In this paper we realize all optical temperature measurement sensor theoretically using Mach Zehnder interferometer. In this study initially a thermistor is taken to sense the change in temperature. However the output is change in resistance. This change in resistance is recorded for the corresponding value of temperature and applied as one of the arm in wheatstone bridge network. The wheatstone bridge gives an equivalent thevenin voltage as output. Then this signal is amplified by the help of differential amplifier. The voltage output of differential amplifier 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 temperatures sensed by the thermistor and normalized intensity of the optical signal. The optical switching phenomenon in the MZI structure can be effectively used as an efficient temperature sensor. The paper includes the suitable expression for the temperature resistance relation of the thermistor, the thevenin voltage of the wheatstone bridge, the amplified voltage of the differential amplifier and the intensity of optical signal for MZI. The result is effectively supported by Beam propagation method based OPTI-BPM software. Copyright © 2015 American Scientific Publishers All rights reserved.