Optical network is the infrastructure of telecommunicationnetwork. More than 95% of information istransported over optical network in China, wherecore network is the main trunk. How to increase thebit rate of the single wavelength channel, raise thetotal capacity of the DWDM system, extend theoptical transportation distance of electrical repeaterfree of the DWDM system and optical network intelligenceare key problems demanding high attention.The evolution trend of the optical core network isdescribed with some examples in this paper. Optical network is the infrastructure of telecommunicationnetwork. More than 95% of information is transmitted over optical network in China. Wherecore network is the main trunk. distance of electrical repeaterfree of the DWDM system and optical network intelligenceare key problems demanding high. the evolution trend of the optical core network isdescribed with some examples in this paper.