Optical network based on wavelength-division multiplexing (WDM) technology will be a most active research topic in the 21st century. This paper describes a WDM multiple-wavelength transmitter and several key corresponding devices for optical network, including amplified spontaneous emission (ASE) spectrum-sliced multiple-wavelength optical source, optical add/drop multiplexer (OADM), semiconductor optical amplifier (SOA), as well as the spectrum noise suppression scheme. The new research results are reported, and the applications of these developed devices are also introduced.