Details of a Researcher - Koike, Yasuhiro

Papers - Koike, Yasuhiro

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A wide color gamut lcd with a polarized laser backlight

Komura S., Okuda K., Onoda K., Kijima H., Tagaya A., Kikutani T., Koike Y.

Digest of Technical Papers - SID International Symposium (Digest of Technical Papers - SID International Symposium) 51 ( 1 ) 5 - 8 2020

ISSN 0097966X

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Analysis of nano-creep deformation of epoxy adhesive in optical fiber connector for long-term reliability prediction

Shikama K., Aratake A., Koike Y.

Optical Fiber Technology (Optical Fiber Technology) 52 2019.11

ISSN 10685200

© 2019 Elsevier Inc. We describe a comprehensive analysis of the nano-creep deformation of an epoxy adhesive used in physical-contact optical fiber connectors. To design a highly reliable multicore fiber connector and predict the long-term reliability of commercially installed optical connectors, we focus on the change in fiber withdrawal, which is a key parameter for achieving physical-contact connection. We also propose an adhesive creep model that includes long-term time dependence by detailing through a finite element analysis the parameters that influence the fiber withdrawal, such as shear stress with connection, thermal stress, residual stress, swelling, and cure shrinkage. The measurement results for fiber withdrawal under several environmental conditions provided in this paper support the behaviors considered in our proposed model. From our obtained short-term results and rheological approach, we predict the nano-creep deformation observed in the connector over the long term by applying the time-temperature superposition principle, and discuss the correspondence with exposure test results. Our verified mechanism and estimated values of creep deformation prove the high reliability of the optical connectors and also provide guidelines for determining the need to update installed connectors and for designing future connection devices such as physical-contact multicore fiber connectors.

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Nonlinear Distortion Reduction Effect of Graded-Index Plastic Optical Fiber

Muramoto K., Inoue A., Koike Y.

IEEE Photonics Technology Letters (IEEE Photonics Technology Letters) 31 ( 10 ) 791 - 794 2019.05

ISSN 10411135

© 2019 IEEE. We experimentally demonstrate that a graded-index plastic optical fiber (GI POF) can significantly reduce transmitted signal distortion caused by the nonlinear response of a multimode fiber (MMF) link based on a vertical-cavity surface-emitting laser (VCSEL). The low distortion of the signal transmission is attributed to the strong mode coupling in the GI POF, which suppresses the increment in signal distortion due to the external optical feedback, by reducing the self-coupling of problematic back-reflected light into the VCSEL cavity. The strong mode coupling is closely associated with polymer-specific microscopic heterogeneous structures in the fiber core materials, suggesting that the signal distortion can be further reduced by controlling the microscopic properties. The nonlinear distortion reduction effect of our developed GI POF will be invaluable for next-generation MMF links based on multilevel modulation in the ultrahigh-definition era.

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Unconventional plastic optical fiber design for very short multimode fiber link

Inoue A., Koike Y.

Optics Express (Optics Express) 27 ( 9 ) 12061 - 12069 2019.04

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement We introduce a graded-index plastic optical fiber (GI POF) design for very short-distance household applications, in which the transmission quality is predominantly determined by system noise rather than the loss and bandwidth. The developed GI POF has strong mode coupling with low accompanying scattering loss, which is closely related to the specific microscopic heterogeneities in the core material. Such characteristic mode coupling significantly decreases reflection noise, improving the transmission quality compared with silica GI multimode fiber (MMF) for lengths below 30 m. Moreover, in the GI POF link, the transmission quality tends to improve with increasing fiber length, despite the increased loss and decreased bandwidth. This feature suggests that the system noise can be controlled by the microscopic heterogeneous properties of the GI POF for a very short MMF link, where the fiber loss and bandwidth are sufficiently low and high, respectively. This unconventional concept for optical-fiber design can advance fiber-optic communication in emerging applications in households located near optical network terminals.

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Low-Noise Radio over Plastic Optical Fiber for TV Broadcasting in Ultrahigh-Definition Era

Inoue A., Koike Y.

2019 Optical Fiber Communications Conference and Exhibition, OFC 2019 - Proceedings (2019 Optical Fiber Communications Conference and Exhibition, OFC 2019 - Proceedings) Part F160-OFC 2019 2019.04

ISSN 9781943580538

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Intrinsically Stabilized Plastic Optical Fiber Link Subject to External Optical Feedback

Inoue A., Koike Y.

IEEE Photonics Journal (IEEE Photonics Journal) 11 ( 1 ) 2019.02

© 2009-2012 IEEE. We develop a graded-index plastic optical fiber (GI POF) that can significantly stabilize a multimode fiber (MMF) link with a vertical-cavity surface-emitting laser (VCSEL) subject to external optical feedback. It is demonstrated that the dominant mechanism for this stabilization effect is the strong mode coupling of the GI POF, which is closely related to the polymer-specific microscopic heterogeneities in the GI POF core material. Such mode coupling decreases correlation between the problematic reflected light field and VCSEL cavity field, increasing tolerance of the MMF link for external optical feedback. Our developed GI POF with specific microscopic heterogeneities prevents the external-optical-feedback-induced critical destabilization observed for silica GI MMFs. These results suggest that the stabilization effect can be controlled by microscopic properties regardless of the fiber attenuations and core refractive indices.

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Low-noise graded-index plastic optical fiber for significantly stable and robust data transmission

Inoue A., Koike Y.

