Receiver design for an optical MIMO testbed

Within the last years multiple-input multiple-output (MIMO) systems have attracted a lot of attention in the optical fibre community. Although the theoretical background of MIMO transmission is well understood, there is still a need for practical investigations regarding mode combining, mode maintenance and mode splitting. Since these components represent an essential part of an optical MIMO system, in this work a (2 × 2) MIMO testbed using fusion couplers and a multi-mode fibre (MMF) length of 1.9 km is set up for an operating wavelength of 1326 nm. Together with the MIMO receiver-side signal processing the successful transmission of parallel data streams is presented.