Abstract

Abstract
The overall procedure toward the implementation of a compact tunable athermal filter mounted on a piezoelectric actuator and based on a pi-shift chirped fiber Bragg grating is presented. This package ensures an active tunablility over 2 nm with a cross thermal induced Bragg wavelength shift below 100 pm over a temperature range from -20 degrees C to + 80 degrees C. The proposed filter makes use of the overall response of a p-shift chirped fiber Bragg grating and a bulk broadband microfilter that enables a sharp optical transmission spectrum response having a FWHM below 20 pm within a 2 nm region and 20 dB rejection band to be obtained. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3656751]

Abstract
A long-period-grating-based fiber optic Michelson modal interferometer with coherence addressing and heterodyne interrogation is studied as a sensing structure for measuring environmental refractive index, temperature, and liquid level. The effects of several system parameters on the measurements are investigated. Experimental results show that the sensitivity to the external refractive index increases with the order of cladding mode and with a reduction of the fiber diameter. The decrease of the fiber diameter from 125 mu m down to 70 mu m enhances the sensitivity to the external index by a factor of 2.7. It is also shown that the use of a silica-core fiber increases the sensitivity to the external index by a factor of 1.4 and reduces the thermal sensitivity by a factor of 2.5 compared to a standard fiber. (C) 2008 Society of Photo-Optical Instrumentation Engineers.

Abstract
An ultra-narrow transmission filtering scheme that combines the response of a phase-shift fiber Bragg grating and a broadband rejection micro-optical filter is proposed. The full implementation process is disclosed starting from the simulated spectral responses, grating fabrication and final assembling and test. This scheme intends to be an alternative and feasible engineering solution for one-end optical filtering interface for signal processing and analysis. © 2009 SPIE.

Abstract
An optical fiber sensor for the measurement of oxygen in gaseous environments, which is based on the quenching of the fluorescence of a ruthenium complex, is presented. The sensing chemistry is immobilized in a sol-gel based solid matrix that is coated on a tapered optical fiber probe. Oxygen measurement is performed both by phase and fluorescence intensity spectroscopy. Experimental results show that the fluorescence intensity and the lifetime depend both on oxygen and temperature. A scheme for simultaneous determination of the temperature and the oxygen concentration is proposed. Temperature measurement is performed using the excitation radiation and an absorption long pass filter. Preliminary results are presented which show a temperature measurement independent of oxygen and of optical power level.

Abstract