My TN Connection

One of the major problems of the introduction of 1000Base (gig) was the distance limitation of 1000base over fiber optic cables. Most users were aware that 10Base and 100base could run over 2km of multimode fiber optic cable and up to 20Km of single mode fiber optic cable - though advancement in components now allows single optics can now achieve distances of 125Km plus. However, with the introduction and deployment of 1000Base networks over fiber optics users found that their fiber cables could not sustain that rate and were effectively useless. The specification allowed 220 meters over 62.5 micron and 550 meters over 50 micron for multimode and up to 10Km on single mode. Users then had a dilemma, do I not use 1000base, do I replace my multimode cable with single mode or do I look for a new fiber optic system that allows for longer distances.

As for replacing multimode with single mode fiber cable, this would be an expensive option and waiting for advancements could take time and be expensive. Plus not using 1000base at least on the backbone was not an option. Manufacturers of networking equipment started looking at possible solutions, one of them was gigabit extenders which used a proprietary method and proved to be an expensive option - in some cases costing more than the end devices.

In my opinion the easiest and most cost effective solution is to send single mode signals over multimode cable, this allows 1000base to be used up to 2Km on multimode cable (assuming the multimode cable is of good quality and installation).

How is this achieved?

The first component required is a single mode media converter that takes the copper port of your switch and converts it to single mode fiber, you can add a mode condition cable, the mode conditioning cable is a special cable which prepares the single mode signal to be sent over multimode cable (most installers of fiber optic cables can provide this). At the other end of the link you do the reverse - have another mode conditioning cable and a single mode media converter allowing you to continue to use the 1000base network over a longer distance of multimode fiber.

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