Frequency-modulated multimode laser diode for fiber Bragg grating sensors

A demodulation scheme for fiber Bragg grating (FBG) sensors is presented. It is based on the generation of an electrical carrier by using a modulated multimode laser diode to illuminate the fiber grating. The change in Bragg wavelength is measured by tracking the phase of the carrier at the detector output in either an open- or a closed-loop scheme. A theoretical analysis of the interrogation technique in terms of linearity and dynamic range is presented. Experimental data were obtained for both strain and temperature measurements. Sensitivities of 0.7 /spl mu//spl epsiv///spl radic/Hz and 0.05/spl deg/C//spl radic/Hz were obtained over a dynamic range of /spl ap/60 dB. The application of this demodulation scheme to a multiplexed sensing system is also demonstrated.

[1]  Yunjiang Rao,et al.  Simultaneous spatial, time and wavelength division multiplexed in-fibre grating sensing network , 1996 .

[2]  John P. Dakin,et al.  Simultaneous monitoring of multiple fibre gratings with a single acousto-optic tunable filter , 1996 .

[3]  William W. Morey,et al.  IN-FIBER BRAGG-GRATING SENSORS , 1988 .

[4]  G. Meltz,et al.  Formation of Bragg gratings in optical fibers by a transverse holographic method. , 1989, Optics letters.

[5]  Jose Luis Santos,et al.  Demodulation scheme for fibre Bragg sensors based on source spectral characteristics , 1996 .

[6]  Raymond M. Measures,et al.  A structurally integrated Bragg grating laser sensing system for a carbon fiber prestressed concrete highway bridge , 1995 .

[7]  F. Farahi,et al.  Pseudoheterodyne demodulation technique for fiber Bragg grating sensors using two matched gratings , 1997, IEEE Photonics Technology Letters.

[8]  Peter L. Fuhr,et al.  Performance and health monitoring of the Stafford Medical Building using embedded sensors , 1992 .

[9]  Julian D. C. Jones,et al.  Short optical path scan interferometric interrogation of a fibre Bragg grating embedded in a composite , 1997 .

[10]  J. E. Townsend,et al.  Use of highly overcoupled couplers to detect shifts in Bragg wavelength , 1995 .

[11]  J. Bokor,et al.  Bragg gratings fabricated in monomode photosensitive optical fiber by UV exposure through a phase mask , 1993 .

[12]  Raymond M. Measures,et al.  Active wavelength demodulation of a Bragg grating fibre optic strain sensor using a quantum well electroabsorption filtering detector , 1996 .

[13]  Michael A. Davis,et al.  Fiber grating sensors , 1997 .

[14]  F. Farahi,et al.  Simultaneous measurement of displacement and temperature using a low finesse cavity and a fiber Bragg grating , 1996, IEEE Photonics Technology Letters.

[15]  D R Hjelme,et al.  Application of Bragg grating sensors in the characterization of scaled marine vehicle models. , 1997, Applied optics.

[16]  David J. Webb,et al.  Demultiplexing of fibre Bragg grating temperature and strain sensors , 1994 .

[17]  A. Kersey,et al.  High-resolution fibre-grating based strain sensor with interferometric wavelength-shift detection , 1992 .