Tunable Multiwavelength Optical Comb Enabled WDM-OFDM-PON With Source-Free ONUs

In this paper, we propose and experimentally demonstrate a multiuser wavelength-division-multiplexing passive optical network (WDM-PON) system combining with orthogonal frequency division multiple (OFDM) technique. A tunable multiwavelength optical comb (MOC) is designed to supply flat optical lines for assisting the configuration of the proposed multiple source-free optical network units enhanced WDM-OFDM-PON system. Schematized by cascading a phase modulator and an intensity modulator with a recirculation loop, the MOC can output 29 ideal channel optical comb lines with the flatness of 0.85 dB. For the MOC enabled WDM-OFDM-PON system, source-free and interference-free multiuser upstream transmission over a single fiber can be efficiently supported, while downstream transmission channels can convey the baseband data stream and radio frequency OFDM signals simultaneously so that the proposed system can be connected to wire-line users and wireless users simultaneously.