Device offers promise for faster optical communications

Purdue University engineers have discovered that a device commonly used to untangle signals sent over fibre optic lines could be used to make the Internet faster and more powerful.

Optical communication systems transmit signals over hair-thin glass fibres, each capable of carrying huge amounts of data over as many as 100 channels.

The numerous channels, however, are mixed together when they are transmitted and must be untangled, or ‘de-multiplexed’, at the receiving end so the data can be recovered.

An arrayed waveguide grating is currently employed to separate the channels, or wavelengths, in optical fibres. The device is a complex optical circuit contained on a glass-silicon wafer about one or two inches in diameter.

Andrew Weiner, a professor of electrical and computer engineering and research engineer Daniel Leaird have demonstrated that the same device might help to dramatically increase the transmission speed and the amount of data that can be sent over a single channel.

The device reportedly turns a single pulse of laser light into a rapid-fire burst of 21 pulses, each separated by two trillionths of a second, which is at least 10 times faster than the transmission speed of each channel in advanced commercial optical communication systems.

Weiner’s research group earlier pioneered optical systems that ‘shape’ and manipulate pulses of laser light, technology now being used in physics and chemistry research to study and control ultra-fast processes inside molecules.

Recently, Leaird and Weiner developed a new type of ‘pulse shaper’ for generating ultra-fast packets of data sent over optical fibres.

In their new research, they have shown that commercially available arrayed waveguide gratings can be modified to perform a function similar to their laboratory pulse-shaping system. The commercial waveguide gratings are said to be much smaller and sturdier than bulky laboratory equipment, making them ideal for practical applications.

‘We realised that, rather than just being used to separate wavelengths, these arrayed waveguide gratings might have another application that nobody seemed to recognise,’ said Weiner. ‘If you send a pulse of light into one of these devices you can get a burst of pulses coming out.’