Details of a Researcher - Koike, Yasuhiro

Papers - Koike, Yasuhiro

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High-Speed Polymer Optical Fiber Network

KOIKE YASUHIRO

Molecular Crystals and Liquid Crystals (MCLC) Vol.316 1-6 1998.08

Research paper (other academic), Single Work

The status of the POF for high-speed data communication is reviewed. Recently, low-loss, and high-bandwidth perfluorinated GI POF which has no serious absorption loss from visible to near infrared region was successfully prepared at Keio university. Since the core diameter of GI POF is much larger than that of the multimode silica fiber, the serious modal noise in the conventional multimode silica fiber was virtually eliminated, resulting in stable giga bit order data transmission with inexpensive couplers and connectors.

Recent Progress in High-Speed Polymer Optical Fiber

KOIKE YASUHIRO

Molecular Crystal and Liquid Crystals (MCLC) Vol.315 247-256 1998.08

Research paper (other academic), Single Work

Graded-Index Polymer Optial Fiber with High Thermal Stability of Bandwidth

ISHIGURE TAKAAKI, SATO MASATAKA, NIHEI EISUKE, KOIKE YASUHRIO

Japanese Journal of Applied Physics Vol.37 ( Part1,No.7 ) 3986-3991 1998.07

Research paper (scientific journal), Joint Work, Accepted

The development of the perfluorinated (PF) polymer based GI POF for high-speed data communication is described. It was experimentally confirmed that gigabit data transmission for 500-1000m at 1.3µm wavelength was achieved by the low loss PF polymer based GI POF. The thermal stability of PMMA based GI POF is discussed. We selected several kinds of dopants that can maintain a high glass transition temperature (Tg) of the GI POF core. By using the newly selected dopants, we succeeded in maintaining the parabolic refractive index profile of GI POF with no degradation even at 85 to 90℃ for more than 5000h.

高速通信のためのプラスチック光ファイバー（POF）とマルチメディアネットワーク

KOIKE YASUHIRO

KAST REPORT Vol.9 ( No.2 ) 10-17 1998.03

Research paper (other academic), Single Work

High-Speed Photonics Polymer and Its Application

ISHIGURE TAKAAKI, SATOH MASATAKA, NIHEI EISUKE, KOIKE YASUHIRO

Pure and Applied Optics, Journal of The European Optical Society Part A Vol.7 ( No.2 ) 201-210 1998.03

Research paper (scientific journal), Joint Work

光散乱ポリマーの液晶バックライトへの応用

HORIBE AKIHIRO, KOIKE YASUHIRO

光学/日本光学会誌 (Optical Society of Japan, (An Affiliate of The Japan Society of Applied Physics)) 27 ( 2 ) 1998.02

Research paper (other academic), Joint Work

　時々刻々と進歩する科学技術の中で近年の液晶ディスプレイの発展は非常に目覚しいものであり、今だ留まるところを知らず、さらなる性能向上を遂げている。その中で液晶パネルを背面から照射するための平面光源(バックライト)の性能は、消費電力に始まり、薄型軽量、輝度の角度特性、色の均一性等にいたるまで、液晶ディスプレイの性能を広範囲にわたって支配するものである。
　この液晶バックライトシステムにも目的に応じて様々な構成が考えられるが、ここでは特に、低消費電力化を課題とする液晶ディスプレイを対象とした、光散乱ポリマー導光体を用いた高効率バックライトシステムについて詳細に紹介する。

Polymer Optical Fiber Amplifiers for Communication and Sensor Applications

KOBAYASHI TAKEYUKI, SASAKI KEISUKE, KOIKE YASUHIRO, OKAMOTO YOSHIYUKI

Proceedings of The International Society for Optical Engineerng, (SPIE) / Optoelectronics'98, Photonics West, Conference on Polymer Photonics Devices (The International Society for Optical Engineerng, (SPIE)) Vol. 3281 84-91 1998.01

Research paper (conference, symposium, etc.), Joint Work, Accepted

Organic dyes and rare earth chelates have been chosen and incorporated into the core regions of graded index (GI) polymer optical fiber (POF) as gain media. Since the synthetic polymer shows much better compatibility with organic fluorescent materials and is amenable to high active dopant concentrations, the doped POFs produce high gains in short length of fiber. We demonstrated that organic dye-doped polymer optical amplifier (POFA) cover a wide spectral range in the visible with a best observed gain of 37 dB in a Rhodamine B-doped POFA pumped at 550 nm. Also, with a GI POF doped with europium chelate of hexafluoroacetylacetone in tris form, we observed organic dyes and rare earth chelates offers optical amplifiers and superfluorescence source for a variety of communication and sensor applications.

