Experimental characterisation of Raman gain efficiency of holey fibre

The Raman gain efficiency of a 2.3 μm-core-diameter holey fibre was measured using three different techniques. A ∼4.65×10^-3 W^-1 m^-1 efficiency is obtained by all techniques with mismatches lying within the estimated errors. It is shown that the high efficiency is due to small mode-field diameter of the holey fibre, as expected. The use of the fibre as a continuous-wave-pumped Raman amplifier is discussed.