Splice Loss Investigation of Single-Mode Fiber and Photonic Crystal Fibers and Its Potential Refractometric Sensing Applications

In this letter, we theoretically and experimentally investigate the splicing loss mechanism from a single-mode fiber (SMF) coupled to an endlessly single-mode (ESM) photonic crystal fiber (PCF) via fusion splicing. We show that this phenomenon can be advantageously used to estimate the refractive index (RI) value of the external medium surrounding the PCF, thereby paving the way for potential sensing applications. The splice loss induced in the PCF is mainly due to the difference in numerical apertures (NA) between the SMF and the PCF. To estimate the splice loss as well as the refractometric performance, a mathematical model is proposed in this letter, which exhibits good agreement with experimental measurements. Based on the refractometric response, the best resolution of 1.2 × 10
⁻⁴
refractive index unit (RIU) has been achieved.