Abstract: Methods and apparatus for coherent PMD generation are provided. A PMD generator can include at least four birefringent stages in optical series, thereby forming at least three pairs of adjacent stages. Each of the stages includes a harmonic differential group delay element and a phase-compensating element. The generator can be made colorless (i.e., made to have the same PMD at each WDM channel) and can be operated such that DGD and second order PMD can be independently generated and controlled. These PMD generators can be used in PMD compensators and PMD emulators.

Abstract: A polarization mode dispersion generator for generating polarization mode dispersion (“PMD”) spectra is provided. The generator includes a plurality of birefringent stages, each stage including a differential group delay (“DGD”) element and a phase-shifting element. The generator is capable of inducing an amount of polarization mode-mixing between at least one adjacent pair of stages. The shape of a PMD spectrum can be preserved while frequency shifting the spectrum in either direction. Alternatively, the shape of the PMD spectrum can be changed without frequency shifting.

Abstract: Methods and apparatus for coherent PMD generation are provided. A PMD generator can include at least four birefringent stages in optical series, thereby forming at least three pairs of adjacent stages. Each of the stages includes a harmonic differential group delay element and a phase-compensating element. The generator can be made colorless (i.e., made to have the same PMD at each WDM channel) and can be operated such that DGD and second order PMD can be independently generated and controlled. These PMD generators can be used in PMD compensators and PMD emulators.

Abstract: Methods and apparatus for coherent polarization mode dispersion generation are provided. A generator can include at least four birefringent stages. The birefringent stages are in optical series, and each includes a differential group delay (“DGD”) element. The intermediate stages' DGD elements are harmonic. Also, these intermediate stages each include a phase-shifting element. The generator can also include a polarization mode-mixing apparatus and a variable phase-shifting apparatus. The mode-mixing apparatus is capable of inducing polarization mode-mixing between at least one pair of adjacent stages to generate DGD and second order PMD independently at at least one optical frequency. The variable phase-shifting apparatus can include a phase-shifting controller coupled to each of said phase-shifting elements. A graphical user interface for PMD emulation, a PMD compensator for reducing PMD impairment, and calibration methods are also provided.

Abstract: Methods and apparatus for coherent PMD generation are provided. A PMD generator can include at least four birefringent stages in optical series, thereby forming at least three pairs of adjacent stages. Each of the stages includes a harmonic differential group delay element and a phase-compensating element. The generator can be made colorless (i.e., made to have the same PMD at each WDM channel) and can be operated such that DGD and second order PMD can be independently generated and-controlled. These PMD generators can be used in PMD compensators and PMD emulators.

Abstract: A stack of two or more birefringent crystals having complimentary properties is arranged to have zero net beam walk-off at off-normal incidence and a finite free-spectral range. In another embodiment, the birefringent crystal materials are selected to provide reduced temperature dependence. The result is an optically and mechanically stable composite birefringent crystal unit. A variety of folded birefringent filters are implemented using the composite birefringent crystal.

Abstract: A stack of two or more birefringent crystals having complimentary properties is arranged to have zero net beam walk-off at off-normal incidence and a finite free-spectral range. In another embodiment, the birefringent crystal materials are selected to provide reduced temperature dependence. The result is an optically and mechanically stable composite birefringent crystal unit. A variety of folded birefringent filters are implemented using the composite birefringent crystal.

Abstract: A stack of two or more birefringent crystals having complimentary properties is arranged to have zero net beam walk-off at off-normal incidence and a finite free-spectral range. In another embodiment, the birefringent crystal materials are selected to provide reduced temperature dependence. The result is an optically and mechanically stable composite birefringent crystal unit. A variety of folded birefringent filters are implemented using the composite birefringent crystal.

