LAUSR

The dependence of the confinement loss of unjacketed and jacketed single-ring fibres on structural parameters and the wavelength is analysed with reference to an anti-resonant model for which an analytic expression for the loss is available. Provided leakage through the gaps between the cladding capillaries is suppressed, the loss of unjacketed structures follows the prediction of the analytic model closely in terms of the scaling with respect to the radius and glass thickness of the capillaries, and the ratio of the wavelength to the core radius. The absolute value of the confinement loss and its dependence on the dielectric constant differ significantly from the analytic model; these differences are discussed in terms of the negative curvature of the core-cladding boundary. The loss of jacketed structures does not follow the anti-resonant model as closely, but there is sufficient similarity to conclude that anti-resonance in the glass and air regions of the cladding is key to understanding the guidance mechanism.