Robust Super-Resolution TOA Estimation against Doppler Shift for Vehicle Tracking

This letter proposes a robust super-resolution TOA estimation algorithm against Doppler shift for vehicle tracking. The proposed method is developed to make use of the dual shift invariant structure to eliminate the Doppler induced bias from TOA estimation. To verify the effectiveness of the proposed method, we compare the performance of the proposed method with that of conventional algorithms, such as MUSIC and ESPRIT. © 2012 IEEE.

OPTICAL FIBER ARTERIAL PULSE WAVE SENSOR

An optical fiber arterial pulse wave sensor is proposed using an in-line Michelson interferometer that is a hollow optical fiber spliced to a single-mode fiber at one end and cleaved at the other end. The proposed optical fiber arterial pulse wave sensor consists of an in-line Michelson interferometer and steel reinforcement enclosed in a heat-shrinkable tube. The sensor was directly attached onto a wrist and signals corresponding to arterial pulse waves successfully obtained. The signal-to-noise ratio of the sensor signals was better than 20 dB. © 2010 Wiley Periodicals, Inc.

An Improved MVDR-Like TOA Estimation Without EVD for High-Resolution Ranging System

This letter proposes an improved minimum variance distortionless response (MVDR)-like TOA estimation algorithm for a high-resolution ranging system. Although the proposed method has some similarity with MVDR, it is based on subspace interpretation, resulting in improved resolution and accuracy. To verify the effectiveness of the proposed method, we compare its performance with that of MVDR, MUSIC, and ESPRIT. © 2014 IEEE.

Easy fabrication of long-period fiber grating by winding a wire around an optical fiber fixed to cylindrical ROD

A new approach is presented for the easy fabrication of wire-winding long-period fiber grating based on the periodic winding of a wire around an optical fiber attached to a cylindrical rod. The periodic pressure of the wire induces change of the refractive index of the optical fiber core, and so the resonance wavelengths of the grating can be easily controlled according to the winding-wire pitch controlled by a microprocessor. At the winding-wire pitch of 500 μm, the spectra show resonance-wavelength dips corresponding to the LP02, LP03, LP04, and LP05cladding modes; the resonance wavelengths go to longer wavelengths at the increased winding pitch of 510 μm; these are in good agreement with theoretical values. The polarization dependence of a resonance wavelength shift of 9 nm and transmission power difference of 2.5 dB was shown at the 520 μm grating pitch. When the diameter of the cylindrical metal rod was smaller, or higher tension by the winding pressure was applied, stronger mode coupling resulted in deeper dips in the transmission spectra according to induced higher index variation. © 2012 Wiley Periodicals, Inc.

Enhanced temperature sensitivity of fiber Bragg grating temperature sensor using thermal expansion of copper tube

The temperature sensitivity of fiber Bragg grating (FBG) temperature sensor is enhanced when using a copper tube to jacket of the FBG.Both sides of the FBG are glued with epoxy to cylindrical ferrules tubes that in turn is inserted and glued to a cylindrical copper tube. As the high thermal expansion coefficient of the cylindrical copper tube pulls both sides of the FBG, the temperature sensitivity is improved 3.3-fold when compared to that of a bare FBG. Copyright © 2011 Wiley Periodicals, Inc.

Visible Light Sensitized Production of Hydroxyl Radicals Using Fullerol as an Electron-Transfer Mediator

Fullerenes and their derivatives are known to photosensitize the production of singlet oxygen (O-1(2)), but their role in generating hydroxyl radical ((OH)-O-center dot) under visible, light has not been reported. Here, we demonstrate that fullerol can mediate the electron transfer from Rhodamine B dye to O-2 under visible light irradiation, achieving simultaneous dye decolorization and (OH)-O-center dot-induced degradation of 4-chlorophenol. The hydroxyl radical is proposed to be produced via a consecutive reduction of molecular oxygen by fullerol anion radical, which is formed through the electron transfer from the dye to the triplet state of fullerol. Mechanistic investigations using various probe reagents such as superoxide dismutase (superoxide quencher), t-butanol ((OH)-O-center dot quencher), and coumarin ((OH)-O-center dot probe) provided indirect evidence for the generation of (OH)-O-center dot under visible light. Furthermore, spin trapping technique directly detected the oxidizing species such as (OH)-O-center dot, HO2 center dot, and O-1(2) in the visible light irradiated solution of RhB/fullerol mixture. It was proposed that the photochemical oxidation mechanism depends on pH: (OH)-O-center dot production is favored at acidic pH through fullerol-mediated sequential electron transfer vale O-1(2) is generated as a main oxidant at neutral and alkaline condition through the energy-transfer process. Therefore, the photochemical oxidation can be switchable between (OH)-O-center dot-driven and O-1(2)-driven mechanism by a simple pH adjustment.1175Nsciescopu

High Sensitivity Refractive Index Sensor Based on a Wet-Etched Fused Fiber Coupler

We propose a novel method for fabricating fused fiber couplers whose transmission spectrum and sensitivity can be controlled in the wet-etching process. A wide tuning of the transmission spectrum during wet etching was observed experimentally. It was demonstrated that etched fused fiber couplers with reduced waist size had high sensitivity to the refractive index of an external medium. The sensitivity achieved by the present fiber coupler sensor was a 1125 nm/refractive index unit.

4 x 4 Plastic Optical Fiber Star Coupler Incorporated with a Common Polymer Waveguide Optical Power Distribution Region

Two types of 4×4 plastic optical fiber star couplers incorporated with a polymer waveguide as the optical power distributor are proposed, and their high performances are demonstrated. The characteristics of the proposed star coupler are investigated based on ray optics, and its power distribution performance is evaluated in terms of the flatness of the coupling ratio and the amount of the excess loss. Under the best conditions, the flatness of the coupling ratio and the excess loss of the fabricated device have been obtained as 2.0 dB and 2.5 dB, respectively. © 2011 Taylor & Francis Group, LLC.