Papers - TSUDA Hiroyuki

Multi-band photonic integrated wavelength selective switch

Kraemer R., Nakamura F., Hout M.V.D., Van Der Heide S., Okonkwo C., Tsuda H., Napoli A., Calabretta N.

Journal of Lightwave Technology (Journal of Lightwave Technology)  39 ( 19 ) 6023 - 6032 2021.10

ISSN  07338724

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As fiber-optic systems turn toward multi-band transmission (MBT), exploiting the complete low loss window of optical fibers, novel optical components, able to operate in bands other than the conventional C-band, become necessary. In light of this, we report on a multi-band photonic integrated 1 × 2 wavelength selective switch (WSS) operating in the O, S, C and L-bands. The photonic integrated WSS presented in this work uses a folded arrayed-waveguide grating (AWG) as the filtering element, while the wideband operation of the thermo-optic switches allows the routing of the individual channels from those bands to any of the device output ports. The operation of the WSS is experimentally validated for different bands and modulation formats. Results show error-free operation with limited penalty with intensity-modulation direct-detection (IM/DD) non-return-to-zero on-off keying (NRZ-OOK) up to 35 Gb/s in O, S, C and L-bands and up to 169.83 Gb/s with coherent 64-quadrature amplitude modulation (QAM) data transmission in the S, C and L-bands.

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Impact of cascaded multi-band 1×2 photonic integrated WSS in metro-access networks

Kraemer R., van den Hout M., van der Heide S., Santana H., Wang Y., Nakamura F., Tsuda H., Napoli A., Okonkwo C., Calabretta N.

Optics InfoBase Conference Papers (Optics InfoBase Conference Papers)   2021

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PIC multi-band WSS is evaluated with 33.3 GBd 64-QAM data. BER values below the FEC-limit for the S, C and L-bands are obtained. The 3dB bandwidth scaling of cascading WSSs is also investigated for a metro-access network.

Guanine crystals regulated by chitin-based honeycomb frameworks for tunable structural colors of sapphirinid copepod, Sapphirina nigromaculata

Kimura T., Takasaki M., Hatai R., Nagai Y., Uematsu K., Oaki Y., Osada M., Tsuda H., Ishigure T., Toyofuku T., Shimode S., Imai H.

Scientific Reports (Scientific Reports)  10 ( 1 )  2020.12

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© 2020, The Author(s). Sapphirinid copepods, which are marine zooplankton, exhibit tunable structural colors originating from a layered structure of guanine crystal plates. In the present study, the coloring portion of adult male of a sapphirinid copepod, Sapphirina nigromaculata, under the dorsal body surface was characterized to clarify the regulation and actuation mechanism of the layered guanine crystals for spectral control. The coloring portions are separated into small domains 70–100 µm wide consisting of an ordered array of stacked hexagonal plates ~1.5 µm wide and ~80 nm thick. We found the presence of chitin-based honeycomb frameworks that are composed of flat compartments regulating the guanine crystal plates. The structural color is deduced to be tuned from blue to achromatic via yellow and purple by changing the interplate distance according to vital observation and optical simulation using a photonic array model. The framework structures are essential for the organization and actuation of the particular photonic arrays for the exhibition of the tunable structural color.

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S-, C- And L-Band Photonic Integrated Wavelength Selective Switch

Kraemer R., Nakamura F., Tsuda H., Napoli A., Calabretta

2020 European Conference on Optical Communications, ECOC 2020 (2020 European Conference on Optical Communications, ECOC 2020)   2020.12

ISSN  9781728173610

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A photonic integrated WSS operating on the S-, C- and L-Band is presented with an average extinction-ratio of -20.40 dB. Crosstalk levels were kept below -20 dB for all bands and experimental results on NRZ OOK data indicate error-free operation for up to 35 Gb/s.

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Silicon photonics platforms for optical communication systems, outlook on future developments

Tsuda H.

IEICE Electronics Express (IEICE Electronics Express)  17 ( 22 ) 1 - 7 2020.11

ISSN  13492543

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This paper reviews recent progress in silicon photonics and compares it with other optical device platforms. The key components for optical communication systems, including arrayed waveguide gratings, optical switches, modulators and optical functional devices fabricated on silicon photonics platforms are explained. The integration of III-V compounds, lithium niobate, polymers, phase change and other functional materials are necessary to strengthen silicon photonics platforms. These are also reviewed, and the feasibilities are discussed. Finally, I express my personal view as to the best research direction for silicon photonics.

