Efficient Chromatic Dispersion Precompensation for Coherent Optical OFDM

To reduce the guard interval, short-cyclic-prefix coherent optical orthogonal frequency division multiplexing (CO-OFDM) divides a band into two subbands and precompensates for chromatic dispersion (CD) with timing offset. Implementation using full band inverse discrete Fourier transformations (IDFTs), however, can excessively increase hardware complexity. We propose an efficient hardware implementation of IDFT with timing offsets for short-cyclic-prefix CO-OFDM. In addition, the residual intersubband CD induced by quantized timing offset is compensated using subcarrier-based phase rotation. By increasing the number of subbands efficiently and compensating for the residual intersubband CD, the transmission performance can be improved. Simulation results show 112-Gb/s single-channel transmission over a 2250-km standard single-mode-fiber with polarization division multiplexing 16 quadrature amplitude modulation (PDM-16 QAM) using 128 DFT with a 16 guard interval.