Hybrid all-fiber sensor for simultaneous strain and temperature measurements based on Mach–Zehnder interferometer

A hybrid all-fiber optic sensor for simultaneous detection of temperature and strain is proposed. The system comprises two different types of Mach–Zehnder interferometers (MZI) and sensing method is based on the joint evaluation of the strain (by a temperature-insensitive photonic crystal fiber (PCF) formed by a pair of long-period gratings (LPGs)) and of strain/temperature measurement (by a conventional single mode fiber (SMF) based MZI). It is shown that shorter wavelength for SMF–MZI and higher wavelength for PCF–MZI leads to larger phase shifts which improves the accuracy of measurements.