Evaluation of Gb/s laser based ®bre LAN links: Review of the Gigabit Ethernet model MARK C. NOWELL 1 , DAVID G. CUNNINGHAM 2 , DELON C. (DEL) HANSON 2 AND LEONID G. KAZOVSKY 3 1 Hewlett-Packard Laboratories, Filton Rd, Bristol, BS34 8QZ, UK (Current address: Cisco Systems, 365 March Rd, Kanata, Ont K2K 2C9, Canada, E-mail: mnowell@cisco.com) 2 Hewlett-Packard Company, Fiber Communications Division, 350 West Trimble Rd., San Jose, CA, 95131-1008, USA 3 Stanford University, Department of Electrical Engineering, Stanford, CA 94305, USA Received 8 January 1999; accepted 28 May 1999 Abstract. The theoretical model used by Gigabit Ethernet to develop the optical physical layer speci®- cations is presented. The model calculates the penalties associated with using laser based transceivers on both multimode and singlemode ®bre Gb/s links. Experimental veri®cation of the model's predictions is also presented along with discussion on the use of the model to predict link performance. The model is generic to laser based ®bre LAN links but speci®c details and examples relevant to Gigabit Ethernet are discussed. Key words: Gigabit Ethernet, modal bandwidth, multimode ®bre, singlemode ®bre 1. Introduction The enterprise networking environment has changed signi®cantly in recent years and the available bandwidth to the desktop has greatly increased. This is due to the shift to switch-based networks from hub-based networks that allow the desktop to have full-duplex access to the available link bandwidth. Added to this is the relatively recent increase in the available link bandwidth to the desktop from 10 to 100 Mb/s. One of the drivers for the growth in enterprise bandwidth is the increased use of applications that send large amounts of data over private Intranets and the Internet. Network trac is no longer limited to just messages or ®le transfers, now data streams, such as audio and video, are becoming common as well as messages with large embedded ®les. The growth of corporate Intranets and the Internet has also made network trac patterns very un- predictable; large ®les can be accessed from distant places. Within private Intranets, there is a growing trend towards using centralised servers. By their very nature, these servers need very high bandwidth connectivity in order to operate eectively. Optical and Quantum Electronics 32: 169±192, 2000. Ó 2000 Kluwer Academic Publishers. Printed in the Netherlands. 169