Hole-Assisted Few-Mode Multicore Fiber for High-Density Space-Division Multiplexing

A seven-core few-mode multicore fiber in which each core supports both the LP
₀₁
mode and the two degenerate LP
₁₁
modes has been designed and fabricated for the first time, to the best of our knowledge. The hole-assisted structure enables low inter-core crosstalk and high mode density at the same time. LP
₀₁
inter-core crosstalk has been measured to be lower than -60 dB/km. LP
₁₁
inter-core crosstalk has been measured to be around -40 dB/km using a different setup. The LP
₁₁
free-space excitation-induced crosstalk is simulated and analyzed. This fiber allows multiplexed transmission of 21 spatial modes per polarization per wavelength. Data transmission in LP
₀₁
/LP
₁₁
mode over 1 km of this fiber has been demonstrated with negligible penalty.