Characterization of Crosstalk in Ultra-Low-Crosstalk Multi-Core Fiber

We describe a newly-developed method to measure inter-core crosstalk of single-mode multi-core fiber (MCF) statistically, and characteristics of the crosstalk of a previously fabricated MCF. To measure the crosstalk lower than -60 dB, we suppressed power floor of the measurement system by employing trench-assisted fiber as launching and receiving fibers. We measured statistical crosstalk distributions by utilizing wavelength dependence of the crosstalk, and the mean crosstalk between the neighboring cores was observed to be about -70 dB after 17.4-km propagation at 1625 nm. The measurement results were in good agreement with the previously proposed model. Based on the measurement results and the model, the crosstalk after 10000-km propagation was estimated to be less than -30 dB. We also confirmed that the crosstalk was varied stochastically depending on polarization state, and on mechanical shock and stress on the MCF.