Temperature–insensitive curvature sensor based on hollow-core fiber assisted microbubble Mach–Zehnder interferometer

A compact fiber-optical curvature sensor based on the hollow-core fiber (HCF) assisted microbubble Mach–Zehnder interferometer (HMZI) is proposed and experimentally demonstrated. Transmission spectral characteristics of the proposed curvature sensor have been investigated with a maximum intensity-interrogated sensitivity of − 1.48 dB/m⁻¹ in a curvature range from 1.22 m⁻¹ to 3.46 m⁻¹. The temperature-induced instability is measured below 0.30 dB in a large temperature range of 35 °C to 60 °C, suggesting a good temperature resistance performance. The overall sensing size is controlled to be around 600 μm. Hence, the HMZI curvature sensor has several desirable merits such as wide measurement range, temperature insensitivity, and ease of integration, which make it a promising candidate in curvature-related mechanical engineering and structural health monitoring applications.