University of Southampton

Peter Jonathan Bennett

David John Richardson

Tanya Mary Monro

Neil Gregory Raphael Broderick

The percentage fraction of fundamental mode power located in the cladding holes of different holey fibers (PF ) is shown as a function of wavelength in microns of the fundamental mode (&lgr;). Properties of two groups of holey fibers are shown. The upper group of three curves shows embodiments of the invention with &Lgr;&equals;0.75 &mgr;m and d/&Lgr;&equals;0.6, 0.7 & 0.8 respectively, where d is the hole diameter and &Lgr; the hole spacing or pitch. The lower group of curves, which are almost superimposed on each other, show properties of holey fibers representative of the prior art with &Lgr;&equals;3.2 &mgr;m and d/&Lgr;&equals;0.6, 0.7 & 0.8 respectively. A huge improvement in the mode power present in the holes is evident. In the prior art curves, the mode power fraction is generally less than 1%, whereas with the illustrated embodiments of the invention, holey fibers with 10-40% of the fundamental mode power in the holes are achieved. Generally the holey fiber should be structured such that the wavelength of the guided light &lgr;>2.2&Lgr;. For telecommunications wavelengths, this means that the hole spacing should be smaller than typical in the prior art, i.e. around 1 &mgr;m or less, and the hole diameter should be as large as possible in relation to the hole spacing, preferably d/&Lgr;>&equals;0.6.

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Chelmsford, United Kingdom

Peter Jonathan Bennett