Embedded fiber sensors with ultra-compact read-out

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Packaging technology enabling flexible optical interconnections

This paper reports on the latest trends and results on the integration of optical and opto-electronic devices and interconnections inside flexible carrier materials. Electrical circuits on flexible substrates are a very fast growing segment in electronics, but opto-electronics and optics should be able to follow these upcoming trends. This paper presents the back-thinning and packaging of single opto-electronic devices resulting in highly flexible and reliable packages. Optical waveguides and optical out-of-plane coupling structures are integrated inside the same layer stack, resulting in complete VCSEL-to-PD links with low total optical losses and high resistance to heat cycling and moisture exposure

Embedded flexible optical shear sensor

Monitoring shear stresses is increasingly important in the medical sector, where the sensors need to be unobtrusive, compact and flexible. A very thin and flexible sensor foil is presented based on the shear stress dependent coupling change of optical power between a laser and photodiode chip that were separated by a deformable sensing layer. These opto-electronic components were embedded in a very thin foil of only 40 mu m thick. The sensitivity and measurement range can be modified by selecting the material properties of the sensing layer. The sensor response showed to be reproducible and the influence of normal pressure on the sensor was very limited

Photonic skins for pressure, shear and strain sensing

Several concepts for new types of artificial skin with integrated pressure and shear sensors will be discussed, based on a process that allows embedding optical compo-nents into very thin and flexible substrates. A flexible shear sensor foil is developed, based on the shear stress dependent coupling change of optical power between a laser and photo-diode chip that are separated by a deformable sensing layer. A flexible tactile sensor is constructed in a similar built-up, in which the principle relies on optical feedback in a vertical cavity surface emitting laser. Novel ways to interrogate optical fibre sensors based on fibre Bragg gratings are introduced, using low cost optoelectronic chips, resulting in a fully flexible sensing foil

Embedding of fibre optic sensors within flexible host

This work deals with the establishment of a UV polymerisation procedure combined with moulding technology towards the development of a mass production technology for the fabrication of flexible polymers with optical fibres embedded. The concept is to provide an artificial sensing skin based on fibre optic sensors which can be applied to irregular or moveable surfaces for distributed pressure applications, as for instance in structural monitoring or rehabilitation. The selected polymers for such an application are here reviewed and their composition adjusted in order to accommodate the required flexibility. As compared to other techniques, UV polymerisation advantages are pointed out when moving towards industrial applications and large scale productions. Meanwhile, curing tests to embed optical fibres in the developed polymers are carried out with an in house developed glass mould set-up and the results are presented. Laser ablation of polymers is also discussed in order to reply the demand of complex fibre layout as for example meandering or curved shape patterns