Abstract
The use of fiber Bragg grating sensors embedded in hybrid composite laminates for simultaneous measurement of strain and temperature is proposed. The hybrid structure, formed by a pre-impregnated thermoset and thermoplastic composites, contains one single fiber Bragg grating embedded in each material, connected in series with each other. A different response is observed when the smart composite laminate is subjected to strain and to temperature. This is expected due to the distinct properties presented by each material. The rms deviation obtained for a temperature range between 20 and 60 degrees C is +/- 0.97 degrees C and for a strain range from 0 to 1100 mu epsilon is +/- 13.04 mu epsilon.

Abstract
A suspended multicore fiber sensor for simultaneous measurement of curvature and strain is proposed. The spectral response shows evidences of several interferences arising from the seven cores of the fiber. Once the sensing head presents different sensitivities for curvature and strain measurements, these physical parameters can be discriminated by using the matrix method. The rms deviations are +/- 19m(-1) and +/- 12:90 mu epsilon for curvature and strain measurements, respectively. (C) 2011 Optical Society of America

Abstract
Several configurations of ultralong Raman fiber lasers (URFL) based on a distributed mirror combined with Bragg gratings or fiber loop mirrors are studied. Two continuous-wave URFL configurations, with single and cascaded cavities using fiber Bragg gratings as mirrors are explored for a 300 km long fiber. For optical sensing, the cavity length was optimized for 250 km using one of the gratings an intensity sensor. Another URFL configuration based in a fiber loop mirror is also reported. For optical sensing using a 300 km long fiber it is shown that the best choice is a hybrid configuration. The sensitivity of the FBG laser sensor range was from (76 +/- 2) x 10(-6) mu epsilon(-1) (for lower strain) to (9.0 +/- 0.4) x 10 -6 mu epsilon(-1) (for higher strain). (C) 2011 Optical Society of America

Abstract
Real-time monitoring of the fabrication process of tapering down a multimode-interference-based fiber structure is presented. The device is composed of a pure silica multimode fiber ( MMF) with an initial 125 mu m diameter spliced between two single-mode fibers. The process allows a thin MMF with adjustable parameters to obtain a high signal transmittance, arising from constructive interference among the guided modes at the output end of the MMF. Tapered structures with waist diameters as low as 55 mu m were easily fabricated without the limitation of fragile splices or difficulty in controlling lateral fiber alignments. The sensing device is shown to be sensitive to the external environment, and a maximum sensitivity of 2946 nm/refractive index unit in the refractive index range of 1.42-1.43 was attained. (c) 2012 Optical Society of America

Abstract
The properties of a Brillouin-Raman comb fiber laser are compared for two different configurations: co-propagating and counter-propagating Raman pump. The optical spectrum is compared for changing the Raman pump power and the power or the wavelength of seed laser. A Brillouin-Raman comb with 400 linewidth lasers in a flat-amplitude bandwidth of 32 nm between 1538 and 1570 nm, with an average optical power 20 dB above the nearby frequencies was generated. The lasers in the comb had an OSNR of 20 dB and a wavelength spacing of 0.08 nm. The results for the counter-propagating configuration were observed to have better quality.

Abstract
We compare the thermal tuning capabilities of two type I gratings written in unloaded and in hydrogen-loaded germanium-doped silica fibers, and a type IIa grating written in unloaded fiber. The hydrogen-loaded grating is annealed after writing, to remove any unreacted hydrogen. We further study the gratings' response stability with temperature, an important property when these devices are used as optical filters in wavelength division multiplexing systems. Experimental results show that the worst option is the type I grating in unloaded fiber, which presents the highest bandwidth and group delay variations with temperature, so that it is the least suitable as a thermotunable optical filter in wavelength-multiplexed systems. For the other two options, the bandwidth and group delay variations are much smaller, the lowest values being obtained with the hydrogen-loaded type I grating, and the best thermal tuning efficiency with the type IIa grating. (C) 2003 Society of Photo-Optical Instrumentation Engineers.