Research And Experiment On Advanced Techniques In Ultra-long Span Repeater-less Optical Transmission

Compare to traditional optical transmission systems, ultra-long span Repeater-less optical transmission systems are characteristic of direct end to end routing without any line amplifier or repeater, which eliminate the need of power supply stations and thus reduce the construction and operating cost. Especially for the ongoing construction of long-span Ultra-High-Voltage transmission, the Repeater-less optical transmission systems can effectively avoid the repeaters in the routings through the no man's land such as deserts, swamps, mountains, thus largely cutting down the construction and maintenance costs of repeater stations. Additionally, the Repeater-less systems can be deployed at the oil pipeline transportation and submarine communication.This paper focus on the research and experiment of advanced techniques in the ultra-long span Repeater-less optical transmission, especially the suppressing of non-linear effect in the fiber, remotely pumped amplifiers, ultra low loss optical fiber and advanced optical modulation formats. The following are the abstract contents:(1) The theories and experiments of Stimulated Brillouin Scattering (SBS) and Self Phase Modulation (SPM) in the fiber are studied. The threshold of SBS is measured in experiment and increased greatly through externally phase modulation. Optical path penalty occurs at large launch power due to SPM. Two SPM suppressing methods are introduced.(2) The theories and experiments of remotely pumped amplifier are studied. An experimental and theoretical algorithm for calculating the optimal position of RGU is introduced, which is testified by the experiment.(3) Research and experiments on the application of ultra low loss optical fiber in ultra-long span optical transmission are introduced. It is proved that ultra low loss optical fiber takes obvious advantages over traditional fibers on the ultra-long transmission.(4) Theoretical and experimental studies on advanced optical modulation formats, especially DPSK, are introduced. DPSK presents better performance over OOK in experiments.