Highly Sensitive Optical Fiber Sensor Enables Bidirectional and Wide-Range Curvature Sensing by Combining With LSTM

A highly sensitive optical fiber sensor based on Mach–Zehnder was designed, which can achieve bidirectional as well as wide-range curvature measurements by combining with long short-term memory (LSTM). The curvature experimental results show that the highest sensitivity is −40.2971 nm/
$\text{m}^{-{1}}$
in the range of 0–10.3580
$\text{m}^{-{1}}$
. The creative introduction of LSTM gets rid of the constraint from the free spectral range (FSR); the demodulation range is significantly increased. This method can reduce the requirement for hardware equipment; the accuracy can still be guaranteed with fewer sampling points. Furthermore, the sensor can be used for curvature measurement in bidirectionality. The proposed method is highly generalizable and can be extended to sense the measured in more complex environments.