Sagnac interferometer based on an etched photonic crystal fiber

Abstract

The transmission characteristics of a Sagnac interferometer based on an etched polarization-maintaining photonic crystal fiber (PM-PCF) incorporating an erbium-doped fiber (EDF) are investigated for simultaneous measurement of strain and temperature. After reducing the cladding diameter of the PM-PCF, we fabricated the Sagnac interferometer to induce peak wavelengths for effective measurement of strain and temperature changes. The pumped EDF is implemented to be both a light source for the sensing signal and a temperature-sensing probe. The applied strain shifts the peak wavelength to a longer wavelength and does not change the peak power in the transmission spectrum of the Sagnac interferometer. The etched PM-PCF improves the strain sensitivity of the proposed sensing probe to 4.7 pm/µɛ, which is three time higher than previous results. However, the pumped EDF only responds to an external temperature change, and the amplified spontaneous emission of the pumped EDF is decreased by an applied temperature change. Eventually, the transmission peak power of the etched PM-PCF-based Sagnac interferometer is only changed by an applied temperature change. Therefore, it is possible to discriminate strain and temperature by measuring variations in the peak wavelength and in the transmission peak power, respectively.