This work studies the performance of a proposed high-speed optical fiber local area network based on wavelength division multiplex- ing (WDM) and asynchronous transfer mode (ATM). The design opti- mizes the usage of resources by assigning different types of traffic to two overlapping sub-networks. The WDM segment is a circuit-oriented net- work for high-speed traffic. The ATM sub-network handles control, low speed traffic and overflows of the WDM network. Each network is sup- ported by one of two types of channels. The ATM channel employs con- ventional ATM cells for all stations using a 1300-nm wavelength carrier. The WDM channel which is assigned dynamically for very high-speed applications operates at 1500 nm band. The application of an ATM net- work to handle the overflow traffic reduces blocking in the system by approximately 13% for a 32 WDM system. However, depending on the load, it may increase the delay between 5% to 30%. In addition, employ- ing an adequate queuing policy, we may reduce the blocking by 30% while increasing the delay by 5%. We may conclude that the network is more efficient handling the traffic load compared to a simple circuit switched WDM network. © 1999 Society of Photo-Optical Instrumentation Engi- neers. (S0091-3286(99)02511-8)