Helically Twisted Microstructured Polymer Optical Fiber and Its Application as a Torsion and Strain Sensor

In this letter, we report for the first time the fabrication and sensor application of a helically twisted polymethylmethacrylate (PMMA) microstructured polymer optical fiber (mPOF). The fabrication was done by mechanically twisting the mPOF while passing it through a miniaturized Peltier element. The structure was created with a helical pitch of ∼700 μm, producing a series of spectral dips at the low loss region of PMMA, namely at the 400 to 500 nm region. The structure has been characterized to torsion showing that it can sense the twist direction with high sensitivities (48--53 nm/(rad/mm)). The strain sensor application has also been demonstrated, showing a negative sensitivity response with absolute values of 0.8--0.9 pm/μϵ. The soft and stretchable nature of mPOFs combined with helical structures will provide new opportunities for the development of highly tunable filters and innovative smart sensors.