Abstract
An orbital-angular-momentum (OAM) mode-group multiplexing (MGM) scheme using high-order mode groups (MGs) in a graded-index ring-core fiber (GIRCF) is proposed, in which a receive-diversity architecture is designed for each MG to suppress the mode partition noise resulting from random intra-group mode crosstalk. The signal-to-noise ratio (SNR) of the received signals is further improved by a simple maximal ratio combining (MRC) technique on the receiver side to efficiently take advantage of the diversity gain of the receiver. Intensity-modulated direct-detection (IM-DD) systems transmitting three OAM mode groups with total 100-Gb/s discrete multi-tone (DMT) signals over a 1-km GIRCF and two OAM mode groups with total 40-Gb/s DMT signals over an 18.4-km GIRCF are experimentally demonstrated, respectively, to confirm the feasibility of our proposed OAM-MGM scheme.
Highlights
Space-division multiplexing (SDM) in optical fiber has recently been intensively investigated, aiming for solving the current single mode fiber (SMF) capacity crunch by utilizing the spatial or mode domain of light [1]
Among various SDM schemes, mode-division multiplexing (MDM) techniques based on multi-mode fibers (MMFs) or few-mode fibers (FMFs) can increase the number of transmission channels within a limited aperture and increase the capacity density of a single fiber core [2,3,4]
Coupled MDM scheme can be considered as one of the most promising solutions to increase the capacity of short-reach transmission systems, since modal crosstalk and dispersion can be neglected for short-reach transmission and the need of coherent optical detection and multipleinput multiple-output (MIMO) processing can be eliminated [9, 10]
Summary
Space-division multiplexing (SDM) in optical fiber has recently been intensively investigated, aiming for solving the current single mode fiber (SMF) capacity crunch by utilizing the spatial or mode domain of light [1]. Coupled MDM scheme can be considered as one of the most promising solutions to increase the capacity of short-reach transmission systems, since modal crosstalk and dispersion can be neglected for short-reach transmission and the need of coherent optical detection and MIMO processing can be eliminated [9, 10]. The coupling strength between adjacent MGs of the RCFs decreases significantly with the increasing azimuthal mode order [18] These characteristics provide RCFs with a higher scalability in the optical mode space. In the receive-diversity scheme, a single-input two-output architecture is designed for each MG channel and simple digital signal processing (DSP) is utilized to adaptively resist the mode partition noise induce by random intra-group mode crosstalk. When the receive-diversity architecture is utilized, MRC-based system performance is superior to that of the system with equal ratio combining (ERC), especially in the case that there is a great difference of BER performance between the two received branches
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