Abstract
In this paper, it is presented a brief review of the sensing applications using photonic crystal fibres. Since the first publication, several authors have studied their properties and possible applications in engineering. Due to their geometry, the great potential in optical sensing is in bio and gas sensing. Recently, with the possibility of inscribing Bragg grating structures on these fibres, it is possible to use them for other applications. Finally, this paper reviews the recent works with different types of photonic crystal fibres for interferometry.

Abstract
In this work, a laser sensor that uses the multipath interference produced inside a ring cavity to measure the power loss induced by a moving taper intensity sensor is described. The laser is created due to the virtual distributed mirror formed by the Rayleigh scattering produced in a dispersion compensating fibre when pumped by a Raman laser. Two laser peaks were formed, one of them is obtained by the Raman gain (1555 nm) inside the ring and the second is created by the combination of the Raman gain and the Rayleigh scattering (1565 nm). A taper sensor is used as displacement sensor and with the increases of losses the second laser peak amplitude is reduced. In the process the first peak is maintained constant and can be used as reference level.

Abstract
The strain and temperature sensing characteristics of a modal interferometer based on two Bragg fibers have been investigated. The special nature of this sensor is that the two Bragg fibers used present a different external cladding shape. It appears that the sensitivity to the sensing parameters are different for the two Bragg fibers, which makes it possible to fabricate several sensing configurations based on the combination of these two Bragg fibers for strain and temperature discrimination.

Abstract
This article analyzes experimentally the limitations observed in lightwave systems using distributed Raman amplifiers operating under large pump power input conditions. The Brillouin effect is observed as the pump power reaches 1 W. The presence of Brillouin peaks degrades the performance of the system. The Raman amplification occurs in single mode and dispersion compensating fibers, being evaluated in a link at transmission rate of 40 Gb/s. (C) 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1331-1335, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25162

Abstract
We present an overview of the applications of the electric arc technique related to optical fibre technology. The use of arc discharges ranges from the well-known fibre splicing, going through the fabrication of basic devices such as fibre tapers and microspheres, to tailoring the spectra of UV-induced gratings such as in the apodization of fibre Bragg gratings and also in the fabrication of phase-shifted and sampled fibre Bragg gratings. However, in the past decade a topic more intensively investigated was probably long-period fibre gratings. Therefore, some devices based on arc-induced gratings, namely, phase-shifted and step-changed gratings and bandpass filters are discussed. We also present an electrically insulated thermocouple assembled in situ using arc discharges. This sensor is very useful in the determination of the temperature attained by the fibre during an arc discharge, this property being fundamental for the discussion of the mechanisms of formation and for the understanding of the thermal properties of arc-induced devices.

Abstract
In this paper, direct UV-laser writing was used to produce channel waveguides and diffraction gratings on thin films of siliceous-based organic-inorganic hybrid materials. The optical quality of the films surface was studied by light scattering measurements. The produced Y-power splitters, optical filters and Fabry-Perot cavities were experimentally characterized for propagation in the near infrared spectral region. © 2010 IEEE.