Introduction to Fibre Networking

Introduction to Fiber Networking

If you are truly interested in overcoming the distance and speed limitations imposed by 10/100 based networking, Fiber Networking is the direction to travel.

Fiber cabling is presently the best way to get the ultimate in speed-intensive performance from your 100Mbps Fast Ethernet network. Known as 100BaseFX, fiber optics can provide you with extremely high levels of bandwidth, network expandability and data integrity, all of which can span distances of up to 2000 meters (6560 ft.) without signal degradation.

Most network component manufacturers, such as 3COM and Linksys offers 100BaseFX add-on components for many of their Fast Ethernet 10/100 Switches, Auto-Sensing Hubs, and Fast Ethernet hubs. Generally, these modules can be used to uplink your hardware to high speed fiber based network backbones, or allow high speed communication between hubs and switches across great distances. Below you will see two of the latest fiber based network cards release by 3COM and Linksys, both of which have been trouble free in our testing, easy to install and relatively inexpensive.

3COM Fiber Network Cards		Linksys Fiber Network card

The modules shown above are just a few of the many fine examples of recent card releases that will enable you to integrate fiber networking. While we don’t know which module is best for your fiber networking needs, the following may help you along with your decision.

Fiber is commonly used for:

• Long hauls of a thousand feet or more between buildings or LANs. This is an excellent solution for school or university networking as well as governmental and business campus environments. Fiber is usually used as a backbone between hubs that branch off to workgroups with hubs and twisted-pair cabling.

• High-bandwidth applications like streaming audio and video or other forms of high bandwidth multimedia.

• Gigabit True 1000Mbps networking.

Fiber optic networking should not be viewed in the same casual nature as 10Base2 or 10BaseT networking. Unlike 10Base2 and 10BaseT, Fiber Optic Networking requires a great deal of planning before the cabling is installed. You must consider factors such as noise loss and connection types. And cabling distances must be calculated in order to ensure a fail-safe networking environment. If you have never worked with fiber before, seek the help of a professional who is familiar with the medium.

The Cabling

Like thin coax (10Base2), fiber optic cabling is used primarily for network backbones. Made from flexible, optically efficient strands of glass coated with a layer of rubber tubing, fiber uses photons of light instead of electrons for sending and receiving data. Although fiber is physically capable of carrying Terabits of data per second, the hardware available today to generate the necessary signaling can only handle a few gigabits of information per second.

Fiber cables come in many different shapes and sizes with a myriad of connector types. The most common form of fiber optic cable in use today is a multi-mode fiber cable (MMF) with a 62.5 micron fiber optic core. This is the form of cabling that is most used by fiber equipment manufacturers today. Single-mode fiber cabling, is another form of fiber cabling that is far more efficient than multi-mode, however it is also far more expensive.

Fiber network segments require two fiber cables, one for transmitting data, and one for receiving data. Each end of a fiber cable is fitted with a plug that can be inserted into a network adapter, hub, or switch. In the U.S., most cables use a square SC connector that slides and locks into place when inserted into a computers network card or connected to another fiber cable. Europeans use a round ST connector instead. See the examples to the right, courtesy of Linksys.

Since light tends to dissipate quickly when moving from one material to another, keeping the number of connections along a network path to a minimum is essential. The more connectors you have and the longer your fiber link cable is, the higher the optical loss will be. Optical loss is measured with fiber optic test instruments that can tell exactly how much optical loss there may be on a given segment at a given wavelength of light. A standard grade fiber optic cable operating at 850 nms (nanometers per second) will have something in the neighborhood of from 4 dB to 5 dB of loss per 1000 meters.

SC or ST Connectors

You will need to decide which type of fiber connectors you will be using. SC-type connectors are square in shape and are most common in North America. ST-type connectors are round and are more common in Europe and some parts of Asia. Both connectors offer the same features when considering distance and reliability, however the wise choice is to stick with same connector type throughout your network, and use one that is readily available in your region. Connectors of different types can communicate with the use of adapters or couplers. Whenever you need to change a connector type or if you require any SC-ST conversion adapters, always seek the help of a professional, as special tools need to be used.

Full Duplex or Half Duplex

Unlike an RJ-45 port, a single fiber port is actually divided into two separate uni-directional ports. One port sends data and the other port receives data. Some fiber add-on modules are capable of sending and receiving data at the same time. This is known as full duplex (FDX) operation. Other add-on modules are only capable of either sending or receiving data and cannot do both at the same time. This is known as half duplex (HDX). Obviously, Fast Duplex or FDX is the faster of the two.

If you are adding fiber capabilities to a Fast Ethernet 10/100 Switch, a 10/100 Dual-Speed hub, or other device capable of handling a full duplex connection, you should always implement a full duplex fiber add-on module. If you are using a fiber add-on module with a 10/100 Auto-Sensing Hub, Fast Ethernet hub, or other fixed half duplex device, then your fiber optic options will be limited to half-duplex performance.

Note: A half duplex connection will not allow the distance of a full duplex connection. If long distance is a concern to you, you should consider upgrading your hardware to allow support for full duplex. It is always better to match the duplex operation of any two devices that are communicating with one another. When a full duplex device tries to communicate with a half duplex device, unstable network connections will result.

Distance Extender or Transceiver

Fiber optic distance extender modules can send data much farther than transceiver add-on modules. Some hub types are only capable of communicating with a transceiver, and transceivers only run at half duplex. If your device is compatible with a distance extender, always choose the type of distance extender you plan on using first.

This chart shows the precise measurements for fiber optic cabling distances.

Type of Distance	Distance
Distance Extender to Distance Extender (FDX)	2000 meters (6560 feet)
Distance Extender to Distance Extender (HDX)	412 meters (1330 feet)
Distance Extender to Transceiver (HDX)	208 meters (672 feet)
Transceiver to Transceiver (HDX)	16 meters (50 feet)

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