High-Bandwidth and High-Thermal Stability Graded-Index Polymer Optical Fiber

ISHIGURE TAKAAKI, SATO MASATAKA, NIHEI EISUKE, KOIKE YASUHIRO

Proceedings of The International Society for Optical Engineerng, (SPIC) / Optoelectronics'98, Photonics West, Conference on Polymer Photonics Devices Vol. 3281 1998.01

Research paper (conference, symposium, etc.), Joint Work, Accepted

Recent progress of the graded-index polymer optical fiber (GI POF) is reviewed. Because the low attenuation of light transmission in the perfluorinated (PF) polymer based GI POF enables 500 to 1000m transmission, more accurate analysis is required in the refractive index profile to realize the order of giga bit transmission. Furthermore, recent improvement of the thermal stability of the GI POF is introduced. We clarify that the stability of the refractive index profile and the attenuation under high temperature and high humidity atmosphere can be improved by selecting the suitable dopant materials.

High-Performance LCD Backlight Using Highly Scatteting Optical Transmission Polymer

HORIBE AKIHIRO, NIHEI EISUKE, KOIKE YASUHIRO

Research paper (conference, symposium, etc.), Joint Work, Accepted

We have proposed a highly scattering transmission (HSOT) polymer for use as a high luminance light source medium. This polymer contains specified microscopic heterogeneous structure for controlling light scattering properties. A LCD backlight using the HSOT polymer has twice the brightness of the conventional transparent PMMA-based backlight because of multiple scattering phenomenons inside the HSOT polymer. In this paper, such a light scattering phenomenon was quantitatively analyzed by a ray tracing based on Mie scattering and Monte Carlo simulations. Subsequently, we propose the new HSOT backlight system having higher luminance and uniformity of white color illumination.

マルチメディア社会の実現へ、期待のインフラ　　　プラスチック光ファイバ

KOIKE YASUHIRO

KDD Technical Journal ( No.31冬号, ) 8-11 1998.01

Research paper (other academic), Single Work

Physical Aging and Light Scattering of Low-Loss Poly(Methyl Methacrylate) Glass

TANIO NORIHISA, KATO HISAO, KOIKE YASUHIRO, HARVEY E. BAIR, MATSUOKA SHIRO, LEE L. BLYLER

Polymer Journal (The Society of Polymer Science, Japan) Vol.30 ( No.1 ) 56-59 1998.01

Research paper (scientific journal), Joint Work

Isothermal aging has been carried out on low-loss PMMA glass at 18℃ below the glass transition temperature (Tg). The effect of enthalpy relaxation on light scattering loss of PMMA glass which had no excess scattering was investigated by the use of differential scattering calorimeter (DSC) and light scattering measurement. The light scattering intensity of PMMA glass did not increase with increasing aging time. It is seen that the light scattering loss of glassy PMMA is not affected inherently by physical aging as a result of its approach to thermodynamic equilibrium at a temperature 18℃ below its Tg.

Graded Index Polymer Optical Fiber Amplifiers

KOBAYASHI TAKEYUKI, SASAKI KEISUKE, KOIKE YASUHIRO

Function & Materials (The Japan Society of Plastic Technology) Vol.18 ( No.1 ) 76-82 1998.01

Research paper (other academic), Joint Work

Giga Bit Transmission in High-Bandwidth Low-Loss Perdeuterated Polymer Base Graded-Index Polymer Optical Fiber Link

ISHIGURE TAKAAKI, NIHEI EISUKE, KOIKE YASUHIRO

Journal of Fiber Science and Technology,Japan, (The Society of Fiber Science and Technology, Japan) Vol.53 ( No.12 ) 520-525 1997.12

Research paper (scientific journal), Joint Work, Accepted

This paper describes the high speed transmission characteristics of the Perdeuterated PMMA (PMMA-d8) based GI POF. The PMMA-d8 base GI POF was obtained by the interfacial-gel polymerization technique. We succeeded in 1Gb/s 160m transmission at 650-nm wavelength in the 160m GI POF link. In general, the possible transmission distance of the PMMA POF link is limited to approximately 100m because of high attenuation. However, substitution of hydrogen atoms in the polymer for deuterium atoms decreases the intrinsic absorption loss. The total attenuation of the PMMA-d8 base GI POF at 650nm wavelength was about 60dB/km which is approximately half of the attenuation of PMMA base GI POF. Therefore, the low-loss PMMA-d8 base GI POF enables longer distance communication. We also analyzed the dispersion property of the PMMA-d8 base GI POF by utilizing WKB method in which both modal and material dispersion were taken into consideration. It was clarified that approximately 2Gb/s transmission can be achieved by PMMA-d8 base GI POF with 200m length when 650nm wavelength is adopted as the signal wavelength. The PMMA-d8 base fiber has two optical windows of light transmission which are located around 650-680nm and 780nm wavelength. As the material dispersion decrease with increasing the signal wavelength, the use of the light source operating at 780nm is effective for higher bit rate transmission. It was also confirmed that the PMMA-d8 base GI POF can transmit about 3Gb/s for 200m when the signal wavelength is 780nm. These experimental and theoretical results indicate that the PMMA-d8 base GI POF could be one of the promising candidates of the physical layers in the high speed multimedia network.

