Data-Aided Iterative Algorithms for Linearizing IM/DD Optical Transmission Systems

• Published in: Journal of lightwave technology Vol. 39; no. 9; pp. 2864 - 2872
• Main Authors: Hu, Shaohua, Zhang, Jing, Tang, Jianming, Jin, Wei, Giddings, Roger, Qiu, Kun
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.05.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adaptive optics; Algorithms; C band; Convergence; Digital signal processing; field reconstruction; IM/DD system; Iterative algorithms; Iterative methods; Optical communication; Optical fibers; Optical filters; Optical modulation; Parameter estimation; Physical layer; Signal processing algorithms; Signal to noise ratio; Signal transmission; Tolerances
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2021.3063689

DSP-enhanced intensity-modulation direct-detection (IM/DD) systems can support up to 56 Gb/s over 100 km signal transmissions at C-band. To achieve higher data rates and longer transmission distances, we propose data-aided iterative algorithm (DIA) and decision-directed DIA (DD-DIA) to digitally mitigate signal-signal beating interference (SSBI) without requiring any modifications to physical layer structures. DIA utilizes pilot symbols with uniformly spaced insertions to relax the modified Gerchberg-Saxton (G-S) algorithms that suffer from the local optimum problem. To further improve the symbol error rate (SER) performance and convergence speed, DD-DIA introduces a decision process to generate pseudo-pilots. We numerically compare DIA with other algorithms and find that DIA can recover signals subject to large fiber dispersions corresponding to which conventional IA and Volterra filter (VF) fail, while DD-DIA significantly accelerates the convergence speed and improves the reconstruction performance compared with DIA, it can support 100-Gb/s PAM4 over 400-km IM/DD transmissions within just 50 iterations. Two orders of magnitude reductions in SER is observed for 100 Gb/s PAM4 signal transmission over 100-km SSMFs. Compared with conventional IA, the proposed techniques have higher convergence speeds, better global optimum features and large tolerances to physical model errors. In particular, DD-DIA results in larger optical signal-to-noise ratio (OSNR)/ received optical power (ROP) improvement, higher transmission capacities and less computational complexity. DD-DIA is a promising algorithm for efficiently reconstructing 2-dimensional optical field for conventional IM/DD optical transmission systems.