Abstract: The present invention provides an optically-amplified bidirectional optical adddrop multiplexer for a bidirectional WDM optical communication system including two counterpropagating WDM optical signals. Each counterpropagating WDM signal enters the bidirectional add-drop multiplexer and is placed on an optical path, which does not include the other WDM optical signal. Each WDM optical signal may be amplified and have one or more optical channels added to or dropped from the respective signal. In an exemplary embodiment, one of the bidirectional WDM signals includes optical channels located in the C-band of an EDFA while the other bidirectional WDM signal includes optical channels located in the L-band of and EDFA. In this manner, an optical amplifier particularly selected for channels in a particular gain region may separately amplify each the separated bidirectional WDM signals. Each counterpropagating WDM signal exits the bidirectional add-drop multiplexed and rejoins the bidirectional optical waveguide.

Abstract: The present invention provides a wavelength division multiplexed optical communication system with dynamically stabilized wavelength selectors. To accurately correlate the wavelength of a wavelength selector to the wavelength emitted by an optical transmission source, the present invention uses an optical detector and feedback loop to optimize the wavelength of an optical selection element in accordance with a wavelength of an incident optical channel. In one embodiment, the optical selection element is a Bragg grating associated with a grating wavelength controller, such as a temperature regulator or strain tuning system, to adjust the wavelength band of maximum reflectivity of the grating. The feedback loop communicates with the optical detector and the wavelength controller to modify the grating's reflection wavelength band in accordance with the wavelength of an incident optical channel.

Abstract: The present invention relates to an optical network including a bridge for selectively transferring information from an optical channel carried on a first WDM optical waveguide to at least two optical channels on a second WDM optical waveguide. The first and second optical waveguides carry WDM optical signals each having plural optical channels. A bridge is interposed between the first and second optical waveguides which includes an optical add-drop multiplexer optically communicating with each waveguide. At least one optical channel having first and second data bits streams is dropped from the first waveguide. The first and second data bit streams are respectively encoded on two different optical channels which are then added to the second optical waveguide.

Abstract: 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.

Abstract: The present invention relates to a bidirectional optical network including a bridge for selectively transferring information from an optical channel carried on a first bidirectional WDM optical waveguide to at least two optical channels on a second bidirectional WDM optical waveguide. The first and second bidirectional optical waveguides each carry two counter-propagating WDM optical signals each having plural channels. A bridge is interposed between the first and second bidirectional optical waveguides which includes an optical add-drop multiplexer optically communicating with each bidirectional waveguide. At least one optical channel having first and second data bits streams is dropped from the first bidirectional waveguide. The first and second data bit streams are respectively encoded on two different optical channels which are then added to the second bidirectional optical waveguide.

Abstract: The present invention provides a wavelength division multiplexed optical communication system with dynamically stabilized wavelength selectors. To accurately correlate the wavelength of a wavelength selector to the wavelength emitted by an optical transmission source, the present invention uses an optical detector and feedback loop to optimize the wavelength of an optical selection element in accordance with a wavelength of an incident optical channel. In one embodiment, the optical selection element is a Bragg grating associated with a grating wavelength controller, such as a temperature regulator or strain tuning system, to adjust the wavelength band of maximum reflectivity of the grating. The feedback loop communicates with the optical detector and the wavelength controller to modify the grating's reflection wavelength band in accordance with the wavelength of an incident optical channel.

Abstract: The present invention provides a bidirectional wavelength division multiplexed optical communication network having a protection switching capability within a bidirectional optical waveguide. A bidirectional optical waveguide having plural optical nodes carries counterpropagating wavelength division multiplexed optical communication signals: M optical channels in a first direction and N optical channels in a second direction. The network includes the capacity to generate X+Y protect optical channels which respectively propagate in the first and second directions. Upon detecting loss of an optical signal means are provided for switching the affected M work optical channels to the Y protect optical channels and the affected N work channels to the X protect channels. In this manner, protection switching may be accomplished in a bidirectional optical network on a single bidirectional optical waveguide.

