Abstract
Integrated optics (IO) technology has been primarily used in optical communication applications but it is expanding fast into the field of optical sensing. In this work we report the fabrication of integrated devices using hybrid sol-gel technology and in particular its application in the fabrication of a refractive index integrated sensor based in a Mach-Zehnder interferometric configuration. In one of the interferometer arms, a analysis chamber is created by exposing the waveguide through the removal of the device cladding. On the same arm, two Bragg gratings with the same period are fabricated: one in the unprotected waveguide area and another in close proximity (cladded area); because of the different effective index in the two grating regions, two peaks are observed in reflection if the device is tested with a broadband source. Any change of the refractive index of the material filling the analysis chamber can be detected in two ways: by measuring the intensity of the interferometric output (at a wavelength different from the Bragg wavelength of the two gratings) or by measuring the spectrum of the reflected signal. The high sensitivity is obtained by measuring the interferometric output, while the high dynamic range can be achieved by measuring the reflected signal from the grating structures.

Abstract
The major achievements in the field of optical sensors in the past two decades have remained mostly limited to the laboratory demonstrations. There are very few examples of optical sensors, which have been reduced to practice, and have established themselves in major markets. The main bottleneck in this field is the issue of manufacturability. In this paper we present optical sensors based on slotted multimode interference waveguides. We show that the sensitivity increases proportionally to the number of slots. The sensor can be tuned to highest sensitivity in the refractive index ranges necessary to detect protein-based molecules or other water-soluble chemical or biological materials. The material of choice is a sol-gel (ORMOCER) matrix that after completion of the process becomes mostly glass and it is highly stable. Sensors made with this technology are suited to high volume manufacturing.

Abstract
An all-optical scheme for simultaneous determination of oxygen and temperature is presented. A ruthenium complex immobilized in a non-hydrolytic sol-gel matrix is used as oxygen sensor. Temperature information is provided by CdSe quantum dots immobilized in the same material. While the dye luminescence is quenched by oxygen and temperature, the nanocrystals luminescence depends only on temperature. Results presented demonstrate that the combined luminescence response allows to simultaneously assess both parameters using a single optical fiber system.

Abstract
In this work it is presented a novel in-fibre modal interferometer based on a non-adiabatic biconical fused taper that couples light between the cladding and the core, combined with the Fresnel reflection at the fibre end. It is observed that the returned liaht from this fibre structure shows a channelled spectrum similar to that of a two-wave Michelson interferometer. The application of this device as a fibre optic flowmeter sensor is demonstrated.

Abstract

Abstract
We study the origin of antisymmetric perturbation of the fiber in are-induced long-period gratings that couple the core mode into the antisymmetric cladding modes. We demonstrate that this perturbation is caused by a temperature gradient in the fiber, which is induced, in turn, by a temperature gradient in the arc discharge.