Versatile in-fiber sensing by use of core-replaced D-fiber

We present a method of replacing a section of the core of a D-shaped optical fiber with sensing materials as a platform for various extrinsic fiber sensors. In this configuration light guides within the sensing material allow for strong interaction between the sensing material and the optical field. Initial experimental results indicate that replacing the fiber core with polymer enhances its temperature sensitivity by at least a factor of 5. The new technique is promising as a means for incorporating various sensing materials into the path of a beam traveling in an optical fiber.