Reconfigurable Inter-Core Signal Switching Within Multicore Fibers Based on Long-Period Gratings

For future-oriented space-division multiplexing (SDM) networks based on multicore fibers (MCFs), intentional inter-core signal coupling and reconfigurable switching are desired to transfer signals between cores and establish various network topologies. In this paper, we inscribed long-period gratings (LPGs) into the MCF using the programmable electrical arc discharge (EAD) method. When the MCF is held straight, the LPGs initiate resonations between core modes and cladding modes for each individual core, with the signals at certain wavelengths transferred among cores through shared cladding modes. When the MCF-LPG is directionally bent, the inter-core power coupling is blocked due to the bending loss. We realized efficient power coupling among three ambient cores in a seven-core fiber at the C-band. The minimum end-to-end insertion loss is 11.3 dB, including that of the fan-in/fan-out multiplexers, and the maximum extinction ratio between the switching ON/OFF states is 39 dB. A six-wavelength SDM coherent transmission system is established to evaluate the performance of signal switching, with each wavelength channel modulated with a 224 Gb/s 16QAM-OFDM signal. The transmission results validate that all spatial output ports have good performances in both switching states, which indicates that reconfigurable inter-core signal switching is feasible for enabling flexible network functions within MCFs.