Abstract: A network node is provided for use in a WDM optical transmission system that includes a plurality of network nodes interconnected by communication links. The network node includes an optical switch having at least one input port for receiving from the transmission system a WDM signal having a plurality of wavelength components. The network node also includes a regenerator arrangement having sufficient regeneration capacity to regenerate a prescribed fraction of the plurality of wavelength components. The prescribed fraction is less than a maximum number of wavelength components that may be received by the node. A network management element is provided so that the network node can for communicate with a network management center in the transmission system.

Abstract: A method and apparatus is provided for reducing impairment to an adiabatically chirped optical signal propagating in an optical communication system. The method begins by receiving an adiabatically chirped optical signal that has traversed one or more network components in the optical communication system. The optical signal has a parameter characteristic of signal quality (e.g., an extinction ratio) that is reduced at least in part by a fidelity-degrading transmission slope accumulated in the one or more network components. A fidelity-enhancing transmission slope imparted to at least one wavelength of the adiabatically chirped optical signal at one or more select points along a transmission path of the communication system so that the optical signal experiences an increase in said parameter characteristic of signal quality.

Abstract: In a WDM optical communication system that includes a plurality of nodes interconnected by communication links, a node is provided that includes a first plurality of transponders each generating and/or receiving an information-bearing optical signal at a different channel wavelength from one another. An optical coupling arrangement, which may include one or more reconfigurable optical switches, transfers the channel wavelengths between a link connected to the node and the first plurality of transponders. The arrangement is adaptable to reconfigure its operational state to selectively direct different ones of the channel wavelengths from the link to different ones of the transponders without disturbing the optical path through the node traversed by any other channel wavelengths. A communications and configuration arrangement is provided, which transfers data identifying the respective channel wavelengths at which the transponders operate from the transponders to the optical coupling arrangement.

Abstract: In a WDM optical communication system that includes a plurality of nodes interconnected by communication links, a node is provided that includes a first plurality of transponders each generating and/or receiving an information-bearing optical signal at a different channel wavelength from one another. An optical coupling arrangement, which may include one or more reconfigurable optical switches, transfers the channel wavelengths between a link connected to the node and the first plurality of transponders. The arrangement is adaptable to reconfigure its operational state to selectively direct different ones of the channel wavelengths from the link to different ones of the transponders without disturbing the optical path through the node traversed by any other channel wavelengths. A communications and configuration arrangement is provided, which transfers data identifying the respective channel wavelengths at which the transponders operate from the transponders to the optical coupling arrangement.

Abstract: An optical transmission system designed for gigabit pulse rates and Raman pumping in which there is essentially no pre-dispersion compensation and the in-line dispersion compensation at the start of each span is overcompensation of between 110 and 120 of the compensation needed to neutralize the dispersion of its immediately preceding span.

Abstract: An optical attenuator and a method of making an optical attenuator is disclosed. The method begins by arranging a first end of a first optical fiber and a second end of a second optical fiber so that they face one another in close proximity. The first and second ends of the optical fibers are then laterally offset from one another and the first end of the first fiber is fused to the second end of the second fiber to create a fusion splice. Next, the attenuation imposed on an optical signal transmitted from the first to the second optical fiber and through the fusion splice is measured to determine an initial deviation in attenuation from a prescribed value. The fusion splice is then re-fused while exerting an axially directed force on the first and second ends of the optical fiber. The measurement step is repeated to determine a subsequent deviation in attenuation from the prescribed value and the re-fusion step is repeated to reduce the subsequent deviation in attenuation.

Abstract: A network node is provided for use in a WDM optical transmission system that includes a plurality of network nodes interconnected by communication links. The network node includes an optical switch having at least one input port for receiving from the transmission system a WDM signal having a plurality of wavelength components. The network node also includes a regenerator arrangement having sufficient regeneration capacity to regenerate a prescribed fraction of the plurality of wavelength components. The prescribed fraction is less than a maximum number of wavelength components that may be received by the node. A network management element is provided so that the network node can for communicate with a network management center in the transmission system.

Abstract: An optical wavelength add/drop multiplexer (WADM) is configured to add or drop two or more signals each associated with one of a plurality of channels in a wavelength division multiplexed (WDM) signal. The WADM comprises an optical circulator that is optically coupled at one port to two or more serially interconnected fiber Bragg gratings (FBGs), and is optically coupled at another port to a thin film filter including two or more serially interconnected thin film filter elements. Each of the two or more FBGs is matched with a thin film filter element, both arranged to be responsive to signals associated with one of the plurality of channels. Bandwidth and dispersion properties for the FBGs are selected to permit operation of the WADM at two distinct signal data rates.

Abstract: In a WDM optical communication system that includes a plurality of nodes interconnected by communication links, a node is provided that includes a first plurality of transponders each generating and/or receiving an information-bearing optical signal at a different channel wavelength from one another. An optical coupling arrangement, which may include one or more reconfigurable optical switches, transfers the channel wavelengths between a link connected to the node and the first plurality of transponders. The arrangement is adaptable to reconfigure its operational state to selectively direct different ones of the channel wavelengths from the link to different ones of the transponders without disturbing the optical path through the node traversed by any other channel wavelengths. A communications and configuration arrangement is provided, which transfers data identifying the respective channel wavelengths at which the transponders operate from the transponders to the optical coupling arrangement.

