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Types of fiber use from edge to the core.

Does anybody here know about the difference between using a single mode and a multimode fiber from edge to the core? Right now we are using all multimode fiber to connect all the switches. Is it true that using a singlemode is much faster and can handle more bandwidth? all our closet or remote connected through other buildings are less than a mile. I have also found that there are multimode fibers connected to a GBIC single mode in our network. It's weird but they said it's been working fine ever since they became a cisco shop. I kind a know what the difference between the two but I still wanted to ask for a 2nd opinion.


Re: Types of fiber use from edge to the core.

Hi Bauti

AFAIK its the distance which decides the mode.

If its in your local lan you can make use of multimode fiber to connect your equipments.

Again the same will be connecting your SX modules and once the distance goes out of reach then you need to look for LX or ZX modules to have the connectivity established.

do find this link for more info on wavelength,distance matrix..


Re: Types of fiber use from edge to the core.

The distance that can be traversed is the main difference between single and multi-mode fiber. Rule of thumb: within a building you use multimode, between buildings or sites that are more than approximately 250m apart, you will need to use single mode. Throughput is actually less important when you have to choose between the two.

There is however a considerable difference in pricing and hence you need to have good reasons to choose single mode.

In modern cabling systems, a multimode fiber of 50/125 is the most suitable cable.




Re: Types of fiber use from edge to the core.

A single mode fiber supports only 1 wavelength of light.Its core diameter is around 9um. Multimode carries multiple wavelengths in its core (about 50 to 62.5um). This accounts for more loss of the signal when it is transmitted down the line. This is due to wave dispersion, basically the different wavelengths beat each other up and there is cancellation of signal strength. SingleMode has less dB loss for a set distance then multimode. Usually Single mode uses Lasers for its xmitters as opposed to multimode which uses LED's. Singlemode is more expensive then multimode. You will usually see singlemode fiber handed off from the carriers into your building. This way they can get the signal to you with the least amount of repeaters. You will also see singlemode used for DASD applications for storage (Ficon). Hope this helps...

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Re: Types of fiber use from edge to the core.

Also, regarding LH/LX GBICs with Multi-Mode fiber. It is possible to allow this with proper conditioning cables as discussed here:

I wouldn't recommend it due the higher cost of Long Haul media, but it will work.

rate if helpful.


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