Holey fibers with randomly arranged air holes

Summary form only given.A holey optical fiber (HF) guides light by making use of air holes that run down the fiber and form the cladding. When the air holes are arranged periodically, photonic band-gap effects can be used to guide light. Another form of guidance arises from average index effects, and so does not rely on any periodicity of the holes. Although the fact that periodicity is not required in this instance has previously been recognised, almost all work to date has concerned periodic structures, which has led to a degree of confusion as to how these fibers operate. Here we seek to eliminate such misconceptions, and even provide the first direct confirmation that light can be guided in HFs with randomly distributed holes. This is done using a model which has been extended so that it can accurately describe asymmetric structures and modes.