Abstract: A unique structure of microbend optical fiber sensor (MOFS) for measuring tensile and compressive strain is described in this paper. The average measuring sensitivity for tensile strain is 35 $mu$epsilon using 3 MOFS arrays. The repeatability and stability of MOFS are better than 18 $mu$epsilon. The loss sensitivity of single-mode (SM) fiber and multi-mode (MM) fiber used in MOFS, as well as the relationship between the pulse width of diode laser and loss sensitivity are also studied in this paper. From these studied, some conclusions have been obtained. There are 1) the los sensitivity and repeatability of SM fiber are better when compared to MM fiber in MOFS, and 2) the variation of pulse width of laser would only influent the signal-to-noise ratio and dynamic range, but has no contribution to loss sensitivity. Experimental result also show that loss of SM fiber highly depends on the wavelength of laser, but MM fiber has no such property. The loss of Sm fiber between the wavelength of 1550nm and 1310nm is about the ratio of 6.5. Therefore, the experiments reported in this paper used wavelength of 1310nm to measure tensile strain and 1550nm to measure compressive strain based on the above property of SM fiber, without changing the configuration of MOFS. !8
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