Open AccessMitigation of optical multipath interference impact for directly detected PAMn system
Author(s) -
Yang Jing Wen,
Yan Cui,
Yusheng Bai
Publication year - 2020
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.413054
Subject(s) - chirp , computer science , multipath interference , optics , modulation (music) , multipath propagation , interference (communication) , laser linewidth , laser , electronic engineering , physics , telecommunications , acoustics , channel (broadcasting) , engineering
This paper investigates solutions for mitigating multipath interference (MPI) impact for intensity modulation direct detection systems, particularly for PAM4 systems. We propose a scheme that uses a high pass filter (HPF) at the receiver to remove the MPI induced carrier-carrier beat noise and therefore improve the MPI tolerance. The scheme has been verified via theoretical analysis, numerical simulation, and experiment. For a typical optical transmitter based on Mach-Zehnder modulator (MZM) without frequency chirp, over 5dB MPI tolerance can be improved for 106.4Gb/s PAM4 by using the proposed scheme. Investigation was also extended to electro-absorption modulated laser (EML) and directly modulated laser (DML) based optical transmitters. Results show that transient chirping in EML reduces the effectiveness of proposed MPI mitigation scheme. For EML with chirp factor smaller than 1.5, MPI tolerance gain of 2dB is still achievable. However, the scheme is ineffective for typical DML where the adiabatic chirp significantly broadened the laser linewidth.