System And Protocol Considerations For A High Density Wavelength Switched All-optical Network

Abstract

great interest in effecting an all-optical network, particularly WAN, to overcome the electronic bottleneck. The currently widely accepted approach is to employ automatic wavelength Full connectivity and network scalability can be accomplished by employing wavelength reuse and Thus the operation of these systems requires a protocol that can pre-coordinate the routing and wavelength translations and also can handle collisions. In addition, means to achieve efficient broadcasting, multi-casting and packet switching need to be developed. A parallel approach is to use wavelength switching which so far has received much less attention. The fruitful operation of the wavelength switching system requires the use of fully tunable transmitters and/or receivers which are now technically sufficient mature. The wavelength switching system can be very attractive even for WAN, if a large number of wavelengths is available and can be multiplexed and de-multiplexed quickly. We have recently demonstrated a high density multiplexing technique which incorporates closely spaced multiple optical carriers within each division of a high density WDM system. An effective channel density of 10 channels/nm can be The high density optical carriers can be quickly de-multiplexed by optical (AOTF) and microwave By using accurate reference beamsi4], all the high density optical carriers can be generated and detected independently. This high density multiplexing system would permit us to use as many as 250 independent channels (250 Gb/s) within the optical amplifier’s bandwidth. The large number of parallel channels offers an opportunity to build general all-optical networks (such as WAN) with high capacity and a great flexibility. For instance, we can use traditional star or linear bus to build a LAN. Many LAN’s can be interconnected to form MAN’s. Interconnecting many MAN’s will result in a large WAN which could encompass the entire continental U. S. A large portion of the wavelengths is effectively reused at different levels within the network. Let’s assume that the network is organized into five levels and that the 250 wavelengths are also divided, for simplicity, into 5 equal groups. Each level uses only the pre-designated 50 wavelengths (50 Gb/s) and is connected to the next level through a Gate. The Gate regulates and isolates the wavelengths between different levels. Higher-level bypass sections may be added in parallel with the main trunk (not shown in Fig. 1) to relieve regional traffic and also to provide network self-healing. It can be shown that 100 million computers can be interconnected simultaneously! The topology of this multi-level system is symbolically shown in Fig. 1. Like the wavelength routing system, pre-coordination or reservation is, actually more, important for the wavelength switching system. Since not only the transmitters need to pick a wavelength, but also the receivers need to be informed. The demonstrated high density WDM system conveniently provides many control channels for the reservation purpose. It