Four-wave mixing fits ultrasensitive refractive index sensing with suspended-core microstructured Fiber

An ultrasensitive refractive index sensor based on the four-wave mixing in a suspended-core microstructured fiber (SC-MOF) is proposed. It presents that, due to much power penetration into the air holes of the SC-MOF, the refractive index (RI) sensitivity is up to 2.43 × 105 nm/RIU for the produced idler wave of the four-wave mixing in SC-MOF. The RI responses of idler wave and signal wave are analyzed as pump wavelengths locate in the normal dispersion region and anomalous dispersion region, respectively. The simulation results show that, if the pump wavelength locates in normal dispersion region and the idler wave is used for wavelength-encoded demodulation, it would be more appropriate for RI sensing. The influence of incident power on RI sensitivity, power fluctuation induced RI measurement error and sensing quality are also analyzed. It is demonstrated that moderate incident power must be selected, and pump wavelength away from transition point would be beneficial for RI measurement stability.