Simultaneous Refractive Index and Temperature Sensing With Precise Sensing Location

An ultracompact optical fiber inline Mach-Zehnder interferometer for simultaneous refractive index and temperature sensing is demonstrated. The device is featured with precise sensing location and fabricated by femtosecond laser micromachining together with fusion splicing technique and followed by a slightly tapering process. There are two dips in the transmission spectrum of our proposed optical fiber sensor, which allows using the standard matrix inversion method for simultaneous two parameter determination. The refractive index and temperature sensitivity achieved are 103 nm/RIU (refractive index unit) and 73.07 pm/°C, respectively.