Convention restricts the distance that a 10/100Base T(X) Ethernet network can be connected over CAT5e to a maximum of 100 metres. This is a physical limitation of the cable and of the devices which are transmitting and receiving the Ethernet traffic between them. For simplicity in the example below we will use a switch as our transmitting and receiving device.
In a Cat5e based LAN you would normally have to add at every 100 metre increment a Switch to regenerate the Ethernet transmission and pass it on to the next LAN segment for a further 100 metres. All these Switches would need to be powered, so a local power source is necessary at each network node point.
Example of a Cat5e based LAN segment of 200 metres between Points A and B
(Assumed local power available at both End points, no power available mid-span)
If your Cat5e based LAN has a 200 metre segment between points A and B you would need 3 Switches to make the LAN operate correctly (one mid-span and one at each end)
In many Industrial and CCTV applications it is not easy to site a mid- span switch, as the CAT5e cable may have to be run in ducting or cable trays. Even if the Cable can be broken out to a mid-span switch, a local power source may be difficult to establish to power the switch and the switch will need to be housed in a suitable enclosure. All these things add complexity and cost to the project.
There is the possibility to use a mid-span POE powered switch (acting as a PD) to solve the mid-span power source issue. These devices are not that common to find and command quite a price premium. One of the end point switches will also need to be a POE Switch (acting as a PSE) and be the power source for the mid-span switch. If you try to extend the LAN segment over several 100 metre segments this technique becomes complicated to use in practice, as you need to ensure suitable power levels are reaching each mid-span device.
There are other Ethernet transmission technologies which can also be considered, two of the most common options being:
- Transmission over fiber-optic cabling
- Transmission over WLAN (Wi-Fi)
Transmission over fiber-optic
Using Fiber Optic cable (glass-fiber) will easily achieve the required transmission distance between points A and B. Two media convertors will be required and these can be purchased relatively cheaply. The cost of installation and termination of glass-fiber optic cable will be considerably more compared to Cat5e cabling. It is also much harder to install and terminate fiber-optic cable correctly – it requires expensive specialised equipment and trained staff. Multi-mode grade glass-fiber transmits 100Mbps Ethernet typically 3Km between nodes.
Transmission over WLAN (Wi-Fi)
With the second option of WLAN, straightaway full 100Mbps throughput over a 200 metre link using IEEE802.11a/b/g or even 802.11n will not be achievable; something approaching 40 Mbps is more likely. The Wireless units will also need true L.O.S (line of sight) to achieve this, so no large obstructions in the path are acceptable. A Radio Site Survey is recommended to be carried out to ensure that a WLAN link is achievable. Installation costs of the WLAN units and suitable antennas can be expensive with Industrial grade WLAN equipment being significantly more expensive than Enterprise grade equipment.
For this example the above two options will inevitable be expensive and in the case of the WLAN will not offer full 100Mbps throughput.
There is a new alternative to these traditional technologies which offers a low cost solution with full 100Mbps throughput over CAT5e cable for distances greater than 100 metres
The Veracity OUTREACH line powered LAN extender meets this requirement.
No configuration of the devices is required. All that is needed is a POE switch at one end of the link (or alternatively a low cost POE Injector is introduced into the LAN with a Non POE switch) to power the OUTREACH LAN Extender device via the Cat5e cable. The switch at point A is connected to the OUTREACH (IN port) by a 100 metre length of CAT5e cable. The OUTREACH (OUT port) is then connected to another 100 metre length of Cat5e cable to the end Switch at point B.
The OUTREACH units are very compact and can easily be sited in ducting or Cable Trays with minimal intrusion. The OUTREACH units are also significantly cheaper than equivalent Industrial grade POE switches.
The diagrams below show two ways of easily achieving the required LAN segment using OUTREACH.
In addition OUTREACH can also provide safe POE power to POE end devices, if required. These applications will be covered in a separate Application note.
Conclusion
In the above example of a 200 metre link the most cost effective solution without doubt would be to use the OUTREACH LAN extender with an OUTSOURCE POE Injector and conventional Switches.
If the LAN is within an Office or Factory environment then use of the OUTREACH LAN extenders becomes particularly attractive in terms of cost and ease of installation. OUTREACH devices can easily be daisy chained to create extended LAN segments of up to 1000m with all the OUTREACH devices powered from the Cat5e cable.
Using OUTREACH LAN extenders is a very cost effective alternative to using fiber-optic and WLAN technologies.
It is also important to realise there may be other reasons why Cat5e may not be the best technical option and an alternative solution should be used instead. In particular if galvanic isolation is required (to reduce ground loop problems) or if there is localised electrical noise interference issues.
Special Note: Using Cat5e Outdoors
Standard Cat5e is not designed to be used outside. There are suitable outdoor grade CAT5e cables available, but these are much more expensive than standard Cat5e. With any long piece of Copper cable being used outdoors the possible effects of Lightning strikes also have to be considered. Networking equipment is particularly susceptible to transient spike damage, so special precautions need to be taken, such as fitting in-line Lightning Arrestors into the LAN segment. This naturally adds to the cost of the installation.
For advice on selecting the best solution for your application please contact us by phone on 0203 086 9569 Extn 10# or by e-mail at sales@industrialcomms.com
For details on the OUTREACH product range please see the relevant product section on our website - Ethernet Extenders & PoE Forwarders
Click to download this Application note: Expanding Cat5e LAN Segments over 100 metres v3.pdf