Abstract: A Raman amplified transmission includes at least two pump sources to provide amplification to optical signals residing in the C-band (1530-1562 nm) and L-band (1574-1604 nm). The pump signals are chosen so as to provide for a relatively flat and wide composite gain spectrum with a width at least 50% greater than that generated by a monochromatic pump, while also chosen so as to prevent any four-wave mixing products from being in either the C- or L-bands.

Abstract: The use of a co-propagating fiber Raman amplifier in an optical WDM transmission system has been found to be practical in the situation where the fiber amplifier is operated into depletion and the characteristics of the input signals are controlled to exhibit a reduced integrated relative intensity noise (RIN) over the fiber crosstalk bandwidth. In particular, the reduction in the integrated RIN can be achieved by increasing the number of input channels (by adding more messages or simply using dummy channels), encoding the data in a particular fashion to reduce the integrated RIN, or decorrelating the plurality of N input signals below a predetermined, relatively low frequency (for example, 2 MHz).

Abstract: The use of a co-propagating fiber Raman amplifier in an optical WDM transmission system has been found to be practical in the situation where the fiber amplifier is operated into depletion and the characteristics of the input signals are controlled to exhibit a reduced integrated relative intensity noise (RIN) over the fiber crosstalk bandwidth. In particular, the reduction in the integrated RIN can be achieved by increasing the number of input channels (by adding more messages or simply using dummy channels), encoding the data in a particular fashion to reduce the integrated RIN, or decorrelating the plurality of N input signals below a predetermined, relatively low frequency (for example, 2 MHz).

Abstract: An optical filtering and multiplexing scheme obtains very high spectral density and increased maximum transmission distances without costly dispersion compensating equipment. The invention combines the filtering features of a multiplexing apparatus, such as a Waveguide Grating Router (WGR), to provide the bandwidth limitation necessary for maximizing the tolerance to dispersion. At the same time the WGR defines the bandwidth and center frequency spacing for the channels of the transmission system providing a robust interface which eliminates the possibility of non-compliant channels degrading the performance of the other channels.

Abstract: In accordance with the invention, an optical communication system is provided with one or more automatic dispersion compensation modules. Each module has an adjustable dispersion element, a data integrity monitor and a feedback network whereby the monitor adjusts the dispersion element to optimize system performance. In a preferred embodiment the dispersion compensating modules comprise chirped fiber Bragg gratings in which the chirp is induced in the grating by passing a current along distributed thin film heaters deposited along the length of the fiber. The magnitude of the applied current determines the dispersion of the grating. A data integrity monitor is configured to sense the integrity of transmitted data and to provide electrical feedback for controlling the current applied to the grating.

Abstract: In an optical communication system, the signal power level injected into each of one or more optical fiber spans is reduced so as to suppress undesired non-linear effects. This reduction in injected signal level is made possible by remotely pumped amplification in the spans that are affected.

Abstract: The present invention is directed to an optical communication system and optical signal amplifier for amplifying said optical signal having at least a first and a second wavelength as it propagates therethrough. The optical signal amplifier includes an input port; an output port; an optical medium, wherein a portion of the optical medium comprises a plurality of optical paths corresponding to the first and second wavelengths of the optical signal; a light radiation generator capable of coupling light radiation of a plurality of light radiation wavelengths related to the first and second wavelengths of the optical signal into each of the optical paths, whereby the first and said second wavelengths are amplified by Raman amplification; and an optical combiner for recombining the first and second wavelengths of the optical signal to generate the amplified optical signal.

Abstract: A Differential Phase Shift Keying (DPSK) optical transmission system provides time division multiplexing, channel routing and channel add/replace functions. The DPSK transmitter comprises a laser to generate an optical carrier signal; a delay encoder to provide a different delay for each of a plurality, M, of input signal channels; and a M channel phase modulator which phase modulates the optical carrier signal with each of the differently delayed M input signal channels to form a Time Division Multiplexed (TDM) phase modulated optical signal. A DPSK receiver demodulates a received TDM phase modulated optical signal. The system may also include apparatus to route, add, and replace TDM channels.

Abstract: A variable dispersion optical unit is used to vary the relative dispersion between an input signal and an output signal of the optical unit under control of a control circuit. The control unit uses an optical homodyne detector to beat the input optical signal with the output optical signal to generate a control signal to adjust the relative dispersion a variable dispersive element. The variable dispersive optical element may be selected from a group of dispersive elements including at least a Bragg grating, a Fabry-Perot filter, a Mach-Zehnder filter, and a waveguide routing element. The variable dispersive optical unit can be used as part of a variable wavelength selective optical circuit (e.g., a tunable wavelength filter) where the varying dispersion characteristics is used to control the selection of the wavelength of the tunable wavelength filter, or is used to select the drop/add wavelength(s) of an Add/Drop circuit.

Abstract: In accordance with the invention a multiwavelength optical fiber cross connect is provided with an active all-fiber optical router for multiplexing/demultiplexing. The router is comprised of one electronic component--a phase controller--and four fiber components: 1) a fiber directional coupler, 2) a fiber reflective grating filter, 3) a fiber tap, and 4) a fiber phase modulator. The application describes how to make optical routers from these components ranging in complexity from a single wavelength drop router to an N-port, N-wavelength router for add/drop multiplexing. The application also describes how optical wavelength routers can be combined to create optical fiber Cross connect (OXCs), ranging in complexity from 2.times.2 single wavelength OXCs to NXN, M-wavelength OXCs.