The work is related to the design of vibration sensor's head represented by MOEMS structure. The head consists of two optical fibers and micro beam that lays between them. The principle of operation of the head is free space light modulation by micro beam. The elaborated head model enables analysis of influence of head and stimulation parameters on measured output light. The main parameters of the head are material used for micro beam fabrication and beam dimensions. The micro beam can be fabricated monolithically or as added component so it can be made from silicon or glass. The micro beam types qualify the sensor type as amplitude or frequency transformer. These head types require different types of detection block. What is interesting, technologically simpler frequency transformer requires more complex detection device than amplitude transformer.