A Multiplane-Light-Conversion Device Supporting Single-Fiber Bi-Directional Few-Mode PONs with Net Gain in Upstream Loss Budget

The conventional time-division multiplexed passive optical networks (TDM-PON) suffer from significant power loss in upstream introduced by a power splitter. This power loss resulting from unequal degrees of freedom of electrical fields at the input and output of the power splitter restricts PONs in reach, splitting ratio and cost per subscriber. To effectively decreases this power loss, we study and design a multiplane-light-conversion (MPLC) device, which supports mode multiplexing for upstream and power splitting for downstream at two different wavelengths. Simulation results indicate that a net gain of ~4-dB and ~5-dB in the upstream loss budget can be achieved with an MPLC supporting 10 and 15 modes, respectively, in which internal reflection loss and diffraction loss as well as external coupling loss are all included. By replacing the power splitter, this device enables TDM-PON operating bi-directional transmission over a single few-mode fiber with improved reach or splitting ratio.