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 bidirectional add-drop multiplexers for bidirectional wavelength division multiplexed optical communication systems. In a first configuration, the bidirectional add-drop multiplexer includes six three-port optical circulators. The bidirectional add-drop multiplexer is placed at any point along a bidirectional transmission waveguide configured to carry two counter-propagating wavelength division multiplexed optical signals. The bidirectional waveguide places the west-east wavelength division multiplexed optical signal into the first port of the first circulator where it is routed to the first port of the second optical circulator. A channel selector is positioned between the second and third optical circulators for add/dropping optical channels. The through channels and any added channels exit through the first port of the fourth circulator as a counter-propagating east-west WDM optical signal enters the first port.

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 position-sensing system which employs sensors incorporating magnetoresistive materials. The position of a magnetic information input member is determined through the resistance change of the magnetoresistive sensor in response to the magnetic field from the magnetic information input member. Exemplary magnetoresistive materials are lanthanum manganites having high magnetoresistive ratios. Two-dimensional position sensing systems for graphics tablets are also described.

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: The present invention provides an optical add-drop multiplexer for wavelength division multiplexed optical communication systems which includes first and second optical couplers which optically communicate with each other through an optical filter. The first optical coupler includes a first input port and first and second output ports while the second optical coupler includes first and second input ports and an output port An optical path optically communicates with the first output port of the first optical coupler and with the first input port of the second optical coupler and includes an optical filter for selecting portions of a wavelength division multiplexed optical signal input to the first optical coupler. The portions of the wavelength division multiplexed signal which are not sent to an input port of the second optical coupler exit the add-drop multiplexer.

Abstract: The present invention provides a gratings-based add-drop multiplexer in which plural optical channels can be added and/or dropped by the same optical device in a manner which avoids transmitting an optical channel through a radiation mode loss region of a Bragg grating. In one embodiment, the add-drop multiplexer comprises a three-port optical circulator, an optical coupler, and a transmission path communicating with both the circulator and the optical coupler. A set of one more Bragg gratings is positioned in the transmission path for reflected signals to be dropped towards the circulator and onto a "drop" path. The through optical signals enter the first coupler input port and are combined with the "add" signals transmitted by the second coupler input port. The coupler optically combines these optical signals and outputs the combined optical signal.

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 WDM optical communication system includes a first set of optical transmitters for creating a set of east-west optical channels and a second set of transmitters for creating a set of west-east optical channels. The respective channel sets are multiplexed by optical combiners and output to an optical transmission path. A bidirectional optical amplifier optically communicates with the optical transmission path for amplifying the east-west and west-east WDM signals. In an exemplary embodiment, the bidirectional optical amplifier comprises a first and second four-port optical circulators and a section of doped optical fiber with optical pumps interconnecting the two circulators.

Abstract: A WDM optical communication system is described which is capable of placing information from incoming information-bearing optical signals onto N optical signal channels for conveyance over an optical waveguide. The optical system includes a first set of one or more optical transmitters, each of which emits an information-bearing optical signal at one or more transmission wavelengths, .lambda..sub.Ti. At least M optical receiving systems are provided, each receiving system configured to receive an information-bearing optical signal at a particular reception wavelength .lambda..sub.j, where M is a whole number greater than or equal to N and j is from 1 to M. Each receiving system includes at least one Bragg grating member for selecting the particular reception wavelength .lambda..sub.j. An optical waveguide optically communicates with each of the M receiving systems for transmitting a plurality of optical signals.

Abstract: The present invention provides a remodulating channel selector for a wavelength division multiplexed optical communication system. The remodulating selector receives a WDM input signal, selects a particular optical channel from the WDM signal and places the information from the selected signal onto a newly-generated optical output signal. The wavelength of the output optical signal can be the same as or different from one of the optical channels which comprises the WDM input signal. When used in a WDM optical communication system with remodulators at the transmission input, the remodulating selectors provide complete control over the interfaces with optical transmitters and receivers, permitting use with a broad range of optical equipment.

Abstract: The present invention provides reconfigurable wavelength division multiplexed systems which include configurable optical routing systems. Through the use of the configurable optical routing systems, optical channel traffic patterns may be flexibly and dynamically determined based on overall system conditions at any particular time. In one embodiment, a dynamically reconfigurable wavelength selector system for a wavelength division multiplexed optical communication system is provided. An optical transfer system includes an input port for receiving at least one of N optical channels from an optical transmission medium. An optical switch is coupled to a first output port of the optical transfer system and includes an optical filter comprised of at least one Bragg grating configured to reflect at least one optical channel toward the optical transfer system on a first switch path and a transmission medium for transmitting the N optical channels on a second switch path.

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.