In this paper, a new scheme has been proposed to achieve high performance local area network adopting 5～15 nm separated coarse wavelength division multiplexing (CWDM) technique. Using this scheme, the current single wavelength gigabit Ethernet can be seamlessly upgraded to multi wavelength network. Not only can the network bandwidth be broadened, but also wavelength routing can be achieved among different sub networks. The data packet communication latency can be reduced one to two magnitudes in comparison with that of the current gigabit Ethernet. To expand the network scale, multi wavelength window CWDM technique can be adopted. Two kinds of network interface cards have been designed using opto electronics devices at the 850 nm and 1300 nm wavelength windows, respectively. Experiments indicate that the two kinds of CWDM signals can be selectively received at the corresponding optical detectors. By introducing two optical dropping devices in the network, multi wavelength-window (850 nm, 1300 nm and 1550 nm) CWDM system can be achieved. Using this scheme, the current single wavelength gigabit Ethernet can be seamlessly upgraded to multi wavelength network (CWDM) technique. . Not only can the network bandwidth be broadened, but also wavelength routing can be reduced among to two magnitudes in comparison with that of the current gigabit Ethernet. To expand the network scale, Two kinds of network interface cards have been designed using opto electronics devices at the 850 nm and 1300 nm wavelength windows, respectively. Experiments indicate that the two kinds of CWDM signals can be selectively received at the corresponding optical detectors. By introducing two optical dropping devices in the network, multi wavelength-w indow (850 nm, 1300 nm and 1550 nm) CWDM system can be achieved.