Abstract
An intensity-referenced temperature-independent curvature measurement technique using a smart composite comprising two chirped fiber Bragg gratings is demonstrated. The two gratings are embedded on opposite sides of a composite laminate and act simultaneously as curvature sensors and as wavelength discriminators, enabling an unambiguous measurement of the composite radius of curvature.

Abstract
A multiplexer/demultiplexer for 100 GHz channel spacing based on chirped fibre Bragg gratings with different bandwidths and optical circulators is presented. The spectral characteristics, specifications and operation of these passive devices are described, showing its potential use in DWDM applications.

Abstract
The refractive index distribution and birefringence of electron-beam directly-written waveguides in flame-hydrolysis silica have been characterized by means of micro-reflectivity and mode characterization. These results allow the detail design and fabrication of complex optical devices using this fabrication technique. © 2003 Optical Society of America.

Abstract
The hybrid sol-gel process is recognized to be an alternative route for production of low cost silica-based integrated optic devices, since it allows the elaboration of ridge waveguides without recourse to high cost processing, like ion etching. However, the high absorption of these materials in the NIR region (1300 and 1550 nm) has limited so far their use. The main objective of this article is to describe the major factors that lead to high losses in the final material and to give solutions to overcome this drawback. The choice of hybrid precursors and the influence of the experimental conditions of gel preparation are of paramount importance. Appropriate synthesis conditions allow a significant decrease of the gel losses (to 0,5 dB/cm) while keeping good wetability and UV-patternability. Each step of the waveguides elaboration was studied separately (UV-irradiation, etching, overcladding, storage) regarding the losses of the material. Post-baking of the waveguides is a way to significantly decrease the losses at 1550 nm. Under appropriate conditions, the losses measured in the waveguides can be kept below 1 dB/cm.

Abstract
Symmetric buried channel waveguides fabricated on silicon substrates by the organic-inorganic hybrid sol-gel process are reported. The buffer/cladding layer material is composed of methyl-modified silanes and presents high network flexibility and low refractive index, at low cost. Film thickness above 10 mum is possible without cracks, even after thermally baking the films at 150degreesC, and the refractive index is 1.468 at 632.8 nm. The influence of the methylsiloxane species on the material absorption loss was investigated, in particular at 1.55 mum. For channel waveguide core definition, a photopatternable layer was polymerised by 248 nm laser radiation through an amplitude mask, and the unexposed material was simply removed by an organic solvent. The transmission spectrum of the waveguides is presented and reveals an acceptable loss level of 0.3dB/cm at 1300 nm, but larger loss in the 1550 nm region. The procedure developed is compatible with optoelectronic integration in silicon.

Abstract