Optical OFDM for higher spectral efficiency system

Optical OFDM is a promising technology for highly spectrally efficient (SE) wavelength-division-multiplexing (WDM) system. Furthermore, the bit-rate 400 Gbit/s per WDM channel with SE of 8 bit/s/Hz is expected to be adopted for the next generation WDM system. For the application, optical OFDM is one of promising candidates because of the scalability for higher SE and higher bit-rate using multi-band OFDM technique. In this paper, the SE of multi-band OFDM is explained first, and WDM transmission experiments of multi-band OFDM signals with SE of over 8bit/s/Hz are introduced.