Abstract
In this work, two all-fiber loop mirrors using a clover microstructured fiber for the simultaneous measurement of temperature and strain are presented. The sensing heads are formed by a short piece of clover microstructured fiber with 35 mm and 89 mm length respectively. The geometry of the fiber allowed observing different interferences created by the microstructured fiber core section. Different sensitivities to temperature and strain were obtained and, using a matrix method, it is possible to discriminate both physical parameters. Resolutions of +/- 2 degrees C and +/- 11 mu epsilon for the first structure and +/- 2.3 degrees C and +/- 18 mu epsilon for the second one, for temperature and strain, respectively, were attained.

Abstract
This work reports the theoretical investigation of optical fiber surface plasmon resonance sensors incorporating an internal metallic layer of silver covered with an oxide layer. This research is supported by the application of an effective analytical model combining geometrical optics with the transfer matrix theory for stratified optical media. Different oxide materials like titanium dioxide, silicon dioxide, and aluminum oxide are considered aiming to achieve increased/enhanced sensitivity to refractive index variations of the external medium, particularly when addressing phase interrogation. It is shown that the combination of a 50-nm thickness silver inner layer with a dielectric titanium oxide layer of a specific thickness enables high-performance phase sensitivity reading and is compatible with tailoring the sensor working region to the third telecommunication wavelength window around 1550 nm.

Abstract
Many optical systems based on surface plasmon resonance (SPR) have been developed for working as refractometers, chemical sensors or even for measuring the thickness of metal and dielectric thin films. Sensors based on SPR present very high sensitivity to refractive index (RI) variations when compared to the traditional RI sensors. However, these kinds of systems are usually large, expensive and therefore cannot be used for remote sensing. Optical fibre sensors based on SPR are usually implemented using multimode optical fibres cope with the requirements for remote sensing. In this section a new type of SPR sensor based in a single mode fibre (SMF) is proposed. A section of the SMF was chemically etched by emersion in a 48 % hydrofluoric acid solution, resulting in a tapering effect, with the cladding removing while the core is kept intact. Simulation results are in good agreement with the experimental spectral resonance dip attained around 1550 nm. Sensitivities of 3800 and 5100 nm/RIU were achieved for the reflection and for the transmission modes, respectively, for RI in the 1.33 to 1.37 range.

Abstract
A hybrid Fabry-Perot cavity sensing head based on a four-bridge microstructured fiber is characterized for temperature sensing. The characterization of this cavity is performed numerically and experimentally in the L-band. The sensing head output signal presents a linear variation with temperature changes, showing a sensitivity of 12.5 pm/degrees C. Moreover, this Fabry-Perot cavity exhibits good sensitivity to polarization changes and high stability over time.

Abstract

Abstract
In this paper, we analyze numerically and experimentally a remote optical sensor system based on Raman Amplification, composed by one long period grating operating as a sensor head separated by 50 km from the optical source and the interrogation unit composed by two fiber Bragg gratings. Since the active components of the system and the sensor head are separated over such a large distance, it is necessary to consider optical amplification to strengthen the optical signal. The use of Raman amplification allows reaching the desirable gain bandwidth by changing the pump lasers parameters such as the power, number of pumps and spectral position. We present the obtained measurement results of the environmental temperature for two different setups that was analyzed a priori by the numerical model. We show that the power ratio between the two central wavelengths of the FBG has a linear relation with the change of LPG resonance with temperature.