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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 evaluate the requirements for future spatial-division multiplexing networks operating at throughput higher than 1 Pb/s and discuss possible solutions to support ultra-high capacity.

We perform transfer learning across different lightpaths for failure-cause identification using OSNR traces collected over NICT's Sendai optical-network testbed. Results suggest that limited additional data on the target lightpath allow to achieve satisfactory accuracy.

We developed a high-speed optical power control system with an acoust-optics-tunable-filter and a multiple RF signal generator and demonstrated collective power equalization for 8-wavelength multiplexed optical signals with power difference less than 0.3 dB.

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.

Recent progress of computer networks realizes advanced network services such as high-resolution video streaming and Internet of things (IoT) but it requires further huge amount of traffic. To expand transmission capacity, various studies develop time division multiplexing (TDM), wavelength division multiplexing (WDM), and spatial division multiplexing (SDM) technologies. Time-division packet spatial super-channel (pSSC) is expected as one of promising solutions to realize high throughput with low cost. We have developed a switching node system for the pSSC transmissions. The pSSC is suitable for large data transmission. On the other hand, overhead of pSSC is not negligible in the case of small size data transmissions. This paper proposes a fractional pSSC switching system design for both large and small data transmissions. We introduce the spatial super-channel slicing concept and ILP solution for effective data transmission having bimodal distribution of data size. Effect on slice spatial channel was validated through simulation where it is 50% better than no slicing system.

Crosstalk-aware algorithms need to check candidate optical paths to find final solutions and mitigate the influence of crosstalk. To address this issue while lower processing complexity, we propose a strict and less computationally method which decreases the influence of crosstalk.

This paper experimentally demonstrates a data center network based on multi-core fiber (MCF) and packet spatial super-channels (pSSCs) with 8 spatial channels, 64 wavelength channels and PDM-8PSK modulated payloads with a capacity of 83.33 Tb/s/port. The electro-absorption switching gate transparency is also demonstrated for PDM-QPSK and PDM-8PSK modulation formats.

We experimentally demonstrate a record 83.33 Tb/s switching capacity on a time-division spatial super-channel 2×2 switching node making use of core-joint, ns switching-speed and transparent electro-absorption optical switches.

We compare fractionally and whole spatial super-channel time-slotted switch architecture designs in terms of network-wide performance of its switching granularity and experimentally demonstrate collision avoidance functionality of SDM based transmission.

We experimentally demonstrate a 7-core 2×2 switching node for time-division spatial superchannels with a record data-rate of 53 Tb/s on SDM networks, full packet-granularity by nanosecond-fast electro-absorption gate array switching and network protection capabilities with 7-core microsecond-fast acousto-optical modulator switches.

We introduce a simple crosstalk index to efficiently switch packets in OPS networks, which counts spectrum overlaps causing inter-core crosstalk in MCFs. Our proposed wavelength and core selection reduces the crosstalk by exploiting this index.

We propose crosstalk-aware spectrum allocation with crosstalk-prohibited frequency slot to suppress the crosstalk occurring in the multi-core fiber environment with lower processing complexity and demonstrate the effectiveness of the path loss rate.

Optical circuit and packet integrated network is a promising network architecture that can deal with various sizes/types of data efficiently. In this integrated network, paths (routes) for circuit and packet switching are assumed to be calculated and selected independently. However, this approach is insufficient in terms of efficiency and rapidity of total path calculation. Calculating appropriate paths with shorter computation time is necessary. In this paper, we propose and evaluate a high-speed multipath computation method that quickly calculates end-to-end paths for optical circuit switching by making use of the calculation results of next hop information for packet switching.

Optical Burst Switched (OBS) networks are considered as promising candidates for the next generation network architecture which does not need high-speed switch technologies. In OBS networks, contention resolution is one of the significant problems. Generally, setup reservations are operated per burst in OBS networks. To transmit multiple successive bursts successfully, the effective wavelength reservation must be implemented and enhanced network performance must be realized. In the proposed method, when an optical burst is generated and its destination is the same as that of the preceding burst or the path until the destination includes the entire path of the preceding burst, the subsequent burst is assigned to the same wavelength as the preceding burst and transmitted sequentially. The main aim in the proposed method is the efficient use of wavelength resources and the reduction of burst loss probability. We simulate and evaluate the effectiveness of the proposed method. As a result, it is verified that the proposed method can reduce the burst loss probably.

In Multiple Fibers Optical Packet Switched (MF-OPS) networks, multiple data on one wavelength can be transmitted over multiple fibers. Therefore, it is important to consider the multiple fibers' resources in wavelength assignment problem. This paper focuses on this problem and proposes a wavelength assignment method smoothing available fiber resources for MF-OPS networks. As a result, the paper clarifies the effectiveness of considering multiple fiber resources.

In OPS networks, the contention resolution is one of the main problems. To reduce these contention events, we aim the effective use of wavelength resources with a routing and wavelength assignment method. In addition to this, the collision avoidance devices, such as wavelength converters, can improve the network performance more flexibly. The proposed method focuses on not only how to assign route and wavelength but also how to use these wavelength converters. We confirm the effectiveness of the proposed method by computer simulation. The proposed method can reduce the packet loss probability and the number of wavelength conversions.

We have proposed a packet contention resolution scheme that is based on the reflection routing, and furthermore enables to detour the reflected packet to alternate path by making better use of the link reflection latency. In this paper, we newly propose priority control using buffer threshold, evaluate the influence of optical buffer size and buffer threshold as parameters, and analyze what condition is suitable for our method.

This paper presents the cooperation method, which cooperatively deals with RWA problem in distributed optical burst switched networks. The simulation results show that this method improves the burst loss probability.

In the past few years, many researchers have studied elastic optical networks, which exhibit a dramatically improved transmission capacity compared with conventional optical networks. However, the transmission capacity per fiber will soon reach the physical limit for traditional single-mode fibers. Multicore fiber (MCF) is among the innovative fibers based on space-division multiplexing technology. MCF has multiple cores and achieves a far larger transmission capacity than traditional single-mode fibers. However, signals transmitted in these crowded multiple cores interfere with each other and are degraded. This degradation has a serious impact on the network resource management in elastic optical networks. Previous research indicates that the crosstalk effect of MCF is dependent on an arrangement of signals regarding the spectrum and core. Therefore, we approach the problem of the crosstalk in MCF with regard to the spectrum and core allocation, from the network perspective. First, this paper summarizes the related work regarding elastic optical networks and MCFs. Next, we propose an “on-demand” spectrum and core allocation method that reduces both the crosstalk and fragmentation in elastic optical networks with MCFs. This proposed method is based on two predefined policies related to the crosstalk and fragmentation. The first, the core prioritization policy, is based on the MCF's structure, and the other is a core classification policy based on the required bandwidth of the connections. The core prioritization policy realizes the core allocation that reduces crosstalk by avoiding filling adjacent cores. The core classification policy reduces the spectrum fragmentation by allocating a uniform bandwidth connection for each core. Finally, we evaluate the proposed method using computer simulations. The results indicate that the proposed method can, under various network conditions, improve both the crosstalk and blocking probability of the total network through our two policies.