Several transducers have been demonstrated to determine the refractive index of liquids either dark or transparent in the past few decades. In the present work a novel optical absorption based U-shaped glass probe sensor has been developed to study the refractive index of various liquids in the temperature range between 10oC to 60oC using Toluene and Acetonitrile mixtures at a source wavelength of 660nm. The sensitivity of the sensor also studied, by increasing the length of interaction between the light transmitting through the U-shaped glass rod and the analyte at the region of the sensing. The variation of the output power was observed to be a function of the optical absorption related change in refractive index of the analyte around the glass rod. The output power data related to different interaction lengths reveals that, as the length of interaction increases, the output power decreases. The investigation on temperature dependent variation of refractive index was carried out, and the results show that higher is the temperature of the active medium around the glass rod, lower is the refractive index and hence greater is the output power. The sensor is calibrated with respect to refractive index and output power at operating range of temperatures between 10oC and 60oC. With the help of this sensor a response time as short as the measurement precision of the order of 8×10-6 can be obtained.