Tunable optical fibres

Optical fibres regularly carry billions of phone conversations and other data transmissions every day and are a fundamental part of optical sensing and numerous medical applications. The photonic devices responsible for this traffic are being made even more efficient and versatile by handing over some of the switching and reconfiguring chores to the fibres themselves - the trunk lines linking all the optical nodes.

An active optical fibre, which can tunably filter light at different frequencies, has been created by infusing microfuidic plugs, spaced at characteristic (periodic) intervals along the fibre, into air holes running parallel to the passageway for the light at the centre of the fibre. The arrays of microfluidic plugs along the light path serves as a diffraction grating for fluids is used to change the refractive index periodically, and hence the transmission properties of the fibre.

The creators of this new microstructure optical fibre. (MOF) Charles Kerbage (OFS Laboratories in Murray Hill) and Ben Eggleton (University of Sydney) say that this is the first time a tunable grating has been achieved with microfluids and that this provides (in addition to the switchability) a high index of refraction when compared to conventional gratings.