A novel technique to measure the cryogenic temperature distribution of a helically coiled Tube-in-Tube (TIT) heat exchanger using Fiber Bragg Grating (FBG) array has been reported. The measured temperature distribution will help in estimating the heat exchanger efficiency and will be used to investigate its performance. The measurement of the temperature distribution has previously only been simulated, as using a standard temperature sensor would inadvertently hamper the flow. This issue can be solved by using a small sized FBG sensor array. In this paper, the principle, design and installation of sensors are explained and the initial experiments are carried out to demonstrate the measurement technique. The experimentally measured temperature distribution was found to be agreeable with the simulated values with minor deviations.