This paper describes a high capacity, scalable and modular d-optical dense WDM WAN. The network assumes a ring-tree (tree of rings) topology and employs all-optical packet switching, wavelength reuse, conversion, and routing schemes for data transport. The optical fiber four-wave mixing (FWM) nonlinear phenomenon is used for wavelength conversion, and erbium-doped fiber amplifiers (EDFAs) are used for signal amplification, in the network.The proposed network can be implemented at various scales, from a LAN to a global communication framework. Its transport protocols can be adapted for any dense wavelength-reuse WDM network. I N T R O D U C T I O NIn recent years, there has been an exponential growth in the demand for data network bandwidth and resource. As traditional electronic networks approaching their performance limits, all-optical communication networks are attractive alternatives with extremely high data transmission capacity, reliability, flexibility, and potentially excellent cost/benefit ratios. An all-optical network offers an entirely optical path for data transmission. Such a network does not call for optical to electronic data conversion, or vice versa, between any two transmitting and receiving nodes. This is in contrast to semioptical or optoelectronic systems that simply replace parts of the conventional communication system with optical counterparts. This paper describes a fully scalable and modular alloptical WAN. The proposed network incorporates several novel concepts including wavelength channel redundancy to address issues of contention and recovery. The system also reuses spectral channels, through wavelength conversions, to overcome the disadvantage of having to work with a relatively small bandwidth (x 35 nm in the 1.55 pm wavelength region) because erbium-doped fiber amplifiers (EDFAs) are used. Wavelength conversion, in this case, is achieved through the four-wave mixing (FWM) nonlinear effect in optical fibers and EDFAs.The dense WDM scheme in the proposed optical communication network is unique. Unlike many optical communication networks proposed or demonstrated to date [1]-[2], the proposed optical network does not rely on any actively tunable sources, filters, or detectors to achieve WDMA, thus avoiding the limitations imposed by the relatively modest switching speed of these tunable devices. Moreover, the 0-7803-3636-4/97 $10.00 0 1997 IEEE 1157 proposed optical network uses an optical address-decoding scheme. This eliminates the delay in optical-to-electrical and electric$-to-optical signal conversion and avoids the electronic bottleneck which limits the speed and performance of the network. As a result, this high performance network is potentially capable of providing data transmission rates of up to tens of gigabits per second (Gb/s), carrying multiple bit streams of various formats and nature (voice, data, image, video, etc.) simultaneously.This paper is organized as follows: Section 2 discusses the characteristics of the EDFAs in relation to channel allocation of the proposed...

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