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All-fiber, long-active-length Fabry-Perot strain sensor

This paper presents a high-sensitivity, all-silica, all-fiber Fabry- Perot strain-sensor. The proposed sensor provides a long active length, arbitrary length of Fabry-Perot cavity, and low intrinsic temperature sensitivity. The sensor was micro-machined from purposely-developed sensor-forming fiber that is etched and directly spliced to the lead-in fiber. This manufacturing process has good potential for cost-effective, highvolume production. Its measurement range of over 3000 ??, and strainresolution better than 1 ?? were demonstrated by the application of a commercial, multimode fiber-based signal processor.

In-line short cavity Fabry-Perot strain sensor for quasi distributed measurement utilizing standard OTDR

This paper presents an in-line, short cavity Fabry-Perot fiber optic strain sensor. A short air cavity inside a single-mode fiber is created by the fusion splicing of appropriately micro machined fiber tips. A precise tuning of the cavity length is introduced and used for the setting of the sensor static characteristics within the quasi-linear range around a quadrature point, which significantly simplifies signal processing. Sensor insertion losses achieved by short cavity design and optimized fusion splicing proved to be below 1 dB. Low insertion loss allows for effective cascading of the proposed strain sensors into a quasi-distributed sensor array. A practical 10-point quasi-distributed strain sensor array was demonstrated in practice, where each in-line sensor was tuned to the same operating point in the static characteristics, thus allowing for simple interrogation of the sensor array by using standard telecommunication OTDR. In addition, precise tuning of the short cavity Fabry Perot sensor was applied for an effective compensation of temperature-induced strain errors and for an increase in the unambiguous measuring range, while improving the overall linearity of the sensor system.