This paper discusses the use of pyrometers in harsh environments where the temperature position to be measured is difficult to access due to space limitations and/or the presence of strong electromagnetic fields. To overcome these challenges, optical fibers are used to guide the infrared radiation to the photodiode that converts it into an electrical signal. It also investigates commercially available optical fibers for their material properties, such as toxicity, and presents a detailed analysis of the components of the measurement chain, including the optical fiber, photodiode, and transimpedance amplifier. Using an optical fiber results in a lower radiation power, mainly due to the limiting acceptance cone of the fiber. A theoretical analysis of the radiation power losses and a practical test rig to verify the results are presented. Overall, the paper provides valuable insights for researchers and engineers in the field of non-contact temperature measurements.