Optical fiber Fabry–Perot interferometer for microorganism growth detection

• The optical fiber FPI based on HCPCF is proposed.
• The refractive index of the FPI investigated.
• To yeast growth detection and results confirm feasibility in biosensing.

An optical fiber Fabry–Perot interferometer (FPI) based on hollow-core photonic crystal fiber (HCPCF) for microorganism growth detection is proposed and demonstrated. The FPI is formed by splicing both ends of a short section of HCPCF to SMFs and cleaving the SMF pigtail to a proper length. By measuring the fringe contrast of interference pattern, the refractive index (RI) changes of analyte during microorganism growth can be obtained. RI response of the sensor was investigated theoretically and experimentally. It shows linear response with sensitivity of −136 dB/RIU and good repeatability. Temperature response was also tested and the result confirms the low temperature cross-sensitivity of the sensor. Detection of yeast growth in liquid medium by the FPI sensor was conducted and the result shows the characteristic of typical yeast growth curve. With its advantages of high RI sensitivity, low temperature cross-sensitivity, capability for real-time measurement and so on, this FPI sensor has great potential in biosensing.