Research On Coaxial Dual-waveguide Optical Fiber Based Modal Interferometer And Its Sensing Characteristics

Coaxial dual-waveguide optical fiber (COF) has a central core and an annular core in the cladding. COF can be used as optical transmission medium or be used to make optical devices,to realize the function just like light power exchanging and light wavelength selection, etc.In-fiber modal interferometer manufactured by COF, when the external factors such as strain,temperature, refractive index (RI) changes, the interference spectral correspond change,therefore this feature can be used for sensing measurement. In this paper, the COF based in-fiber interferometers and their sensing properties have done a comprehensive theoretical analysis and experimental research.This paper has a review about the research dynamic and sensing applications of integrated optical fiber interferometer. Then, build a model of the interfermometer based on mode field mismatch (core-offset, cascading MMF), and the sensing characteristics is analyzed. We designed and built the model interferometers' fabrication system, the fabrication process was introduced in detail (Mach-Zehnder interferometer based on core-offset,Michelson interferometer and Mach-Zehnder interometer based on cascading MMF), and the spectrums of interferometer in different parameters were analysised as well. Benefit from the special structure of COF,The three kinds of interferometer not only has the advantages of compact, high integration, and also has a series of unique sensing properties. Through the theoretical calculation and experiment validation, the sensing characteristics such as temperature, RI, strain of the interferometer that proposed in this paper have carried on the systematic study.