Polymer microstructured optical fibres are a relatively recent development in optical fibre technology, supporting a wide variety of microstructure fibre geometries, when compared to the more commonly used silica. In order to meet the automated design requirements for such complex fibres, a representation was developed which can describe radially symmetric microstructured fibres of different complexities; from simple hexagonal designs with very few holes, to large arrays of hundreds of holes. This representation uses an embryogeny, where the complex phenotype is `grown' from a simpler genotype, and the resulting complexity is primarily a feature of the reuse of gene elements that describe the microstructure elements. Most importantly, the growth process results in the automatic satisfaction of manufacturing constraints. In conjunction with a multi-objective genetic algorithm, this formed a robust algorithm for the design of microstructured fibres for particular applications of in...