Abstract
In this letter, a new configuration for simultaneous strain and temperature discrimination is, presented using two concatenated high-birefringence (Hi-Bi) fiber loop mirrors. The first loop mirror includes a Hi-Bi photonic crystal fiber, while the second one contains a length of internal elliptical cladding fiber. It is shown that by monitoring the wavelength and optical power of one of the peaks of the system spectral transfer function, it is possible to obtain information that permits the simultaneous measurement of strain and temperature.

Abstract
This work presents an optical sensor based on a highly birefringent photonic crystal fiber (Hi-Bi PCF) loop mirror. The length of the sensing head is 380 mm and its corresponding wavelength spacing between two interferometer minima is 8 nm. The optical sensor was characterized in strain and in temperature with an uncoated Hi-Bi PCF and with an acrylate coated Hi-Bi PCF. Different results for strain and temperature sensitivity were obtained. Relatively to the strain measurement, the sensor with the uncoated Hi-Bi PCF presents slightly less sensitivity (1.11 pm/mu epsilon) when compared with coated Hi-Bi PCF (1.21 pm/mu epsilon). For the temperature measurement and with the uncoated Hi-Bi PCF, the optical sensor is insensitive to temperature (0.29 pm/K).

Abstract
Recent advances in devices and applications of high-birefringence fiber loop mirror sensors are addressed. In optical sensing, these devices may be used as strain and temperature sensors, in a separate or in a simultaneous measurement. Other described applications include: refractive index measurement, optical filters for interrogate gratings structures and chemical etching control. The paper analyses and compares different types of high-birefringence fiber loop mirror sensors using conventional and microstructured optical fibers. Some configurations are presented for simultaneous measurement of physical parameters when combined with others optical devices, for example with a long period grating.

Abstract
In this work, a simple sensing head geometry using fibre Bragg gratings for strain and temperature discrimination is presented. The sensing head geometry consists in one fibre with two FBGs bonded with a dummy optical fibre. Due to this new configuration, different strain sensitivities of the two FBGs are obtained (approximate to 65% difference), while temperature sensitivities remain the same. This difference in strain sensitivities is substantially larger than in all previously reported dual grating sensors. The obtained experimental errors were +/- 13.48 mu epsilon and +/- 2.44 degrees C, respectively. It is also demonstrated that this new configuration can be used as a temperature-independent strain sensor.

Abstract
A novel in-fiber modal interferometer is presented that is based on a nonadiabatic biconical fused taper that couples light between the cladding and the core, combined with the Fresnel reflection at the fiber end. It is observed that the returned light from this fiber structure shows a channeled spectrum similar to that of a two-wave Michelson interferometer. The application of this device as a fiber optic flowmeter sensor is demonstrated. 2007 (c) Optical Society of America.

Abstract
A novel Mach-Zehnder interferometer based on a fiber multimode interference structure combined with a long-period fiber grating (LPG) is proposed. The multimode interference is achieved through the use of a MMF section spliced between two single-mode fibers, with a length adjusted to couple a fraction of light into the cladding modes. A LPG placed after the MMF couples light back into the fiber core, completing the Mach-Zehnder interferometer. This novel configuration was demonstrated as a bending sensor. (c) 2007 Optical Society ofAmerica.