Distributed Fiber Sensors
In the last five years, the activity in The Photonics Engineering Research Group GRIFO has been very intense in terms of scientific production. In particular, in the research line of distributed fiber optic sensors 2016 was a particularly important year as a new technique for distributed acoustic sensing (DAS) was demonstrated by the group. Since then, this technique has been at the core of many investigations of this group in the last five years, as it offers disruptive properties that have not only spurred the interest of the scientific community, but also from commercial companies which license the patents associated to the technique and have developed it into commercial products (particularly Omnisens, CH, and Aragon Photonics, ES).
Different works related to this new technique have been carried out since that moment, diversifying the research line into different sublines, which has made possible the elaboration of different doctoral thesis works as well as obtaining significant funding through different projects and industrial contracts, as well as the generation of several licensed patents which are the ones generating the highest annual revenue in the UAH. Along the years, the group has worked on the study of the intrinsic limits of this technique and has proposed new techniques that try to compensate, correct or overcome these limitations. The previous experience of the members of the research group in Raman distributed amplification has also been used to increase the measurement range of this type of DAS sensors. In the field of applications, the excellent performance of these new sensors has made it possible to explore new uses in a wide variety of fields. In particular, work has been done on the study of these sensors for use as temperature sensors for environments with high concentrations of ionizing radiation. In the line of temperature measurement, the feasibility of the technique for use as a distributed radiometer has been demonstrated in solar energy generation facilities. The measurement of other parameters both external and internal to the optical fiber has also been the subject of study in recent years. For example, the electric field through the Kerr effect and the Pockels effect or the distributed measurement of the fiber birefringence through local variations of the refractive index. Another high-impact application that has been developed in the last five years has been the monitoring of different types of seismic events. In this line, important efforts have been invested in recent years in the research group. The feasibility of using as transducer fiber for the distributed measurement of acoustic signals the optical fiber already installed for communication purposes, makes this technique very attractive for this application. The possibility of replacing traditional seismographs by hundreds of thousands of sensitive points, which will behave as seismographs, by simply installing an interrogator equipment at one end of the sensing fiber, has recently revolutionized this area. A proof of the great interest aroused by the DAS technology developed in the group for this application is the award of the European OCEAN DAS project, awarded to Professor Miguel Gonzalez under the highly competitive ERC Proof of Concept call. Also, very high impact publications have been achieved in this area in the last years. Lastly, the development of pattern identification strategies applied to this type of distributed sensors has been another sub-line in which important results have been achieved in recent years. The challenge of providing artificial intelligence to this type of distributed sensors is of great interest in both research and industry, particularly in ensuring the integrity of pipelines.