Abstract
A fiber-optic Fabry-Perot sensing structure based on the utilization of a suspended-core fiber is presented. The interferometric structure is formed when a small length of the suspended-core fiber is spliced to the end of a standard single-mode fiber. The interfering waves are generated by the refractive-index mismatches between the two fibers in the splice region and at the end of the suspended-core fiber. Thermal and strain responses of two different sensing heads associated with suspended-core fibers with three and four holes are characterized.

Abstract
We report on the use of erbium doped fiber ( EDF) amplification to enhance a frequency modulated continuous wave (FMCW) technique for referencing optical intensity sensors located between two Bragg grating structures. The experiment combines the concept of FMCW with the spectrally selective mirror properties of Bragg gratings to interrogate with referencing properties intensity based sensors. The interrogation system without amplification yields a sensor resolution of around 0.078 dB. When the EDF amplifier is introduced into the experimental set up, the sensor sensitivity does not change, but the signal-to-noise ratio is improved, resulting into an enhanced resolution of 0.025 dB. We also obtain a remote sensing operation at a location of 50 km, showing the feasibility of this configuration to be used as a remote sensing application.

Abstract
A hybrid Fabry-Perot/Michelson interferometer sensor using a dual asymmetric core microstructured fiber is demonstrated. The hybrid interferometer presents three waves. Two parallel Fabry-Perot cavities with low finesse are formed between the splice region and the end of a dual-core microstructured fiber. A Michelson configuration is obtained by the two small cores of the microstructured fiber. The spectral response of the hybrid interferometer presents two pattern fringes with different frequencies due to the respective optical path interferometers. The hybrid interferometer was characterized in strain and temperature presenting different sensitivity coefficients for each topology. Due to these characteristics, this novel sensing head is able to measure strain and temperature, simultaneously.

Abstract
An all fiber Mach-Zehnder interferometer using suspended twin-core fiber is described. Due to the birefringence of the fiber cores, two interferometers are obtained when the fiber is illuminated by a polarized light. Applying curvature or temperature to the sensing head, different sensitivities are observed. In order to discriminate curvature from temperature in the suspended twin-core fiber Mach-Zehnder sensor, the matrix method is used.

Abstract
In this paper, we demonstrate the interrogation of fiber optic intensity sensors by using the combination of the frequency-modulated continuous wave concept with the spectral selective reflectivity of fiber Bragg gratings. Thus, we multiplex these kinds of sensors with this technique having simultaneously a referenced system. The basis of this dual functionality is described and results are presented for the case of interrogation of two multiplexed intensity sensors. Their evaluation permits to establish the conditions to address a sensor network of this type. Also, it is proposed a strategy to implement this sensing approach without the requirement of using optical fiber delay lines in the sensor heads.

Abstract
An electrical dynamic interrogation technique is reported for long-period grating sensors relying on the modulation of fibre Bragg gratings located in the readout unit that permits us to attenuate the effect of the 1/f noise of the photodetection, amplification and processing electronics on the sensing head resolution. The concept is tested to detect variations of curvature, and a resolution of 9.4 x 10(-3) m is achieved.