Single-Crystal Optical Fiber-Based Raman-Distributed Temperature Sensing for Applications in Energy Systems

Modern energy generation systems often exhibit some of the most challenging measurement environments on Earth. Coal, oil and gas, or nuclear based systems can present extremely high-temperatures, corrosive or erosive environments, extreme radioactivity, a wide-range of pressures, and extreme levels of vibration. To access the highest value components for sensor applications in these systems, we implement a distributed fiber optic temperature sensing system that measures temperature variations along the full length of the sensor fiber. In contrast to standard distributed fiber sensors, this system uses single-crystal optical fibers made from sapphire or yttrium aluminum garnet as the sensor element. Here, we provide a perspective and overview of our team’s combined efforts to grow single-crystal sapphire optical fibers with 125 µm outer diameters and a range of core sizes via the laser-heated pedestal growth (LHPG) method and refine or clad those fibers using a second LHPG system. These efforts are integrated with our Optical Interrogator Development Program, in which we construct distributed fiber-sensing interrogator units that are tailored to specific energy applications. In closing, we detail recent comparisons with our Raman distributed temperature sensing system and commercially available distributed sensing equipment.