Aspects of the present disclosure relate to a method of producing data indicative of a multi-core optical fibre configuration, comprising: (a) determining at least one fibre configuration constraint; (b) determining at least one initial parameter set, each initial parameter set comprising a plurality of initial fibre configuration parameters; (c) calculating a fitness value for each initial parameter set; (d) modifying each initial parameter set to produce at least one modified parameter set, said modifying being to improve the fitness value of at least some of the initial parameter sets; (e) iteratively repeating said modifying until it is determined that a ceasing condition is met; (f) determining whether at least one said modified parameter set satisfies the at least one fibre configuration constraint; (g) responsive to said at least one modified parameter set satisfying the at least one fibre configuration constraint, and based on said modified parameter set, generate data indicative of a multi-core optical fibre configuration; and (h) outputting said data.