Abstract: Methods, systems and computer-implemented processes for analyzing transactions for fraud are presented. A plurality of risk tables used by a fraud detection model is augmented with temporal change data related to risk variables associated with the plurality of risk tables. The fraud detection model is then executed using the augmented plurality of risk tables to generate a score for transaction data representing a new transaction, the score representing a numerical probability of the existence of fraud based on the fraud detection model.

Abstract: Techniques for compensating for PMD in multiple WDM channels by processing all WDM channels in the same manner without demultpliexing the channels. A feedback control is provided to decrease the worst-case power penalty and the channel fading probability by optimizing over the entire group of WDM channels.

Abstract: Techniques and devices for emulating polarization-mode dispersion in an optical signal that transmits through an optical fiber by using multiple birefringent wave-guiding sections that are interconnected to have adjustable polarization-changing connectors. The polarization of light transmitting from one section to another adjacent section can be modified differently between different adjacent sections according to a distribution function to produce one PMD state to represent one possible PMD state of a real PMD fiber. The connectors can be adjusted to produce different sets of polarization modifications to produce different PMD states to represent different possible PMD states of the real PMD fiber.

Abstract: Techniques for compensating for PMD in multiple WDM channels by processing all WDM channels in the same manner without demultpliexing the channels. A feedback control is provided to decrease the worst-case power penalty and the channel fading probability by optimizing over the entire group of WDM channels.

Abstract: A nonlinearly chirped fiber grating for achieving tunable dispersion compensation, dispersion slope compensation, polarization mode dispersion, chirp reduction in directly modulated diode lasers, and optical pulse manipulation. A dynamical dispersion compensation mechanism can be implemented in a fiber communication system based on such a nonlinearly chirped fiber grating.

Abstract: Techniques and devices for emulating polarization-mode dispersion in an optical signal that transmits through an optical fiber by using multiple birefringent wave-guiding sections that are interconnected to have adjustable polarization-changing connectors. The polarization of light transmitting from one section to another adjacent section can be modified differently between different adjacent sections according to a distribution function to produce one PMD state to represent one possible PMD state of a real PMD fiber. The connectors can be adjusted to produce different sets of polarization modifications to produce different PMD states to represent different possible PMD states of the real PMD fiber.

Abstract: Techniques and devices based on a wave-guiding element which has a spatial grating pattern that is an oscillatory variation along its optic axis. The wave-guiding element is configured to receive an input optical signal and to produce an output optical signal by reflection within a Bragg reflection band produced by the spatial grating pattern so as to produce time delays of different reflected spectral components as a nonlinear function of spatial positions along said optic axis at which the different reflected spectral components are respectively reflected. Such a wave-guiding element may be a nonlinearly chirped fiber grating A control unit may be engaged to the wave-guiding element and is operable to change a property of the spatial grating pattern along the optic axis to tune at least relative time delays of the different reflected spectral components nonlinearly with respect to wavelength.