Low-frequency strain sensor using a fiber Bragg laser

摘要

We have developed a Fiber Lasei Strain Sensor (FLSS) which shows noise-equivalent sensitivity equal to or better than 150pet m s /(Hz)1'2 at very low frequencies, from 50mHz to several tens of Hz The strain acts on the fiber laser emission wavelength, and an imbalanced Mach-Zender Interferometer (MZI) 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 50mHz, with a resolution better than 1 net m s . The device can find application in many fields, primarily in geological prospecting and in monitoring of civil structures.