Comparative Study on Transmission Mechanisms in a SMF-Capillary-SMF Structure

Using a segment of silica capillary sandwiched by two single mode fibers (named as SMF-Capillary-SMF), we compare transmission mechanisms in various forms including multimode interference (MMI), Fabry-Perot (FP), Mach-Zehnder (MZ) and antiresonant (AR) mechanisms. The MMI mechanism can be suppressed or triggered effectively by optimizing the discharge intensity and propulsion distance to affect the fusion surface. Various devices with different silica capillary lengths and inner diameters are demonstrated, where transmission and reflection spectra are used to verify the transmission mechanisms, respectively. Simulated transmission spectra also valid at mechanisms contained in this structure. Evolutions of transmission spectra show that inner diameter of 15 μm is the transition state for MZ from being to disappearing. And the emergence of one type or hybrid responses from different mechanisms is determined by the inner diameter and length of the capillary. This comparative study of transmission mechanisms in a SMF-Capillary-SMF structure is instructive for studies on waveguide devices with a hollow core. Moreover, these combined mechanisms can be also employed for multi-parameters sensing.