Abstract
In this work, we demonstrate the possibility of fabricating short LPGs and rocking filters in highly birefringent Photonic Crystal Fiber using CO(2) laser. In our experiments both kinds of gratings were made in the same Boron doped highly birefringent PCF using similar exposure parameters. We also present the sensing capabilities of both fabricated gratings to temperature, strain and hydrostatic pressure by interrogation of the wavelength shifts at the different resonances.

Abstract
Birefringence monitoring of a Hi-Bi fibre under chemical etching is conducted. The Hi-Bi fibre (a bow-tie type) was inserted in a fibre loop mirror and the optical spectral response was measured while chemical etching of the Hi-Bi fibre was taking place. The birefringence of the bow-tie fibre has decreased due to the etching and the wavelength spacing of the fringe minima of the fibre loop mirror has increased.

Abstract
The underground movement of water through soil and rock is an important phenomenon in Civil Engineering. Its study is made more appealing to students if small scale prototypes are used, where several layouts of soil and water in steady state/transient conditions can be studied in detail. A water tank prototype was built with a reflective optical fibre pressure sensor based on a GRIN lens and a mirror. The mirror is connected to an elastic membrane that is deformed when water pressure is applied and the lens is correctly aligned with the mirror and fixed. The distance between the mirror and the lens changes, so the reflective optical power changes as well and it is directly proportional to the water pressure inside the tank. The results obtained for water pressure up to 4 kPa for filling and emptying operations show that the sensor has a linear response for pressure changes between 1.7 kPa and 3.4 kPa with a slope of 181 mu W/kPa for filling and 191 mu W/kPa for emptying. It is also observed some hysteresis that may possibly be reduced by choosing another material for the membrane. Using this type of sensor head it is possible to monitor different pressure points in the small scale prototype using the standard OTDR (Optical Time Domain Reflectometer) equipment.

Abstract
It is reported a LPG dynamic interrogation technique based on the modulation of fibre Bragg gratings located in the readout unit that permits to attenuate the effect of the 1/f noise of the electronics in the resolution of the LPG-based sensing head. The concept is tested to detect variations of the external refractive index and a resolution of 2.0x10 (4) NIR was achieved without system optimization. Additionally, the effect in the sensor resolution when introducing Erbium and Raman optical amplification is experimentally investigated.

Abstract
A novel interrogation technique for multiplexing LPG-fiber loop mirrors has been proposed and experimentally demonstrated. Each displacement sensor is formed by a fiber loop mirror combined with a long period grating. This high reflectivity variable mirror is suitable to be interrogated by an OTDR and to be multiplexed in a crosstalk free setup with temperature independence.

Abstract
The measurement of micro-displacement or bending using a long-period fibre grating (LPG) in a self-referenced fibre optic intensity sensor is presented. The sensing head is based on a LPG whose attenuation peak changes as a function of its micro-displacement or bending and the fibre optic intensity sensor is referenced in frequency. Two other LPGs were used as rejection filters. located at the output of the optical source to shorten its spectral width. The implemented experimental set-up is described and, the results are presented being considered the measurement range and the intrinsic resolution.