Miguel Ángel Morante Rábago

Optical fiber and integrated optics accelerometers for real-time vibration monitoring in harsh environments: in-lab and in-field characterization

The reliability of rotating machines such as electrical generator is critical to the overall reliability and operation of electrical power plants. The very high cost of these machines, makes it necessary to improve the lifetime of a wide set of currently installed hydrogenerators around the world and avoid costly maintenance. Vibration monitoring is essential in maintenance and protection programs. However, due to the harsh environment and the very low frequency spectrum of the vibrations, the above mentioned machines cannot be appropriately monitored by piezoelectric sensors. Several combination of optical fiber with silicon microstructures or in integrated optics, but because of technical or economic reasons, up to now, these sensors are not fully suited for the above-mentioned applications. In this paper both optical fiber and integrated optics accelerometers developed in order to satisfy specifications required for these applications are presented. Their developments were a part of a European project dedicated to real time defect detection and predict forthcoming failures of a generator group in an electric power plant in Spain. In-laboratory and in-field test are reported.

New low-cost fiber optic accelerometer system for stator winding monitoring of hydroelectric generating machines

A new fiber optic accelerometer system for stator winding simultaneous multi-point vibration monitoring of hydroelectric generating sets is presented. It is composed of as many sensor heads as points to be monitored, an optical channel and a processing unit distant from the sensing area, which is exposed to strong electromagnetic interference. The evaluation scheme is based on an intensity modulation and differential detection technique so that the measure is not influenced by external perturbations. The system is able to measure accelerations ranging from 30 to 450 Hz, with a maximum amplitude of 200 m/s2 RMS. Experimental results for the previous prototypes developed are showed. This sensor is intended to be integrated in a new complex system aimed to reach the goals of instantaneous protection, real time detection and evaluation of defects, failures and malfunctions in the above mentioned machines.

Phenomenological approach to the analysis of the polarization effects in fiber optic interferometers

Using the scattering matrices and the graph theory, three basic structures of all-fiber interferometers, Mach-Zehnder, Michelson, and Sagnac have been analyzed. The influences that, the couplers with losses and constant coupling polarization dependent, and the birefringent of the optical fibers, both used for making these optical systems, introduce in the performances of the three interferometers, are studied and compared.

Accuracy-enhanced compensated optical fibre two-dimension microdisplacement transducer based on direct intensity modulation

Several industrial applications require precise microdisplacement measurements. Optical intensity modulated sensors are very suitable to meet these needs because they are simple and cost-effective. Many have been presented that monitor one-dimension displacement in the direction of the optical axis of the system.

Analog optical U-shaped fibre transducer based on index modulation for quasi-distributed sensing

Optical time domain reflectometry (OTDR) is a very useful tool used in optical fibre communications and in sensor networks. The cost of an OTDR instrument prohibits sometimes its use in fibre optic sensor networks. Desforges et al presented a scheme that allows the monitoring of 10 to 50 on/off microswitches along a fibre in industrial environments using retroreflected light.