TY - GEN
T1 - A fiber bragg grating based tunable laser source for quasi-static and dynamic strain monitoring
AU - Balogun, Oluwaseyi
AU - Krishnaswamy, Sridhar
PY - 2009
Y1 - 2009
N2 - Fiber Bragg gratings (FBGs) are excellent tools for monitoring mechanical and thermal strains, and have widespread application in the structural health monitoring (SHM) of aerospace, civil, and mechanical structures. A common approach used for interrogating FBG sensors involves the illumination of the sensor with a broadband laser source and the narrowband reflected light reflected from the FBG is monitored with a wavelength sensitive optical detection system. The thermal or mechanical perturbations experienced by the FBG sensor lead to a shift in its reflectivity spectrum. In this work, an alternative interrogation scheme is presented that uses an FBG based narrowband tunable laser source produced by incorporating the FBG into a fiber ring laser cavity as an optical feedback element. The laser cavity consists an erbium doped fiber (EDF) connected to the FBG at the output of the fiber ring, which allows for the generation of the required amplified stimulated emission (ASE) in the C-band and lasing at the center wavelength of the FBG reflectivity spectrum. With this interrogation scheme, the wavelength of the resulting narrowband laser source tracks the center wavelength of the FBG sensor as it drifts due to quasi-static and/or dynamic mechanical and thermal strains. In addition, the instantaneous spectral line-width of the laser source is effectively narrowed owing to the long length of the laser cavity, which facilitates highly sensitive demodulation of dynamic shifts of the lasing wavelength with a high coherence optical interferometer. In this paper, experimental results are presented that illustrate the monitoring of strain induced quasi-static and dynamic shifts of the wavelength of the tunable laser in both single and multiple FBG sensor configurations. The quasi-static wavelength shifts are monitored with a spectrum analyzer while a path stabilized Michelson interferometer is used to demodulate the dynamic wavelength shifts.
AB - Fiber Bragg gratings (FBGs) are excellent tools for monitoring mechanical and thermal strains, and have widespread application in the structural health monitoring (SHM) of aerospace, civil, and mechanical structures. A common approach used for interrogating FBG sensors involves the illumination of the sensor with a broadband laser source and the narrowband reflected light reflected from the FBG is monitored with a wavelength sensitive optical detection system. The thermal or mechanical perturbations experienced by the FBG sensor lead to a shift in its reflectivity spectrum. In this work, an alternative interrogation scheme is presented that uses an FBG based narrowband tunable laser source produced by incorporating the FBG into a fiber ring laser cavity as an optical feedback element. The laser cavity consists an erbium doped fiber (EDF) connected to the FBG at the output of the fiber ring, which allows for the generation of the required amplified stimulated emission (ASE) in the C-band and lasing at the center wavelength of the FBG reflectivity spectrum. With this interrogation scheme, the wavelength of the resulting narrowband laser source tracks the center wavelength of the FBG sensor as it drifts due to quasi-static and/or dynamic mechanical and thermal strains. In addition, the instantaneous spectral line-width of the laser source is effectively narrowed owing to the long length of the laser cavity, which facilitates highly sensitive demodulation of dynamic shifts of the lasing wavelength with a high coherence optical interferometer. In this paper, experimental results are presented that illustrate the monitoring of strain induced quasi-static and dynamic shifts of the wavelength of the tunable laser in both single and multiple FBG sensor configurations. The quasi-static wavelength shifts are monitored with a spectrum analyzer while a path stabilized Michelson interferometer is used to demodulate the dynamic wavelength shifts.
KW - Dynamic Strain Monitoring
KW - Path Imbalanced Optical Interferometer
KW - Tunable Laser Source
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U2 - 10.1117/12.815651
DO - 10.1117/12.815651
M3 - Conference contribution
AN - SCOPUS:66749141595
SN - 9780819475558
T3 - Proceedings of SPIE - The International Society for Optical Engineering
BT - Health Monitoring of Structural and Biological Systems 2009
T2 - Health Monitoring of Structural and Biological Systems 2009
Y2 - 9 March 2009 through 12 March 2009
ER -