Abstract
Fibre optic Bragg gratings (FBGs) written in normal and reduced diameter high birefringence (HiBi) fibres are studied. Chemical etching is used to reduce the diameter of fibres while the optical properties of the FBG spectrum are measured. The results obtained agree qualitatively with the stress enhanced chemical etching. The birefringence of the fibre is determined as a function of the diameter. Optical characterization of the FBG under transverse strain and temperature is also performed. The results obtained show the feasibility of the simultaneous measurement of those parameters with a HiBi FBG sensor.

Abstract
A polarization mode dispersion (PMD) emulator and compensator device is proposed. The PMD device is obtained using a Hi-Bi Fibre Bragg Grating (Hi-Bi FBG) and a stress induced bireffingence in a uniform FBG. This birefringence is achieved by applying transverse and uniform distributed force on the uniform fibre Bragg grating creating a tuneable differential group delay (DGD). Maximum and minimum slopes of 377 ps/nm and 0 ps/mn in the DGD is obtained for the PMD emulator/compensator device, respectively.

Abstract
In this work, we present a fiber Bragg grating interrogation based on high-birefringence fiber loop mirror for strain-temperature discrimination. Due to spectral response of the optical filters it is possible to determine the variation of the wavelength and the optical power of the Bragg grating sensor when subject to strain or temperature. Maximum errors of +/- 0.4 degrees C and 12 mu epsilon are reported over 80 degrees C and 2000 mu epsilon measurement ranges. (c) 2006 Wiley Periodicals, Inc.

Abstract
All-optical switching devices based on fibre Bragg grating (FBG) structures written on a standard single-mode fibre and in an erbium-doped fibre have been experimentally demonstrated in the third telecommunication window. The switching devices work due to the thermal changes induced by a high-power continuous-wave laser diode. The filters tunability characteristics have been demonstrated for different pump powers (up to 900 mW) and different pump laser wavelengths (at 980 and 1480 nm), presenting different thermal absorption behaviour within different working regimes. (c) 2006 Wiley Periodicals, Inc.

Abstract
The symmetry of cladding modes excited in microbend and arc-induced long-period fiber gratings is investigated. An optimization technique is developed to determine the fiber parameters and to associate grating resonances with cladding modes of a particular symmetry. Using this optimization procedure, we show that the gratings induced in a standard fiber by arc discharges and microbends couple light to the antisymmetric cladding modes. In the case of a boron-germanium codoped fiber, the cladding modes excited by arc-induced gratings are found to be symmetric. Measurements of the near-field intensity distribution of cladding modes confirm the mode symmetry ascertained by the optimization technique. (c) 2006 Optical Society of America

Abstract
Long-period gratings were written using arc discharges in pristine nitrogen doped fibres. Comparison of the resulting gratings spectra show that the resonant positions of gratings in fibres pre-annealed at 1050 degrees C for 30 min are shifted towards shorter wavelengths and their coupling strength is considerably higher. The refractive index and residual stress profiles were measured before and after annealing, as well as the two-dimensional stress profiles inside the grating region. Arc discharges induce periodic and strong asymmetric stresses in the fibre core of the pre-annealed nitrogen doped fibre.