Abstract
The possibility of fabricating efficient optical amplifiers in LiNbO3, realized by localization of the dopant on surface areas was theoretically evaluated and the feasibility of fabricating efficient amplifiers in such doped structures was experimentally verified. The model of amplifiers based on 3-level laser systems realized by local doping incorporates dopant localization, the influence of the interaction length, as well as that of the effective pump area and of the pump power in the amplifier performance. It was verified that localized doping allows optimization of amplifier performance through adjustment of the active region geometry to the mode intensity profile. The experimental results confirmed that the width of the metal stripe deposited on the surface must be optimized so that gain is maximum, for a given value of the pump power. It was experimentally demonstrated that transverse localization of the active ions reduces the threshold pump power, which may be relevant for realization of integrated lasers in Er:LiNbO3.

Abstract
A new wavelength multiplexing configuration for self-referenced fiber optic intensity sensors using fiber Bragg gratings and wavelength division multiplexing (WDM) couplers is investigated. First, the network multiplexing concept is characterized, and then the self-referenced intensity sensor is presented, which is the basis of each individual sensor in the network. The implemented experimental setup of the multiplexing network is described, and results are presented considering the crosstalk, resolution, and power budget of the sensing multiplexing network. The characteristics and features of the configuration proposed are addressed. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

Abstract
A fiber optic sensing system for simultaneous measurement of temperature and salinity based on fiber Bragg grating technology is presented. The fabrication process, which relies on chemical etching of the fibre, is described and its performance is evaluated. Theoretical and experimental results are given, which are summarized on the obtained resolutions of +/-0.06degreesC/ rootHz and +/- 0.2parts per thousand./ rootHz for temperature and salinity, respectively. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

Abstract
Semiconductor nano-particles, or quantum dots, with their relatively high quantum yields, narrow luminescence spectrum, outstanding photostability and the ability to tune their optical properties, are ideal for biological tagging applications and a very powerful tool for chemical sensors. In this paper an overview of this rapidly expanding area of research is presented. Additionally, some results are shown, in the framework of optical oxygen sensors, which establish quantum dots as suitable temperature and intensity references for application in luminescence based chemical sensors.

Abstract
A fibre Bragg grating sensing configuration is presented for simultaneous measurement of strain and temperature. The proposed concept relies on writing a single Bragg grating on the splice region of two fibres with different levels of germanium doping. Doing so, a grating structure appears with three resonance peaks, which show distinct temperature sensitivities but similar strain responses. The experimental validation of the concept indicated resolutions of +/-1.5 degreesC Hz(-1/2) and +/-5.6 muepsilon Hz(-1/2) over measurement ranges of 80 degreesC and 1000 muepsilon for temperature and strain, respectively.

Abstract
We used a pair of Bragg gratings written in high birefringence fibre optics to measure, simultaneously, longitudinal and transverse strain and temperature. The Bragg gratings are superimposed in the same position of the fibre optic, so as to behave as a punctual sensor. The sensitivity of the spectral response of the device to longitudinal strain, transverse strain and temperature are all characterized, and the results of its application as a three-parameter sensor are also presented.