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The introduction of the space domain in optical communications, collectively referred as space division multiplexing (SDM), have recently gained a lot of research attention motivated by the capacity exhaustion of conventional wavelength division multiplexing (WDM) systems. SDM not only increases the capacity, but also introduces new challenges and opportunities owing to the properties of the spatial channels in the form of fiber cores, modes or a combination of both. One promising application of SDM systems could be in future edge optical networks, where multi-core fibers (MCFs) with low inter-core crosstalk may be used with packet spatial super-channels (pSSCs) and core-joint SDM optical switches in a time-slotted network. We first briefly review the state-of-the-art of SDM transmission systems and other important technologies for edge networks such as burst-mode transmission. Finally, we focus on two recent experimental demonstration of such a switching system, achieving a capacity of 53.3 Tb/s for 7 spatial channels and QPSK modulation formant and an upgraded version with 8 spatial channels and 8PSK modulation format that achieves 83.33 Tb/s.

This paper presents and experimentally demonstrates a novel high-capacity switching system with several types of optical switches, based on time division multiplexing, space division multiplexing, and coherently modulated packet spatial super-channels (pSSCs), suitable for converged inter/intradata center networks. The fundamental subsystem of this network is the core-joint optical switch which enables efficient switching of all the spatial channels of the multicore fibers (MCFs) used for data transmission. Three novel core-joint optical switches, for 7-core MCFs and varying granularities to accommodate different network functions, are developed: 1) an electroabsorption-based, ns-fast joint switch, 2) an acoustooptic modulator-based, $\mu$ s-fast joint switch, and 3) a free-space mirror-based, ms-fast joint switch. We use these three subsystems in a 2 $\times$ 2 switching node that makes use of 64 wavelength channels, 7-core MCFs, and coherently modulated pSSCs to experimentally demonstrate a record switching capacity of 53.3 Tb/s/port and network protection capabilities in less than 10 ms in the event of an MCF failure.

We experimentally demonstrate a novel, time-slotted, converged inter/intradata center optical network that employs multi-core fibers (MFCs), packet spatial super-channels (pSSCs), and core-joint optical switches. The fundamental switching subsystem is a high-granularity core-joint electro-absorption optical switch, based on an array of electro-absorption 1×4 switching gates with a switching time of approximately 10 ns, and is able to jointly switch all the wavelength and spatial channels of the pSSCs simultaneously. Lower granularity core-joint switches may be used in the pSSC switching nodes for other tasks, such as network protection or bypass. Previously, we experimentally demonstrated a 2×2 pSSC switching system with a capacity of 53.3 Tb/s/port in a testbed with pSSCs composed of 64 wavelength channels, 7 spatial channels, and PDM-QPSK-modulated payloads. In this paper, we enhance our testbed experimental setup to demonstrate a record switching capacity of 83.33 Tb/s/port with pSSCs composed of 64 wavelength channels, 8 spatial channels, and PDM-8PSK-modulated payloads. We also demonstrate the transparency of the core-joint electro-absorption switch by comparing the new results with the previous PDM-QPSK results in terms of the error-vector magnitude.

This paper extends a recent demonstration of a hierarchical spatial division network architecture testbed for petabit per second throughput. A spatial cross-connect is implemented to handle 1.08 Pb/s per line side. The spatial cross-connect is based on a low loss 44 × 44 MEMS switch, which enables switching up to 22 spatial channels, each carrying 202-channel, 24.5 GBaud polarization-multiplexed 64-ary quadrature amplitude modulated signals. Transmission is performed using a 22-core homogeneous multicore fiber. The demonstration includes spatial bypass and spatial add and drop scenarios as well as optical bypass and optical add and drop scenarios. The latter uses wavelength cross-connects implemented using conventional wavelength selective switches. A network scenario implementing 1 + 1 spatial multiplex section protection is also demonstrated using three 7-core joint spatial switches to protect 21 spatial channels. Finally, the use of hybrid spatial division multiplexing networks with multi-core and few-mode fibers is addressed, showing that skew between spatial channels may be the most significant obstacle to the implementation of such networks. This work concludes with an analysis of the inter-core skew introduced by the 22-core multicore fiber and its impact on a potential implementation of a hierarchical spatial division network.