A fibre optic system may have very high bandwidth, sometimes operating at data rates of 10Gb/s, equivalent to more than 120,000 standard telephone calls over one pair of optical fibres (one transmitting and one receiving). Under Lab conditions, data rates as high as 10 terabits per second have been demonstrated (150 million telephone calls). Datacomms type fibres have a lower information carrying capacity but are capable of 1Gb/s with some 10 Gigabit systems now in use.
Due to the low attenuation (or signal loss) exhibited by optical fibres, signals can be transmitted very long distances. In subsea telecommunications, distances of up to 280km have been used without the requirement for repeaters or boosters. Repeatered systems can span as much as 10,000 to 15,000km, where optical amplifiers are used to boost the signal levels typically around every 80km or so. Datacomms optical fibres have higher losses but can easily cope with the longest cable runs likely to be encountered in LANS.
Lightweight and compact
An optical fibre is extremely light, a 2km bobbin would only weigh approx. 1lB, therefore it is ideal for use in applications where weight is critical. Equally, a coated optical fibre is only 250 microns (a quarter of a millimetre) in diameter, a 12 core (12 fibre) cable may be less than 8mm in diameter for indoor use.
Operational fibres do not radiate any signal, the optical signal is completely contained in the middle of the fibre. This means that fibres are frequently used for applications where data security is important such as military and government communications.
Even if attempts are made to ‘tap into’ a fibre optic cable by isolating a bare fibre and putting a tight bend onto it so that some of the signal escapes, this intrusion can be detected by monitoring the power of the transmitted signal, and located using an OTDR technique (Optical Time Domain Reflectometry).
A fibre optic communications cable does not need to carry any electrical current. It is possible to construct completely non-metallic cables so that full electrical isolation can be achieved, particularly important in the Electric supply industry. There are no risks of short circuits generating sparks which may ignite explosive gases etc. Non-metallic cables are not prone to lightning strikes in exposed areas. All these intrinsically safe characteristics have led to the widespread use of fibre optics in hazardous environments such as oil refineries, chemical works, coal mines e.t.c.
A Compared to copper communications cables, there is little use of resource in manufacturing, transporting and installing fibre optic cables because of the lightweight, compact nature of optical fibres.
No scrap value
Fibre optic cable is worthless as scrap and therefore not worth stealing unlike copper telecoms cable.
Any fibre optic system currently installed will only be using a very small fraction of the potential information carrying capacity of the fibre. Therefore, as demand for communications capacity increases the system can be upgraded by attaching more sophisticated transmission equipment.
Many people view fibre optics as being very expensive, but for any application where there is a lot of data to move over long distances then fibre is likely to provide the cheapest solution.
There is a general downward trend in prices of fibre optics cabling, components, tools and installation equipment. However, the transmission equipment which converts electricity into light and back again is still relatively expensive. As prices continue to fall, and the price of copper continues to rise, fibre optics will become the most cost-effective solution for more and more applications – bringing all the other benefits as well.