Fibre-optics technologies


Dense wavelength-division multiplexing (DWDM), which is a technology that allows multiple optical signals with different wavelengths (think of it as different colours of light) to be carried over the same fibre-optic cable, allows single fibre-optic cables to carry incredibly high bandwidths. For example, NEC transmitted a 6.4 terabit per second (Tbps) signal over a single 186 km-long fibre-optic cable using DWDM in 2000. This 6.4 Tbps transmission consisted of 160 different wavelengths (commonly referred to as 'lambdas', which is the Greek letter that is typically used to signify wavelength in engineering), with each wavelength carrying a 40 Gbps bitstream. 6.4 Tbps is the equivalent of 64 million people all downloading at 1 Mbps simultaneously.


Gigabit Ethernet

Advances in fibre-optics has also allowed faster Ethernet standards to be developed. Although most people associate Ethernet with LANs in an office or at home, Ethernet is also the most common standard for carrying data over Internet links as well, with the 1 gigabit Ethernet (1 GbE) standard being the most commonly used standard. However, take-up of the 10 Gbps Ethernet (10 GbE) standard is increasing due to the technology becoming cheaper, and there are currently 40 Gbps and 100 Gbps Ethernet standards in the pipeline as well. Bob Metcalfe, the inventor of Ethernet, and the person behind Metcalfe's Law, is even suggesting that 1 terabit Ethernet could be used for 'core' Internet links by 2015.

The following figure shows the number of ports shipped worldwide for the different Ethernet standards. The figure includes Ethernet ports shipped for LANs, but the price of technologies is dependent on sales volume, so the price of 10 Gbps Ethernet for WAN (wide area network — i.e. Internet) links will also reduce as take-up increases.



Gilder's Law

There's a Moore's Law-style prediction that's mainly associated with the increasing speed of fibre-optics technologies, called Gilder's Law, named after its orginator, the American technologist George Gilder, which states that:


"Bandwidth grows at least three times faster than computer power. While computer power doubles every eighteen months (Moore's law), communications power doubles every six months."