In this paper we propose and analyse an optical MEMS pressure sensor consisting of a ring resonator located over the edge of a circular silicon diaphragm. As the diaphragm deflects due to the applied pressure, stress induced refractive index change in the waveguide leads to change in phase of the light propagating through resonator. Shift in the resonance frequency due to this phase change gives the measure of the applied pressure. The phase response of the sensor is found to be about $19{mu}rad/Pa$ for 1 mm radius $65{mu}m$ thick circular diaphragm. The wavelength shift of 0.78 pm/kPa is obtained for this sensor and can be used up to a range of 300 kPa. Since the wavelength of operation is around $1.55{mu}m$, hybrid integration of source and detector is possible on the same substrate. This type of sensor can be used for blood pressure monitoring, precession instrumentation, aerospace propulsion application and other harsh environments with suitable design.
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