Fibre-optic sensors need to be more established in the sensor market. Their advantages have unquestionably been verified by numerous demonstrations. However, there are some open questions leading now and then to restraints in the userÕs community. The paper discusses examples where fibre-optic sensors provide outstanding knowledge about the structureÕs behaviour, but application is often challenging. Requirements are listed and open questions to be solved are discussed. Short outlook to standards useful for better design, characterization and application is given. Standards are the basis for establishing SHM systems, especially for safety-critical structural diagnostics.