Fig. 7 shows a schematic diagram of the transmission system developed.
① 552 optical carriers with different wavelengths are collectively generated in a frequency comb.
② Polarization multiplexed 16QAM modulation is performed on the output light of the optical frequency comb light source, and a delay added to create different signal sequences.
③ Each signal sequence is launched into one core of a 4-core optical fiber.
④ After propagating through a 69.8 km long 4-core optical fiber, transmission loss is compensated by optical amplifiers in the S, C, and L-bands, and the optical fiber is introduced into the 4-core optical fiber via a loop switch. By repeating this loop transmission, the final transmission distance reached was 3,001 km.
⑤ The signal of each core was received and the transmission error was measured.