Information Technology Journal1812-56381812-5646Asian Network for Scientific Information10.3923/itj.2012.1337.1340DiXu XiaoJiangnan ChenLin YuJianjun 92012119We have theoretically and experimentally investigated the timing offset estimation methods based on training symbol with three different structures (Two-segments, Four-segments and Eight-segments) in direct-detection (DD) optical orthogonal frequency division multiplexing (OOFDM) systems. The performance of the proposed method is evaluated in terms of mean and mean-square error (MSE) of timing offset estimation in one experimental system with 4 Gbits sec-1 DD-OOFDM signal transmission over 100 km standard Single Mode Fiber (SMF). The experimental results show that the two-segments timing offset estimation method has smaller MSE than the other methods and achieves higher acquisition probability of timing synchronization in DD-OOFDM transmission system.]]>Armstrong, J.,200927189204Cao, Z., J. Yu, W. Wang, L. Chen and Z. Dong,201022736738Pollet, T., M. van Bladel and M. Moeneclaey,199543191193Giddings, R.P. and J.M. Tang,20111928312845Moose, P.H.,19944229082914Van de Beek, J.J., M. Sandell and P.O. Borjesson,19974518001805Kim, T., N. Cho, J. Cho, K. Bang, K. Kim, H. Park and D. Hong,19991999pp: 543547 Schmidl, T.M. and D.C. Cox,19974516131621Minn, H., M. Zeng and V.K. Bhargava,20004242244Park, B., H. Cheon, C. Kang and D. Hong,20037239241Hao, X., K. Qiu, C. Zhang and Y. Li,20092009pp: 12Gudmundson, M. and P.O. Anderson,19961996pp: 918922