Optical Orthogonal Frequency Division Multiplexing System Synchronization Technology

Optical orthogonal frequency division multiplexing (OOFDM) technology is a recent emerging optical transmission technology, which combines orthogonal frequency division multiplexing and fiber-optic communication technology, with all the advantages of both. While being used in optical fiber transmission channel ,OOFDM system can significantly improves the performance of existing optical fiber communication system, with very low cost. It is a very promising optical transmission technology.OFDM systems have harsh demands on the synchronization. Optical OFDM system is no exception. Timing synchronization errors will bring inter-symbol interference (ISI),carrier frequency synchronization errors will bring inter-carrier interference (ICI),and sampling frequency deviation will introduce ISI and ICI. All these will seriously affect the performance of the system. Today a variety of synchronization algorithms have been proposed for electronic OFDM systems. OOFDM systems generally have a very high bit rate. The traditional OFDM synchronization methods require a lot of floating-point operations at the receiving end, which is a major challenge for the optical OFDM systems.Based on its system structure,some optical OFDM systems need for timing synchronization and frequency synchronization at the same time, others just need timing synchronization. Therefore,this paper discusses timing synchronization and frequency synchronization separately. The main work of this paper can be summarized as follows:1.A matlab-based multi-mode intensity modulation direct detection (IMDD) OOFDM simulation system is established. Based on this,several typical data-aided synchronization algorithms have been done by a simulation and comparative studies, and two kinds of improved methods are proposed.2.For the single-mode fiber OOFDM system , a new time synchronization algorithm is proposed.Corresponding theoretical model is established and two key issues are settled, and the simulations are done on OptiSystem7.0 .3.Analysis of two typical optical OFDM system structures which need frequency synchronization is given.And a new frequency synchronization method corresponding to the pilot proposed in this paper is described.