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115 results on '"Ohara S"'

30. Bismuth-oxide-based nonlinear fiber with a high SBS threshold and its application to four-wave-mixing wavelength conversion using a pure continuous-wave pump.

Author

Ju Han Lee, Nagashima, T., Hasegawa, T., Ohara, S., Sugimoto, N., and Kikuchi, K.

Abstract

The unique and practical benefits of the use of bismuth-oxide-based nonlinear fiber (Bi-NLF) in implementing a four-wave-mixing (FWM)-based wavelength converter for fiber-optic-communication-system applications are experimentally demonstrated. First, the Kerr-nonlinearity and stimulated-Brillouin-scattering (SBS) characteristics of our fabricated Bi-NLF are experimentally investigated. The Bi-NLF is found to have the superior advantage of a significantly high SBS threshold in addition to its ultrahigh Kerr nonlinearity γ of ∼1100 W-1·km-1, compared to the conventional silica-based highly nonlinear fiber. Next, the authors perform an experiment for the FWM-based wavelength conversion of a non-return-to-zero (NRZ) signal within a 40-cm length of the Bi-NLF fusion spliced to standard silica fibers by using a continuous-wave (CW) high-power pump beam. Error-free tunable wavelength conversion over a 10-nm bandwidth is readily achieved. No SBS-suppression scheme is employed for the pump due to the high SBS threshold, which simplifies the system configuration and improves the quality of the wavelength-converted signal. [ABSTRACT FROM PUBLISHER]

Published
2006
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33. Self-linearizing technique for L-band HBT power amplifier: effect of source impedance on phase distortion.

Author

Yamada, H., Ohara, S., Iwai, T., Yamaguchi, Y., Imanishi, K., and Joshin, K.

Subjects
*PHASE shift keying, *HETEROJUNCTION bipolar transistors, *UHF power amplifiers, *MICROWAVE communication systems, *MOBILE communication systems, *ELECTRONIC linearization, *SEMICONDUCTOR devices, *POWER amplifiers, *PHASE distortion (Electronics)
Abstract

L-band power amplifiers operating with high efficiency and high linearity at a single and low supply voltage are in strong demand for mobile communication systems. This paper presents a new self-linearizing technique for power heterojunction bipolar transistors (HBTs). Utilizing the nonlinear input conductance of the device itself and setting the source impedance to the self-linearizing impedance, the phase distortion and the adjacent channel leakage power (ACP) for /spl pi//4-shift QPSK modulated signal of our InGaP/GaAs power HBTs have been greatly improved. As a result, the HBT exhibited the ACP at 50 kHz offset frequency of -49.2 dBc with a power-added efficiency (PAE) of 56% at an output power (P/sub out/) of 31 dBm under a supply voltage of 35 V. [ABSTRACT FROM AUTHOR]

Published
1996
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40. Clock recovery and demultiplexing of high-speed OTDM signal through combined use of bismuth oxide nonlinear fiber and erbium-doped bismuth oxide fiber.

Author

Ju Han Lee, Ohara, S., Nagashima, T., Hasegawa, T., Sugimoto, N., Igarashi, K., Katoh, K., and Kikuchi, K.

Abstract

We explore the ultimate potential offered by state-of-the-art Bismuth oxide-based optical fiber technology in a high-speed optical phase-locked loop-based clock recovery subsystem for an optical time-division multiplexed (OTDM) signal, in which the use of optical fiber-based devices has been considered to be inappropriate due to its tight requirement of short optical loop length. Here, we experimentally demonstrate the implementation of a compact all-fiber-based OTDM receiver incorporating both clock recovery and demultiplexing functions by use of short lengths of Bismuth oxide-based nonlinear fiber and erbium-doped Bismuth oxide fiber. Successful clock recovery and subsequent error-free demultiplexing are readily achieved at a data rate of 80 Gb/s. The clock recovery subsystem is also shown to be operable at 160 Gb/s. [ABSTRACT FROM PUBLISHER]

Published
2005
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