Seneca Networks, Inc.

Graham R Allan

Gary Lynn Duerksen

Patrick Foy

The present invention provides a wavelength division multiplexed optical communication system including an optical fiber ring configured to carry at least one wavelength division multiplexed optical communication signal having plural optical channels at different wavelengths. Optical amplifiers are interposed along the optical fiber ring for optically amplifying the wavelength division multiplexed optical communication signal. Each optical amplifier produces amplified spontaneous emission as well as amplifying the optical channels of the WDM signal. At each amplifier, amplified spontaneous emission is selected by an optical feedback selector and is fed back to the optical amplifier input via an optical feedback path; the created wavelength travels along the ring and is dropped near the input of the next adjacent amplifier, reducing ASE in the optical fiber ring. Using this technique, closed-ring amplified WDM metropolitan networks can be formed without the need to &ldquo;break the ring&rdquo; in order to avoid uncontrolled build-up of ASE.

Reduction of ASE in WDM optical ring networks

The present invention improves the performance of optical networks, particularly optical ring networks, by reducing amplified spontaneous emission thereby increasing the available gain of optical amplifiers within that network. In one embodiment, the invention provides a WDM optical communication system having an optical fiber ring with optical fiber amplifiers interposed along the ring. An optical wavelength is injected into the optical fiber ring at a first location; the optical wavelength is selected to be located within a region of amplified spontaneous emission for the optical fiber amplifier. The optical wavelength is dropped from the optical fiber ring at a second location positioned such that the injected optical wavelength is dropped at or prior to returning to the first location within the ring. The optical wavelength passes through at least two of the plurality of optical amplifiers before being dropped from the optical fiber ring.

The present invention provides a bidirectional wavelength division multiplexed optical communication network useful in numerous network configurations. The network includes a bidirectional optical waveguide carrying counter-propagating wavelength division multiplexed optical signals each including plural channels. Several optical nodes are positioned along the bidirectional optical waveguide, each of which includes an optically-amplified bidirectional optical add-drop multiplexer. Each bidirectional optical add-drop multiplexer includes channel selectors for selecting at least one optical channel from each of the counter-propagating WDM optical signals. Each optical node further includes at least one optical transmitter for supplying an optical channel to be added by the bidirectional optical add-drop multiplexer to the bidirectional optical waveguide and at least one optical receiver for receiving an optical channel dropped from the bidirectional optical waveguide by the bidirectional add-drop multiplexer. Preferably, each optical node includes a bidirectional optical service channel transmitter and receiver and a network control element. Through measurement of optical launch powers and optical amplifier gain, the optical power levels of the optical channels are controlled to within a specified range. The bidirectional optical systems of the present invention can be used to create flexible network topologies that are easily expandable to include additional optical nodes and have particular application in metropolitan area networks.

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Columbia, MD, United States of America

Graham R Allan