This thesis deals with the conceptual design and prototype development of a fiber optic sensor for measuring vibrations. The requests and working conditions for this sensor are given in a project which is being carried out at the Faculty of Electrical Engineering and Computing (FER) in Zagreb, named “Designing and production of a fiber optic sensor for measuring vibrations in remote monitoring of high-powered electrical machinery”. First part of the thesis shows theoretical basis of optical measurements and also consists of analytical calculations of sensor’s optical characteristics in order to determine the maximal allowable amplitude of membrane’s vibrations. The computed amplitude is then used as input data in further calculations of mechanical vibrations. In addition, numerical simulations of the problem carried out in commercial software package ZEMAX (licensed to FER) were used to confirm the accuracy of optical analytical calculations. As part of the thesis, a specific program code was developed in MATLAB software package in order to optimize the mechanical components of fiber optic sensor. The developed program code is based on analytical mathematical models, which are also elaborated within this thesis. Using the program code, various implementations of sensor and their different vibrating modes were examined on the basis of optical calculations data. Additionally, preliminary dimensions of the sensor were established at this stage. For several different conceptual designs, control of results obtained by the MATLAB code was done by comparing them with results of dynamic finite element analysis in FEMAP / NASTRAN software package. In regard to conducted analysis, optimal dimensions of sensor’s mechanical parts were determined. A structural solution for the sensor was designed according to overall results. Materials and production technologies for all of prototype sensor’s mechanical parts were defined by taking into account financial constraints and the constraints arising from sensor’s area of application. The paper contains a detailed description of the design and the accompanying manufacturing sheets and drawings. The prototype was made using 3D printing technology and its images can be seen in penultimate chapter of this paper. Finally, effect of drag (from the surrounding air) on vibrations of the membrane was investigated using computational fluid dynamics (CFD).