Journal of Lightwave Technology (Journal of Lightwave Technology) 36 ( 24 ) 5887 - 5892 2018.12

ISSN 07338724

© 1983-2012 IEEE. Internet traffic continues to grow with the increase of network-connected smartphones, tablets, televisions, and monitoring devices in the Internet-of-Things (IoT) era. This trend will be significantly accelerated by the introduction of ultrahigh-definition (UHD) imaging technologies in various applications, and existing optical networks including datacenter networks are under urgent development to accommodate this traffic. However, optical fibers have not been introduced into households located in optical network terminal areas, even though UHD device connections require decompressed high-volume data transmission at more than 100 Gb/s, where a multilevel modulation scheme is vital. In UHD applications, very short optical cables (typically less than several meters) are connected and disconnected by consumers in a manner similar to metal interface cables. Under such conditions, a data transmission quality is predominantly limited by noise and instability rather than bandwidth and loss. Here, we propose low-noise graded-index plastic optical fibers (GI POFs) that enable significantly stable and robust data transmission through strong mode coupling, whose mechanism is fundamentally different from that of silica optical fibers. The low-noise GI POF link eliminates the need for the precise fiber alignment, angled fiber facets, and optical isolators typically used in conventional links. Our proposed GI POF material paves the way for quick optical fiber connections for multilevel UHD video transmission, becoming the first 'capillaries of light' from optical network terminals in the IoT era.

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Development of Graded-Index Plastic Optical Fiber for Significantly Low-Noise Data Transmission

Inoue A., Koike Y.

European Conference on Optical Communication, ECOC (European Conference on Optical Communication, ECOC) 2018-September 2018.11

ISSN 9781538648629

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Pump-Polarization Effects in Dye-Doped Polymer Optical Fibers

Asuncion Illarramendi M., Zubia J., Bikandi I., Ayesta I., Parola I., Aramburu I., Arrue J., Tagaya A., Koike Y.

Journal of Lightwave Technology (Journal of Lightwave Technology) 36 ( 18 ) 4090 - 4098 2018.09

ISSN 07338724

© 1983-2012 IEEE. This paper presents a study on the influence of the polarization of the pump beam on the emission properties of dye-doped polymer optical fibers. The fiber samples, which are pumped transversely with linearly polarized light, are graded-index polymer optical fibers doped with rhodamine 6G. The variation of the intensity and angular distribution of the output emission are theoretically and experimentally analyzed as the polarization direction of the pump is changed. The analysis is carried out both in the regime of fluorescence and in the regime of amplified spontaneous emission. It is shown that a pump polarization perpendicular to the fiber symmetry axis yields not only higher emission efficiency but also narrower axial angular width. The effect of the polarization of the pump beam on the properties of the amplified spontaneous emission is also measured, including its threshold-like energy, relative efficiency, and optical gain. The results indicate that the pump polarization determines the light-emitting performance of dye-doped polymer optical fibers.

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Significantly robust data transmission by ballpoint-pen interconnect for graded-index plastic optical fiber

Kaseda Y., Inoue A., Koike Y.

Journal of Lightwave Technology (Journal of Lightwave Technology) 36 ( 18 ) 4167 - 4173 2018.09

ISSN 07338724

© 1983-2012 IEEE. We have developed a novel optical interconnect for graded-index plastic optical fibers based on the use of ballpoint-pen connectors, where ball lenses are precisely mounted on fiber end faces by a simple and low-cost ballpoint-pen production technology. This report demonstrates that the ballpoint-pen interconnect allows us for significantly robust data transmission with sufficient misalignment tolerance and mating durability for consumer applications, where very short optical fibers are frequently connected and disconnected to the consumer electronics in a manner similar to metal cables. In the ballpoint-pen interconnect, power penalties are barely affected even by misalignments with a lateral offset of 50 μm or a connector separation of 1.0 mm, allowing for optical fiber connections without the requirements of precise alignment or high manufacturing accuracy. Moreover, it is suggested that modal noises due to dusts and scratches on fiber end-faces are generated for conventional butt-coupling based on physical contact in applications that require frequent connection and disconnection of optical fibers. This modal noise generation can be prevented using nonphysical contacts with the ballpoint-pen connectors. We achieve high-speed data transmission that is barely influenced by 2500 mating cycles. These results suggest that the ballpoint-pen interconnect allows us for consumer-friendly optical fiber connections without the requirement of any cleanings in a manner similar to electrical interconnect.

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Depolarization effect of graded-index plastic optical fiber with strong mode mixing

Suzuki H., Inoue A., Koike Y.

Optics InfoBase Conference Papers (Optics InfoBase Conference Papers) Part F98-BGPPM 2018 2018

ISSN 9781557528209

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Reflection noise characteristics in graded-index plastic optical fiber link based on ballpoint-pen interconnect

Yagi T., Inoue A., Koike Y.

Optics InfoBase Conference Papers (Optics InfoBase Conference Papers) Part F98-BGPPM 2018 2018

ISSN 9781557528209

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Significant reduction of nonlinear signal distortion by graded-index plastic optical fiber with intrinsic strong mode mixing

Muramoto K., Inoue A., Koike Y.

Optics InfoBase Conference Papers (Optics InfoBase Conference Papers) Part F111-SOF 2018 2018

ISSN 9781557528209

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Proposal of novel random polarization film with birefringent crystal for real-color displays

Udono M., Koike Y.

Proceedings of the International Display Workshops (Proceedings of the International Display Workshops) 2 467 - 469 2018

ISSN 9781510883918

Optical Characterization of Doped Thermoplastic and Thermosetting Polymer-Optical-Fibers

I. Ayesta, M. A. Illarramendi, J. Arrue, I. Parola, F. Jiménez, J. Zubia, A. Tagaya and Y. Koike

Polymers Vo. 9 ( No. 3 ) Article No. 90 2017