Plasmonic multi-mode interference (MMI) couplers have been investigated both numerically and experimentally at the telecommunication wavelength of 1.55 mum. In this study, the couplers are implemented using thin Au stripes that support long-range surface plasmons. We first detail the operation principle of these devices with numerical simulations and show that useful effects can be obtained despite the high material losses inherent to metallic structures. A series of MMI couplers is subsequently fabricated and experimentally characterized, showing a quantitative agreement with our numerical predictions. We conclude by discussing some of the possible applications for these structures.