In this paper we first time realize the all optical pressure sensor using the Mach Zehnder interferometer. In this study, initially a circular shape clamped diaphragm is taken and pressure is applied. The deflection which is maximum at the centre is taken across a potentiometer (POT hereafter) and corresponding output voltage is noted. This voltage is applied across the electrode of Mach Zehnder Interferometer (MZI) and depending upon the specific value of electrode voltage the intensity of the optical signal varies, which provides the proper relation between the applied pressure and normalized intensity of the optical signal. The optical switching phenomena in the MZI structure can be effectively used as an efficient pressure sensors. The paper includes the suitable expressions for the central deflection of clamped edge pressure sensor diaphragm, the voltage output by POT and intensity of optical signal for MZI. The results are very effectively supported by the use of Solidworks and Opti-BPM. The error for the said parameters is also calculated and it is found in good agreement with the desired results. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.