{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,15]],"date-time":"2026-06-15T14:27:09Z","timestamp":1781533629754,"version":"3.54.5"},"reference-count":49,"publisher":"Optica Publishing Group","issue":"5","license":[{"start":{"date-parts":[[2026,4,20]],"date-time":"2026-04-20T00:00:00Z","timestamp":1776643200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/doi.org\/10.1364\/OA_License_v2#VOR"},{"start":{"date-parts":[[2026,4,20]],"date-time":"2026-04-20T00:00:00Z","timestamp":1776643200000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/opg.optica.org\/policies\/opg-tdm-policy.json"}],"funder":[{"DOI":"10.13039\/501100001691","name":"Japan Society for the Promotion of Science","doi-asserted-by":"publisher","award":["21H04878"],"award-info":[{"award-number":["21H04878"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["opg.optica.org"],"crossmark-restriction":false},"short-container-title":["J. Opt. Commun. Netw."],"published-print":{"date-parts":[[2026,5,1]]},"abstract":"<jats:p>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 \u201cXT-free condition\u201d 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\u00a0\u00b5m) 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.<\/jats:p>","DOI":"10.1364\/jocn.579445","type":"journal-article","created":{"date-parts":[[2026,3,26]],"date-time":"2026-03-26T11:00:09Z","timestamp":1774522809000},"page":"454","update-policy":"https:\/\/doi.org\/10.1364\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Network-oriented metric for core pitch optimization in bidirectional multi-core fiber networks"],"prefix":"10.1364","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-8898-2994","authenticated-orcid":true,"given":"Yuya","family":"Seki","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01hvx5h04","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yosuke","family":"Tanigawa","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01hvx5h04","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yusuke","family":"Hirota","sequence":"additional","affiliation":[{"name":"National Institute of Information and Communications Technology"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9443-7446","authenticated-orcid":true,"given":"Hideki","family":"Tode","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01hvx5h04","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"285","published-online":{"date-parts":[[2026,4,20]]},"reference":[{"key":"jocn-18-5-454-R1","doi-asserted-by":"publisher","first-page":"1776","DOI":"10.1109\/COMST.2015.2431731","type":"journal-article","volume":"17","author":"Chatterjee","year":"2015","journal-title":"IEEE Commun. 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