Strain optical fiber sensor with modified sensitivity based on the vernier effect

An optical fiber strain sensor with adjustable sensitivity is proposed and demonstrated. The strain sensing setup employs a fiber optic Michelson interferometer (sensing element) and an extrinsic Fabry-Perot interferometer, in which both structures excited the Vernier effect. By adjusting the cavity length of the extrinsic Fabry-Perot interferometer, it is possible to control the M-factor. The set-up offers both sensitivity enhancement and magnification mode, where the maximal sensitivity is 4.38 pm/mu epsilon (M-factor = 2.3). This design improves the sensor performance and its implementation is not intricate.