Fiber Mach-Zehnder interferometer based on double cladding fiber for high curvature measurement

This study proposes a Mach-Zehnder interferometer (MZI) based on double cladding fiber (DCF) for high curvature measurement. In this proposed design, two optical paths are paved in the core and in the inner cladding of the DCF. The outer cladding of DCF provides confinement of light in the inner cladding, hence enabling higher curvature to be imposed without any significant optical loss. The experiment revealed that the sensor exhibited the highest sensitivity values at 1.3484 nm/m−1 and −0.1367 nm/m−1 for low and high curvature ranging from 0.0 to 3.32 m−1 and from 62.5 to 142.8 m−1, respectively. To the best of the author’s knowledge, this has been the largest curvature range measured by a fiber interferometer sensor. With such capability, the proposed sensor displays exceptional potential to be deployed in applications that involve high curvature measurement, such as in soft robotic, wearable medical device, and structural health monitoring system.