Orthogonal Frequency Division Multiplexing Offset Quadrature Amplitude Modulation(OFDM/OQAM) For Optical Communication System

The fast growth of information speed promotes optical backbone network to achieve ultra- large capacity, ultra- long distance and ultra-high speed(3U) optical transmission. Therefore, new techniques are widely studied to realize higher speed beyond the present 100Gbit/s for the required larger capacity communication system. In addition, optical access network also requires more flexible structure, lower cost, larger capacity and higher spectral efficiency. In order to tackle this trend, more advanced modulation techniques become one of the essential parts. Optical orthogonal frequency division multiplexing(OOFDM) technique has becoming one of the candidates for the next Tbit/s transmission because of the excellent resistance for chromatic dispersion(CD) and polarization mode dispersion(PMD) as well as the high spectral efficiency. But this technique also has some drawbacks such as high peak-to-average power ratio(PAPR) and high out-of-band spectral leakage.There are two main improved techniques to tackle these drawbacks: Discrete Fourier Transform spread OFDM(DFT-S-OFDM) and Orthogonal Frequency Division Multiplexing Offset Quadrature Amplitude Modulation(OFDM/OQAM). The former can reduce the PAPR to improve the transmission performance. And the latter has higher sidelope(>35d B) Compared with the conventional OFDM technique. Therefore, this can decrease the interference from the adjacent band, shrinking dramatically the guard-band spacing between adjacent signal bands(<20MHz) in multi-band system. So the limit of conventional WDM can be broke by using the optical superchannel transmission scheme. Another improvement is that the cyclic prefix(CP) is not required by the merit of the orthogonality between subcarriers and the perfect reconstruction condition of the prototype filter. So the system can resist Inter-symbol Interference(ISI) and Inter-channel Interference(ICI).So far, optical OFDM/OQAM is only reported in a simulation study. We are the first to apply this technique to practical optical communication system. The content includes as following:1. In this paper, we study the theory and demonstrate the simulation of the system in Matlabsoftware;2. Then we first study the performance of OFDM/OQAM in coherent optical communicatio nand experimentally demonstrate the first 110-Gbit/s multi-band superchannel coherentoptical OFDM/OQAM system at optical back-to-back. In the experiment, the guard-bandspacing is reduced from 50GHz/100 GHz to 20 MHz and there is no performancedegradation without using CP. We also experimentally demonstrate the 400-Gbit/s coherentoptical OFDM/OQAM system over 400 km single mode fiber and compare the sidelopeleakage performance with the conventional OFDM system; 3. In addition, we also apply the OFDM/OQAM to optical direct detection system, especiallyresearch the large capacity 100Gbit/s transmission scheme.