A 6-LP-mode ultralow-modal-crosstalk double-ring-core FMF for weakly-coupled MDM transmission

• Published in: Optics communications 2019-11, Vol.451, p.97-103
• Main Authors: Ge, Dawei, Gao, Yuyang, Yang, Yu, Shen, Lei, Li, Zhengbin, Chen, Zhangyuan, He, Yongqi, Li, Juhao
• Format: Article
• Language: English
• Subjects: Fiber characterization; Fiber design and fabrication; Fiber optics communications; Multiplexing
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2019.06.015

Weakly-coupled mode division multiplexing (MDM) technique based on few mode fiber (FMF) with low linear-polarized (LP) modal crosstalk is promising for capacity enhancement of short-reach transmission. In this paper, we propose a double-ring-core FMF for simultaneous 6-LP-mode weakly-coupled MDM transmission. FMF with ring-core structure is theoretically analyzed by deriving from a step-index circular-core FMF with perturbed ring areas. Then simplified method is proposed to define boundaries of ring areas in FMF and increase the minimum effective refractive index difference (min|Δneff|) among all the modes. Fabricated by commercial fabrication technique, the FMF achieves a min|Δneff| up to 1.49×10−3 while its maximum Δn between core and cladding is only 0.828%, which greatly reduces the difficulty of fiber fabrication. Thanks to the ultralow modal crosstalk of the FMF, we successfully demonstrate simultaneous 6-LP-mode (LP01, LP11, LP21, LP02, LP31 and LP12) 4-wavelength 71-km weakly-coupled MDM transmission using 10 Gb/s optical on-off-keying (OOK) intensity modulation and direct detection (IM/DD) without any digital signal processing (DSP). The design method can be extended to weakly-coupled FMFs with more ring areas.