Photonic data routing in satellite payloads

AIM-94-1 109-CP PHOTONIC DATA ROUTING IN SATELLITE PAYLOADS R. M. GAGLIARDI A. MENDEZ COMMUNICATION SCIENCES INSITUTE m R S I T Y OF SOUTHERN CALIFORNIA LOS ANGELES CALIF 90089-2565 A study was carried out to evahate candidate designs for a photonic switchable gate matrix for routing high bandwidth data over an input-output plane in a satellite payload. The application is to replace standard RF and baseband gate switches presently being used by higher rate compact photonic devices. Several design formats were examined at USC, based on both multiple access techniques and circuit (spatial) switching. A theoretical study of several candidate designs were investigated, and parametric studies using real hardware were c a r r i e d ou t t o c o m p a r e expec t ed communication performance. It was concluded that photonic space switches, using basic opt ical shut ter principles, appear to be a viable candidate for this application. It was found that under typical operating conditions, the overall performance of a shutter system compares favorably with the more expensive routing networks based on wavelength multiplexing, the latter often considered the optimal network format. Optical, shutters can be constructed with relatively inexpensive spa t ia l l igh t modula tors , swi tchable s emiconduc to r ampl i f i e r s , o r ga t ed photodetector arrays. I Copyright O 1993 American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Internal data dis tr ibut ion is an important operation in modern satellites with extensive on-board processing[l] . Data d i s t r i bu t ion ne tworks a r e commonly implemented with electrical components. Bandwidth constraints and electrical crosstalk in these components limit the maximum data rate and the maximum number of users that such networks can handle. Also, once designed these networks often have a narrow range of rates or bandwidths at which they can operate and a single data type which they can accommodate. Networks of the future are likely to require a large number of users, ever increasing data rates, and a large variety of signal types. It is this expectation that motivates the search for a f lexible distribution system which can meet these requirements. One possible solution is to use an all-optical (photonic) approach to signal distribution. Emerging technologies will make it possible to construct such distribution networks in the near future. In this paper the results of a study of both the theoretical and practical aspects of candidate optical networks will be presented. The basic diagram of a data distribution system is shown in Figure 1. A set of input waveforms are to be coupled through the network fabric to the output ports. The network should be switchable, so that inputs can be reconnected in a controlled, reconfigurable manner. The input waveforms can be baseband data (bits) or can be RF on microwave carriers modulated with data. The objective of the network is to route, or redistribute, the input data over the output