How to get 1 or 2Km of optical fiber?

Steve Alligood steve at betterlinux.com
Mon Mar 18 10:02:24 MDT 2013


Multimode is cheaper overall, roughly half the price for optics, connectors, etc.  It is more forgiving in some scenarios, and generally is easy to use. (plug it in and go)

It's disadvantage is distance.  For GigE, you are limited to roughly 550 meters, though with quality optics and 50 micron fiber, I have gotten decent signal at almost twice that distance (mileage may vary).  10GigE is limited a lot more, based on quality of fiber.  OM3 will get you up to 300 meters, with the new OM4 going to 400 meters.

Singlemode can easily do 10 km, and with more expensive optics, can do 40 km and even 80 km.  You have to be careful of signal strength, so you don't burn out the receiver, or have a weak enough signal that you don't link up.  (There are optical pads that can be used to reduce a too hot signal.)  You also have different wavelengths for the laser that have different properties or strength, distance, and price, and both ends must match up on the wavelength (sounds obvious, doesn't it?).  Singlemode can also have rolloff and wavelength attenuation issues at some distances, but 10 km and even most 40 km runs are pretty straightforward, and even longer can work fine if you put a switch in the middle rather than just amplify the signal.

Multimode optics are $50-$150, depending on many factors - type of optic (SFP, GBIC, XFP, etc), speed (1G, 10G), quality, etc.

Singlemode optics are $100 - $3500, same factors of type, speed, quality, but also distance (10km, 40km, 80km).


Also to consider, a lot of switch manufacturers try to lock in their optics to their hardware, so you cannot get third party ones at half the price.  Good news is that places like OSI (osihardware.com) write custom firmware so if you specify the hardware vendor, they can often make optics that will work.  At half the price.

-Steve

On Mar 18, 2013, at 9:38 AM, Michael Torrie wrote:

> On 03/18/2013 08:24 AM, David Landry wrote:
>> Unjacketed fiber is commonly sold in spools between 10km and 50km. That
>> would require you to jacket them and connectorize them yourself. I also ran
>> across jacketed, pre-terminated spools here:
>> http://www.lanshack.com/Outdoor-Pre-Terminated-Assembly-C51.aspx
> 
> So does anyone know what fiber one would use for a short link, say 250
> meters or so?  Multimode or singlemode?  Singlemode is slightly cheaper
> and has no significant bandwidth cap on it.  But I can't get a clear
> answer on the interwebs as to which kind is best to use for what.
> 
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