He has been engaged in pioneering research on all-optical signal processing for ultrafast and broadband optical communications for more than 30 years, proposing ultrafast OTDM (optical time-division multiplexing) based on all-optical demultiplexing in 1987, and coherent supercontinuum generation over 200 nm for WDM (wavelength-division multiplexing) transmission and optical signal processing in 1994, and initiating SDM (space-division multiplexing) studies in Japan in 2007. He was involved in the first one Tbit/s OTDM/WDM (100 Gbit/s x 10 ch) transmission using a single supercontinuum laser source in 1996 and the first Pbit/s transmission in 2012.