Fast and High-Resolution Simultaneous Measurement of Temperature and Strain Using a Fabry–Perot Interferometer in Polarization-Maintaining Fiber With Laser Diodes

Abstract

Fast and high-resolution simultaneous measurement of temperature and strain is experimentally demonstrated. A Fabry–Perot interferometer fabricated in a polarization-maintaining fiber has sharp transmission peaks, which are divided into two sets corresponding to the polarization of the transmitted light. The sharp transmission peaks shift in response to changes in temperature and strain, and because the dependence coefficients are different for each set, temperature and strain can be simultaneously measured with high resolution. To read the position of a sharp transmission peak, wavelength sweeping with narrowband light is necessary. By using injection current modulation in a laser diode, high-speed wavelength sweeping and short measuring time are realized. We performed simultaneous measurements with a measurement time of 20 $\mu$ s; measurement resolution of 0.1 $^\circ$ C and 0.8 $\mu \epsilon$ for temperature and strain, respectively; and noise spectral density of 30 n $\epsilon /\sqrt{\rm Hz}$ . We further experimentally demonstrated that vibration with an amplitude of 20 $\mu \epsilon$ and a frequency of 1 Hz and heating at a rate of 0.7 $^\circ$ C $/$ s can be simultaneously measured.