A simple, full-polymer tilt and displacement sensor for planar-optical measurement

Strain and/or displacement sensing based on optical principles is complementary to electrical strain measurement with advantages in corrosive or explosive environments or in applications where strong electric or magnetic fields prevent the use of electrical components. The most prominent example of optical strain measurement systems is based on Fiber Bragg Gratings (FBG). The achievable sensitivity of such systems equals or surpasses that of electrical devices, although relatively expensive readout equipment is needed. We aim at the realization of a simple strain and displacement sensor whose main features are a full-polymer 2D approach, inexpensive readout equipment requirements, and compatibility to large-scale production. The sensor consists of five arrayed emitter and receiver waveguide pairs in a butt-coupling configuration. We discuss the manufacturing process, the readout algorithm as well as the hardware for readout. While the sensitivity is not yet as high as for current FBG systems, our sensor can be useful for distributed sensing, e.g. for crack monitoring in civil structures or wearable applications where large elongations are to be detected with moderate sensitivity.