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Proceedings Paper

Fiber Bragg grating sensor monitoring with thermally tuned Fabry-Perot cavity integrated in an all-silicon rib waveguide
Author(s): Giuseppe Coppola; Mario Iodice; Nunzia Saffioti; Rocco Cristian Zaccuri; Maurizio Indolfi; Ivo Rendina; Alessandra Rocco; Pietro Ferraro
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Paper Abstract

Fiber Bragg Gratings (FBG) sensors are a very promising solution for strain and/or temperature monitoring in hostile or hazardous environments. In particular, their typical immunity to EMI and the absence of electrical signals and cables, encourage the use of FBG sensors in aerospace structure. Moreover, FBG sensors can be embedded in composite materials, allowing the fabrication of the so-called smart-materials. In this paper we experimentally demonstrate that a Fabry-Perot cavity, integrated in a low-loss all-silicon rib waveguide, and realized by standard dry etching technique, is suitable for FBG monitoring. The reflected signal for the sensor passes through the cavity which is tuned by means of thermo-optic effect. The optical circuit ends with a photodetector that, for each tuning step, produces a photocurrent proportional to the convolution integral between the FBG and the FP spectral response. Because the finesse of a silicon FP cavity in air is not so high (about 2.5), it is advantageous an extended tuning over a wavelength range longer than the cavity free spectral range, that is convolving the FBG response with more than one FP transmission peak. The photodetector output signal, once acquired, is elaborated using standard FFT algorithm and pass-band filtered, in order to extract the main harmonic. After a final I-FFT step, a fitting procedure returns the FBG reflection peak position. The experimental accuracy, using as reference the peak wavelength measure made with a commercial high-performance Optical Spectrun Analizer, is in the order of few tenths of picometers.

Paper Details

Date Published: 7 March 2005
PDF: 8 pages
Proc. SPIE 5730, Optoelectronic Integration on Silicon II, (7 March 2005); doi: 10.1117/12.590650
Show Author Affiliations
Giuseppe Coppola, Istituto per la Microelettronica e Microsistemi, CNR (Italy)
Mario Iodice, Istituto per la Microelettronica e Microsistemi, CNR (Italy)
Nunzia Saffioti, Istituto per la Microelettronica e Microsistemi, CNR (Italy)
Rocco Cristian Zaccuri, Istituto per la Microelettronica e Microsistemi, CNR (Italy)
Maurizio Indolfi, Istituto per la Microelettronica e Microsistemi, CNR (Italy)
Ivo Rendina, Istituto per la Microelettronica e Microsistemi, CNR (Italy)
Alessandra Rocco, Istituto Nazionale di Ottica Applicata (Italy)
Pietro Ferraro, Istituto Nazionale di Ottica Applicata (Italy)

Published in SPIE Proceedings Vol. 5730:
Optoelectronic Integration on Silicon II
Joel A. Kubby; Ghassan E. Jabbour, Editor(s)

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