A Fiber Bending Vector Sensor Based on M–Z Interferometer Exploiting Two Hump-Shaped Tapers

A novel, compact, and simple in-line Mach-Zehnder interferometer (MZI) formed by cascading two hump-shaped tapers in a segment of single-mode fiber is proposed and fabricated. This optical fiber device has recognizable features for different bend directions while high sensitivities for ambient temperature and axial force. In the range of 0-1.2 m
^-1
, the sensitivities of the sensor with the length of 13.4 mm are 10.224 and -4.973 nm/m
^-1
for opposite bending directions 0° and 180°, respectively. The responses for temperature and force of the MZI are also investigated in experiment. The results show that the shift of the dip wavelength is linearly proportional to the change of temperature or force. The sensitivities of temperature and force are 0.049 nm/°C in the range of 20°C-80°C and -3.643 nm/N in the range of 0-0.98 N.