Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: In an optical data communications link, a modulated optical signal is emitted from an optical transmitter, coupled into one end of an optical fiber, and received by an optical receiver at the opposite end of the fiber. The present invention relates to reducing the polarization-mode dispersion (PMD) of the modulated optical signal caused by the birefringence of the fiber, which tends to limit the usable bandwidth of the fiber. A polarization controller is applied to the modulated optical signal substantially near the transmitter. The receiver measures the quality of the received signal and issues commands to the polarization controller to improve the received signal quality. In various embodiments, the signal quality measurement may be based on observed bit-error-rate (BER), estimated best attainable BER, or estimates of PMD affecting the received signal.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.