To satisfy the demand of evolving network business in future access networks

a high speed Mode-Division-Multiplexing Passive Optical Network（MDM-PON）scheme utilizing self-homodyne detection is proposed.In the proposed scheme

one of the spatial modes is used to transmit a portion of signal carrier（namely pilot-tone）as the Local Oscillator（LO）

while the others are used for signal-bearing channels.At the receiver

the pilot-tone and the signal are separated by mode demultiplexer and then sent to the receiver for coherent detection.Due to the low modal-crosstalk Few-Mode Fiber（FMF）and all-fiber mode multiplexer/demultiplexer（MUX/DEMUX）

the pilot-tone and the signal can be effectively separated without Multiple-Input Multiple-Output（MIMO）processing.Compared with Polarization Division Multiplexing（PDM）self-homodyne detection

the spatial efficiency is enhanced.Meanwhile

the self-homodyne detection can effectively suppress the laser phase noise

which relax the requirement for lasers line-width at the Optical Line Terminal or Optical Network Units（OLT/ONUs）.At the receiver side

the Digital Signal Processing（DSP）is also simplified since self-homodyne detection reduces the receiver complexity by eliminating the LO from the coherent receiver

removing the need for frequency offset compensation and reducing the requirement for carrier phase recovery by several orders of magnitude.Using the proposed scheme

aproof of concept 4×40 Gbit/s Orthogonal Frequency Division Multiplexing（OFDM）signal transmission over 55 km FMF using low modal-crosstalk twomode FMF and MUX/DEMUX with error free operation is experimentally demonstrated.Compared with the back to back case

less than 1 dB Q-factor penalty is observed after transmission over 55-km FMF.