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Why Network Designers Specify Particular Brands of Optical Fibre for Their Systems

People sometimes wonder why network designers specify particular brands of optical fibre for their systems, such as Corning SMF-28e. Usually, the designer wants to guarantee the highest optical performance in the network for his customer and ensure fibre compatibility. Incidentally, all of the cables provided by Rustyice Solutions contain genuine Corning fibre.

On a large network installation, there may be several installation contractors working on the project. Using compatible fibre is essential for ensuring that the part of the network you install will work correctly with the rest of the system. Before you bid a job, make sure that your cable vendor can provide the correct fibre.

Singlemode Compatibility Issues

There are several domestic fibre manufacturers that produce “standard” SMF-28e singlemode fibre. These companies spec their fibre as being fully compatible with or equivalent to “standard” singlemode fibre. However, if you are adding “sub standard fibre” to an existing network, you may run into some compatibility issues. These include:

* Operating Wavelengths: Corning has enhanced their product to carry wavelengths from 1280-1700nm. However, some “sub standard” fibre still has an attenuation peak in the 1400-1500nm window. These fibres won’t be compatible with many of the new Fibre-to-the-Home networks that need to operate at around 1490nm.

* Index of Refraction (IR): The IR of some “sub standard” fibres is slightly different from the IR of Corning fibre. This difference can cause additional optical loss in a system where the two different fibres meet. This can also cause confusing OTDR results. Under certain conditions, a slight difference of IR between two spliced fibres can produce a “gainer” on an OTDR trace. A “gainer” is an OTDR splice event that appears to gain optical power through the splice instead of showing a slight loss.

* Splicing: Fusion splicing an “sub standard” fibre to a Corning fiber may require you to set custom splicing parameters in order for your fusion splice machine to fuse properly.

Multimode Considerations

Compatibility problems are not confined to singlemode fibre. There is an issue with multimode fibre regarding “On-Center Laser Launch.”

Newer Corning InfiniCor multimode fibres are designed to work in laserbased protocols, such as Gigabit Ethernet, without requiring mode-conditioning patchcords. These new fibres allow you to launch a laser directly into the center of the fibre core without inducing modal dispersion at fast transmission speeds. However, older multimode fibres, and some “sub standard” fibres, won’t work in a gigabit network without some sort of off-center launch mode conditioning. If a non-compatible multimode fibre is placed directly into a gigabit network, the network’s transmission rate will drop significantly.

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