Formation of The Refractive Index Profile in The Graded Index Polymer Optical Fiver for Gigabit Data Transmission

ISHIGURE TAKAAKI, SATOH MASATAKA, TAKAHASI OSAMU, NIHEI EISUKE, NYU TAKAYUKI, YAMAZAKI SYUNNTAROU, KOIKE YASUHIRO

Journal of Lightwave Technology Vol.15 ( No.11 ) 2095-2100 1997.11

Research paper (scientific journal), Joint Work, Accepted

Bandwidth characteristics of the large core GI POFs are theoretically and experimentally clarified in this paper. The refractive index profile of the GI POF was controlled by the interfacial-gel polymerization to investigate the relation between the index profile and the bandwidth characteristics. It was experimentally confirmed that the maximum bandwidth of the PMMA base GI POF is at most 3GHz for 100m transmission with using the typical laser diode emitting at 650-nm wavelength (3nm source spectral width) when its refractive index profile is optimized. The maximum bandwidth theoretically estimated by considering both modal and material dispersion is approximately 3GHz which is exactly the same as the measured value, while higher than 10GHz for 100m was expected if only modal dispersion was taken into account. The optimum refractive index profile of the PMMA base GI POF is theoretically and experimentally clarified by further considering the profile dispersion.

Fabrication and Superfluorescence of Rare Earth Chelate-Doped Graded Index Polymer Optical Fibers

KOBAYASHI TAKEYUKI, NAKATSUKA SHIRO, IWAFUJI TAKAMI, KURIKI KEN, IMAI NANA, NAKAMOTO TAKASHI, CHARLED D. CLAUDE, SASAKI KEISUKE, KOIKE YASUHIRO, OKAMOTO YOSHIYUKI

Applied Physics Letters, Vol.71 ( No.17 ) 2421-2423 1997.10

Research paper (scientific journal), Joint Work, Accepted

Rear-earth chelate-doped GI POFs are proposed and fabricated. The attenuation loss was measured to be 0.4dB/m at 650nm for a GI POF doped with 1wt% of Eu chelate. Lifetime shortening and spectral narrowing verified the occurrence of Superfluorescence at 614nm in the Eu chelate-doped GI POF pumped with xenon flashlamps. The demonstration of Superfluorescence shows that rare-earth chelate-doped GI POFs are appealing as optical amplifiers and superfluorescent sources in a variety of communication and sensor applications.

Transparent Zero-Birefringence Copolymer and Its Optical Properties

IWATA SHUICHI, TSUKAHARA HISASI, NIHEI EISUKE, KOIKE YASUHIRO

Applied Optics Vol.36 ( No.19 ) 4549-4555 1997.07

Research paper (scientific journal), Joint Work, Accepted

Birefringence is caused by both orientation of polymer chain and photoelasticity. These birefringence were compensated by random copolymerization of negative birefringent MMA and positive birefringence BzMA, but orientational and photoelastic zero birefringence were achieved by quite different compositions of the copolymer. Note that the birefringence of the copolymer that occurred in the process of injection molding was almost completely eliminated with a composition for orientational zero birefringence. The orientational and photoelastic zero-birefringence copolymer processed enough transparency as optical materials that the total scattering losses were 30.4 and 19.5 dB/km, respectively, competing with the transparency of homopolymers.

Highly Scattering Optical Transmission Polymer

小池康博

Miyazaki International Symposium The 11^th^Symposium on Optical and Electorical Properties of Organic Materials 1997.06

Single Work

Highly Scattering Optical Transmission Polymer

小池康博

Miyazaki International Symposium The 11th Symposium on Optical and Electrical Properties of Organic Materials 1997.06

Single Work, Accepted

光ファイバーの新しい展開

KOIKE YASUHIRO

Polyfile Vol.34 ( No.400 ) 33-37 1997.06

Research paper (other academic), Single Work

High Gain and High Power Organic Dye-Doped Polymer Optical Fiber Amplifiers:Absorption and Emission Cross Sections and Gain Characteristics

TAGAYA AKIHIRO, KOBAYASHI TAKEYUKI, NAKATSUKA SHIRO, NIHEI EISUKE, SASAKI KEISUKE, KOIKE YASUHIRO

Japanese Journal of Applied Physics, Vol.36, Part 1 ( No.5A ) 2705-2708 1997.05

Research paper (scientific journal), Joint Work, Accepted

Amplification of high signal gain and high output power was achieved in a Rhodamine B (RB)-doped GI POFA based on a prediction in which absorption and emission cross section data were used. The absorption and emission cross section spectra of RB, R6G, and DCM in PMMA bulk were determined. The cross section data enable us to predict gain characteristics of RB, R6G, and DCM-doped GIPOFA. The wide spectral coverage in the visible is achievable with GI POFAs doped with several selected dyes.

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