Efficient Frequency-Domain Block Equalization for Mode-Division Multiplexing Systems

• DOI: 10.3390/photonics12020161
• Publication Date: 2025-02-17T12:48:22Z
• Authors: Yifan Shen; Jianyong Zhang; Shuchao Mi; Guofang Fan; Muguang Wang
• Keywords: adaptive moment estimation; Applied optics. Photonics; mode division multiplexing; frequency-domain block equalization; TA1501-1820

In this paper, an adaptive frequency-domain block equalizer (FDBE) implementing the adaptive moment estimation (Adam) algorithm is proposed for mode-division multiplexing (MDM) optical fiber communication systems. By packing all frequency components into frequency-dependent blocks of a specified size B, we define an adaptive equalization matrix to simultaneously compensate for multiple frequency components at each block, which is computed iteratively using the Adam, recursive least squares (RLS) and least mean squares (LMS) algorithms. Simulations show that the proposed FDBE using the Adam algorithm outperforms those using the LMS and RLS algorithms in terms of adaptation speed and symbol error rate (SER) performance. The FDBE using the Adam algorithm with B=1 has the fastest adaption time, requiring about ntr=100 and ntr=900 less training blocks than the RLS algorithm at the SER of 3.8×10−3 for the accumulated mode-dependent loss (MDL) of ξ=1 dB and ξ=5 dB, respectively. The Adam algorithm with B=16 and B=8 has 0.4 dB and 0.3 dB SNR better than the RLS algorithm with B=4 for MDL and ξ=1 dB and ξ=55 dB, respectively.