Fibre Optic Cabling
A computer network uses fibre optic cable as a backbone to link buildings together, because of the low loss and high bandwidth a signal can be sent over greater distances than copper cables.Whilst copper cable is still the favourite method for the desktop user, the future of higher network speeds and higher bandwidth may one day make fibre the only suitable option. In today’s FTTD networks fibre to the desk is being used as the standard PC connection
A Significant benefit using an non electrical conductor is its immunity to Electromagnetic interference, they can be routed through Electrical environments or potentially hazardous areas which are flammable There are two types of fibre optic solutions, multimode and SinglemodeSinglemode fibres have a small core size of 8.3 microns to 125 micron of cladding. A laser is used to transfer data at multiple frequencies along a single path( Wave- Division-multiplexing). Because of this single light wave there is less dispersion of the signal allowing or higher bandwidth or capacity. This cable is designed for long transmissions up to 50 times longer than multimode; it’s predominant use is for telecom exchanges. Development of new lasers and diodes, may one day allow networks to carry trillions of bits of data per second. Multimode fibres can either be 50 micron or 62.5 micron in a 125 micron cladding. n LED is used for data transfer along multiple light-waves along the fibre core. Light waves are dispersed into numerous paths, or modes, as they travel through the cable's core.The disadvantage of having multiple waves is the dispersion of the signal and different data rates. Whilst this offers less bandwidth than Singlemode it still is incredibly high with speed rates of up to 10/100 mbs/ Gigabit up to 2Km. The cost of multimode hardware is far lower than that of Singlemode which is why multimode is still the favoured choice for data networks. A micron is a millionth of a metre.
The most common core sizes used for data networking are 4,8,16 and 24 which can be terminated inside a 1u 24way patch panel. Larger size panels are available and cables can be constructed with as many as 144 separate fibres. Another option to consider is the type of connectors used to present the fibre optic cable. There are over 80 styles of connectors but the most popular are the ST, SC and FCPC.ST – is the most popular connection, it has a round bayonet mount and a long cylindrical ferrule. The connector is spring loaded, with a push in and twist design.SC – The connector is a snap in design which provides accurate alignment, it has a push on – pull off connector with a locking tab. An OTDR ( optical time domain reflectometer) is used to test the cables parameters and losses. The OTDR transmits a signal along the fibre link and produces a graphical representation of the changes or events. These trace results are recorded and stored then presented to the network administrator.