Optical Communications Group has a broad experience on fiber-optic sensors. From 1992 we have developed fiber sensors and sensors networks. Nowadays we develop both single-point and distributed sensors using our own fabrication technology. We also develop new multiplexing networks for our sensors or commercial ones using optical amplification when needed.

This research field has five main topics:

Multiplexing networks for sensors

Our group has a broad experience in optical sensors multiplexing. We have developed a number or different sensors networks in research and development projects from 1994.

We have developed several multiplexing fiber-optic sensor networks for projects involving companies, using commercial interrogation systems and sensors, for example we have monitored 30 fiber-optic sensors (temperature, strain and vibrations) in a telecommunications tower in order to check the behavior of new cladding materials for buildings.

- Fiber-optics sensors distribution and installation -

We have also developed networks that combine telecommunications data and sensors signals using WDM techniques. When needed, we have used both Erbium doped fibers and Raman amplification for the development of these networks.

The analysis of power-budget, carried out for the most common multiplexing topologies (star and bus configurations), has proven that the inclusion of optical amplification, either in the lumped or distributed versions, can increase the number of nodes (taps) multiplexed in a single network.

In order to experimentally demonstrate these advantages, various active networks have been implemented. The experimental networks developed are focused on bus configurations, since it is in these networks where the use of amplification shows its greater advantages, not only providing better power budgets, but also compensating for power differences between sensors by employing distributed amplification. The aim of the different topologies demonstrated has been to reduce the amplification noise, improving the quality of the received signals.

We have experimentally demonstrated several new networks incorporating erbium-doped active-fiber and/or Raman amplification. This amplification inserted between the network couplers into bus or ring topologies, has been proven to provide good coupler-loss compensation, being the optical power approximately constant at each sensor position. The remnant power at the bus-spine after the last sensor is approximately equal to the power launched into the first sensor, proving the network’s capacity to incorporate more nodes or sensors while maintaining the same power-budget.

We have also developed WDM networks to provide “resilience”, the ability to survive failures at one or more points. We use double bus or double ring topologies to interconnect fibre Bragg gratings (FBGs), which serve two purposes: (a) where necessary, to fulfil the sensing function in their own right and (b) through the judicious choice of reflected wavelengths, to provide unique sensor identification.

- Resillient double bus multiplexing structure using Ramang amplification -

Related Videos:

• Fiber optic sensors for monitoring a concrete beam high strain bending test
• Fiber Bragg grating fundamental

Contact: Manuel López-Amo, Silvia Díaz, Rosa Ana Pérez Herrera