High sensitivity compact Mach Zehnder interferometer based on the cascade application of seven-core fiber and graded index multimode fiber

Abstract

Mach Zehnder interferometric sensor fabricated by graded index multimode fiber has high sensitivity, but due to the defects of wide interference valley and low extinction ratio, it is difficult to be applied, and there are few studies about the MZI made of graded index fiber. In this paper, a Mach Zehnder interferometer cascaded with seven-core fiber and graded index multimode fiber was proposed and demonstrated. While maintaining the high sensitivity of the graded index multimode fiber interferometer, it overcomes its series of defects. The testing results indicate that the full width at half maxima (FWHM) of the interference valley can be less than 30 nm, and the valley depth is close to 10 dB when the length of the graded index multimode fiber is less than 2 dm. The maximum strain sensitivity of the sensor is 20.71 pm/με, and the temperature sensitivity is 261.14 pm/℃. The proposed sensor has compact structure and high strength, which will promote the practical process of graded index multimode fiber in the field of fiber interference sensing.