In-fiber modal interferometer based on dual-concentric-core photonic crystal fiber and its strain, temperature and refractive index characteristics

An in-fiber modal interferometer is demonstrated by splicing a section of homemade dual-concentric-core photonic crystal fiber (DCCPCF) and two segments of single-mode fibers (SMFs) with collapsing the air holes in the splice regions. By analyzing the transmission spectra and the spatial frequency spectra of the interferometers, it's observed that the main interfering modes are the high-order ring modes, which are different from the previously reported interferometers using the single-, few- or multi-mode fibers. The influences of the lengths of DCCPCF and the first collapsed region on the interferometers were investigated experimentally. The strain, temperature and refractive index characteristics of the interferometer were analyzed.