Collective measurement of DMD in 6-mode 19-core fiber using low-coherence digital holography

In the space division multiplexing system, differential mode delay (DMD) is an essential parameter for transmission quality and signal processing. In this paper, we proposed the collective measurement method for the DMD of each core in few-mode multi-core fiber (FM-MCF) using low-coherence digital holography (LCDH). In the conventional method, given that the DMD of each core needs to be measured individually, the number of measurements increases in proportion to the number of cores, which causes fluctuation of the measurement conditions. In contrast, the proposed method reduces the measurement time and realizes the accurate measurement under the same conditions for all cores. We experimentally demonstrate the proposed method by using 6-mode 19-core fiber as a fiber under test. As a result, DMD values were successfully measured for all 19 cores.