The performances of singularity-avoidance CMA equalizers in real-time system

• Published in: Optics communications 2022-05, Vol.510, p.127843, Article 127843
• Main Authors: Xu, Jialin, Li, Yan, Hong, Xiaobin, Qiu, Jifang, Zuo, Yong, Guo, Hongxiang, Wu, Jian
• Format: Article
• Language: English
• Subjects: DSP; Fixed-point; Parallelization; Real-time; Singularity-avoidance CMA
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2021.127843

In this paper, we compare the performances of conventional CMA, two-stage CMA and constrained CMA, from cases of fixed-point, parallelization and delay periods which are necessary in real-time system. We implement an 112Gbit/s dual polarization channel model to simulate conventional CMA and other modified CMAs. When OSNR (Optical Signal to Noise Ratio) and PDL do not vary, compared with float-point case, reducing bit width of input data can worsen singularity problem of these three equalizers. Besides, when OSNR and PDL do not vary, compared with serial case, increasing parallels number can reduce singularity probabilities of these three equalizers. Then, when PDL does not change, increasing delay periods can deteriorate singularity problem. Furthermore, in float-point case, fixed-point case, serial case, parallels case and delay periods case, compared with other two equalizers, constrained CMA all shows best performances to decrease singularity probabilities. Therefore, among these three equalizers, constrained CMA is the most suitable to be employed in real-time system. •We compare the difference between singularity-avoidance performances of float-point case and fixed-point case.•We compare the difference between singularity-avoidance performances of serial case and N-parallels case.•We compare the singularity-avoidance performances under different delay periods.•We compare the convergence speeds of these three equalizers.•We compare hardware costs of these three equalizers by Quartus 2 15.0.