  A novel joint symbol timing and carrier frequency offset (CFO) estimation
algorithm is proposed for reduced-guard-interval coherent optical orthogonal
frequency-division multiplexing (RGI-CO-OFDM) systems. The proposed algorithm
is based on a constant amplitude zero autocorrelation (CAZAC) sequence weighted
by a pseudo-random noise (PN) sequence. The symbol timing is accomplished by
using only one training symbol of two identical halves, with the weighting
applied to the second half. The special structure of the training symbol is
also utilized in estimating the CFO. The performance of the proposed algorithm
is demonstrated by means of numerical simulations in a 115.8-Gb/s 16-QAM
RGI-CO-OFDM system.
