Measurement of differential mode group delay in few-mode fibers based on Fresnel reflection peaks

Mode-division multiplexing communication based on few-mode fibers (FMFs) is the most competitive scheme to address the bandwidth exhaustion in single-mode fibers. The differential mode group delay (DMGD) among different modes in FMFs is an important aspect in characterizing FMFs, and the convenient, fast, and accurate measurement of DMGD in different modes of FMFs is a crucial task. This paper presents a single-ended measurement method for DMGD in FMFs based on Fresnel reflection peaks. Experimental measurements were conducted to determine the DMGD of a 3.689 km six-mode fiber and a 9.7 km three-mode fiber, and the results were compared with the traditional time-of-flight method. The findings demonstrate that our proposed method based on Fresnel reflection peaks exhibits good accuracy in measuring the DMGD of FMFs. Moreover, this method enables single-ended measurement and offers simplicity and practicality.