two big ones. As you're dealing with 10G ethernet, rate isn't in question. (if we were talking about fibre channel, or SONET, then it would matter.) For your specific case, they are providing service through a 1310nm "LR" (long-reach) interface. The "SR" (short-reach) optics will not work -- wrong wavelength (850nm) and wrong ...


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