The internet appears to be everywhere, all the time, on your computer, on your phone, on your refrigerator, and even your car. The infrastructure that supports this technological marvel is more humble that most people guess: wires and radio signals. In the case of ethernet cables, the limitations may even seem laughable. In a county criss-crossed with millions if not billions of miles of telecommunications cables, a single, twisted-pair ethernet cable is only cable of carrying a clear signal for 100 meters before it needs to be boosted.
Few people ever encounter this limitation in residential applications, but commercial IT departments must contend with it on a regular basis when building out local area network (LANs). Fortunately there are a number of ways to extend the reach of ethernet cables and achieve the desired level of performance.
It’s useful to distinguish between LAN extensions that allow you to expand your network to new locations servicing multiple devices and LAN extensions that service single devices installed at far-flung locations, such as IP surveillance cameras and sensors. While the fiber-optic option discussed below can be used to service single devices, it is by far the preferred solution for creating new LAN hubs for multiple devices. The other three solutions work better for reaching isolated devices.
One way to overcome the distance limitations of copper structured cables is to integrate fiber optic cabling into your infrastructure. Fiber optic cables can greatly extend the range of your wired network. Multi-mode fiber optic cable can operate reliably up to 550 meters, whereas single-mode fiber optic cables can go up to 30 km — that’s 300 times farther than one continuous copper ethernet cable can go.
This blended approach requires media converters and other infrastructure to transform the electrical signal from the ethernet cable into the optical wavelengths required for fiber optic cables. A common approach is to run fiber optic cable between two media converters so that you can use your ethernet equipment at the destination as well as the origination point.
You will need to budget for additional equipment and installation costs for fiber optic cable. And even though fiber optic cable is capable of higher speeds and bandwidth than copper ethernet, you’ll still be constrained by the slowest link in the chain: copper ethernet at either end.
It’s possible to use a similar approach to the copper-fiber-optic-copper “daisy chain” outlined in the previous section, but use a digital subscriber line (DSL) converter to deliver up 50 Mbps speeds over 300 meter distances (3 times the limit of ethernet), before converting back to standard ethernet. In this case you sacrifice some speed using DSL, but your equipment costs should be lower compared to fiber optics — DSL is a legacy technology.
Wireless extension of a LAN operates similarly to the ubiquitous household technology of running a copper cable to a router that projects signal wirelessly for nearby devices. However, industrial applications differ in some key ways. Wireless extenders can bridge distances of several miles, provided there is line-of-sight between the transceivers. Speed and signal integrity will not compare equally to hard-line extensions, such as copper or fiber optics, but the simplicity of installing two transceivers without digging trenches or laying cable between is very attractive from a cost perspective.
The power-over-ethernet (PoE) protocol allows IT professionals to install a single PoE-compatible cable and supply power and signal to the device — extremely useful for far-flunch surveillance cameras and other sensors installed far from the existing electrical infrastructure. A PoE injector works by delivering DC power into the ethernet cable, which is subsequently connected to an ethernet extender (or signal booster), which terminates at the device requiring signal and power (such as an IP surveillance camera or sensor). A single PoE injector can be daisy-chained with up to four PoE-compatible ethernet extenders, allowing for a LAN reach of up to 500 meters.