Hot answers tagged

42

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 (...


24

Connecting two fiber trunks is a tedious process. Those are splice cassettes for optical fiber - each single fiber is fusion spliced and looped into one of the cassettes for protection. Afterwards the whole box is sealed and buried or put in a cabinet.


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 ...


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 ...


17

They're a fiber splicing crew. The white plastic trays are used to organize fiber connections. A waterproof enclosure will protect the whole assembly from debris when their job is finished, and the enclosure will be stowed somewhere, e.g. in an underground chamber or an above-ground pedestal.


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 ...


13

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 ...


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).


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

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 ...


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

Most likely they mean a wavelength on a DWDM path. With DWDM, a fiber operator can use one single pair of fibers to carry a number of different colors (wavelengths) of light using multiplexing. Each of these colors can then be used to transmit its own signal, for example 10Gbps ethernet. This way, they are able to use a fiberpair more efficiently.


10

Do I need to protect the physical empty SFP port? What's a good way to do so? Empty SFP slots should be covered when not in use, so no dust is sucked up by the system fan - depending on how dusty the environment is, pressure of the fan etc, this isn't required at all times. Do make sure the slot is clean before inserting a module though. You can use just ...


10

ANSI/TIA-568.3-D is the appropriate and up-to-date standard for fiber installations. You should ask your contractor to comply with these guidelines. When we hire a subcontractor, we always ask for the fiber technician to be Fiber Optics Technician-Inside Plant (FOT-ISP) certified. This means: A Fiber Optics Technician – Inside Plant (FOT-ISP) must be ...


10

OM1 or OM3 makes a lot of difference. Please check https://en.wikipedia.org/wiki/Multi-mode_optical_fiber . You will see that OM1 cable can carry 10G for 33 meters while OM3 can carry it for 300 meters. OM3 application first started in 1998 but standardized in 2002. Most probably, your fiber is OM1 like your patch cords. Best practice would be 1- Check for ...


9

This is directly addressed by the ANSI/TIA/EIA 568-B Commercial Building Telecommunications Cabling Standard: Connecting Hardware and Polarity Optical fiber shall be installed with odd numbered fibers having Position A at one end and Position B at the other. Even numbered fibers will have position A and B reversed from the odd numbered fibers. ...


9

Can a single optical fiber support full-duplex communication? Yes. There are "BX" standards, e.g. 100BASE-BX, which use different wavelengths for send and receive. The transmit wavelength on one end needs to be the receive wavelength on the other end. For example, Cisco has these transceivers: 1000BASE-BX10-D and 1000BASE-BX10-U SFP for Single-Fiber ...


9

300m of OM1 will NOT work with 10GBASE-SR, as JFL and kaya atabey have already pointed out. From 2003, it's quite likely OM2 which won't work with 10G-SR either at that distance. Additionally, patch cables should always match the plenum cable, OM1 won't help here either. You need to make sure what kind of cable you've got. If it is less than OM3 you'll need ...


8

Ethernet over fiber works the same as Ethernet over copper wire (for the most part), so the networking configuration will essentially be the same. But you mention a bag of tools -- you should know that the tolerances for fiber connecters are way more strict than RJ45 connectors. Fiber ends need to be cut a certain way, cleaned, polished to remove ...


8

Your biggest risk comes from Single Mode ER (40 Km) and ZX (80 Km) optics, which can overdrive and even burn inputs without sufficient attenuation. There is no risk of burning Multi Mode optics, as long as you're connecting MM to MM.


8

Due to the way that fiber lasers work, common digital encoding on fiber is <20% is a 0 and >80% is a 1 so the beam is never "off" it just varies between low and high power. Turning the laser OFF is much more of an event than varying its power level, so this method is faster. The transmitted data is put through various encodings before going on the fiber ...


8

Part 1: Using fiber to run a 1000 foot ethernet link Using fiber to run a long ethernet link is not quite as simple as you make out but it's certainly not unreasonable to DIY. A few things you have missed. Putting connectors on the end of fiber is a specialist job. If you don't want to involve any specialists then you need to buy pre-terminated fiber ...


8

My question is: is it such a big deal to put cabling into a closed rack? No. It can make working on the cabling more difficult and add time (i.e. labor costs) to the work, but I have seen this done well plenty of times. Of course, many organizations choose to use top of rack switches or extenders rather than cabling. Is it such a big deal to have a ...


8

The light levels will decrease (0.3 - 0.5)dBm in best case scenario. Why aren't you using direct SC to LC patch cord without the adapter?


8

From the J9150D datasheet you linked, the max transmission distance over an OM1 fiber is 33m. Thus you need other transceivers, or to change the fiber.


7

In a word: YES. Unless you want to do something like force a 10G SFP+ to link at 1G, you don't have to do anything but plug it in.


7

If you have a fiber scope (you really should, to check if connections are clean) the core size (but not OM level) is obvious by inspection, especially if you look at a known connector and then the unknown connector (or better yet, two known connectors, one of each size.) Image from theFOA.org


7

You are conflating many things here, so let's try to detangle the issues in your question. Data rate is data rate, regardless of the physical medium. A 1Gb connection has the same data rate whether it is fiber or copper. As @toddwilcox mentions, the advantages of fiber over copper are longer spans and electromagnetic isolation. Data rates are independent ...


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