PHOSFOS


PhoSFOS is a research and technology development project co-funded by the European Commission.

Project Description

The PHOSFOS project is developing flexible and stretchable foils or skins that integrate optical sensing elements with optical and electrical devices as well as onboard signal processing and wireless communications, as seen in Figure 1. This flexible skins can be wrapped around, embedded in, attached and anchored to irregularly shaped and/or moving objects or bodies and will allow quasi-distributed sensing of mechanical quantities such as deformation, pressure, stress or strain. This approach potentially gives a significant advantage over conventional sensing systems because of the portability of the resulting systems and the extended measurement range.
The sensing technology is based around sensing elements called Fiber Bragg Gratings that are fabricated in standard single core silica fibers, highly birefringent Microstructured fibers and Plastic optical fibers. The silica MSFs are designed to exhibit almost zero temperature sensitivity to cope with the traditional temperature cross-sensitivity issues of conventional fiber sensors. These specialty fibers are being modeled, designed, fabricated within the programme. FBGs written in POF fibers will also be used since these fibers can be stretched up to 300% before breaking. This allows them to be used under conditions that would normally result in catastrophic failure of other types of strain sensors.
Once optimized the sensors are embedded into the sensing skin and on the interfaced to the peripheral optoelectronics and electronics. These skins are really flexible, see Figure 2.
The photonic skins developed in PHOSFOS have potential applications in continuously monitoring the integrity and the behavior of different kinds of structures in e.g. civil engineering, in aerospace or in energy production and therefore provide the necessary means for remote early failure, anomaly or danger warning. Applications in healthcare are also being investigated.
There is a describing the technology on YouTube.

Key results

A summary of the key developments can be found on the PhoSFOS EU webpage and include the demonstration of a fully flexible opto-electronic foil.
Figure 3 shows the scattering of HeNe laser light from noise gratings recorded in PMMA using a 325 nm HeCd laser.
One of the early results from the project was the successful demonstration of a repeatable method of joining the polymer fiber to standard silica fibre. This was a major development and allowed for the first time POF Bragg gratings to be used in real applications outside of the optics lab. One of the first uses for these sensors was in monitoring the strain of tapestries shown in Figure 4,. In this case conventional electrical strain sensors and silica fiber sensors were shown to be strengthening the tapestries in areas where they were fixed. Because the polymer devices are much more flexible they do not distort the material as much and therefore give a much most accurate measurement of the strain in flexible materials. Temperature and humidity sensing using a combined silica / POF fiber sensor has been demonstrated. Combined strain, temperature and bend sensing has also been shown. Using a fiber Bragg grating in an eccentric core polymer has been shown to yield a high sensitivity to bend.
Other recent progress includes the demonstration of birefringent photonic crystal fibers with zero polarimetric sensitivity to temperature, and a successful demonstration of transversal load sensing with fibre Bragg gratings in microstructured optic fibers.
The key areas where significant progress has been made are listed below:
The PHOSFOS consortium has developed a means for reliably splicing POF to silica fibre and produced the first gratings in the 800 nm spectral region where losses are almost 2 orders of magnitude less than at 1550 nm. These developments have allowed POF grating sensors to be used outside the laboratory for the first time.
pressure sensing can be more challenging especially when space is limited. The PHOSFOS project consortium developed a new polymer multipoint FBG sensor that can measure the pressure in various medical applications. The fact that polymer fiber is used rather than silica fiber is beneficial in terms of patient safely. The low Young's modulus of polymer fiber improves the strain transfer from the surrounding medium to the sensors.

Consortium

The 2nd "Benefits for Industry" Meeting of the EU FP7 Project PHOSFOS will take place on Sunday 22 May 2011 in Munich.
The meeting is co-located with the Industry Meets Academia Workshop organized by SPIE SPIE as part of the Optical Metrology Conference. It will be followed by the World of Photonics Congress and the Laser World of Photonics Trade Fair in Munich, in the week from 23 to 26 May 2011.
This Meeting is the second in its kind gathering all companies that have expressed their possible interest in the technology developed by the EU FP7 project PHOSFOS.
18 companies/institutes have registered for the , new members are welcome.