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High extinction ratio and low crosstalk C and L-Band photonic integrated wavelength selective switching

Kraemer R.M.G., Nakamura F., Wang Y., Tsuda H., Calabretta N.

International Conference on Transparent Optical Networks (International Conference on Transparent Optical Networks)  2020-July 2020.07

ISSN  9781728184234

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A photonic integrated 1×2 Wavelength Selective Switch (WSS) based on a loopback configuration is shown to operate on the C and L-Bands due to the cyclic nature of the employed arrayed-waveguide gratings (AWGs). An average of -22.59 dB and -20.40 dB were observed in the C and L-band channels respectively. Crosstalk levels are kept below -40 dB on the output port A and below -30 dB on output port B. Experimental results on NRZ OOK data indicate a bit-error-rate (BER) below 1×10-11 with very limited penalty at both bands up to a bit rate of 30 Gbps.

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Silicon Based 1 × M Wavelength Selective Switch Using Arrayed Waveguide Gratings with Fold-Back Waveguides

Nakamura F., Asakura H., Suzuki K., Tanizawa K., Ohtsuka M., Yokoyama N., Matsumaro K., Seki M., Ikeda K., Namiki S., Kawashima H., Tsuda H.

Journal of Lightwave Technology (Journal of Lightwave Technology)  39 ( 8 ) 2413 - 2420 2020.04

ISSN  07338724

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The design of a novel 1 × M fold-back type wavelength selective switch (WSS), which has fewer waveguide crossings than a conventional integrated WSS, is reported. The WSS is composed of interleavers, 1 × M optical switches, and arrayed waveguide gratings (AWGs). Switches are combined with AWGs by fold-back waveguides, and each AWG works as both a demultiplexer and multiplexer thus avoiding center wavelength mismatch caused by fabrication errors. Waveguide crossings cause excess crosstalk and loss in lightwave circuits. By using a fold-back architecture the number of crossings can be reduced to less than half that of a conventional design. We discuss the operating principle, the design method, and the scalability of the fold-back type WSS. Furthermore, the switching operation of a 200-GHz spacing, 20-channel, 1 × 2 silicon WSS in a fold-back configuration on a 5 mm × 10 mm SOI chip is demonstrated. This has 15 waveguide crossings in a path, of which six are additional crossings with monitor waveguides. The average insertion loss and average extinction ratio are 29.6 dB and 10.9 dB, respectively.

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SDN enabled flexible optical data center network with dynamic bandwidth allocation based on photonic integrated wavelength selective switch

Xue X., Nakamura F., Prifti K., Pan B., Yan F., Wang F., Guo X., Tsuda H., Calabretta N.

Optics Express (Optics Express)  28 ( 6 ) 8949 - 8958 2020.03

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© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement Optical switching techniques featuring the fast and large capacity have the potential to enable low latency and high throughput optical data center networks (DCN) to afford the rapid increasing of traffic-boosted applications. Flexibility of the DCN is of key importance to provide adaptive and dynamic bandwidth to handle the variable traffic patterns generated by the heterogeneous applications while optimizing the network resources. Aiming at providing the flexible bandwidth for optical DCNs, we propose and experimentally investigate a software-defined networking (SDN) enabled reconfigurable optical DCN architecture based on novel optical top of rack (OToR) switch exploiting photonic-integrated wavelength selective switch. Experimental results show that the optical bandwidth per link can be automatically reallocated under the management of the deployed SDN control plane according to the variable traffic patterns. With respect to the network with inflexible interconnections, the average packet loss of the reconfigurable DCN decreases 1 order of magnitude and the server-to-server latency performance improves of 42.2%. Scalability investigation illustrates limited (11.7%) performance degradation as the reconfigurable network scale from 2560 to 40960 servers. Both the numerical and experimental assessments validate the proposed DCN with reconfigurable bandwidth feature and lower latency variations with respect to the inflexible DCNs.

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Figure of merit of phase change materials for Mach-Zehnder interferometer-based and directional-coupler-based optical switches

Sakamoto K., Kuwahara M., Tsuda H.

Proceedings of SPIE - The International Society for Optical Engineering (Proceedings of SPIE - The International Society for Optical Engineering)  11276 2020

ISSN  9781510633155

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© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. For further improvement of phase change material switches, relationships between optical characteristics of phase change materials(PCM) and the performance of optical switches were investigated. PCM optical switch is optimized for the both states of the insertion loss to be balanced. With optimized three-channel directional coupler switch, the refractive index difference between amorphous and crystalline state was inversely proportional to the insertion loss.