Abstract: The present invention provides a system for protection switching in a wavelength division multiplexed optical communication network including optical transponders within optical nodes. A work optical transponder receives a first work optical channel dropped by an optical add-drop multiplexer from an optical waveguide while a second work optical transponder adds a work optical channel to the optical add-drop multiplexer. Similarly, a first protect optical transponder is positioned to receive a protect optical channel dropped by the optical add-drop multiplexer while a second protect optical transponder is positioned to add a protect optical channel to the optical add-drop multiplexer.

Abstract: The present invention relates to a bidirectional optical network including an optical bridge for selectively transferring optical channels between two bidirectional wavelength division multiplexed optical communication systems. Two counter propagating WDM optical signals are carried on each bidirectional waveguide. An optical bridge is interposed between the bidirectional waveguides and includes an optical coupler and channel selector configured to select one or more optical channels from a first WDM optical signal and a second optical coupler and channel selector configured to select one or more optical channels from the counter propagating WDM optical signal. At least one optical path is positioned between the first bidirectional optical waveguide and the second bidirectional optical waveguide which carries at least the selected one or more first optical channels to an optical combiner interposed along the second bidirectional optical waveguide.

Abstract: The present invention provides a flexible WDM optical communication system in which each optical channel of the WDM optical communication signal can simultaneously accept multiple data formats. In one embodiment, the WDM optical system includes an optical waveguide having an optical add-drop multiplexer to selectively add and/or drop one or more optical channels to/from the WDM signal carried on the waveguide. A first source of data imparts information onto a first optical channel in a packet format while a second source of data imparts information onto the first optical channel in a time division multiplexed format. Other data sources having other data formats may also be included. An optical network interface electrically communicates with the data sources, placing the data from these sources onto the first optical channel which is generated from an optical source such as a laser. An optical path carries the optical channel from the optical source to the optical add-drop multiplexer.

Abstract: The present invention provides a wavelength division multiplexed optical communication system with dynamically stabilized wavelength selectors. To accurately correlate the wavelength of a wavelength selector to the wavelength emitted by an optical transmission source, the present invention uses an optical detector and feedback loop to optimize the wavelength of an optical selection element in accordance with a wavelength of an incident optical channel. In one embodiment, the optical selection element is a Bragg grating associated with a grating wavelength controller, such as a temperature regulator or strain tuning system, to adjust the wavelength band of maximum reflectivity of the grating. The feedback loop communicates with the optical detector and the wavelength controller to modify the grating's reflection wavelength band in accordance with the wavelength of an incident optical channel.

Abstract: In an optical add/drop multiplexer, an optical switch is coupled to one or more outputs from a demultiplexer. Accordingly, a dropped optical channel can be switched between a receiver optical path for directing the dropped optical signal to an optical receiver and between a combiner optical path for routing the dropped optical channel back towards the optical transmission path, optionally passing the dropped optical channel through a remodulator. Alternatively, the optical switch routes the dropped optical channel towards an optical receiver while permitting a new optical channel to be routed to add port of the static add-drop multiplexer.

Abstract: The present invention provides an optical monitoring system for a WDM optical communication system. In an exemplary embodiment, the monitoring system includes a wavelength selecting device which receives a WDM optical communication signal comprising plural optical channels and optical noise (e.g., ASE). The wavelength selecting device separately outputs optical signals corresponding to each of the optical channels and at least one optical noise sample taken at a wavelength which is not occupied by one of the optical channels. At least one optical power meter optically communicates with the wavelength selecting device for measuring the optical power of each of the optical channels and the optical noise sample. The optical power meter outputs an electrical signal indicating the strength of a measured optical channel or of the optical noise sample.

