Duncan graduated from the University of St Andrews in 1986 with a BSc in Physics with Electronics, and from the University of Southampton (Optical Fibre Group) in 1991 with a PhD. The PhD studies were centred around an investigation of different techniques to incorporate permanent phase gratings into optical fibres ('fibre bragg gratings'). In 1991 he moved to Heriot-Watt University, initially employed as a Research Associate. In 1997 he was appointed Lecturer in Physics and subsequently promoted to Reader (2001) and Professor of Applied Photonics (2003).