Fiber optic: Lay the right connectors and cables yourself


The thinnest part of a fiber optic cable is the fiber optic cable itself. In the middle is the core, and around it the jacket – the latter has an outer diameter of only 125 micrometers (µm). Everything around it no longer belongs to the fiber optic cable itself and is only used to protect against external influences. The first decision when buying a cable depends on the planned transmission method: should the transceivers work in singlemode or multimode?

The fibers for multimode transmission have the designation OM in their name, singlemode fibers OS. In the multimode world, new standards were regularly invented and improved: Very old cables according to OM1 (introduced in 1989) still have a core diameter of 62.5 micrometers and a sheath of 125 micrometers. This is often printed as “62.5 / 125”.

Anyone who has laid such lines and has a stable gigabit link does not need to do anything. However, the probability of being able to convert an OM1 fiber with SFP + modules to 10 Gbit / s is low – according to the data sheet, it’s over after 33 meters. Since OM2 (introduced in 1998), the core to clad ratio is 50 microns to 125 microns. 10 GBit / s over 80 meters are not provided. In 2002 OM3 came on the market as the successor, in 2009 OM4. The diameters have not changed, but the fibers have been optimized for the lasers used in new transceivers. OM4 is still the most widely used fiber. 40 GBit / s and 100 GBit / s can also be transferred over it. OM5 came onto the market in 2014 and is optimized for the wave multiplex method SWDM, in which several wavelengths are used at the same time in order to be able to send several connections in parallel over one fiber – in everyday administration this technology is rather uninteresting and therefore OM5 has only been used in a few so far Data centers in use. If you want to lay new cables and use multimode fibers, you usually go for OM4.

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