Abstract: The present invention provides add-drop multiplexers which are compatible with dense wavelength division multiplexed (WDM) systems having large numbers of optical channels. The add-drop multiplexers employ sets of Bragg gratings separated by an optical isolator to reliably add or drop optical channels without crosstalk. The Bragg grating sets and the optical isolator are interposed between first and second optical couplers. Optical channels to be dropped from a WDM optical signal are reflected by the first set of Bragg gratings and exit the add-drop multiplexer through the first coupler. Optical channels to be added to a WDM optical signal enter the add-drop multiplexer through the second optical coupler.

Abstract: The present invention provides improved compatibility between optical transmitters of various data rates and WDM optical communication systems. In the present invention, optical remodulators are configured to receive an optical signal, separate the information from that optical signal into N information streams (where N is a whole number greater than or equal to 2), and place the information onto N optical channels within the channel plan of a WDM optical system. Alternatively, the present invention provides optical remodulators configured to receive N optical signals, combine the information from the N optical signals, and place the information onto a single output optical channel having a wavelength within the channel plan of a WDM optical system.

Abstract: The present invention provides a bidirectional WDM optical communication system with bidirectional optical amplifiers for optically amplifying two counter-propagating WDM optical signals. The bidirectional system includes two sets of optical transmitters for respectively creating a set of west-east optical channels and a set of counter-propagating east-west optical channels. The respective channel sets are multiplexed by optical combiners and output to an optical transmission path. A bidirectional optical amplifier positioned in the optical transmission path amplifies the west-east and east-west WDM signals. In an exemplary embodiment, the amplifier includes at least two optical circulators with at least first, second, and third circulating ports. A gain block interconnects the circulators for optically amplifying the WDM signals. Bragg gratings configured to reflect either the west-east or the east-west channel band are positioned in optical paths which optically communicate with the optical circulators.

Abstract: The present invention provides a wavelength division multiplexed optical communication system which includes an optical monitoring channel which is capable of surviving the failure of an optical amplifier. The optical communication system comprises a plurality of optical transmitters which optically communicate with an optical waveguide which carries the multiplexed optical transmission signal. At least one multiple-stage optical amplifier having at least first and second stages is positioned along said optical waveguide. The optical amplifier includes a first and second stages comprising doped fibers having a first gain wavelength band. An optical connecting element having a plurality of ports is positioned between the first and second stages.

Abstract: The present invention provides a WDM optical communication system with remodulators at the transmission input and remodulating channel selectors adjacent the optical receivers, providing complete control over the interfaces with optical transmission equipment. In an exemplary embodiment, the WDM system includes optical transmitters which input transmitted optical signals into optical remodulators. The optical remodulators place the information from each of the transmitted signals onto separate optical channels in the WDM system channel plan. The optical channels are multiplexed onto an optical waveguide. At the receive end, remodulating channel selectors each receive a portion of the WDM optical signal, select a particular optical channel, and place the information from the selected channel onto a newly-generated optical signal. This newly-generated optical signal is output to a receiver or to a further WDM optical system.

Abstract: The present invention provides modular optical amplifier constituents suitable for constructing optical amplifiers of various designs and modular fiber optic cassettes. Each stage of a multiple stage optical amplifier is housed in a separate optical cassette. Optical pump(s) are separately packaged in pump modules to further simplify amplifier design and enhance amplifier manufacturability. In an exemplary embodiment, a modular optical amplifier is constructed comprising a first amplifier housing including a first optical cassette for holding a first amplifier stage. Cassette regions are provided for receiving one or more passive optical components used with the first stage of the optical amplifier. A first length of rare-earth doped optical fiber is retained by cassette retaining projections and optically communicates with a pump interconnection element.

Abstract: Fabrication of devices of micron and submicron minimum feature size is accomplished by lithographic processing involving a back focal plane filter. A particularly important fabrication approach depends upon mask patterns which produce images based on discrimination as between scattered and unscattered radiation by accelerated electrons.