Typically, the fiber optic cabling inside a storage subsystem or between servers, switches, storage and other devices will be MMF. SMF cable is capable of supporting longer distances by using a smaller diameter modal dispersion that is more expensive to produce. MMF fiber cabling has a shorter distance, thus easier to manufacture, more commonly used and less expensive. Note that as you migrate to faster interfaces including 10 Gb Fibre Channel and 10 Gb Ethernet where MMF might have worked for some extended campus and data center distances, you may be better off investing in SMF moving forward. Another cost factor to consider regarding fiber optics for Fibre Channel, Ethernet and other optics-based networks is the cost of the transceivers (GBICs, SFPs, XFPs, etc.). You can read more about fiber optic cabling in Chapter 5 "Fiber Optic Essentials" in my book Resilient Storage Networks.
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This was first published in September 2004