Isao Ohyama
The Furukawa Electric Co., Ltd.
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Isao Ohyama.
Journal of Lightwave Technology | 1992
Hisaharu Yanagawa; Takeo Shimizu; Shiro Nakamura; Isao Ohyama
A mode-field-converting optical channel waveguide with tapered refractive index and cross-sectional dimensions is proposed. In this waveguide, both the refractive index and cross-sectional dimensions of a core are adiabatically varied along a propagation direction in such a way that the normalized frequency V of the waveguide may be kept constant. Since radiation loss caused by waveguide imperfections is strongly dependent on the V value, the waveguide has good mode-field-converting capability without causing high radiation loss. Layer thickness and index of a core of a silica waveguide were tapered by modulating a raw material gas flow in a flame hydrolysis deposition method, and a channel width taper was formed by a photolithographical technique. In order to confirm the usefulness, taper waveguides have been used (1) to achieve good field matching between a fiber and a guided-wave optical switch, and (2) to fabricate a fiber-compatible monolithic 32*32 star coupler in a small chip. >
Journal of Lightwave Technology | 1990
Hisaharu Yanagawa; Shiro Nakamura; Isao Ohyama; Ken Ueki
A broadband optical waveguide star coupler with asymmetric directional couplers is proposed. A coupling or splitting ratio of the coupler is flattened with respect to wavelength by choosing appropriate values for Delta beta and complete power transfer length. The wavelength characteristics of uniform and alternating Delta theta b directional couplers are investigated, and their broadband operation is shown theoretically. To demonstrate the feasibility of the new proposal, 8*8 star couplers composed of such asymmetric directional couplers are fabricated by using high-silica waveguides on a silicon chip. A star coupler composed of asymmetric directional couplers exhibited 2-dB loss variation in the wavelength range of 1.3-1.55 mu m, and this value was almost one fourth of that of a star coupler composed of symmetric directional couplers. >
Archive | 1993
Hisaharu Yanagawa; Takeo Shimizu; Shiro Nakamura; Isao Ohyama; Izumi Sankawa
Archive | 1992
Hisaharu Yanagawa; Takeo Shimizu; Shiro Nakamura; Isao Ohyama
Archive | 1995
Ken Ueki; Takeo Shimizu; Isao Ohyama; Shiro Nakamura; Hisaharu Yanagawa
Archive | 2001
Yoshinobu Nekado; Hiroshi Kawashima; Kazutaka Nara; Isao Ohyama; Kazuhisa Kashihara
Archive | 1995
Isao Ohyama; Shiro Nakamura; Takeo Shimizu; Hisaharu Yanagawa; Hideyuki Iwata
Archive | 1993
Hisaharu Yanagawa; Takeo Shimizu; Shiro Nakamura; Isao Ohyama; Izumi Dipl Ing Sankawa
Archive | 2000
Hiroshi Kawashima; Hiroyuki Koshi; Isao Ohyama; Shiro Nakamura
Archive | 1993
Hisaharu Yanagawa; Takeo Shimizu; Shiro Nakamura; Isao Ohyama; Izumi Sankawa