Acoustic sensing through optical transduction represents a promising alternative to the conventional capacitive sensing used in MEMS microphones, especially when aiming at ultra-low noise applications. In fact, the traditional acoustic to electrical transduction stages are decoupled by the intermediate conversion of the signal into the optical domain. As a result, the mechanical design of the sensor has no direct influence on the electrical readout performance, this allows for a significant reduction of the MEMS transducer noise through aggressive acoustically semi-transparent stator designs, that represent one of the limits of the standard capacitive technologies. This paper reports the design and the modeling of the sensing elements of a MEMS optical microphone. The basic transduction mechanism is presented and the main design parameters and challenges are explained and analyzed with advanced modeling techniques, the measurement results are finally compared to the expected performance.