Abstract: A multi-wavelength device to compensate for chromatic dispersion in an optical transmission by inducing a phase shift which varies quadratically as a function of the different frequencies within the transmission. The quadratic phase variation can be applied by dispersing the input optical signal such that different wavelength components are spatially spread, and disposing an array of phase shifting elements along the dispersion direction, such that different wavelengths pass through different phase shifting elements. The elements are actuated to provide a phase shift which varies at least partially quadratically along the dispersion axis, and thus generates at least a partially quadratic phase variation to the wavelength components. This compensates for a phase shift having a quadratic dependence on frequency, generated as a result of the chromatic dispersion. The device is tunable, such that changes in chromatic dispersion can be compensated for dynamically.

Abstract: A fiber-optical, wavelength selective switch, especially for channel routing with equalization and blocking applications. The input signals are converted to light beams having predefined polarizations (41). The beams are then laterally expanded (43), and then undergo spatial dispersion in the beam expansion plane. The different wavelength components are directed through a polarization rotation device, pixilated along the wavelength dispersion direction such that each pixel operates on a separate wavelength. Each beam is passed into a pixilated beam steering array (48), for directing each wavelength to a desired output port. The beam steering devices can be MEMS-based or Liquid crystal-based, or an LCOS array. When the appropriate voltage is applied to a pixel and its associated beam steering element, the polarization of the light passing through the pixel is rotated and the beam steered to couple to the selected output port.

Abstract: A birefringent, electrically-controlled, wavelength selective, pixelated optical phase shifting device, in which the correct drive voltage for a desired phase shift through any pixel can be determined independently of changes in the drive voltage arising from changes in the environmental conditions, generally temperature. This is achieved by mounting a monitor phase shifting element controlled by its own drive voltage, in close proximity to the pixelated phase shifter, such that the monitor element and the phase shifter experience the same environmental condition. A probe optical beam of predefined wavelength is directed through the monitor element, and the transmitted beam measured as a function of the monitor drive voltage. This functional relationship is used to define the environmental condition in which the monitor element and the phase shifter, are situated, and the correct drive voltage for application to any phase shifter pixel can be determined.

Abstract: An isolator assembly, for use internally within a multi-port optical switch, and which operates on a preselected number of input port channels. The assembly incorporates a sequence of a birefringent crystal with a half wave plate on part of its output face acting as a linear polarizer, a 45° Faraday rotator element and a half wave plate aligned at 22.5° to the polarization direction of the light rotated by the Faraday rotator. This arrangement ensures that any light spuriously returned from a reflective beam switching element of the switch is blocked from transmission out of the paths of light which the isolator assembly covers because of the orientation of the light polarization returned to the birefringent crystal. The isolator assembly is arranged such that it does not cover the beam path leading to the output port or ports, such that legitimate output beams are transmitted unhindered.

Abstract: A fiber-optical, wavelength selective switch, especially for channel blocking applications. The input signal is converted to light beams having predefined polarizations relative to the plane in which optical manipulation of the beam is performed. The beams are then preferably laterally expanded in this system plane only, and then spatially dispersed in the beam expansion plane, preferably by means of a diffraction grating. The light is directed through a polarization rotation device, preferably a liquid crystal cell, pixelated along the wavelength dispersive direction such that each pixel operates on a separate wavelength. When the appropriate control voltage is applied to a pixel, the polarization of the light signal passing through that pixel is rotated. The wavelength dispersed beams from all of the pixels are then recombined, and are passed towards a polarization selective device, aligned such that only selected polarization components are transmitted out of the switch.

Abstract: A single-pole, wavelength selective switch in which thee input optical signal (18, 19) is converted to a light beam having a defined polarization, such as S-polarization, with respect to the system plane. The beam is laterally expanded in the system plane, and then spatially dispersed in the same plane as that of the beam expansion, preferably by means of a diffraction grating (34). The light is directed through a polarization conversion device, preferably a liquid crystal cell (24), pixelated along the wavelength dispersive direction such that each pixel operates on a separate wavelength. When the appropriate control voltage is applied to a pixel, the polarization of the light signal passing through that pixel is rotated, such as from S to P. The wavelength dispersed beams from the pixels are recombined, and are passed towards another polarizer at the switch output, aligned such that only the selected polarization components are allowed to exit.

Abstract: An optical beam processing device with two serially disposed birefringent elements, each element having its own direction of orientation. At least one element is pixelated with electrodes activated by control signals. The directions of orientation of the elements are aligned such that the phase shift imparted to the beam by an unactivated pixel of one element, cancels the phase shift imparted to the beam by the other element, such that the beam traversing that pixel undergoes zero phase shift. An appropriate control signal adds a phase shift to the beam passing through that pixel, so as to generate an overall phase shift through the device for any desired wavelength, which could not be readily achieved by either of the elements alone. The resulting device is thus able to provide switchable phase shifts of exactly zero and pi, for different wavelengths, generally unattainable by a single element device.

Abstract: A birefringent, electrically-controlled, wavelength selective, pixelated optical phase shifting device, in which the correct drive voltage for a desired phase shift through any pixel can be determined independently of changes in the drive voltage arising from changes in the environmental conditions, generally temperature. This is achieved by mounting a monitor phase shifting element controlled by its own drive voltage, in close proximity to the pixelated phase shifter, such that the monitor element and the phase shifter experience the same environmental condition. A probe optical beam of predefined wavelength is directed through the monitor element, and the transmitted beam measured as a function of the monitor drive voltage. This functional relationship is used to define the environmental condition in which the monitor element and the phase shifter, are situated, and the correct drive voltage for application to any phase shifter pixel can be determined.