Abstract
A low-coherence technique in a Michelson interferometer for measuring polarization mode dispersion (PMD) was tested. The measured PMD mean value for one reel, in a period of several days, was 0.0405 +/-. 0.0008 ps/km(1/2) and for the other reel, it was 0.0463 +/- 0.0004 ps/km(1/2). Stochastic and random PMD behavior was observed. (C) 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2310-2312, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25428

Abstract
Differential group delay (DGD) generation by inducing birefringence in uniform fiber Bragg gratings (FBG) is studied. Applying a transverse load, a birefringence is induced on a uniform FBG creating a tunable differential group delay. A theoretical behavior of this phenomenon is presented being in good agreement with the experimental results obtained. A maximum experimental tunable DGD of similar to 60 ps was obtained with this induced birefringent process in the uniform FBG. (C) 2007 Wiley Periodicals. Inc.

Abstract
A linear tunable dispersion compensation device based on a chirped grating (CFBG) mounted on a stretching mechanical structure is described. The tunability is obtained changing the CFBG bandwidth without modification of the total length structure. (c) 2007 Wiley Periodicals, Inc.

Abstract
In this contribution we compare the thermal stability of type I and type IIa gratings written in germanosilicate fibers. We study and compare their central wavelengths drifts and variations of the maximum reflectivity with temperature. Also, two other important factors, the bandwidth and group delay characteristics are characterized, compared, and the differences justified, based on the gratings physical structure.

Abstract
In this work, it is presented a Sagnac interferometric configuration based on a suspended twin-core fibre for sensing applications. Using the suspended twin-core fibre, the fringe pattern is due to the differential optical path of the light in the two cores associated with a refractive index difference of similar to 10(-3), which indicates an advantage of this approach compared with those based on Hi-Bi fibres, namely the possibility to use a small length of suspended twin-core fibre. The sensing configuration was characterized for torsion, temperature and strain. Using the Fast Fourier Transform technique it is possible to obtain the measurand induced amplitude variations of the fringe pattern. The results obtained indicate the viability of a temperature and strain independent torsion sensor.

Abstract
In this work, a simple real-static nanostrain sensor based on a Bragg grating structure is presented. The setup is constituted by a narrow linewidth laser as light source, an optical circulator and a photodetector. The sensing head is formed by a chirped Bragg grating inscribed in a standard single mode fiber (SMF-28) by the phase technique. The fiber face end is cleaved and coated with a silver mirror, obtaining a Fabry-Perot interferometer. It is observable that the fringes period increases along the grating, due to the chirp spectrum (0.4 nm/cm) characteristics. The laser is fixed in one slope region of the fringe pattern. When strain is applied, the optical power changes linearly. A sensitivity of 5.72 mu W/mu epsilon in a range of 2 mu epsilon. The sensing head resolution is 70 n epsilon for a measurement step of 875 n epsilon.