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T/O バンドを用いた1000 チャネル級波長ルーティング技術による大容量かつ多様な光ネットワークの実現に向けて

久保亮吾、吉沢勝美、友松泰則、須藤誠、初鹿野圭、津田裕之

電子情報通信学会論文誌C (電子情報通信学会)  J102–C ( 12 ) 320 - 331 2019.12

Research paper (scientific journal), Joint Work, Accepted

Large-scale wavelength multi/demultiplexer using a spatial grating combined with arrayed waveguide gratings

Ohori A., Tsuda H.

Proceedings of SPIE - The International Society for Optical Engineering (Proceedings of SPIE - The International Society for Optical Engineering)  11184 2019

ISSN  0277786X

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The C- and L-bands (1530 nm ∼ 1625 nm) are used for long-haul optical communication systems. The operating wavelength range needs to be extended to realize much broader transmission capacity with a low-cost modulation format. In this paper, we propose a large-scale wavelength multiplexer/demultiplexer using a conventional spatial grating in combination with arrayed-waveguide gratings (AWGs) to cover the whole fiber transmission wavelength range. The diffracted light from the spatial grating is spectrally decomposed and coupled to several AWGs for further demultiplexing. In this study, we designed a multi/demultiplexer which covers the O∼L-bands (186.2 THz ∼ 243.7 THz) with a channel spacing of 100 GHz. This has 9 sub-bands and 576 wavelength channels. The groove density of the spatial grating and the beam diameter on it are assumed to be 300 lines/mm and 1 mm x 1 mm, respectively. The diffracted light is coupled to 9 tapered waveguides on the edge of a planar lightwave circuit (PLC). The shape of the beam is changed by a cylindrical lens, to enhance the coupling efficiency. Each tapered waveguide is connected to an AWG with a center wavelength corresponding to the particular sub-band. AWGs with 64 output channels have a frequency spacing of 100 GHz. The transmission loss in the AWGs was calculated to be between -14.9 dB and -6.6 dB. The relatively large transmission loss was due to misalignment between the beam and the tapered waveguides.

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Polarization Diversity Circuit Using Photonic Crystal Waveplates for 1.2-μm Quantum Dot Semiconductor Optical Amplifiers

Okuno Y., Sugiyama K., Hajikano T., Tomomatsu Y., Yoshizawa K., Tsuda H.

Proceedings of the 2018 Photonics in Switching and Computing, PSC 2018 (Proceedings of the 2018 Photonics in Switching and Computing, PSC 2018)   2018.09

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Silica-based polarization diversity circuit for QD-SOA operating in T-band was fabricated. By connecting polarization diversity circuits to QD-SOA chip, the polarization dependent gain of less than 0.8 dB and the optical gain of 3.2 dB were achieved.

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T/O-band wavelength routing system using quantum dot semiconductor devices and 1081-channel AWG router

Kubo R., Fujimoto T., Shobudani T., Okuno Y., Suzuki M., Tsuda H., Sudo M., Hajikano T., Tomomatsu Y., Yoshizawa K.

2018 Optical Fiber Communications Conference and Exposition, OFC 2018 - Proceedings (2018 Optical Fiber Communications Conference and Exposition, OFC 2018 - Proceedings)     1 - 3 2018.06

ISSN  9781943580385

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© 2018 OSA. We demonstrate a wavelength routing system that covers a broad wavelength range of 1000-1360 nm, i.e., T/O-band. The system includes our developed T/O-band-specific quantum dot semiconductor devices and 1081-channel arrayed waveguide grating (AWG) router.

Integrated silicon photonic wavelength-selective switch using wavefront control waveguides

Nakamura F., Muramatsu K., Suzuki K., Tanizawa K., Ohtsuka M., Yokoyama N., Matsumaro K., Seki M., Koshino K., Ikeda K., Namiki S., Kawashima H., Tsuda H.

Optics Express (Optics Express)  26 ( 10 ) 13573 - 13589 2018.05

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© 2018 Optical Society of America A wavelength selective switch (WSS) can route optical signals into any of output ports by wavelength, and is a key component of the reconfigurable optical add/drop multiplexer. We propose a wavefront control type WSS using silicon photonics technology. This consists of several arrayed waveguide gratings sharing a large slab waveguide, wavefront control waveguides and distributed Bragg reflectors. The structure, design method, operating principle, and scalability of the WSS are described and discussed. We designed and fabricated a 1 × 2 wavefront control type WSS using silicon waveguides. This has 16 channels with a channel spacing of 200 GHz. The chip size is 5 mm × 10 mm. The switching operation was achieved by shifting the phase of the light propagating in each wavefront control waveguide, and by controlling the propagation direction in the shared large slab waveguide. Our WSS has no crossing waveguide, so the loss and the variation in loss between channels were small compared to conventional waveguide type WSSs. The heater power required for switching was 183 mW per channel, and the average extinction ratios routed to Output#1 and Output#2 were 9.8 dB and 10.2 dB, respectively.

