We describe some of the results of the Advanced Research Projects Agency (ARPA) sponsored Consortium on Wideband All-Optical Networks in developing architectures, technology components, and applications for the realization of scaleable, wideband, and transparent optical wavelength-division multiplexing (WDM) networks. Our architecture addresses all-optical transport over the wide, metropolitan, and local areas. It utilizes wavelength partitioning, routing, and active multiwavelength cross-connect switches to achieve a network that is scaleable in the number of users, data rates, and geographic span. The network supports two services which can be point-to-multipoint or multipoint-to-multipoint simplex or duplex connections. The A service is a transparent physically circuit-switched service and the B-service is a scheduled time-slotted circuit which is transparent within its time slots. We have developed a 20-channel local and metropolitan area WDM testbed deployed in the Boston area, now undergoing characterization and experimental applications.

A metropolitan-area radio system that, from a centrally located base station, provides continuously 360 degrees coverage over a large service region is proposed. The base station blankets the service region with a raster of very narrow pencil beams that can be rapidly scanned to any position in synchronism with the switching sequences of a time-division-multiple-access (TDMA) assignment. By deploying multiple scanning spot beams, the allocated spectrum can be reused many times. A centralized network controller, executing an efficient TDMA assignment algorithm, dynamically allocates the resources of a small transceiver pool among the far larger number of beam positions in response to real-time requests for service. By varying the dwell time at each beam position in response to the traffic intensity of the position, highly efficient resource utilization is provided. The high antenna gain of the base station antenna provides adequate arain fade margin to permit operation in the uncongested portion of the ratio spectrum above 20 GHz. The system is particularly well suited to emerging, direct-to-end-user wideband digital service offerings.>

A satellite system with several independent spot beams is considered, wherein each spot beam can be scanned over a limited portion of some large service region. The spectral band is totally reused in each spot beam, thereby providing high system capacity. Such a system combines the high antenna gain advantages of a fixed beam system while providing access to the satellite from any point within the overall service region. Moreover, the transmission resources of the satellite can be dynamically allocated to match time-varying changes of the possibly nonuniform terrestrial traffic patterns. The limited-scan antenna forms multiple spot beams, each of which scans only in one dimension; by alternating polarizations among scan strips, high isolation between beams is guaranteed. We show that nearly equal volumes of traffic can be served by each limited scan beam by proper orientation of the scan regions, and complete interconnectivity among all points in all scan regions is achieved easily. A practical antenna design to implement this concept is presented.