Abstract
Weakly-coupled mode-division multiplexing (MDM) technique based on linearly-polarized (LP) modes in ultralow-modal-crosstalk few-mode fiber (FMF) has been considered as a promising candidate for capacity enhancement of next-generation optical transmission systems. Similar to polarization mode dispersion in single-mode fibers (SMFs), signals in weakly-coupled FMFs suffer from the impacts of intra-LP-mode dispersion (ILMD) for both degenerate and non-degenerate LP modes.In this paper, we propose an effective method for ILMD monitoring in weakly-coupled MDM systems. The ILMD evaluation method for degenerate LP modes is designed by the analysis of channel transfer matrix in a digital coherent receiver. Then the ILMD monitoring scheme is experimentally validated for all the 6 LP mods in a weakly-coupled FMF. The influences of chromatic dispersion, optical signal to noise ratio and inter-LP-mode crosstalk to the method are also investigated.
Highlights
Weakly-coupled mode-division multiplexing (MDM) technique based on linearly-polarized (LP) modes in ultralow-modal-crosstalk few-mode fibers (FMFs) has attracted great interests as a promising candidate to break the capacity bottleneck of conventional single-mode optical transmission systems [1,2,3,4]
There will be intra-LP-mode dispersion (ILMD) for non-degenerate LP0n (n ≥ 1) and degenerate LPmn (m ≥ 1, n ≥ 1) modes in FMFs [7], which comes from the joint influences of imperfect fiber fabrication, random external perturbations and extra effective index difference [8,9,10]
The ILMD in FMFs is a dynamic impairment that significantly degrades the received optical signals [10], the optical performance monitoring (OPM) for ILMD may be an important issue for dynamic network diagnosing and management in optical transmission systems and networks [12, 13], which helps to track the ILMD magnitude of each LP mode for allocating resources efficiently and adopting appropriate impairment mitigation techniques
Summary
Weakly-coupled mode-division multiplexing (MDM) technique based on linearly-polarized (LP) modes in ultralow-modal-crosstalk few-mode fibers (FMFs) has attracted great interests as a promising candidate to break the capacity bottleneck of conventional single-mode optical transmission systems [1,2,3,4] In this approach, modal crosstalk among different LP modes is greatly suppressed for FMFs, optical components and their coupling so that multiple-inputmultiple-output digital signal processing (MIMO-DSP) is not necessary among multiple modes [3,4]. For a weakly-coupled doublering-core 6-LP-mode FMF, the monitored ILMD coefficients of degenerate LPmn modes show a good agreement with those previously measured results by Improved Fixed Analyzer Method [14] The robustness of this method to CD, optical signal to noise ratio (OSNR) and inter-LP-mode crosstalk is investigated experimentally
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