Temperature Insensitive Optical Fiber Laser Bend Sensor With a Low Detection Limit

Abstract

A fiber in-line Mach–Zehnder interferometer based on a sandwich structure of single mode fiber-thin core fiber-single mode fiber is inserted into a fiber ring laser cavity to form a fiber laser bend sensor. Such a sensor is temperature insensitive, has a large output light intensity $\sim 0.61$ dBm, a high optical signal-to-noise ratio of $\sim 63$ dB, a narrow spectral width of $\sim 0.01$ nm at the lasing wavelength and a good bending sensitivity of $\sim 1.04$ nm/ $\text{m}^{-1}$ , which gives a low detection limit of $\sim 4.37\times 10^{-2}~\text{m}^{-1}$ .