Abstract: According to an exemplary embodiment of the present invention, an apparatus for selectively introducing birefringence in an optical fiber includes an actuator which selectively exerts a force on the fiber, and a registration key which selectively orients an axis of the optical fiber at predetermined azimuths. According to another illustrative embodiment of the present invention, an apparatus for changing the polarization state of an optical signal includes a plurality of sequentially connected phase shifters, wherein each of the phase shifters is adapted to exert a force on an optical fiber disposed therein. Each of the plurality of phase shifters includes a registration key which selectively orients an axis of the optical fiber disposed in the registration key at a predetermined azimuth.

Abstract: A polarization mode dispersion compensator corrects polarization mode dispersion in an optical signal having a fast polarization mode component, a slow polarization mode component and a time differential between the components. The compensator includes a phase shifter and a variable delay section. An input of the phase shifter is coupled to an optical device that provides an optical signal that exhibits polarization mode dispersion. The phase shifter functions to rotate the optical signal principal states of polarization to a desired orientation. The variable delay section includes an input, an output and at least one optical fiber delay line. The input of the variable delay section is coupled to the output of the phase shifter and the desired orientation of the optical signal principal states of polarization are substantially rotated to be in alignment with one of a fast axis and a slow axis of each of the one or more fiber delay lines.

Abstract: A method for controlling a dispersion compensation in optical communications is disclosed. The illustrative method includes receiving a first measurement of dispersion at a first step; receiving a second measurement of dispersion at a second step; calculating a gradient of dispersion between the first measurement of dispersion and the second measurement of dispersion; and sending a command to a dispersion compensator based on the value of the gradient.

Abstract: A method of controlling a plurality of stages, each having a finite range of operation, is disclosed. The method comprises determining a state of operation of a selected one of operation is approaching a threshold; and, thereafter, selectively altering a state of operation of the other devices so that a desired output is continuously maintained for each input.

Abstract: An optical device for detecting chromatic dispersion is described. The optical device includes a receiver, which converts an optical signal into an electrical signal having a plurality of frequency components. A bandpass section separates the plurality of frequency components and a gain section amplifies each of the plurality of frequency components of the electrical signal. Each of the spectral components has a corresponding voltage level and each voltage level may be compared to known voltage levels of a signal having little or no chromatic dispersion. From this comparison, the amount of chromatic dispersion may be determined. The optical device may be used as an element of a chromatic dispersion compensation device, or as a stand-alone device for measuring the amount of chromatic dispersion in an optical signal. A method of compensating for chromatic dispersion in real-time based on the optical device and dispersion compensator is also described.

Abstract: A system for compensating polarization mode dispersion of optical signals in an optical transmission line. The device includes first and second optical lines and a polarization splitter adapted to be operably connected to an optical transmission line. The polarization splitter is configured to split the principle states of polarization of an optical signal from the optical transmission line into first and second optical signal components that travel along the first and second optical lines, respectively. The device includes a stretcher that is configured to selectively vary the length of at least a selected one of the first and second optical lines. A controller is operatively connected to the stretcher, and controls the stretcher to compensate for polarization mode dispersion present in the optical transmission line. The device also includes an optical output line and a polarization combiner operatively connected to the first and second optical lines.

Abstract: According to an exemplary embodiment of the present invention, an apparatus for selectively introducing birefringence in an optical fiber includes an actuator which selectively exerts a force on the fiber, and a registration key which selectively orients an axis of the optical fiber at predetermined azimuths.

Abstract: Communications systems and methods employ receivers which utilize estimators, such as extended Kalman filters, to estimate a transmitted information signal based only upon initial parameters in a transmitter and a single transmitted state of the transmitter. This arrangement facilitates the use of inherently secure chaotic modulation schemes in the transmitter. In one embodiment, one or more parameters of nonlinear transmitter elements are modulated with one or more information signals to generate a chaotically varying transmission signal. A communication scheme known as Parameter Division Multiple Access (PDMA) is thus created in which multiple information signals from multiple transmitters can be combined and transmitted to corresponding multiple receivers in a single transmission signal. A special Kalman filter known as a feedback Kalman filter is employed for separating each receiver's corresponding portion of the transmitted signal.