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

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 ~0.61 dBm, a high optical signal-to-noise ratio of ~63 dB, a narrow spectral width of ~0.01 nm at the lasing wavelength and a good bending sensitivity of ~1.04 nm/m^-1, which gives a low detection limit of ~4.37 × 10^-2 m^-1.