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 single-pole, wavelength selective switch in which the input optical signal 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. The light is directed through a polarization conversion 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, 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: 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 wavelength selective switch, in which an input optical signal is wavelength-dispersed and polarization-split in two angularly oriented planes. A polarization rotation device, such as a liquid crystal polarization modulator, pixelated along the wave-length dispersive direction such that each pixel operates on a separate wavelength channel, rotates the polarization of the light signal passing through the pixel, according to the control voltage applied to that pixel. The polarization modulated signals are then wave-length-recombined and polarization-recombined by means of similar dispersion and polarization combining components as were used to respectively disperse and split the input signals. The direction of the output signal is determined by whether the polarization of a particular wavelength channel was rotated by the polarization modulator pixel, or not. In this way, a fast, wavelength dependent, optical switch is provided, capable of use in WDM switching applications.

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 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 liquid crystal cell fabrication method is presented that utilizes a deposited metal gasket moisture barrier bonding two opposing plates of glass each having a spacer layer to accurately control cell gap thickness along with an optional integrated thermal sensor and heater deposition layer sandwiched between both opposing plates of glass.

Abstract: A liquid crystal cell is presented that utilizes a deposited metal gasket moisture barrier and support membrane bonding two opposing plates of glass, a thin film spacer layer to accurately control cell gap thickness, and an optional integrated thermal sensor and heater deposition layer sandwiched therebetween.

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.

Abstract: A wavelength locker operates with a reference tunable liquid crystal filter having integrated photodetectors deposited on the front and backside of the liquid crystal cell to track power intensity of the accepted passband signal and its rejected signal compliment at a 50% power point where the two signals cross on the side of the filter transmission peak. The tunable filter is tuned by an offset wavelength from the laser wavelength such that 50% power is transmitted through the filter at the center wavelength of the laser. The wavelength locker may be configured with a liquid crystal tunable etalon or a liquid crystal tunable bandpass filter. A method for locking an optical signal to a desired frequency is also included and provides a substantially linear feedback signal computed by dividing the rejected signal power by the accepted signal power and passing it to laser transmitter to enable it to correct for frequency drift.

Abstract: A multi-pixel optical processing system includes a multi-pixel liquid crystal cell platform having a deposited metal gasket moisture barrier bonding two opposing substrates each having a spacer layer to accurately control cell gap thickness. A library of specialized pixel constructs is included that can be configured to yield predetermined optical functions at referential locations in the platform. A control system is provided utilizing a time division scheme that multiplexes temperature sensing and heating functions across an optional integrated active thermal element that may be integrated inside the liquid crystal platform. A calibration process characterizes the profile of the cell and generates a polynomial regression formula that provides the voltage drive output for all pixels in the platform based on the platform temperature and state of each pixel.

Abstract: A fiber optical device, whose wavelength profile can be dynamically controlled in real time by the application of control voltages. The device can be used as a fiber optical gain equalizer or a wavelength selective filtering device which is compact, polarization insensitive, and of low manufacturing costs. The device comprises a stepped transparent substrate, through which the input beam is passed. Within the optical paths of the stepped regions of the substrate, electronically variable phase shifting elements are located, each operative to change the phase of the light passing through its associated step, and thus effectively adding tunability to the height of each step. Planar liquid crystal elements may be used as these elements. The elements may be pixelated, each pixel preferably affecting the phase of the light passing through a fraction of the area of the associated step, such that the interference so can be used to vary the transmission through that step.

Abstract: A tunable optical filter is provided that includes an array of independently tunable filter elements. Each of the elements is located along a different optical path that extends between an input and an output port. Optical assemblies for receiving an incident optical signal for providing a filtered optical signal are also provided. In one embodiment, polarization independent spectral filtering can be achieved. Wavelength selectable add/drop multiplexers and demultiplexers, dynamic gain equalizers and attenuators, optical channel blockers and branch filters, switches, and modulators are also provided. Furthermore, methods for constructing and operating filters consistent with this invention are also provided.

Abstract: A fiber optical attenuator utilizing the cut-off phenomenon for single mode propagation of an optical wave down a single mode fiber, comprising an element such as a pixelated liquid crystal element, capable of spatially changing the phase across the cross section of an input optical signal. Such a spatial phase change is equivalent to a change in the mode structure of the propagating wave. The signal propagating in the single mode output fiber is attenuated in accordance with the extent to which higher order modes are mixed into the low order mode originally present. When the mode is completely transformed to higher order modes, the wave is effectively completely blocked from entering the output single-mode fiber, and the attenuation is high. The level of attenuation is determined by the fraction of the wave which is converted to modes other than the lowest order mode, and is thus controllable by the voltage applied to the pixels of the liquid crystal element.

Abstract: A polarization insensitive narrowband tunable filter utilizes an active liquid crystal cell to change the index of refraction and tuning of a waveguide resonant filter employing a nanostructured waveguide grating and polarization beam splitters to independently channel and convert S- and P-polarization states into optically and geometrically parallel beams which pass through the device. A multi-pixel configuration offers extended tuning range by employing a 1×N optical switch or splitter and N tunable pixel-filters each having offset center frequency enabling the tuning range of one pixel to partially overlap another pixel rendering the device and 1×N switch or splitter capable of scanning pixels to yield an expanded continuous tuning range mode. Optional features of the present invention include deposited photodetectors, deposited metal gasket moisture barrier, deposited spacer layer with high cell gap tolerance, a deposited thermal sensor and heater and related temperature compensation control schemes.

Abstract: A thermal control system for a liquid crystal cell is presented that may utilize a time division scheme to multiplex temperature sensing and heating functions across active thermal elements such that the cell may generally be kept at a constant temperature. A calibration process characterizes the profile of the cell and generates a polynomial regression formula that provides the voltage drive output for a temperature and cell state input. The control system stores the state of the liquid crystal cell, the regression formula, and reads the temperature of the liquid crystal cell to compute end assert the temperature compensated voltage drive.