Simple evaluation of confinement losses in holey fibers

An easy-to-evaluate method is described for the prediction of confinement losses in a photonic crystal fiber with a triangular air-hole lattice, also called a holey fiber (HF). First, a HF with a finite number of holes is replaced by a doubly clad fiber with a depressed-index inner cladding and then, a simple expression for leakage losses in the doubly clad fiber is revived for the evaluation of confinement losses in the HF. Calculated confinement losses agree approximately well with those of numerical simulations.