Understanding bending losses in holey optical fibers

Extremely large mode area fibers that are single-moded over a broad wavelength range can be created using holey fiber technology. However, as with any fiber, the largest mode areas that are practically feasible are ultimately determined by bending losses. It is therefore essential to gain an understanding of the factors that influence bend loss in these fibers in order to form accurate predictions that can facilitate improved bend loss design. Here, we present the first detailed study of transition loss and pure bend loss in a holey fiber, and consider the impact of the fiber structure. A theoretical model is derived that retains the full refractive index profile of a holey fiber. This approach is used to predict the bend loss in large mode area holey fibers and is validated through comparison with experimental data. For the fibers under study here, we demonstrate that pure bend loss is the dominant component of macro-bend loss and that the hole configuration within the cladding can strongly influence this loss.