Offset-QAM based coherent WDM for spectral efficiency enhancement

Jian A. Zhao, Andrew D. Ellis

    Research output: Contribution to journalArticlepeer-review


    Optically multiplexed multi-carrier systems with channel spacing reduced to the symbol rate per carrier are highly susceptible to inter-channel crosstalk, which places stringent requirements for the specifications of system components and hinders the use of high-level formats. In this paper, we investigate the performance benefits of using offset 4-, 16-, and 64-quadrature amplitude modulation (QAM) in coherent wavelength division multiplexing (CoWDM). We compare this system with recently reported Nyquist WDM and no-guard-interval optical coherent orthogonal frequency division multiplexing, and show that the presented system greatly relaxes the requirements for device specifications and enhances the spectral efficiency by enabling the use of high-level QAM. The achieved performance can approach the theoretical limits using practical components.
    Original languageEnglish
    Pages (from-to)14617-14631
    Number of pages15
    JournalOptics Express
    Issue number15
    Publication statusPublished - 18 Jul 2011

    Bibliographical note

    © 2011 OSA
    This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.


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