The improvement of transmission properties for multi-mode fiber based on launching optical field shaping and feedback equalization

Recently, as the continual development of services and needs, people have a higher expectation on the optical communication system especially the passive optical network (PON). Deciding which kind of fiber to be the optimal media for PON is becoming a critical problem. This paper analyzed the feasibility for the applying of multimode fiber (MMF) in the future long haul, high bit-rate, and large capacity PON, and summarized the strengths and weakness of MMF. Then, initiating from the waveguide theory in the weakly guiding fiber and neglecting the intra-modal dispersion as well as nonlinearity, we built a simple model for multimode fiber, based on which we made analysis, research and comparison through simulation experiments on some performance improving techniques of MMF: offset launching, mode size changing, ring launching and feedback equalization. The simulation results demonstrated that the combination of field shaping and feedback equalization can obviously improve the transmission properties of MMF, because of which, the 10Gbit/s data can travel in the MMF for more than 1km.