Fiber optic sensors are increasingly used because of their outstanding performance or if special requirements avoid the application of conventional electrical sensors. The scientific background for optical fiber sensors is well developed; however, the characteristic of sensors applied in rather harsh environment are almost always different from characteristics determined in laboratory or before its installation. In order to achieve long-term stable function and reliable measurement data after application and under harsh environmental conditions, guidelines for characterization and specification of sensor components are needed as well as methodologies for testing the sensor performance must be developed. Performance tests carried out revealed that there are still some restrictions with respect to long-term reliable use: first, some sensor products available on the market are not very often appropriately characterized, described and validated; second, application procedures are not always defined due to a lack of understanding the micromechanical issues in the interface zone between sensor and measuring object. Application procedures and profound knowledge of materials behaviour are necessary to get results from the sensor that can be reliably used. The paper describes first guidelines to prove the quality of fiber optic strain sensors, a testing facility developed for unbiased tests and certification of surface-applied sensors as well as result from comparison of commercially available strain sensors.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.