Field-Deployed Multi-Core Fiber Testbed - Tetsuya Hayashi; Takuji Nagashima; Tetsuya Nakanishi; Tetsu Morishima; Reiji Kawawada; Antonio Mecozzi; Cristian Antonelli (2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC), Fukuoka, Japan, July 7-11, 2019, 2019)