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T/O-band wavelength routing system using quantum dot semiconductor devices and 1081-channel AWG router

Kubo R., Fujimoto T., Shobudani T., Okuno Y., Suzuki M., Tsuda H., Sudo M., Hajikano T., Tomomatsu Y., Yoshizawa K.

Optics InfoBase Conference Papers (Optics InfoBase Conference Papers)  Part F84-OFC 2018 2018

ISSN  9781557528209

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© OSA 2018. We demonstrate a wavelength routing system that covers a broad wavelength range of 1000-1360 nm, i.e., T/O-band. The system includes our developed T/O-band-specific quantum dot semiconductor devices and 1081-channel arrayed waveguide grating (AWG) router.

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Silicon photonics based 1 × 2 wavelength selective switch using fold-back arrayed-waveguide gratings

Nakamura F., Asakura H., Suzuki K., Tanizawa K., Ohtsuka M., Yokoyama N., Matsumaro K., Seki M., Koshino K., Ikeda K., Namiki S., Kawashima H., Tsuda H.

IEICE Electronics Express (IEICE Electronics Express)  15 ( 14 )  2018

ISSN  13492543

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© 2018, Institute of Electronics Information Communication Engineers. All rights reserved. We report on a novel design of a wavelength selective switch (WSS) using silicon photonics technology. It comprises of 1 × 4 interleavers, arrayed-waveguide gratings (AWGs) connected to fold-back waveguides, and 1 × 2 optical Mach-Zehnder interferometer switches. In the proposed WSS, fold-back waveguides enable the AWGs to be used for both demulti-plexing and multiplexing. Therefore the WSS has less waveguide crossings than a conventional configuration. Moreover, a 20-channel, 200-GHz spacing, 1 × 2 fold-back type WSS was fabricated on 5 mm × 10 mm SOI chip using CMOS technology.

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Demonstration of 10-Gbit/s transmission over G.652 fiber for T-band optical access systems using quantum-dot semiconductor devices

Kubo R., Matsunaga M., Shobudani T., Fujimoto T., Tsuda H., Sudo M., Hajikano T., Tomomatsu Y., Yoshizawa K.

IEICE Electronics Express (IEICE Electronics Express)  15 ( 18 )  2018

ISSN  13492543

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© IEICE 2018. The wavelength range of 1000–1260 nm, known as T-band, where T denotes “thousand”, is one of the promising wavebands suitable for the future moderate-range optical networks. We have developed T-band specific semiconductor devices based on quantum-dot technology. However, the cut-off wavelength of optical fiber cables currently utilized in access networks, i.e., G.652 fibers, is specified to be less than 1260 nm. Therefore, the fibers do not fully support the T-band. This letter presents a demonstration of the feasibility of 10-Gbit/s transmission over G.652 fibers in the T-band by experiments.

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量子ドットゲインチップおよびアレイ導波路回折格子を用いたTバンド波長分割多重通信用外部共振器レーザ

TSUDA HIROYUKI

電子情報通信学会論文誌C J100-C ( 8 ) 342 - 347 2017.08

Research paper (scientific journal), Joint Work, Accepted

Current-driven phase-change optical gate switch using indium–tin-oxide heater

Kentaro Kato, Masashi Kuwahara, Hitoshi Kawashima, Tohru Tsuruoka, and Hiroyuki Tsuda

Appl. Phys. Exp. 10 ( 7 ) 072201 2017.07

Research paper (scientific journal), Accepted

Polarization diversity circuit based on silica waveguides and photonic crystal waveplates for a 4×4 silicon optical switch

Koki Sugiyama, Takafumi Chiba, Ken Tanizawa, Keijiro Suzuki, Takayuki Kawashima, Shojiro Kawakami, Kazuhiro Ikeda, Hitoshi Kawashima, Hiroshi Takahashi, Hiroyuki Tsuda

IEICE Electron. Express 14 ( 10 ) 20170252 2017.05

Research paper (scientific journal), Joint Work, Accepted