Authorship：Lead author   Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

This study presents a framework for optimizing the core pitch of multi-core fibers (MCFs) in bidirectional MCF-based space-division multiplexing elastic optical networks (SDM-EONs). Existing studies have predominantly adopted hexagonal-lattice core layouts for the MCF structure and have overlooked indirect inter-core crosstalk (IC-XT), which can be the dominant impairment in bidirectional MCF-based SDM-EONs. In this study, existing IC-XT calculation models are re-evaluated, demonstrating that square-lattice-structure (SLS) MCFs are preferable for bidirectional MCF-based SDM-EONs, and an “XT-free condition” is derived to determine the optimal core pitch. Numerical simulations on three network topologies (EURO28, Kanto11, and TMN12) under multiple resource-allocation strategies reveal that the blocking probability is minimized whenever the XT-free condition is satisfied, independent of topology size or resource-allocation policy. For standard-cladding 4-core SLS MCFs, optimal core pitches (34.4, 34.0, and 30.7 µm) yield a minimum lightpath blocking probability, acceptable IC-XT, and ITU-T recommendation-compliant splicing loss. The proposed framework provides a general method for MCF design and offers valuable insights into realizing high-core-count MCF-based SDM-EONs. Beyond immediate design implications, the proposed framework may serve as a foundation for redefining benchmarking standards in resource-allocation models and guiding the future standardization of MCF designs.

DOI： 10.1364/JOCN.579445

Other URL： https://ieeexplore.ieee.org/document/11489297

Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

Optical packet-switching (OPS) networks remain an emerging technology, as exemplified by the feasibility challenges of optical RAM. Nevertheless, OPS networks possess significant potential advantages, including a high data transfer rate and low power consumption due to the elimination of optical–electrical–optical conversion, compared to conventional electronic packet-switching networks, flexibility in handling traffic fluctuations due to packet-switching principles, and low latency as they do not require overhead for communication path establishment. However, effective data recovery from non-negligible packet loss due to optical packet collisions remains a critical challenge in OPS networks. Packet-level forward error correction (FEC) is regarded as an effective data recovery method for lossy networks, such as OPS ones, because it does not rely on packet-by-packet feedback, which could be lost, and avoids the delays associated with feedback and retransmission. On the other hand, FEC requires the transmission of additional packets beyond the original data, increasing the computational load associated with encoding and decoding. In this paper, we propose a data transfer method based on erasure coding, which is useful not only in OPS networks but also in other network environments suffering from severe packet loss due to collisions or signal degradation, such as optical circuit switching networks and wireless networks. This method improves effective data transfer throughput by limiting the number of transmitted packets and reducing the computational overhead of the encoding and decoding processes. This improvement is achieved through the appropriate configuration of the distribution of XOR operation target packets that constitute XOR packets, thereby restricting the number of symbols encoded in each XOR operation and introducing cumulative feedback of which symbols were already recovered at the receiver. To validate the proposed method, we conducted not only simulation evaluations but also what we believe to be the world’s first packet transmission demonstration experiment using packet-level erasure coding over an actual OPS network testbed, taking actual computational overhead into account. The experimental results show that, in high transmission rate environments, the proposed method achieves up to a 188.7% increase in effective data transfer throughput compared to the benchmark LT-Codes-based packet-level FEC transmission method while reducing the processing time on the sender side by up to 15.6% and on the receiver side by up to 39.4%. In addition, the number of packets required for data decoding can be reduced by up to 63.3%.

DOI： 10.1364/JOCN.550555

Other URL： https://ieeexplore.ieee.org/document/10976339

Authorship：Lead author   Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

The suppression of inter-core crosstalk (IC-XT) that affects each lightpath is crucial for resource allocation in space-division multiplexing elastic optical networks (SDM-EONs) with multi-core fibers (MCFs). Resource allocation approaches that limit the simultaneous use of adjacent cores in the same frequency band to the MCFs composing each lightpath have been widely adopted to suppress IC-XT. However, in principle, such methods are inefficient because they cannot fully utilize all cores. This study examines the core density from the perspective of the core layout in weakly coupled MCFs and the IC-XT suppression requirement. The densest MCF layout maximizes the network capacity while restricting the amount of IC-XT within the tolerance threshold for each lightpath. Specifically, we propose an XT-free condition, maintaining the IC-XT to each lightpath within the acceptable tolerance level. In addition, we evaluated numerous MCFs that satisfy or do not satisfy the XT-free condition with various network topologies and cladding diameters. This evaluation also validates the IC-XT reduction performance of the proposed framework compared with that of the conventional resource-allocation approach. Here, we incorporate our indirect IC-XT calculation method that affects lightpaths from other cores via its nearest cores, which was overlooked in the resource allocation problem. Based on these comprehensive examinations, we propose a method to determine the densest core layout for a given network topology and route and modulation format selection algorithm.

DOI： 10.1364/JOCN.531706

Other URL： https://ieeexplore.ieee.org/document/10740958

Publishing type：Research paper (international conference proceedings)   International / domestic magazine：International journal  

DOI： 10.1109/NoF62948.2024.10741410

Authorship：Lead author   Publishing type：Research paper (international conference proceedings)   Kind of work：Joint Work   International / domestic magazine：International journal  

DOI： 10.1049/icp.2023.2081

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Poster presentation  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (invited, special)  

Type：Peer review 

Type：Peer review 

Type：Peer review 

(Rereview)

Type：Peer review 

Type：Peer review