Low-frequency strain sensor using a fiber Bragg laser

We have developed a Fiber Laser Strain Sensor which shows noise-equivalent sensitivity equal to or better than 150 picostrain at very low frequencies, from 50 mHz to several tens of Hz. The strain acts on the fiber laser emission wavelength, and an imbalanced Mach-Zender Interferometer converts wavelength variations into phase-amplitude variations. In the time domain the device shows a good signal to noise ratio also at the lowest tested frequency of 50 mHz, with a resolution better than 1 nanostrain. The device can find application in many fields, primarily in geological prospecting and in monitoring of civil structures.