Abstract: Methods and apparatus for coherent polarization mode dispersion generation are provided. A generator can include at least four birefringent stages. The birefringent stages are in optical series, and each includes a differential group delay (“DGD”) element. The intermediate stages' DGD elements are harmonic. Also, these intermediate stages each include a phase-shifting element. The generator can also include a polarization mode-mixing apparatus and a variable phase-shifting apparatus. The mode-mixing apparatus is capable of inducing polarization mode-mixing between at least one pair of adjacent stages to generate DGD and second order PMD independently at at least one optical frequency. The variable phase-shifting apparatus can include a phase-shifting controller coupled to each of said phase-shifting elements. A graphical user interface for PMD emulation, a PMD compensator for reducing PMD impairment, and calibration methods are also provided.

Abstract: Methods and apparatus for coherent PMD generation are provided. A PMD generator can include at least four birefringent stages in optical series, thereby forming at least three pairs of adjacent stages. Each of the stages includes a harmonic differential group delay element and a phase-compensating element. The generator can be made colorless (i.e., made to have the same PMD at each WDM channel) and can be operated such that DGD and second order PMD can be independently generated and controlled. These PMD generators can be used in PMD compensators and PMD emulators.

Abstract: A polarization mode dispersion generator for generating polarization mode dispersion (“PMD”) spectra is provided. The generator includes a plurality of birefringent stages, each stage including a differential group delay (“DGD”) element and a phase-shifting element. The generator is capable of inducing an amount of polarization mode-mixing between at least one adjacent pair of stages. The shape of a PMD spectrum can be preserved while frequency shifting the spectrum in either direction. Alternatively, the shape of the PMD spectrum can be changed without frequency shifting.

Abstract: A double-pass birefringent filter apparatus comprises an external-interface apparatus (illustratively including of a beam-displacer element and a waveplate element); a birefringent filter comprised of a series of several birefringent waveplates; and a wrap-around unit (illustratively comprised of a beam-displacer element and a retro-reflector). In response to an input beam received at the external-interface apparatus, the double-pass birefringent filter forms two output beams having complimentary intensities which vary periodically with frequency.

Abstract: A polarization-mode-dispersion emulator in accordance with the principles of the present invention includes a plurality of PMD-generating stages aligned in cascade so as to form a clear light-path through the stage concatenation. Each PMD-generating stage includes an optical birefringent crystal or crystals for the purpose of imparting differential group delay and a polarization-rotating plate such as a half-wave waveplate for the purpose of imparting state-of-polarization rotation from one PMD-generating stage to the next. The polarization-rotating plates are mounted to rotation apparatuses and a controller coordinates the relative rotation of each waveplate for the purpose of generating PMD in a controlled manner.

Abstract: Methods and apparatus for generating polarization mode dispersion (“PMD”), especially for use in PMD emulators and compensators, are provided. The apparatus can include a lens assembly, an optical beam turning assembly, and a variable PMD generating assembly located between the lens assembly and the optical turning assembly. The variable PMD generating assembly can include a fixed DGD stage and a variable electro-optically controlled retardation stage. The method involves directing the beam through the variable PMD generating assembly at least twice by folding the beam with the turning assembly. Various phase and temperature compensation techniques are also provided.

Abstract: A birefringent filter includes an input optical apparatus for receiving an input optical beam and producing therefrom parallel first and second optical beams offset in a first direction and having the same polarization. A birefringent filter unit receives the first and second polarized optical beams and produces a first and second elliptically polarized optical beams. An output optical apparatus combines predetermined components of the first and second elliptically polarized optical beams to form a first and second elliptical polarized output beams. The two output beams have intensities that vary inversely, in a periodic manner, as a function of frequency of the input optical beam.

Abstract: A wavelength-selective optical switch having a first input port for accepting a plurality of copropagating optical channels, each of the channels having a distinct wavelength band. The optical switch includes first and second output ports. A wavelength-selective optical filter is connected to receive the copropagating optical channels from the first input port to extract a selected one of the channels while allowing the remaining channels to copropagate to the first output port. An interferometric switch is connected to receive the selected extracted channel; the interferometric switch includes a controller for controlling propagation of the selected extracted channel to either the second output port, the optical filter, or both. The optical filter is connected to receive from the interferometric switch an optical channel to be combined with the remaining copropagating channels and all directed to the first output port.