Probing the Ultimate Limit of Fiber-Optic Strain Sensing

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Science  28 Oct 2010:
DOI: 10.1126/science.1195818


The measurement of relative displacements and deformations is important in many fields such as structural engineering, aerospace, geophysics, and nanotechnology. Optical fiber sensors have become key tools for strain measurements with sensitivity limits ranging between 10–9 ε Hz–1/2 and 10–6 ε Hz–1/2 (ε is the fractional length change). We report on strain measurements at the 10–13 ε Hz–1/2 level using a fiber Bragg-grating resonator with a diode laser source that is stabilized against a quartz-disciplined optical frequency comb, thereby approaching detection limits set by thermodynamic phase fluctuations in the fiber. This scheme may provide a route to a new generation of strain sensors, entirely based on fiberoptic systems, which are aimed at measuring fundamental physical quantities—e.g., in gyroscopes, gravimeters, or gravitational wave detectors.