High temperature optical fiber sensors were developed to measure the in-service stressing that occurs in ceramic barrier filter systems. The optical fiber sensors were based on improvements to the sensor design developed under the DOE/METC Smart Structures for Fossil Energy Applications contract no. DE-AC21-89MC25159. In-house application testing of these sensors on both candle and cross-flow filters were performed in the Westinghouse Science and Technology Center High-Temperature, High-Pressure Filter Test Facility and the results analyzed. This report summarizes the sensor developments, methods to apply the sensors to the filters for in-situ testing, and the test results from the four in-house tests that were performed.