Date Added: Oct 2009
Fujitsu Telecom Networks develops and supplies optical transmission systems for domestic telecommunications carriers. For Japanese telecommunications carriers, it has recently developed the world's first 40-Gb/s Dense Wavelength Division Multiplexing (DWDM) transmission system using the return-to-zero differential quaternary phase shift keying (RZ-DOPSK) modulation format. This system can multiplex and transmit up to forty 40-Gb/s (STM-256) signals (total: 1.6 Tb/s) over one optical fiber. This paper explains the technical problems and solutions for multiplexing 40-Gb/s optical signals on a DWDM system, discuss the characteristics of various optical modulation formats, and show the superiority of RZ-DOPSK.