Antonio Scaglione

Direct laser writing of ridge optical waveguides in silica-titania glass sol-gel films

Abstract Sol-gel process is attracting a growing attention as a rather simple technology with potential for low-cost batch manufacture of integrated optical waveguides. Here experimental results are presented on the fabrication of silica-titania sol-gel films and on their laser densification, a technique which may be very useful for rapid circuit prototyping. Transversally multimode waveguides with propagation loss around 1 dB/cm have been produced by selective densification using a CO2 laser. Data from optical and structural analysis of the sol-gel strips are reported and discussed.

An enhanced fiber optic temperature sensor system for power transformer monitoring

The paper deals with a sensor for temperature measurements in fluids. The sensor is based on a fiber-optic sensing element and on microcontroller-based signal processing hardware. The physical principle behind its operation is briefly reviewed, and its application to power transformer hot-spot temperature measurement is reported. Laboratory experimental results are given for both sensor characterization and measurements carried out on a 25-kVA oil-cooled power transformer.

An optical fiber based technique for continuous level sensing

An optical fiber-based technique for liquid level measurement is proposed. It is based on the power attenuation occurring in an optical fiber, immersed in a liquid, when the liquid level varies. This phenomenon is theoretically approached by using the perturbation theory, which allows information useful for the sensor design to be obtained. The experimental results confirm the theoretical forecasts and allow a low-cost sensor prototype, mainly composed by the optical fiber, immersed in the liquid, and excitation and detection devices, to be set up. This prototype proves to be capable of measuring the liquid level with acceptable sensitivity and repeatability.<<ETX>>

A Gray-code-based fiber optic liquid level transducer

A level transducer based on a six fiber sensing elements is proposed. A 1 m full scale, 4 mm resolution prototype was realized and tested. The adopted hardware and software strategies assure high static and dynamic performance, and good reliability, as confirmed by the experimental tests carried out on fuel liquids. The possibility of remote control together with a low cost suggests its applicability in a large number of applications.

Microcontroller-based performance enhancement of an optical fiber level transducer

The paper proposes a digital microcontrolled transducer for liquid level measurement based on two optical fibers on which the cladding was removed in suitable zones at a known distance one from each other. A 1 m full scale, 6.25 mm resolution prototype was realized and tested. The adopted hardware and software strategies assure a low cost, high static and dynamic performance, good reliability, and the possibility of remote control. These features were confirmed by the experimental tests carried out on fuel liquids.

A digital liquid level transducer based on optical fiber

The paper proposes a digital level transducer based on an optical fiber from which the cladding was removed in n zones at fixed distances from one another. A theoretical analysis of the propagation in this type of modified fiber was carried out, highlighting the good potentiality of the proposed sensor. A 1 m full-scale, 25 mm resolution prototype was then designed using the results of a numerical simulation, and set up by optimizing both the sensing element and the conditioning hardware. The static and dynamic characterization tests carried out show high repeatability, good accuracy, and acceptable dynamic performance.

Simulation and analysis of prismatic bioinspired compound lenses for solar cells

Inspired by the apposition compound eyes of many dipterans, we formulated a fractal scheme to design prismatic lenses to improve the performance of silicon solar cells. We simulated the absorption of light, both directly illuminating and diffuse, using the geometrical-optics approximation. We found that properly designed bioinspired compound lenses (BCLs) can significantly improve the light-harvesting capabilities of silicon solar cells. The degree of improvement will depend on the material chosen to make the BCLs as well as the operating conditions.

A variational method to approximate the field of weakly guiding optical fibers by Laguerre-Gauss/Bessel expansion

In the analysis of weakly guiding single-mode optical fibers, Gaussian and modified-Gaussian approximations appear inadequate to obtain accurate results at low normalized frequency for general refractive index profiles. To overcome such limitations we propose an expansion in terms of Laguerre-Gauss functions to represent the field in the fiber core. A modified Bessel function is instead used to describe the field in the cladding. All parameters defining the approximate field are evaluated by a variational method. We show that the proposed approximation is very accurate in the low normalized frequency limit too and can be particularly valuable to analyze dispersion-shifted fibers with triangular refractive index profile.

Simulation and analysis of prismatic bioinspired compound lenses for solar cells: II. Multifrequency analysis

Multifrequency numerical simulations of the light-coupling efficiency of a prismatic bioinspired compound lens (BCL) of silicon atop a thick silicon substrate were carried out within the framework of geometrical optics. Comparison was made with untextured and groove-textured silicon substrates as well as with untextured silicon substrates with a double-layer anti-reflection (DLAR) coating. Taking into account the broadband nature and the sea-level spectral irradiance of the insolation flux, and averaging over all admissible directions and both linear polarization states of the incident light, we found that the light-coupling efficiency can be almost doubled with respect to the untextured silicon substrate and enhanced by about a third with respect to a DLAR-coated untextured silicon substrate, by adopting a DLAR-coated silicon BCL.

Temperature measurement by multifiber optical sensor

The paper deals with a new multifiber temperature sensor, based on the relationship between temperature and the refractive index of a suitable reference liquid, which replaces a part of the fiber cladding. The sensing element, the microcontroller-based hardware, and the artificial neural network (ANN)-based measurement software are described. The results of the tests carried out in the range 40/spl deg/C-110/spl deg/C showed good prototype accuracy and repeatability (both contained within /spl plusmn/0.5/spl deg/C).