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/με (M-factor = 2.3). This design improves the sensor performance and its implementation is not intricate