For the Nerds out there, this one’s not for you.
While Internet Service Providers are still reluctant to quickly connect all households to the Internet with fast fibre optic lines, end users can already set up an optical fibre connection for their local network with the so-called SFP standard. And at comparatively low cost.
SFP (small form-factor pluggable) is not new at all, but is not yet very well known and widespread in private households and small businesses (SoHo – Small Office Home Office). What we are talking about small modules roughly in the shape and size of a USB stick, which are plugged into slots (SFP cage) of suitable routers or LAN switches. SFP modules serve as connectors for fast Ethernet to connect fibre optic cables. These modules are easily exchangeable (hot-swap capable) and can therefore be replaced with modules with higher transmission rates (SFP+, SFP28 – links to Amazon) if required. – Provided, of course, that the rest of the hardware and the cables also support the higher data rates.
The traditional SFP modules support Gigabit Ethernet and are therefore sufficient for today’s most common LAN installations in private households and SoHos.
What are the advantages of optical connections?
Apart from the already mentioned easy replacement and upgrade-ability of the small SFP modules, one of the main advantages of SFP is the possibility of bridging longer cable distances with comparatively thin and flexible optical fibre cables (optical fibres). Depending on the design, 200 meters to several kilometres are feasible, but of course the fibre optic cables can also be used for shorter distances. The cables designed for duplex connection are “two-core” (one optical fibre each for the outward and return channel) and, thanks to their optical transmission method, do not require complex shielding. Due to their nature, they are completely insensitive to electromagnetic interference on the signal path and provide galvanic isolation between transmitter and receiver. They are also free of metals and thus corrosion-resistant. This also applies in part to the connection plugs. However, the ends of the sensitive optical fibres must be correspondingly well protected against contamination.
Possible areas of application would therefore be the bridging of longer connection paths, for example in flats between the cellar and the attic, or the connection of the garden arbour on an extensive property. The thin fibre optic cables are also easier to hide behind skirting boards than electrical Ethernet cables. This alone could be a reason to set up an SFP connection.
Standard SFP cables are very inexpensive (roughly on par with conventional Ethernet cables) and are generally suitable for faster connections (SFP+, 10 Gb/s).
And the cons?
Apart from the additional hardware required, the benefits are probably small in most cases. It depends very much on personal needs. Even with conventional electrical Ethernet cables, quite long distances can be bridged and, if necessary, extended by repeaters. A disadvantage of SFP could be the lifetime of the optical transceivers. Some manufacturers estimate this to be about 5 years, while others give a “lifetime” guarantee (for mostly more expensive modules). The modules responsible for optical transmission are subject to a certain ageing process. However, I currently have no data on the normal lifetime of SFP modules.
What hardware is required for SFP?
Since common Internet routers and LAN switches for home use usually do not have SFP-enabled ports, some additional hardware is required for optical LAN cabling. However, the effort and costs are kept within limits.
You need this for a simple SFP installation:
1. an Ethernet media converter
First the Ethernet signal coming from the router must be converted into the optical format. This requires a small box like this, which can be purchased for less than 20 Euros. Small drawback: the converter needs its own power connection (wall wart included).
2. an RJ45 patch cable to the media converter
The Internet router is connected to the media converter with a conventional LAN cable.
3. SFP modules (two or more)
Multi mode Gigabit SFP modules like this one from TP Link (approx. 14 Euro/piece) are necessary wherever the signal has to be converted from electrical to optical or vice versa via an SFP port. The first SFP module is plugged into the SFP cage of the media converter.
4. fibre optic cable in suitable length
Order optical connection cables like this one in suitable quantity and length (price for 10 m approx. 10 Euro)
5. another media converter or an SFP-capable switch
At the end of the connecting path, the signal must be converted back to the electrical level. This requires another SFP module which is plugged into the SFP port of a compatible switch (like this one) or terminal device and establishes the connection with the fiber optic cable.
Always remember: An SFP port on a device is not yet a connection! SFP ports are only empty slots into which an SFP module must be plugged. If you have other SFP-compatible devices at your destination that are to be connected with fibre optic cables, you will have to purchase additional SFP modules in addition to the cables.
Apart from the SFP-enabled switch in this example, the cost of hardware and cable is less than 100 Euros. An SFP-capable multi port switch, if required, is available from about 60 Euro, depending on the equipment.
SFP in practice: It just works
My own experiences with SFP in practice are not very old, so I cannot make any statements about reliability over a longer period of time. What I can confirm, however, is the uncomplicated installation, which can be done by any technically halfway talented person, because basically everything is plug-and-play: Connect media converter, plug in SFP modules, connect cable – running. Just like a normal LAN switch, only with the SFP modules plugged in additionally.
By the way, these snap firmly into the SFP slot. To remove them, a small bracket must be folded down on the module. The cables snap into the socket, just like conventional RJ45 connections, with small safety hooks, which are unlocked by pressing a small tab to remove them. The optical fibre ends of the cables are fitted with small plugs for transport, but these can be lost very easily.
As with all sensitive computer components, such as memory modules, care should be taken when handling SFP modules to ensure that the body is earthed to prevent damage from over voltage (spark over).
Changing your own network to an optical Ethernet connection or expanding it in parts with SFP technology is not a witchcraft and is not particularly expensive. Especially the very thin fibre optic cables compared to conventional Ethernet cables could be real problem solvers in certain structural situations.
Perhaps the most common application scenario would be if the router is to be located very far away from a switch for connecting several terminal devices. The galvanic isolation provided by the optical connection could also be of interest in measurement technology environments or for audio applications.
Last but not least: The setup of the SFP connection is very simple and the operation (according to previous experience) is reliable. Thus SFP is a good alternative to conventional electrical LAN connections.