Demonstration of Real-Time DMT-WDM-PON Employing Probabilistic Shaping Based on Intra-Symbol Bit-Weighted Distribution Matching

The probabilistic shaping (PS) technique can effectively reduce the average power of the transmitted signal by transmitting high-energy symbols with low probability and low-energy symbols with high probability, which helps to improve the tolerance of the system to the nonlinear effect of fiber. In this work, a low-complexity intra-symbol bit-weighted distribution matching (Intra-SBWDM)-based PS 16-ary quadrature amplitude modulation (PS-16QAM) scheme is implemented with a commercial off-the-shelf field programmable gate array chip for discrete multi-tone wavelength division multiplexing passive optical network (DMT-WDM-PON) communications. The Intra- SBWDM scheme, which has less computational and hardware complexity than traditional PS schemes like Gallager many-to-one mapping, hierarchical distribution matching, prefix-free code distribution matcher with framing and constant composition distribution matching, does not require look-up table or nor does it need to continuously refine the interval in order to determine the target symbol probability. As a result, it does not add a significant amount of extra redundant bits. The real-time experimental results show that the PS-DMT signals with a net rate of 131.88-Gb/s transmission over 25-km standard single-mode fiber can be achieved with the BER less than 3.8 × 10 ⁻³ compared to uniformly-distributed DMT. More importantly, the BER performance measured in real-time has good stability during the one-hour measurement period for PS-16QAM DMT-WDM-PON transmission system.