JST Strategic Basic Research Programs, ACT-XDevelopment of High-capacity Datacenter Optical Networks
- Program
- JST Strategic Basic Research Programs, ACT-X
- Research area
- Cyber Infrastructure for AI Symbiotic Society
- Grant number
- JPMJAX24M5
- Principal investigator
- Takuma KunoTokai National Higher Education and Research System, Nagoya University
- Period
- October 2024 – March 2027
Objectives
With the spread of AI, communication demand in datacenter networks is rising sharply, and communication equipment must consume less power. Signals have so far been routed by electrical switches, but the repeated optical–electrical–optical conversion they require consumes a great deal of power. This research aims to establish an optical switch architecture for datacenters that combines very large capacity, low power consumption and high scalability, using optical switches that route signals while they remain light.
Work and results
For the optical switches, we evaluated the eight possible ways of applying wavelength-routing and space switches to the stages of a three-stage Clos network and established design guidelines for multistage optical switches. In experiments with a prototype based on the proposed configuration, we demonstrated a 12,288-port optical switch with a throughput of 17.2 Pb/s. We then proposed a new configuration that consolidates the combining and splitting of optical signals in the space and wavelength-routing switches into a single star coupler, limiting the accumulation of optical loss, and demonstrated a 4,096 × 4,096 switch with a throughput of 819.2 Tb/s in a single switching layer. To bring low-cost, low-power intensity-modulation and direct-detection transceivers to large-scale optical switches, we have also proposed a configuration in which the optical switch itself compensates for chromatic dispersion.
For the digital signal processing of transceivers, we proposed a phase estimation method using two pilot tones to counter the phase noise that degrades signals in high-speed coherent transmission. To counter the spectral narrowing caused by the limited bandwidth of electrical devices, we proposed a demodulation method that combines partial-response spectral shaping with sequence estimation by a recurrent neural network, enabling high-quality transmission of broadband signals. This work received the Best Paper Award at OECC/PSC 2025.
Publications
Journal papers3
- Spectrum Narrowing Mitigation via Opto-Electrical Hybrid Partial-Response Spectrum Shaping and RNN-Based Sequence EstimationT. Sekizuka, T. Kuno, Y. Mori, and H. HasegawaIEICE Transactions on Communications, vol. E109-B, no. 11, November 2026.
- Low-Loss and Incrementally Expandable Flat Modular OXC for Scalable Metro-Core Optical NetworksA. Wada, T. Kuno, Y. Mori, and H. HasegawaIEEE/Optica Journal of Optical Communications and Networking, 2026.
- Three-Stage Optical Circuit Switch Architectures for Intra-Datacenter NetworkingT. Mitsuya, R. Higuchi, T. Kuno, T. Ochiai, H. Yuasa, Y. Mori, and H. HasegawaIEEE/Optica Journal of Lightwave Technology, vol. 43, no. 2, pp. 400-407, January 2025.
International conferences8
- Split-Sideband Digital Subcarrier Multiplexing for IQ-Impairment Compensation without Inter-Subcarrier MIMOT. Kuno, T. Sekizuka, Y. Mori, and H. HasegawaEuropean Conference on Optical Communication, paper We4-P54, Málaga, Spain, September 2026.
- Network-Level Impact of EDFA Gain Fluctuations under Dynamic RWA in High-Symbol-Rate WDM NetworksT. Sekizuka, S. Shimoi, T. Kuno, H. Hasegawa, and Y. MoriEuropean Conference on Optical Communication, paper We3-A4, Málaga, Spain, September 2026.
- A 4,096×4,096 Strictly Non-Blocking Optical Circuit Switch Delivering 819.2 Tb/s via Space-and-Wavelength RoutingK. Mano, T. Sekizuka, T. Kuno, H. Hasegawa, and Y. MoriOptica Optical Fiber Communication Conference, paper M3F.3, Los Angeles, USA, March 2026.
- In-Service Laser Anomaly Detection via DSP-Enabled Optical Performance MonitoringT. Sekizuka, K. Mano, T. Kuno, H. Hasegawa, and Y. MoriOptica Optical Fiber Communication Conference, paper Th1I.1, Los Angeles, USA, March 2026.
- Low-Loss and Infinitely Scalable Flat Modular OXC for Metro-Scale Optical NetworksA. Wada, T. Kuno, Y. Mori, and H. HasegawaOptica Optical Fiber Communication Conference, paper W3A.6, Los Angeles, USA, March 2026.
- High-Port-Count Optical Circuit Switch Architecture Enabling IM/DD Transmission through Static Chromatic Dispersion CompensationK. Mano, T. Sekizuka, T. Kuno, Y. Mori, and H. HasegawaSPIE Photonics West, paper 13905-7, San Francisco, USA, January 2026.
- Spectrum Narrowing Mitigation via Optoelectrical Partial-Response Spectrum ShapingT. Sekizuka, R. Higuchi, K. Satake, T. Kuno, Y. Mori, and H. HasegawaOptoElectronics and Communications Conference / International Conference on Photonics in Switching and Computing (OECC/PSC), paper ThB1-2, Sapporo, Japan, June/July 2025.
- EEPN Mitigation by Local Oscillator Phase Isolation with Dual Pilot CarriersT. Sekizuka, T. Kuno, R. Higuchi, R. Shiraki, Y. Mori, and H. HasegawaSPIE Photonics West, paper 13374-18, San Francisco, USA, January 2025.
Domestic conferences4
- 空間・波長ルーティングを用いたデータセンタ向け大規模光スイッチ眞野 幸希，關塚 太成，久野 拓真，長谷川 浩，森 洋二郎電子情報通信学会 フォトニックネットワーク研究会 学生ワークショップ，pn2026-stws-14，沖縄，2026年3月．
- 位相で診るレーザ異常 ～ディジタル信号処理による稼働中監視手法～關塚 太成，眞野 幸希，久野 拓真，長谷川 浩，森 洋二郎電子情報通信学会 フォトニックネットワーク研究会，PN2025-49，沖縄，2026年3月．
- 空間・波長混成型光スイッチ構成におけるIM/DD方式の適用性評価眞野 幸希，關塚 太成，久野 拓真，森 洋二郎，長谷川 浩電子情報通信学会 ソサイエティ大会，B-12-11，岡山，2025年9月．
- スペクトル狭窄を緩和する光電気ハイブリッド信号処理手法關塚 太成，樋口 怜治，佐竹 風人，久野 拓真，森 洋二郎，長谷川 浩電気・電子・情報関係学会 東海支部連合大会，D1-5，長野，2025年9月．
Awards1
- T. Sekizuka, R. Higuchi, K. Satake, T. Kuno, Y. Mori, and H. Hasegawa, Best Paper Award, OptoElectronics and Communications Conference / International Conference on Photonics in Switching and Computing (OECC/PSC), July 2025.