Light transmitted through wood-based optical fibre

Light has travelled through a wood-based optical fibre, offering the possibility of biodegradable Internet of Things (IoT) sensors or simple moisture monitors.

Researchers at VTT made the new fibre, which has a core of wood cellulose modified with ionic solvents developed at the Finnish research centre. The core has a cladding of cellulose acetate.

Light can travel through the fibre because the cladding has a lower index of refraction than the core. The rays are reflected back into the core from the interface of the core and the cladding.

Cellulose is suitable for fibreoptic sensors because it can react and absorb with substances being measured, the researchers said. The index of refraction can also be modified.

The material effectively absorbs and releases water, which can be measured by the change in the attenuation of light transmitted. It is also biodegradable, and the fibre can be disposed of with biowaste.

Many more sensors will be installed throughout the built environment for IoT applications and ‘smart cities’, creating new potential applications that could be suited for the cellulose fibres. They will not compete with glass-based optical fibres for telecommunications, however.

“The R&D is still in its initial phases, so we do not yet know all the applications the new optical fibre could lend itself to,” said senior scientist Hannes Orelma.

The team is still working on the R&D in the FinnCERES programme in collaboration with VTT and Aalto University.

Want the best engineering stories delivered straight to your inbox? The Professional Engineering newsletter gives you vital updates on the most cutting-edge engineering and exciting new job opportunities. To sign up, click here.