Advanced Optical Modulation Formats in High-speed Lightwave System
نویسندگان
چکیده
In the next generation of lightwave systems, high speed datarate like 10Gb/s or 40Gb/s per channel is very attractive. In addition, to pack more channels into one single fiber, channel spacing is decreased from 200GHz to 50GHz or even smaller. The direct side-effect is that linear and nonlinear degrading effects will be severe in such high-speed lightwave systems. An optimal modulation format which is more tolerant to linear and nonlinear impairments is needed urgently. In this thesis, we will detail and compare several different modulation formats in high speed datarate lightwave systems. Five modulation formats are under research: NRZ-OOK, RZ-OOK, CS-RZ, NRZ-DPSK, and RZ-DPSK. First of all, system performance of modulation formats over several existing transmission fibers are compared in both 10Gb/s and 40Gb/s WDM systems. We found that the dominant degrading effect is dependent on datarate; also the choice of optimal fiber is dependent on modulation formats and datarate. Then, a simplified first-order rule concerning of SPM effect is extracted from series of numerical simulations of several modulation formats; in addition, RZ-DPSK is found to be the most tolerant to SPM degrading effect among the investigated modulation formats. Last, we show a 40Gb/s experimental testbed. Based on this testbed, CS-RZ and NRZ have been realized. These researches in both numerical methods and experiments give us an insight view of advanced modulation formats and provide a foundation for future research.
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