A HIGH-CAPACITY METROPOLITAN-AREA NETWORK USING LIGHTWAVE TRANSMISSION AND TIME-MULTIPLEXED SWITCHING

The technical feasibility of a lightwave communication system capable of providing service to thousands of subscribers within cities or large suburban areas is examined. Each subscriber in this system has available upon demand an aggregate bit rate of up to 100 Mb/s. The aggregate bit rate of the entire network is on the order of 5 Tb/s. The network topology is that of a star-on-star wherein each subscriber line terminates on one of a multitude of remote concentrators. Each high-speed link from a remote concentrator to a centrally located time-multiplexing photonic switch consists of a single-mode fiber carrying several wavelength-division multiplexed (WDM) channels. Each channel operates in a time-division multiplexed (TDM) mode at a data rate of 2 Gb/s and is powered by a multimode laser. No regeneration is required at the central switch, and, at the remote concentrators, each channel is terminated by a direct-detection receiver. The approach achieves high throughput by reusing the same channels, that collectively occupy a tiny fraction of the optical band, among all interconnecting links and, with the exception of large-dimensional switch arrays, employs readily available technology. Although each link from a remote concentrator to the central switch carries several WDM channels, it is possible, with no loss of traffic-bearing efficiency or flexibility, to demultiplex and switch these channels by means of a bank of parallel time-multiplexing switches, each of which carries signals of a single wavelength. Analytical models are presented for signal dispersion within the fiber links and crosstalk within the switches to show that the losses caused by these impairments can be managed to provide an end-to-end bit error rates (BER) of 10-9.