Photonic ATM switch based on a multiwavelength fiber-loop buffer

Abstract

An optical ATM switching node has to provide two basic functionalities: cell routing (by means of a space switch) and cell contention resolution (by means of a cell buffer). This paper reports the development of a photonic ATM switch with two inputs, two outputs, and four memory positions, capable of routing 622-Mbit/s cells and of solving contention situations. The switching function1,2 exploits the wavelength domain to encode the incoming cells, to buffer them in a wavelength controlled optical memory when necessary, and to finally route them to the proper output. The basic concept relies on the possibility of simultaneously storing several cells, at different wavelengths, inside the same optical-fiber loop (Fig. 1). The output-port address, written in the first bytes of the cell (routing tag), is read by the tag recognizer; this information is used by the electronic control to identify cell collisions, to subsequently decide which cell(s) will be stored in the memory, and to perform routing.