8723
This innovative measuring system consists of an Optical Backscatter Reflectometry ( OBR ) interrogation unit connected to a distributed fiber optic strain sensor which is embedded during the MEX process .
 Optical, fiber, strain, sensor, process
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 Optical, fiber, strain, sensor, process