Prof. Gerald Farrell, Head of School

My research is focused on the area of Photonics, in particular Optical Sensing. I am the Director of the Photonics Research Centre at The DIT. Further information on the Centre's activities can be found at www.prc.dit.ie

• A list of my journal and conference publications is available at: List of Journal and Conference Publications
• I also maintain a comprehensive range of teaching and learning resources for Optical Communications Systems
  at taught graduate level at this link: Optical Communication Systems: Learning and Teaching Resources

Research Interests

FBG Interrogation Systems The research is concerned with the rapid and accurate determination of an unknown optical wavelength. This is a common measurement in Fiber Bragg Grating (FBG) based optical sensing systems. The aim of this research is to refine and demonstrate a commercially attractive FBG interrogation scheme which is not only accurate, but which is also faster than other approaches to allow the dynamic measurement of strain. The current performance targets are an accuracy of ± 10 pm or better with a speed of at least 1000 measurements per second.

Modeling and Applications of Fiber Bend Loss Fiber macrobending losses have been widely investigated as an important issue in optical fiber communications and sensing applications in recent decades. In our recent research, the wavelength dependence of macrobending loss has shown that it can be employed in an all-fiber based edge filter systems for rapid wavelength measurement in the optical communication systems and optical sensing applications. A couple of theoretical prediction techniques which based on scalar approximation method and beam propagation method have been developed.

Liquid Crystal Tunable Filters The main objective of this research is to explore the feasibility of utilizing fast-switching ferroelectric liquid crystals (FLC) for the development of a tunable filter for interrogation of wavelength multiplexed FBG sensors. The aims of the research is to explore different free-space filter configurations, such as Lyot and Fabry-Perot filters, as well as the tuning properties of Photonic Crystal Fibers (PCF) infiltrated with FLC.

SMS and PLC based Edge filters The research is focused on an accuracy enhancement of a ratiometric wavelength monitor (RWM) using two edge filters with overlapping and opposite spectral responses, a so called, "X-type spectral response". Two platforms are considered in this research, (1) an all-fiber RWM utilizing singlemode-multimode-singlemode (SMS) fiber structure edge filters and (2) an integrated RWM in a planar lightwave circuit (PLC).

Engineering Applications of Optical Sensing (EAOS) The Centre is collaborating with colleagues in the Faculty of Engineering at DIT on two novel applications of optical sensing: the use of fiber sensing for precise force feedback in haptic surgical instruments and on the use of novel optical sensing techniques for sound field measurement.

Disposable Optical Fiber Temperature Sensor The Centre has developed an inexpensive, disposable temperature sensor based on a single-mode fiber. It is a fraction of the cost of alternative sensors and has a wide range up to +300 °C with a competitive resolution of 0.5°C or better. A unique feature of the sensor is that it is disposable, allowing it to be used for example for monitoring the internal temperature of composite components during manufacture. A patent application has been submitted for the technology and the Centre is seeking commercial partners with a view to licencing this novel technology.

Smart Sensors for Engineering Structures (SSES), MATERA-ERAnet Project The Centre recently acquired funding from European MATERA project in collaboration with Warsaw University of Technology and a Polish helicopter manufacturer, PZL-Swidnik S.A. The research will investigate the development of smart composite structures for the aviation industry based on a hybrid sensing approach in a composite in order to provide simultaneous in-situ distributed measurement of strain, temperature and vibration.

For further information on my research activities visit www.prc.dit.ie