Abstract: The present invention provides systems and methods for highly efficient bit error rate (BER) modeling in quasi-linear communication networks. In the present invention, nonlinear noise is treated within a linearization approach along with the amplified spontaneous emission (ASE) noise, and the nonlinear noise is considered as another source of noise in addition to the ASE noise. This enables a quasi-analytical approach to the BER calculation. First, a covariance matrix is analytically computed. An equation is derived for a noise component of a signal and an implicit analytical solution is found depending on the signal and system parameters. Second, probability distribution functions (pdfs) are computed for the signal. An analytical calculation is performed of the characteristic function for the noise statistics. Next, a numerical computation of the Fourier transform of the characteristic function is performed to yield the pdf, and numerical integration is performed on the pdfs to yield the BER.

Abstract: The present invention provides systems and methods for highly efficient bit error rate (BER) modeling in quasi-linear communication networks. In the present invention, nonlinear noise is treated within a linearization approach along with the amplified spontaneous emission (ASE) noise, and the nonlinear noise is considered as another source of noise in addition to the ASE noise. This enables a quasi-analytical approach to the BER calculation. First, a covariance matrix is analytically computed. An equation is derived for a noise component of a signal and an implicit analytical solution is found depending on the signal and system parameters. Second, probability distribution functions (pdfs) are computed for the signal. An analytical calculation is performed of the characteristic function for the noise statistics. Next, a numerical computation of the Fourier transform of the characteristic function is performed to yield the pdf, and numerical integration is performed on the pdfs to yield the BER.

Abstract: A optical communications network including at least one optical phase conjugator for compensating for non-linear effects. The optical communications network includes at least one dispersion compensation module before the optical phase conjugator and at least one dispersion compensation module after the optical phase conjugator. The dispersion compensation modules compensate for linear effects of the transmission path such as dispersion and dispersion slope. This allows the optical phase conjugator to be designed to compensate for non-linear effects such as self-phase modulation and cross-phase modulation. The separate compensation of linear and non-linear effects provides enhanced control of these effects.

Abstract: A method and system for compensating residual dispersion curvature in an optical communication network is disclosed. One embodiment employs two types of dispersion compensating fiber to reduce higher order terms in a residual dispersion profile. The two types of dispersion compensating fiber may be co-located in a dispersion compensation module positioned in each transmission fiber link. Alternatively, the two types of dispersion compensating fiber may be distributed across a span of the optical communication network.

Abstract: A method and system for using optical phase conjugation in an optical communications network including an add-drop multiplexer. The method includes determining a position for an optical phase conjugator such that channel quality for a channel in improved above a threshold. Transmission characteristics such as amplifier launch power or dispersion features may be adjusted to compliment the optical phase conjugation. An alternate method includes positioning the optical phase conjugator to improve a weighted average channel quality for the network.

Abstract: In a wavelength division multiplexed system, optical frequencies are assigned in accordance with a channel plan conforming to an International Telecommunications Union (ITU) grid whereby every third channel position in the grid is vacant. As a result, both four wave mixing (FWM) and cross phase modulation (XPM) are reduced using ITU standard frequencies. In addition, a low bandwidth expansion factor (BEF) can be achieved.

Abstract: A dispersion compensating element having a substantially uniform spectral nonlinearity is described. The dispersion compensating unit is thus suitable for incorporation into high speed wavelength division multiplexed (WDM) optical communication systems. Several examples of dispersion compensating elements are discussed, each of which comprising at least one segment of dispersion compensating fiber.

Abstract: In accordance with the present invention, a dispersion compensation module is coupled to a transmission optical fiber. The dispersion compensation module includes segments of optical fiber of varying length, some of which have a positive dispersion while other have a negative dispersion. Selected optical fiber segments are coupled to one another to provide a desired net dispersion to offset the dispersion associated with the transmission optical fiber. Thus, rather than provide a unique segment of DCF for each span, the same dispersion compensation module can be used for spans of varying length and fiber types by simply connecting appropriate segments of fiber within the module.