O'Driscoll, E.Watson, M.Delmonte, T.Petrovich, M.Finazzi, V.Baggett, J.Monro, T.Richardson, D.2008-03-242008-03-242005[Proceedings of] 2nd EMRS DTC Technical Conference – Edinburgh 2005: paper B8http://hdl.handle.net/2440/41262In this paper we seek to assess the advantages offered by index guiding holey fibres and air-core photonic band-gap fibres for high power beam delivery applications with robust single-mode guidance. We explore the practical performance factors associated with each fibre type and consider how these may affect implementation and operation in real aerospace and defence systems. As an example of such a system, we report the use of a photonic crystal fibre as a pump delivery fibre in an optical parametric oscillator (OPO).enHoley FibrePhotonic Bandgap FibreOptical Parametric OscillatorConference paper00200763772008032015210444954