While optical fibers are widely used for communications between switching nodes in today's telecommunications systems, the data are processed electronically within the switches.  The requirement of optical-to-elecrical (O/E) and electrical-to-optical (E/O) conversion at each switching node limits the maximum data rate and requires that all traffic adhere to a specified data format.  In order to meet the requirements of higher data rates and system throughputs of future systems, there is a need for transparent optical switches that allow data to remain in the optical format from sender to destination.

Specific functions required of the optically transparent switch are the following:

		Recognition of incoming cells by header content.
		Setting of switch controls by destination.
		Measurement of the difference between a cell's arrival time and the system clock.
		Alignment of incoming cells with the system clock through the use of a variable tapped delay line.
		Optical buffering to resolve contention for output ports.

We have assembled a 2x2 switch testbed based on commercial lithium niobate electro-optic modulators.  It incorporates a binary delay line for time alignment and optical memory loops for buffering.  It looks like this.

Publications & Presentations

P. W. Juodawlkis, J. L. A. Hughes, C. M. Verber, and K. Grimble, "Time alignment of cells with arbitrary message payloads," proceedings from the Optical Fiber Communication (OFC) Conference, San Jose, CA, 1996, pp.110-111.

Joseph L.A. Hughes and C. M. Verber , "Architectures and devices for an all-optical routing switch," Proc. SPIE, vol. 2024, pp. 235-243, 1993.

C. M. Verber and J. L. A. Hughes, "Technologies for an all-optical fiber network," proceedings of the Second IEEE International Workshop of Photonic Networks, Components and Applications, Montebello, Quebec, Canada, March 9-11, 1992.

C. M. Verber, "Integrated optical devices for high data rate optical communication," proceedings of the First IEEE International Workshop of Photonic Networks, Components and Applications, Montebello, Quebec, Canada, Oct 11-13, 1990, pp. 36-45.

For more information, contact Dr. Stephen Ralph at stephen.ralph@ece.gatech.edu.