Transmission of 61 C-Band Channels over Record Distance of Hollow-Core-Fiber with L-Band Interferers

We report on two recirculating loop transmission experiments over a hollow-core fiber of the Nested-Antiresonant Nodeless type (NANF). We transmitted 61 channels in C-band at 32 GBaud, with either PM-QPSK or PM-16QAM modulation. In addition, 61 L-band interferers co-propagated in the NANF at all times, though they were not recirculated in the loop, to check for the presence of possible crosstalk effects between C and L-band in the NANF. The loop comprised the longest NANF transmission line yet constructed (7.72 km), as well as 55 km of pure-silica-core fiber (PSCF) needed to provide enough signal buffering and EDFA stabilization for the loop. The launch power into the PSCF was low enough to avoid generation of any significant non-linear noise. Using PM-QPSK, we achieved a record 618 km transmission in NANF (80 recirculations), at an overall average GMI of 3.44 bits/symb. Using PM-16QAM, we achieved a record 201 km transmission, at an overall average GMI of 7 bits/symb. We saw no adverse effect from the presence of L-band interferers in the NANF. If progress in the reduction of NANF loss and inter-modal interference continues at the rate of the last few years, these hollow-core fibers might become a promising alternative in the quest for next-generation higher-throughput fibers, given their theoretical potential of achieving low loss and ultra-low non-linearity over ultra-wide bandwidths, ideally bringing about a many-fold increase in throughput per fiber.