Integrated Vibration Detection System Based on an Optical Fiber SensorJ. A. Herrera-Estévez (1), L. E. Alanís-Carranza(1), J.A. Álvarez-Chávez(2), G E Sandoval-

Romero(3) , A. Gómez-Vieyra(4), G.G. Pérez-Sánchez*(4)

1. Tecnológico de Estudios Superiores de Coacalco,Av. 16 de Septiembre #54, Col. Cabecera Municipal, Coacalco de Berriozábal, Edo. México.

2. Centro de Investigación e Innovación Tecnológica -IPN, Cerrada de CECATI S/N,Col. Santa Catarina, c.p. 02250 D.F. Mexico

3. Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma deMexico, Apartado Postal 70-186, México D. F., 04510, Mexico.

4. Departamento de Ciencias Básicas, Universidad Autónoma Metropolitana, Unidad Azcapotzalco,  Av. San Pablo 180, Azcapotzalco, Col. Reynosa Tamaulipas, Azcapotzalco

México D. F.  02200Corresponding author email: *ggps@correo.azc.uam.mx

ABSTRACT:

The detection of internal and external vibrational changes in structures is currently an important area of theoretical and experimental studies in fields of structural health, building damage prevention and mechanical stress reduction. The main goals are the detection, prediction and the correction of mechanical and structural failures on furniture, buildings and historical monuments.

An integrated vibration detection system is proposed at its development stage. The experimental setup consists on a 980nm laser diode as the pump source, working at an average power of 100mW used to pump a piece of Er-doped fiber which was spliced to 2m segment of SMF-28 fiber. A 5cm segment of this fiber was stripped and then put on top of a long period fiber grating with a 500µm period. The load was placed on top of an acrylic of similar dimensions, in order to determine the minimum force that the set-up is able to measure. Such force will be employed in the final set-up. The proposed device allows for loads from 4.48 Kg to 14Kg, corresponding to voltage values from 422mV up to 804mV, so far with no rupture. The operating principle is the change in refractive index applied by the external force into the core which then modifies the mode propagation observed in the OSA as semi-periodical spectral changes. The maximum operating sensitivity was measured to be at 200gr load changes. The accuracy of the proposed device is still being studied as we still need to validate our measurements.

The signal was detected with a photo-detector, before it was amplified via a trans-impedance circuit and finally acquired using a NI-USB-6212 by National Instruments for up to 64 KS/s. This signal was then processed in real time, via a proprietary code. The code allows to show signal plots on the time and frequency domain.