A DTA instrument has been designed around the Acufiber Model 100C temperature measurement and control system. The temperature of the sample and reference materials are determined by their black body radiation. This radiation is conveyed through single crystal sapphire light-pipes that also act as supports for the sample and reference. The Delta T signal is determined by subtraction and the temperature of the reference material is used to control the furnace temperature. These preliminary investigations on the optical differential thermal analysis (ODTA) have been encouraging and considerations of the effects of emissivity are being explored.