A second order nonlinearity in silica glass, which does not exist intrinsically, can be achieved through thermal poling. The poling process breaks the intrinsic symmetry of the silica allowing for even ordered non-linearities. After poling was first successfully demonstrated in 1991, the achievable nonlinearity has remained weak (after several attempts). Recently, some progress has been made through the development of multi-layer silica structures created through alternating dopant concentration. Larger observed non-linearities in these samples (through the creation of second harmonic radiation) suggest that this may have created a distributed non-linearity that could result in more efficient frequency doubled laser sources. The impact of layer spacing on the observed non-linearity has remained an open question. In this thesis a numerical model is developed with the goal investigating the impact of the quantity and spacing between layers on second harmonic generation. The model describes second harmonic generation in multi-layer structures.