Orthogonal frequency division multiplexing-passive optical network （OFDM-PON） and single-carrier fre- quency division multiplexing （SCFDM）-PON are promising solutions for future high-speed PON-based access. A polarization division multiplexing scheme with direct detection is proposed for OFDM-PON to effectively reduce bandwidth requirements for components. However, the scheme strictly requires spec- trum overlapping of two orthogonal sidebands and the 4 × 4 multi-input-multi-output （MIMO） algorithm to eliminate complex cross-polarization interference. In this letter, we propose a polarization interleaving （PI） approach that significantly reduces bandwidth requirements for optical and electrical components while achieving a high-flexibility and low-complexity MIMO algorithm. Downstream single sideband PI-SCFDM transmission is experimentally demonstrated.
