Passive photonic loop architecture employing wavelength multiplexing

Abstract

A fiber optic subscriber loop architecture is disclosed. The architecture utilizes a double star configuration comprising a Central Office and a plurality of Remote Nodes. Illustratively, in the Central Office, one bank of N lasers supplies wavelengths .lambda..sub.1, .lambda..sub.2 . . . .lambda..sub.N in a first wavelength band to form channels on which downstream information will be transmitted to subscribers. In one embodiment, a second bank of N lasers operating at wavelengths .lambda..sup.N+1, .lambda..sub.N+2 . . . .lambda..sub.2N in a second wavelength band is used to form unmodulated channels to be delivered to subscribers for use in subsequent upstream transmissions. Groups of N wavelength channels are combined via WDM techniques at the Central Office before being transmitted over feeder fibers to the Remote Nodes. In the downstream direction, the Remote Nodes rearrange the wavelength channels received from the Central Office so as to route two wavelength channels, one modulated channel from the first wavelength band and one unmodulated channel from the second wavelength band, to each of a plurality of subscriber premises attached thereto. At each subscriber station, the modulated channel is decoded while the unmodulated channel is modulated with upstream information and transmitted back to the associated Remote Node. Each Remote Node multiplexes groups of the modulated channels from the second wavelength band and routes them back to the Central Office over the feeder fibers. In the above-described double-star subscriber loop architecture, there are no active devices in the Remote Nodes.