Fujitsu Corporation

Mci Communications Corporation

Worldcom, Inc.

Mci Worldcom, Inc.

David G Way

Tiejun J Xia

Cheng C Chen

Merwyn C Bartlett

T J Xia

Yisong Li

Rajesh Kumar

A dispersion compensation system includes a dispersion compensation module and a dispersion enhancement module. The dispersion compensation module receives optical input and provides optical output having a negative dispersion relative to the optical input. The dispersion enhancement module receives optical signals from a transport fiber and may increase positive dispersion in the optical signals by a configured amount such that the positive dispersion provided by the transport fiber and the dispersion enhancement module substantially equals the magnitude of the negative dispersion provided by the dispersion compensation module.

Selectable dispersion enhancement

A method and system for tuning channel spacing for a wavelength division multiplexing (WDM) transport system includes determining a spectrum width for a channel. A bandwidth of a group of base channels covering the spectrum width for the channel is allocated to the channel. A passband of a channel filter at a center frequency of the group is adjusted to correspond to the spectrum width of the channel.

Tunable channel spacing for wavelength division multiplexing (WDM) transport system

An optical transport system that uses tunable filters to vary the central wavelengths and spectrum widths of channels within the system to more efficiently use the bandwidth of the fiber. Higher bit rate channels may be divided into multiple lower bit rate channels, and lower bit rate channels may be combined to form higher bit rate channels.

Transport system with tunable channel spacing DWDM

Method and system for controlling polarization mode dispersion

A state-of-polarization (SOP)-independent device and method for determining polarization mode dispersion (PMD) in an optical communication system having an optical transmission line, including a detector coupleable to the optical transmission line, where the detector is capable of analyzing a pulse shape of an optical signal on the optical transmission line to determine PMD of the optical signal. A corrector may be coupled to the detector , where the corrector is capable of compensating the optical signal for the determined PMD. A controller may be coupled to the detector and the corrector . The pulse shape may comprise an eye diagram, which may contain a first peak and a second peak due to PMD, where the PMD determined by the detector is a function of the distance between the detected first and second peaks, which is indicative of a time delay between the detected first and second peaks. The device and method may also include a verifier coupled to the corrector , where the verifier is capable of verifying that the corrector correctly compensated the optical signal for the PMD.

Device and method for determining PMD independent of SOP

An exemplary composite optical fiber transmission line and method are provided that result in significant advantages. The composite optical fiber transmission line includes a standard single-mode fiber, such as an SMF-28 fiber, a dispersion shifted fiber, such as an NZDSF fiber, and a dispersion compensating fiber. The single-mode fiber receives an input optical signal at a first end and generates a single-mode optical signal at a second end. The dispersion shifted fiber receives the single-mode optical signal at a first end and generates an output optical signal at a second end. The dispersion compensating fiber receives the output optical signal and generates a chromatic dispersion compensated optical signal that, preferably, is at some desired chromatic dispersion level. In one example, the residual chromatic dispersion of the composite optical fiber transmission line is zero or near zero, and the residual chromatic dispersion slope of the composite optical fiber transmission line is zero or near zero.

Composite optical fiber transmission line method

A method, a system and a computer program product configured to determine a differential group delay of two sequential optical beams based on a frequency dependence of a length of an optical path traveled by the two sequential optical beams in a dispersion compensation grating. The determined differential group delay provides a measure of polarization mode dispersion in the dispersion compensation grating.

Method and apparatus for measuring PMD of a dispersion compensation grating

A spare capacity planning tool for planning spare capacity in a transport network during a multiple-span failure following a single failure event. The spare capacity planning tool simulates restoration of a transport network regardless of the sequence of failures. The system and method utilize a permutation reducer to minimize the number of sequences to be verified during simulated or actual restoration activities. The permutation reducer reduces the number of sequences to to during simulated restoration activities to a first order function rather than a factorial function of the number of failed spans.

Spare capacity planning tool

A method of locating concentrator switches in an existing network that includes a plurality of sites interconnected by existing links so as to minimize total network cost in terms of transmission cost, equipment cost, and facility cost, while meeting all traffic demands. The method uses a Lagrange relaxation technique to perform the optimization. First, the method assigns to each site j an initial Lagrange multiplier .lambda..sub.j. Then the method selects from the sites a set of core nodes j such that the facility cost v.sub.j for each selected core node j is less than the Lagrange multiplier .lambda..sub.j for the site multiplied by the number of ports k.sub.1 in a concentrator switch, inherently forming a set of remaining source nodes i. Then the method homes the source nodes i to the core node j such that the cost to connect a source node i to a selected core node j plus the Lagrange multiplier .lambda..sub.j for the selected core node j multiplied by the traffic a.sub.i from said source node i is a minimum. The method calculates an upper bound and a lower bound for the cost of the network. Then, the method subtracts the lower bound from the upper bound and determines whether the difference is less than a predetermined value. If the difference between the upper bound and the lower bound is not less than the predetermined value, the method uses a subgradient technique to adjust the Lagrange multiplier .lambda..sub.j for each site j. The method performs iterations of adjusting the Lagrange multipliers .lambda..sub.j, selecting core nodes j, and homing source nodes i until the difference between the upper bound and the lower bound is less than the predetermined value.

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Garland, TX, United States of America

David G Way