This paper investigates coupling between EM surface waves on parallel wires. Finite Element Method (FEM) based and analytical models are developed for single and double wire Sommerfeld and Goubau lines. Models are validated via measurements for Goubau lines and a comparison between the analytic and the FEM-based computations for coupled Sommerfeld and Goubau type lines. The measurement and calculations show remarkable agreement. The FEM-based and the analytical models match remarkably well too. The results exhibit new favourable effects for surface waves propagation over multiple conductors. The short range behaviour of the coupled wires and, consequently, the existence of an optimum separation of coupled wires, is one of the most significant findings of this paper. We comment on the relevance of our results particularly in relation to applications of high bandwidth demands and cross-coupling effects. 

Matlab source code used to obtain the results of the presented model in the paper is deposited. These files are Galpha.m, Gprop.m and Sline to obtain the single wire propagation charateristics described in the paper.  For the coupled wires we have SommerfeldApproach.m and GoubauTwoWire_1.m for the Sommerfeld and Goubau type coupling described in the article. 

Raw data are 9mm_exp_data and 25mm_exp_data that were collected as described in the text. Additionally, the matlab file CoupledGoubauMeasvsSim_pub.m is used to plot these results and compare them to simulation.