Abstract

Abstract

Abstract

Abstract
The intrinsic advantages of optical sensor technology are very appealing for high voltage applications and can become a valuable asset in a new generation of smart grids. In this paper the authors present a review of optical sensors technologies for electrical current metering in high voltage applications. A brief historical overview is given together with a more detailed focus on recent developments. Technologies addressed include all fiber sensors, bulk magneto-optical sensors, piezoelectric transducers, magnetic force sensors and hybrid sensors. The physical principles and main advantages and disadvantages are discussed. Configurations and strategies to overcome common problems, such as interference from external currents and magnetic fields induced linear birefringence and others are discussed. The state-of-the-art is presented including commercial available systems.

Abstract
Palladium-based fiber-optic sensors have been one of the most promising configurations for hydrogen sensing. In the latest decade, fiber-optic sensors have indeed earned a strong interest owing to their ability to monitor molecular hydrogen at specific spatial points-either as a sensing tip device or in large areas via multiple sensing regions distributed along the optical fiber. This review focuses on the various types of optical fiber hydrogen sensors, containing specifically palladium as active element. Three distinct working principles are described, viz. interferometric-, intensity-, and fiber grating-based sensors; their characteristics and sensing performances are critically overviewed.

Abstract
In this Letter, a hybrid interferometer for simultaneous measurement of the partial pressures of O-2 and CO2 mixtures is reported. The sensing head consists in the combination of two interferometric structures, one a Fabry-Perrot cavity and the other a modal interferometer. The intrinsic Fabry-Perot was formed by splicing a single mode fiber with a graded index fiber length that was then subjected to chemical etching creating an air cavity. The second interferometer is based on a splice of a pure silica tube in series with the Fabry-Perot. It was observed for a particular gas that its refractive index changes with pressure variation in a specific way, a characteristic that permitted the simultaneous measurement of partial pressures of CO2 and O-2 with rms deviations of similar to +/- 48.7 kPa and similar to +/- 20.1 kPa, respectively. (C) 2012 Optical Society of America