A Guide to SFP Modules

The term SFP module in networking relates to a ‘Small Form-factor Pluggable’ (SFP) module. 

As speeds for network traffic broke past traditional copper limitations, network devices with the ability to provide an interface or modular slot for an SFP became a requirement. This meant that a network device was not bound to RJ45 connectivity and could provide both copper and optical line termination.

You have probably heard of, or have possibly used the predecessor, GBIC, or Gigabit Interface Converter. This was a larger module used to increase ethernet speeds beyond the 100Mbps cap. But there are now many variations of the SFP module for different purposes.

The standard SFP has a ceiling of 1Gbps and comes as an RJ45 (ethernet) or LC fibre connector. There are variations to this which will allow up to 1.5Gbps multi-mode and 2.5Gbps single-mode fibre.

SFP+ modules will take you up to the 16Gbps transit rate. For ethernet the max here is 10Gbps and these modules can support the 8Gbps fibre-channel standard.

Following on from the SFP module is the Quad Small-factor Pluggable (QSFP). These ‘four-lane’ modules are different dimensions to the SFP and will look like a wider module on your network device. The reason these are called ‘Quad’ is that they offer four-times the corresponding SFP transit rates. The QSFP+ modules like the SFP+ then doubles down on the original module and can offer 40Gbps through four-10Gbps channels.

There are further variations to the QSFP standard, QSFP14, QSFP28 and QSFP56, allowing 50, 100 and 200Gbps transit rates. These will often be used in data centers where high data transfer rates are required, this could be for switch uplinks and connectivity to enterprise storage devices.

When choosing an SFP, aside from factoring in the required transit rate for SFP, SFP+, QSFP or QSFP+, you will also want to know what connector you will require:

RJ45

This is your standard copper presentation for ethernet connectivity over twisted pair, as you move up the transit rates you will want shielded and foiled twisted pairs. Ethernet cabling is graded in different categories which can offer different speeds and levels of shielding from interference. In most business and production workloads, Cat6 or Cat6a cabling should be used to ensure at least 1Gbps is achievable, this will work up to 100m distance in most environments. Over short distances (usually up to 37m) Cat6 cabling can achieve 10Gbps whilst Cat6a can maintain this speed over 100m.

Multi-Mode Fibre 

SX is 850nm (wavelength) and up to a maximum of 550m in distance

SX+/MX is 1310nm up to a maximum of 2km in distance

Single-Mode Fibre

LX is 1310nm up to a maximum of 10km in distance

EX is 1310nm up to a maximum of 40km in distance

ZX is 1550nm up to a maximum of 80km in distance (depending on loss seen over that distance)

EZX is 1550nm up to a maximum of 160km in distance (depending on loss seen over that distance)

When looking at the figures above, it is apparent that with today’s required transit rates, SFP modules play an important role in achieving speeds beyond the boundaries of twisted pair copper. Transit rates of over 1Gbps are possible through these modules, and at distances well beyond copper limitations.

We would always recommend the flexibility of an SFP+ or QSFP (Data Centre switching) ready network device. You have the option to start at copper 1Gbps rates and then increase transit rates as requirements change through SFP+ modules for fibre. With SFP+ being backward compatible with SFP, this is easily achievable.

This is only an initial guide to SFP modules. If you would like any further information or a free consultation ahead of any project work you have coming up, please do reach out to us and we will be happy to guide you through SFP modules and take the stress out of the task ahead.