Highly sensitive bend sensor based on Mach–Zehnder interferometer using photonic crystal fiber

Optical fiber bend sensor with photonic crystal fiber (PCF) based Mach–Zehnder interferometer (MZI) is demonstrated experimentally. The results show that the PCF-based MZI is sensitive to bending with a sensitivity of 3.046 nm/m−1 and is independent on temperature with a sensitivity of 0.0019 nm/°C, making it the best candidate for temperature insensitive bend sensors. To that end, another kind of bend sensor with higher sensitivity of 5.129 nm/m−1 is proposed, which is constructed by combining an LPFG and an MZI with zero offset at the second splice mentioned above.

Research Highlights
► We fabricated a PCF-based MZI which has smooth and regular interference fringe.
► The PCF-MZI is sensitive to external bending with sensitivity of 3.046 nm/m–1.
► Such a device is insensitive to temperature with sensitivity of only 0.0019 nm/°C.
► Another MZI is constructed by combining a LPFG and a PCF-based MZI with zero offset.
► Such a device has a relative high bending sensitivity of 5.129 nm/m–1.