Optical fiber grating-based strain and corrosion sensors

Optical fiber gratings have recently emerged as attractive sensors for non-destructive evaluation of materials and structures. We present photoinduced Bragg and long-period gratings (LPGs) for monitoring corrosion in aging infrastructure. These two sensors are described based upon fabrication techniques, sensing mechanisms, sensitivities, and cross sensitivities. It will be demonstrated that while Bragg gratings need to be prestrained to detect corrosion of metals, the modulation of the evanescent field of the cladding modes in-long-period gratings can be employed for corrosion monitoring. It will also be shown that sensitivities of LPG-based corrosion sensors to ambient temperature fluctuations can be reduced significantly.