Temperature insensitive fiber Fabry-Perot/Mach-Zehnder hybrid interferometer based on photonic crystal fiber for transverse load and refractive index measurement

An in-line Fabry-Perot/Mach-Zehnder hybrid interferometer based on photonic crystal fiber (PCF) for transverse load and refractive index measurement is proposed and experimentally demonstrated. The interferometer is fabricated by fusion splicing a section PCF between hollow core silica tube air bubble and hollow core silica tube (HCST). The hollow core silica tube air bubble is both a beam splitter for the Mach-Zehnder interferometer (MZI) and a Fabry-Perot interferometer (FPI) component, that is, there are both MZI and FPI functions on one sensor. Thanks to the structure of this special hollow core silica tube air bubble, transverse load measurement can be achieved. Meanwhile, this sensor also can measure refractive index and temperature. Experimental results show that the transverse load and refractive index sensitivities are 1.5277 nm/N and 99.2907 nm/RIU, respectively. In addition, the temperature sensitivity (-13.7 pm/degrees C) is relatively low. This sensor has outstanding advantages of high sensitivity, design flexibility, easy fabrication and compact size, which make it attractive in the field of multiparameter sensing applications.