Terahertz-Range Weak Reflection Fiber Optic Structures for Sensing Applications

This paper describes a series of terahertz-range weak reflection fiber optic structures engineered for distributed temperature and strain sensing applications. Four specific structures are described: an intrinsic Fabry-Perot interferometer, a terahertz-range fiber Bragg grating, a phase-shifted terahertz-range fiber Bragg grating, and a terahertz-range fiber Bragg grating fabricated with an intact optical fiber buffer coating. All four structures were fabricated using a femtosecond laser micromachining system, which inscribed the structures within the core of a single-mode silica optical fiber. Interrogation technique, signal processing, fabrication method, and experimental investigation of each structure are described. The results presented demonstrate that these structures specifically, and terahertz-range optical fiber sensors more generally, hold substantial utility as methods of distributed temperature and strain sensing.