Influence of the lamination process on plastic optical fiber sensors embedded in composite materials

摘要

Silica-based HB fibers have severe limitations due to their coating layers while embedded into a composite: the hard coating layer easily transmits radial stress to the sensing fiber and changes its birefringence. Two coating layers - hard and soft - attached to the HB fiber do not influence fiber birefringence since the second (soft) layer can easily absorb any lateral force. On the other hand, a soft coating does not provide any proper transmission of the longitudinal strain. Additionally, fused-silica fibers have an upper strain limit of approximately 2% strain. In highly loaded engineering structures structural monitoring strain is becoming increasingly important. Hence, soft polymer materials used in the manufacturing process of highly birefringent microstructured polymer optical fibers (mPOFs) can solve this limitation, In this paper we present interactions between a composite material and mPOFs during the manufacturing process. The lamination process can dramatically change the group birefringence of the mPOFs. Measurements for fiber embedded in composite materials and fiber in free space were made and compared. A simple explanation of these differences is presented at the end of the paper.