Abstract
It is proposed the multiplexing of optical fiber-based surface plasmon resonance (SPR) sensors deployed in a ladder topology, addressed in wavelength by combining each sensor with specific fiber Bragg gratings (FBGs) and considering intensity interrogation. In each branch of the fiber layout, the FBGs are located after the sensor and the peak optical power reflected by the FBGs is a function of the relative spectral position between the SPR sensor and the FBG resonances, with the former dependent on the refractive index of the surrounding medium. The concept is tested for the multiplexing of two SPR sensors fabricated in an etched region of a single-mode fiber showing intrinsic refractive index sensitivity up to 5000 nm/RIU, which translates into a sensitivity of similar to 829 dB/RIU from the interrogation approach considered. The obtained refractive index resolution is in the order of 10(-4) RIU, and the crosstalk level between the sensors was found negligible.

Abstract
A study of long period fiber gratings (LPFG) over coated with iron (Fe) and subjected to oxidation in water with different sodium chloride (NaCl) concentrations is presented. The formation of iron oxides and hydroxides was monitored in real time by following the features of the LPFG attenuation band. Preliminary results show that Fe coated LPFGs can be used as sensors for early warning of corrosion in offshore and in coastal projects where metal structures made of iron alloys are in contact with sea or brackish water.

Abstract
In this work an investigation of long period fiber gratings (LPFGs) over coated with iron (Fe) thin layers with different thicknesses and subjected to oxidation in air atmosphere under controlled temperature is presented. The formation of iron oxides was monitored in real time by following the optical features of the LPFG attenuation band. The morphology of the oxide layer was further analyzed by scanning electron microscope (SEM). Preliminary results show that iron coated LPFGs can be used as sensors for early warning of corrosion in projects where metal structures made of iron alloys are in contact with atmospheric air.

Abstract
In this paper real time monitoring of oxidation of transition metals using long period fiber gratings (LPFG) is performed for nickel, copper, titanium, chromium and zinc. A thin layer is deposited over the LPFG with physical process deposition and is annealed up to 700 degrees C in air with a small oven. The whole oxidation process can be monitored by tracking the LPFG features of the attenuation band which results in an abrupt change when the oxidation occurs depending on the metal sample. A preliminary study to optimize optical fiber sensors sensitivity allowing choosing the correct oxide layer in a specific application is presented.

Abstract
Many optical systems based on Surface Plasmon Resonance (SPR) have been developed for work as refractometers, chemical sensors or even for measure the thickness of metal and dielectric thin films. These kinds of systems are usually large, expensive and cannot be used for remote sensing. Optical fiber sensors based on SPR has been widely studied for the last 20 years with several configurations mostly using multimode optical fibers with large cores and plastic claddings. Sensors based on SPR present very high sensitivity to refractive index variations when compared to the traditional refractive index sensors. Here we propose a SPR sensor based in a single mode fiber. The fiber end is chemically etched by emersion in a 48% hydrofluoric acid solution, resulting a single mode fiber with the cladding removed in a small section. A resonance dip around 1580 nm was attained in good agreement with the simulation scenario that takes into account the real characteristics of the fiber.

Abstract
The detection of volatile organic compounds is accomplished with a sensing device based on a long period fiber grating (LPFG) coated with a zinc oxide (ZnO) thin layer with self-temperature compensation. The ZnO coating structure was produced onto the cladding of the fiber by thermal oxidation of a metallic Zn thin film. The morphological characterization of ZnO thin films, grown at the same time on silicon substrates, was performed using X-ray diffraction, X-ray Photoelectron Spectroscopy and Scanning Electron Microscope which shows very good agreement. LPFGs with 290 nm thick ZnO coating were fabricated and characterized for the detection of ethanol and hexane in vapor phase. For ethanol a sensitivity of 0.99 nm / g.m(-3) was achieved when using the wavelength shift interrogation mode, while for hexane a much lower sensitivity of 0.003 nm / g.m(-3) was measured, indicating a semi-selectivity of the sensor with a spectral resolution better than 3.2 g.m(-3).