Contents I. Introduction
Space-division multiplexing (SDM) technology has attracted extensive attentions in recent years as the promising candidate to overcome the Shannon limit of the conventional standard single-mode fiber (SSMF)-based transmission system, by employing the different fiber cores of the multi-core fiber (MCF) or the orthogonal spatial modes carried by each core as independent channels [1], [2]. The recorded spectral efficiency of 1099.9bit/s/Hz [3] and the capacity-distance product of 461.8Pbit/s.km [4] have been demonstrated in such system which the wavelength-division multiplexing (WDM) signals were delivered together with SDM. Although the experiments demonstrated the high-capacity operation, the detailed investigations, including the impact from the random-coupling behavior in the SDM transmission, and the crosstalk from both the spectral and spatial channels remains under-investigated for the WDM over SDM system. The consequence becomes even worse when the high-order modulation format is used in the ultra - wi deb and transmission system. This high-capacity transmission system has been considered the potential solution to the data center or the metro application [5]. Therefore, in this paper, we build up the high-capacity simulation platform over the 6-mode 7 -core (6M7C) SDM channel, delivering the polarization-division multiplexing (PDM)- WDM signals. The broadband operation across C+L band, 16-level quadrature amplitude modulation (16-QAM) format, leading to a total of 8400 independent channels and the capacity-distance product of up to 168Pbit/s.km have been calculated in such system. The random coupling among spatial channels has also been considered in the 100km-length 6M7C fiber, closer to the performance in the real implementation. At the digital receiver, the optimized multi-input multi-output (MIMO) equalizer has been used in the compensation process. The self-recycling training approach proposed in our previous work [6] has also been employed to reduce the training cost. The recovered signal with the error vector magnitude (EVM) of less than 5.77% proves the well-compensation performed in the tested high-capacity WDM over SDM system.
